In the first-year biology class, Unit 14 on Transport is a crucial module that delves into the fascinating world of how organisms move essential substances such as nutrients, gases, and waste products throughout their bodies. These comprehensive notes explore the intricacies of circulatory systems, including the human cardiovascular system, as well as the transport mechanisms in plants.
Students will learn about the structure and function of the heart, blood vessels, and blood components, understanding how they collaborate to maintain homeostasis. Furthermore, the unit delves into plant transport systems, including the xylem and phloem, elucidating the processes that enable water and nutrients to ascend from roots to leaves while photosynthetic products move in the opposite direction. Unit 14 Transport Notes are a foundation for understanding how living organisms sustain life by efficiently distributing essential substances, making it an indispensable part of the biology curriculum.
Short Question Answers Unit 14 Transport 1st Year Biology
What are the different processes involved in the transport of nutrients into cells and removal of wastes from cells?
The processes involved in the transport of nutrients into cells and removal of wastes from cells include diffusion, facilitated diffusion, osmosis, active transport, endocytosis, and exocytosis.
In which systems do materials move within the body in animals?
In animals, materials move within the body in the respiratory, circulatory, digestive, and excretory systems.
What are the processes involved in the movement of materials within and out of plants?
In plants, the processes involved in the movement of materials within and out of the body include respiration, transportation, photosynthesis, absorption by roots, conduction of water, and nutrient movement.
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Why is there a need for the transport of materials in living organisms?
Living organisms need to transport materials within their bodies to obtain essential nutrients and remove waste products. Without transport systems, cells in complex multicellular organisms would be unable to access necessary materials and eliminate waste.
Do unicellular organisms have mass flow systems for material transport?
No, unicellular organisms and lower multicellular organisms do not have mass flow systems for material transport.
What are the three types of nutrients needed by plants?
Plants need carbon dioxide, water, and minerals for their growth and survival.
How do roots provide a large surface area for absorption?
Roots achieve a large surface area for absorption through extensive branching and the presence of tiny hair-like structures called root hairs.
Where does most of the uptake of water and minerals take place in roots?
Most of the uptake of water and minerals in roots occurs at the sites of root hairs.
How do minerals enter root hairs or epidermal cells of roots?
Minerals can enter root hairs or epidermal cells of roots through diffusion, facilitated diffusion, or active transport.
Why are minerals bound by ionic bonds to soil particles not available to plants?
Minerals bound by ionic bonds to soil particles are not available to plants because they are not in solution and cannot be absorbed by the roots.
What are the two main pathways involved in the uptake of minerals by root cells?
The two main pathways are the symplast pathway (through plasmodesmata) and the apoplast pathway (along the cell walls).
What is the function of Casparian strips in the endodermis?
Casparian strips prevent the movement of ions along the apoplast pathway and force them to enter endodermis cells, where they can be transported to the xylem by diffusion or active transport.
What percentage of the total surface area provided by roots is attributed to root hairs?
Root hairs provide approximately 67% of the total surface area of roots.
Which family of trees has the maximum root depth of up to 50 meters?
Prosopis trees of the leguminosae family have a maximum root depth of 50 meters.
How do plants primarily absorb minerals when inorganic or organic fertilizer is applied to soil?
Plants primarily absorb minerals as inorganic ions when inorganic or organic fertilizer is applied to the soil.
What is the main process by which plants take up minerals in higher concentration inside root cells than in the soil solution?
Active transport is the main process by which plants can take up minerals in higher concentration inside root cells than in the soil solution.
What is the energy source for active transport of minerals into root cells?
The energy for active transport of minerals into root cells is derived from ATP, and it is a selective process dependent on respiration.
Do all ions move into roots primarily through active transport?
No, while most ions are taken up by roots through active transport, some ions can also move by passive transport in addition to active transport.
What is the significance of symbiotic relationships in plants?
Symbiotic relationships in plants help them acquire scarce nutrients, such as nitrogen, by partnering with other organisms.
Give examples of beneficial symbiotic relationships in plants.
Examples of beneficial symbiotic relationships in plants include mycorrhizae and nitrogen-fixing bacteria in the root nodules of legumes.
How do mycorrhizae benefit plants in nutrient uptake?
Mycorrhizae facilitate the uptake of minerals, including phosphorus and trace metals like zinc and copper, by the plant. They also increase the plant’s mineral nutrient uptake efficiency.
What do mycorrhizal fungi receive in exchange for their services to plants?
Mycorrhizal fungi receive sugars and shelter from the plant in exchange for increasing the plant’s mineral nutrient uptake efficiency.
What is the role of the apoplast pathway in water and ion movement in plant roots?
The apoplast pathway is important for both water and solute movement in plant roots. It involves the continuous system of adjacent cell walls throughout the plant roots.
Why does the apoplast pathway become discontinuous in the endodermis of plant roots?
The apoplast pathway becomes discontinuous in the endodermis due to the presence of casparian strips, which block the movement of water and solutes through cell walls.
What factors determine water potential in plant cells?
Water potential in plant cells is determined by two factors: solute concentration (osmotic or solute potential) and the pressure generated when water enters and inflates plant cells (pressure potential).
What is the definition of water potential?
Water potential (symbolized by the Greek letter Psi, Ψ) is a measure of the total kinetic energy of water molecules in a system. Pure water has maximum water potential, which is defined as zero.
How does water move in relation to water potential?
Water moves from a region of higher water potential to a region of lower water potential through a partially permeable membrane, a process known as osmosis.
Why do all solutions have a lower water potential than pure water?
All solutions have lower water potential than pure water because they have a negative value of water potential (at atmospheric pressure and at a defined temperature).
Which cell has the higher water potential?
The cell with higher water potential will have a higher ψw value.
In which direction will water move by osmosis?
Water will move from the cell with higher water potential (higher ψw) to the cell with lower water potential (lower ψw).
What will be the water potential of the cells at equilibrium?
At equilibrium, the water potential of both cells will be the same, so their ψw values will be equal.
What will be the solute potential and pressure potential of the cells at equilibrium?
At equilibrium, the solute potential (ψs) of both cells will be equal, and the pressure potential (ψp) may or may not be the same, depending on the conditions. If both cells are in the same environment, their pressure potentials may be equal.
What is the process responsible for the upward movement of water and dissolved minerals in plants?
The process responsible for the upward movement of water and dissolved minerals in plants is known as the ascent of sap.
What are the three main components of the Cohesion Tension Theory?
The Cohesion Tension Theory consists of three main components: cohesion, tension, and adhesion.
How does cohesion contribute to the ascent of sap in plants?
Cohesion is the attraction among water molecules that allows them to form a solid chain-like column within the xylem tubes. This cohesion helps in pulling water upward in the plant.
What provides the necessary energy for the tension in the Cohesion Tension Theory?
Transpiration provides the necessary energy or force for the tension in the Cohesion Tension Theory.
What is the role of adhesion in the ascent of sap?
Adhesion allows water molecules to adhere to the cell walls of xylem cells, preventing the column of water in the xylem tissue from breaking.
What is the significance of strong xylem walls in the Cohesion Tension Theory?
Strong xylem walls, composed of lignin and cellulose, provide the necessary tensile strength to prevent them from buckling inwards.
What percentage of the water pulled up in the leaves is typically transpired?
The majority of the water pulled up in the leaves is transpired, with approximately 1% being used by the plant for various activities, including photosynthesis.
What causes the transpiration pull in the Cohesion Tension Theory?
Transpiration, which is the evaporation of water from the aerial parts of the plant, causes the transpiration pull by reducing the water potential of mesophyll cells, leading to the movement of water by osmosis.
What is root pressure, and how does it contribute to the movement of water in plants?
Root pressure is created by the active secretion of salts and other solutes into the xylem sap, which lowers the water potential. This influx of water into the xylem cells increases hydrostatic pressure and pushes water upwards in the plant.
What is guttation, and what causes it?
Guttation is the loss of liquid water through water-secreting glands or hydathodes. It is caused by positive pressure, known as root pressure, developed in the xylem tissue of plant roots.
What is imbibition in the context of plant physiology?
Imbibition is the process in which cell wall components such as cellulose, pectin, and lignin absorb water without dissolving, causing an increase in volume. This force can be significant and plays a role in the ascent of sap in plants.
How does imbibition contribute to the germination of seeds?
Imbibition is crucial for germinating seeds as it can cause the volume of a dry seed to increase up to 200 times. This expansion ruptures the seed coat, facilitating effective germination.
What is bleeding in plants, and when is it commonly observed?
Bleeding is a phenomenon where certain plants release sap from cut or wounded surfaces, often with considerable force. It is commonly observed in spring in plants like grapevines, some palms, and sugar maple.
What are the two main factors responsible for bleeding in plants?
The two main factors responsible for bleeding in plants are hydrostatic pressure in xylem and phloem elements and root pressure exerted by the xylem tissues of roots. These factors contribute to the flow of sap from the cut ends or surfaces of the plant.
What are the three types of transpiration based on the route of escape of water vapors from the plant’s aerial parts?
Cuticular transpiration, lenticular transpiration, and stomatal transpiration.
What is cuticular transpiration, and how much of the total transpiration does it account for?
Cuticular transpiration is the loss of water in the form of water vapors through the cuticle of leaves. It constitutes about 5-7% of total transpiration.
What is lenticular transpiration, and where does it occur in the plant?
Lenticular transpiration is the loss of water vapors through lenticels present in the stem of some plants. Lenticels are typically found on the surface of the stem.
How does light and temperature affect lenticular transpiration?
Strong light and high temperature can increase the rate of lenticular transpiration because it is governed by diffusion.
What are lenticels, and how do they function in gas exchange and water loss?
Lenticels are aerating pores in the bark of a plant stem that facilitate the exchange of gases with the environment and lead to water loss in the form of water vapors.
What is stomatal transpiration, and where does it occur in leaves?
Stomatal transpiration is the type of transpiration where water vapors escape through stomata. Stomata are found on the surface of leaves.
What is the role of guard cells in stomatal transpiration?
Guard cells control the opening and closing of stomata. When turgid, they open the stomata, and when flaccid, they close them.
How much of the total transpiration in a plant is attributed to stomatal transpiration?
Stomatal transpiration accounts for approximately 90% of the total transpiration in a plant.
Which part of the leaf is involved in providing a large surface area for the loss of water in the form of vapors during stomatal transpiration?
The cells of the mesophyll in the leaf provide a large surface area for the loss of water in the form of vapors during stomatal transpiration.
What are the environmental factors sensed by guard cells that influence stomatal responses?
Guard cells sense environmental factors such as light intensity and quality, temperature, relative humidity, and intracellular CO2 concentration, which are integrated to regulate stomatal responses.
What are the two hypotheses explaining the opening and closing of stomata?
i) The Starch Sugar Hypothesis suggests that photosynthesis in guard cells produces sugars during the day, leading to stomatal opening, while sugar conversion to starch or respiration at night causes stomatal closure.
ii) The Influx of K+ Ions Hypothesis states that active transport of potassium ions (K+) into guard cells from the surrounding epidermis opens stomata, and reverse processes involving K+ diffusion and water movement cause closure.
How does the level of carbon dioxide affect stomatal opening and closing?
A low level of carbon dioxide favors stomatal opening, allowing increased carbon dioxide uptake for photosynthesis. Higher carbon dioxide levels promote stomatal closure to conserve water.
What causes stomata to open during the day and close at night?
Stomata open during the day due to the active pumping of potassium ions (K+) into guard cells, followed by water uptake, resulting in increased turgidity. At night, K+ leaves the guard cells, leading to water loss, guard cell wilting, and stomatal closure.
How does light affect the rate of transpiration?
Strong light increases the rate of transpiration because it promotes the active entry of potassium ions (K+) into guard cells, which leads to water uptake and stomatal opening.
How does temperature influence the rate of transpiration?
Higher temperatures, especially in strong sunlight, increase the rate of transpiration. The rate of transpiration doubles with every 10°C rise in temperature. However, very high temperatures (e.g., 40-45°C) can cause stomatal closure to prevent excessive water loss.
Why is transpiration important for plants?
Transpiration is important for plants as it helps distribute dissolved mineral salts, transport water to photosynthesizing cells, and cool the plant, especially in higher temperatures. It also prevents wilting of leaves and herbaceous plants.
What stimulates the active transport of Potassium ions into guard cells during the day?
Low carbon dioxide concentration, which occurs when photosynthesis exceeds respiration.
What causes stomata to open and allow CO2 to diffuse into mesophyll cells of leaves?
The active transport of Potassium ions into guard cells.
What happens to stomata at night in the absence of photosynthesis?
Stomata close due to the halt in the inward transport of K+ caused by raised CO2 levels during cellular respiration.
What hormone is released by mesophyll cells when leaf cells start wilting at high temperatures?
Abscisic acid.
What is the role of abscisic acid in stomatal movement?
It stops the active transport of K+ into guard cells, overriding the effect of light and CO2 concentration, causing stomata to close.
How does humidity affect the rate of transpiration in plants?
In dry air, the rate of diffusion of water molecules increases, leading to more transpiration. In humid air, the diffusion rate is reduced, decreasing transpiration.
What effect does wind have on the rate of transpiration?
Wind increases the rate of diffusion of water molecules, leading to higher evaporation from the surfaces of mesophyll cells. When the air is still, diffusion is slowed down, reducing transpiration.
How does the availability of soil water affect transpiration?
If there is little water in the soil, less water is transported to the leaf cells and lost through transpiration. Reduced water absorption in root cells leads to a reduction in transpiration.
Why is transpiration sometimes referred to as a “necessary evil” for plants?
Transpiration is called a necessary evil because it is an inevitable consequence of wet cell surfaces, but it can lead to wilting, desiccation, and plant death under drought conditions. Even mild water stress can reduce growth rates and crop yields.
List four important functions of transpiration in plants.
Water transport in tall plants through transpiration pull.
Distribution of minerals dissolved in water throughout the plant by the transpiration stream.
Cooling effect on the plant through the evaporation of water from leaf cell surfaces.
Facilitation of gaseous exchange due to the wet surfaces of leaf cells.
What is the main tissue responsible for the transport of organic solutes in plants?
Phloem tissue is responsible for the transport of organic solutes in plants.
What are sieve elements, and why are they important in phloem transport?
Sieve elements are specialized cells in phloem tissue that conduct sugars and other organic materials throughout the plant. They are important because they play a direct role in the transport of organic solutes.
What are some other cell types found in phloem tissue besides sieve elements?
In addition to sieve elements, phloem tissue also contains companion cells, parenchyma cells, and, in some cases, fibers, sclereids, and latex-containing cells. However, only sieve tube cells are directly involved in the transport of organic solutes.
What are sieve areas, and where are they typically found in sieve tube cells?
Sieve areas are portions of the cell wall in sieve tube cells where pores interconnect the conducting cells. These areas are generally formed in the end walls of sieve tube members where individual cells are joined together to form a longitudinal series called a sieve tube.
How do companion cells contribute to phloem transport?
Companion cells supply ATP and proteins to sieve tubes and facilitate the movement of photosynthetic products from photosynthesizing cells (such as mesophyll and palisade layer cells in leaves) into sieve tubes through plasmodesmata.
In which direction does phloem transport occur, and how is it defined?
Phloem transport does not occur exclusively in an upward or downward direction and is not defined with respect to gravity. It occurs from areas of supply (sources) to areas of metabolism or storage (sinks).
Can you provide examples of sources and sinks in phloem transport?
Sources include mature leaves capable of storing excess photosynthate, storage organs, and organs in their exporting phase of development. Sinks are areas of active metabolism or storage, such as roots, tubers, developing fruits, immature leaves, and growing stem and root tips.
What is the Pressure-Flow Theory, and why is it widely accepted for phloem transport?
The Pressure-Flow Theory is the most widely accepted theory for phloem transport in angiosperms. It suggests that sap moves in phloem due to pressure gradients generated by active transport processes. Active theories that involve energy use for transport have been largely abandoned due to lack of supporting evidence.
What are the passive theories of transport/translocation in plants discussed in the text?
The passive theories of transport/translocation discussed in the text include diffusion and pressure flow theory.
Why is diffusion considered too slow to account for the movement of sugar in the phloem?
Diffusion is considered too slow to account for sugar movement in the phloem because the average rate of sugar movement in the phloem is 1 meter per hour, while the rate of diffusion is 1 meter per eight years.
Who proposed the pressure flow theory, and when was it first proposed?
The pressure flow theory was first proposed by Ernst Munch in 1930.
What is the basic idea behind the pressure flow theory of translocation?
The pressure flow theory of translocation suggests that the flow of solution in the sieve elements is driven by an osmotically generated pressure gradient between the source and sink. This theory explains the movement of sugars in the phloem.
What are the key steps involved in the pressure flow theory of translocation?
The key steps in the pressure flow theory of translocation include:
- Glucose formation in photosynthesizing cells.
- Active transport of sucrose to the sieve tube cells.
- Osmotic movement of water from the xylem into the sieve tube cells, increasing hydrostatic pressure.
- Hydrostatic pressure pushing sucrose and other substances to sinks.
- Osmotic movement of water out of sieve tube cells, lowering hydrostatic pressure.
- The presence of sieve plates increasing resistance and maintaining a pressure gradient.
How does the pressure flow theory account for the mass flow of molecules within the phloem?
The pressure flow theory accounts for the mass flow of molecules within the phloem by establishing a pressure gradient between the source and sink, which physically pushes the contents of sieve elements along the transportation pathway, similar to water flowing through a garden hose.
What types of transport mechanisms are involved in the translocation of photosynthates or carbohydrates in plants?
The translocation of photosynthates or carbohydrates in plants involves diffusion, active transport (carrier-mediated transport), and the pressure flow theory.
How do unicellular animals primarily transport substances into or out of their bodies?
Unicellular animals primarily transport substances into or out of their bodies through simple diffusion, osmosis, active transport, and facilitated diffusion.
What distinguishes complex multicellular animals from simple multicellular aquatic animals in terms of their transport systems?
Complex multicellular animals possess highly organized and well-developed transport systems, such as a blood vascular system, while simple multicellular aquatic animals rely on simple diffusion and other basic mechanisms for transport.
How does Hydra obtain water, dissolved oxygen, and food?
Hydra obtains water, dissolved oxygen, and food by using tentacles and flagella present in most cells of its endoderm to move these substances into its coelenteron (enteron).
What happens to the materials and food absorbed by Hydra’s endodermal cells?
Materials and food absorbed by Hydra’s endodermal cells.
What happens to the materials and food absorbed by Hydra’s endodermal cells?
Materials and food absorbed by Hydra’s endodermal cells may be absorbed through endocytosis. Indigestible and partly digested food is removed from these cells by exocytosis into the digestive cavity (coelenteron). Ectodermal cells also receive nutrients from endodermal cells through diffusion.
How does the ectoderm of Hydra exchange materials with its surrounding water?
The ectodermal cells of Hydra directly exchange materials with the surrounding water through diffusion.
Why does Planaria not require a special transport system?
Planaria does not require a special transport system because its flat body provides a large surface area for the exchange of materials with the environment, and it lacks a body cavity. Materials, including oxygen, diffuse through its ectoderm, pass to mesoderm cells, and then diffuse into endoderm cells for transport.
How does Planaria remove wastes from its cells?
Planaria removes wastes from its cells by reversing the diffusion route. Intestinal caecae reach near almost every cell of the body, and digested food is provided to the cells by diffusion. Endoderm cells can also acquire food, water, dissolved minerals, and to some extent oxygen while removing wastes into the gut.
Why do larger and complex animals need a circulatory system?
Larger and complex animals need a circulatory system because their low surface area-to-volume ratio makes simple diffusion insufficient for efficient material transport between cells. The circulatory system facilitates rapid mass flow of materials throughout the body.
What are the three main characteristics of a circulatory system?
The three main characteristics of a circulatory system are:
- A circulatory fluid (blood).
- A contractile pumping device (such as the heart or modified blood vessels).
- Tubes (blood vessels) for transporting the circulatory fluid to and from cells, enabling material exchange.
What are the two main types of circulatory systems in animals?
The two main types of circulatory systems in animals are:
- Open circulatory system.
- Closed circulatory system.
Give an example of an animal with an open circulatory system.
An example of an animal with an open circulatory system is the cockroach (Periplaneta).
Does blood in a closed circulatory system come in direct contact with other body cells?
No, blood always remains in the blood vessels and does not come in direct contact with other cells of the body.
What components make up the closed circulatory system?
It consists of interconnected arteries, veins, and capillaries.
How does the exchange of nutrients and waste products occur in a closed circulatory system?
Exchange occurs through capillaries where blood and tissue fluid interact.
Does a closed circulatory system transport gases like oxygen and carbon dioxide?
Yes, it transports gases such as oxygen and carbon dioxide.
What is the respiratory pigment in a closed circulatory system, and are there nucleated white blood cells?
Hemoglobin is dissolved in the blood, and nucleated white blood cells are present.
Is a closed circulatory system considered more advanced and efficient?
Yes, it is regarded as the most advanced type, maintaining blood pressure and being more efficient.
How many pairs of lateral hearts are present in an earthworm’s closed circulatory system?
There are 4 or 5 pairs of lateral hearts in an earthworm’s closed circulatory system.
What are the three main longitudinally running blood vessels in a closed circulatory system?
The dorsal, ventral, and sub-neural vessels are interconnected through capillaries and commissural vessels.
Where does the dorsal vessel collect blood in a closed circulatory system?
It collects blood from the 14th segment backward and serves as a distributing channel in the first 13 segments.
Does blood in an open circulatory system come in direct contact with other body cells?
Yes, blood does not remain enclosed in blood vessels and comes in direct contact with other body cells, bathing them.
What components make up the open circulatory system?
There are no typical arteries, veins, and capillaries; instead, the blood (hemolymph) flows in cavities or sinuses in the body cavity.
How does the exchange of nutrients and waste products occur in an open circulatory system?
Exchange occurs when blood directly bathes the tissues.
Does an open circulatory system transport gases like oxygen and carbon dioxide?
No, gases like oxygen and carbon dioxide are transported by the tracheal system in an open circulatory system.
What is the respiratory pigment in an open circulatory system, and are there nucleated white blood cells?
There is no respiratory pigment, and the blood is colorless with nucleated white blood cells absent.
Is an open circulatory system considered less advanced and efficient?
Yes, it is regarded as primitive, with lower efficiency and an inability to maintain blood pressure.
What is the structure of the heart in a cockroach’s open circulatory system?
The heart is a 13-chambered tubular vessel in the pericardial sinus, placed in the mid-dorsal region below the terga in the abdominal region. It has ostia for blood flow.
What is the role of the dorsal vessel in an open circulatory system?
The dorsal vessel extends in the thoracic and head region, opening anteriorly in the head’s haemocoel through a funnel-shaped opening.
What are the components of the vertebrate blood vascular system?
The components of the vertebrate blood vascular system include blood, heart, and blood vessels (arteries, capillaries, and veins). Additionally, there is the lymphatic system that aids in transportation.
What is the purpose of the lymphatic system in vertebrates?
The lymphatic system aids in transportation within vertebrates’ circulatory systems.
How does the heart pump blood to different parts of the body in vertebrates?
The heart pumps blood to different parts of the body through the aorta and arteries. Arteries branch into fine blood vessels known as capillaries, which join to form veins that bring blood back to the heart.
What is the role of capillaries in the vertebrate circulatory system?
Capillaries serve as sites where the exchange of materials between the blood and body tissues takes place.
How does the heart of fishes function in terms of circulation?
The heart of fishes operates as a single-circuit heart, with blood flowing in one direction only: from the sinus venosus to the atrium, then to the ventricle, and finally to the ventral aorta via the bulbus arteriosus or conus arteriosus.
What is the structure of the heart in amphibians?
The heart in amphibians is three-chambered, consisting of two auricles and one ventricle. It also includes the sinus venosus and truncus arteriosus.
How does the heart of reptiles differ from that of amphibians?
The heart of reptiles is typically four-chambered, with two auricles and a partially divided ventricle. In some reptiles like crocodiles, the ventricle is fully divided, resulting in a complete four-chambered heart.
Explain the circulation pattern in reptiles, birds, and mammals.
In reptiles, birds, and mammals, the heart functions as a double-circuit heart. The pulmonary circulation carries deoxygenated blood from the right ventricle to the lungs and returns oxygenated blood to the left atrium. The systemic circulation distributes blood to different parts of the body, with the blood returning to the right atrium.
How does the circulation differ between birds and mammals in terms of systemic arches?
In birds, the left systemic arch disappears, whereas in mammals, most of the right systemic arch disappears.
What prevents the mixing of oxygenated and deoxygenated blood in the hearts of birds and mammals?
The complete separation of the heart into four chambers and the distinct pathways for pulmonary and systemic circulation prevent the mixing of oxygenated and deoxygenated blood in the hearts of birds and mammals.
What are the three basic components of the circulatory system in humans?
The three basic components of the circulatory system in humans are (A) circulating fluid – the blood, (B) the pumping organ – the heart, and (C) the blood vessels, which include arteries, capillaries, and veins.
What are the main components of blood in the human body?
Blood in the human body is made up of two main components: (i) plasma and (ii) cells or cell-like bodies, which include white blood cells, red blood cells, and platelets.
What is the approximate composition of plasma in the blood?
Plasma constitutes about 55% by volume of the blood in a normal person, while cells or cell-like bodies make up about 45% by volume of the blood.
What are the categories of substances dissolved or present in plasma?
The substances dissolved or present in plasma can be divided into six categories: inorganic salts (ions), plasma proteins, organic nutrients, nitrogenous waste products, special products being transported, and gases that are dissolved.
Which component of the blood is responsible for carrying hormones in the body?
Plasma, which is the liquid component of blood, is responsible for carrying all the hormones in the body.
What is the average lifespan of red blood cells, and where are they primarily formed?
The average lifespan of red blood cells is about four months. Red blood cells are primarily formed in the red bone marrow of short bones, such as the sternum, ribs, and vertebrae, in adults. In embryonic life, they are formed in the liver and spleen.
What are white blood cells, and why are they colorless?
White blood cells are colorless because they do not contain pigments.
How many white blood cells are typically found in one cubic millimeter of blood?
One cubic millimeter of blood contains 7000 to 8000 white blood cells.
How do granulocytes and agranulocytes differ in white blood cells?
Granulocytes and agranulocytes are two main types of white blood cells. Granulocytes include neutrophils, eosinophils, and basophils, while agranulocytes include monocytes and lymphocytes (B and T).
Where are granulocytes and agranulocytes formed in the body?
Granulocytes are formed in the red bone marrow, while agranulocytes are formed in lymphoid tissues such as lymph nodes, spleen, tonsils, adenoids, and the thymus.
What is the role of monocytes in the body?
Monocytes enter tissues from the blood and become tissue macrophages, performing phagocytic functions.
What is the lifespan of lymphocytes, and where are they primarily formed?
Lymphocytes can have lifespans of months or even years, and they are primarily formed in lymphoid tissues.
How do white blood cells protect the body against foreign invaders?
White blood cells use the circulatory system to travel to the site of invasion, where they engage in phagocytosis and immune responses against invaders.
What is the role of basophils in the body?
Basophils produce heparin, inhibit blood clotting, and produce chemicals like histamine, which participate in allergic reactions and responses to tissue damage and microbial invasion.
What is the function of platelets in the blood?
Platelets are not cells but fragments of large cells called megakaryocytes. They help convert fibrinogen into insoluble fibrin, which forms blood clots to seal wounds and prevent bleeding.
List some of the functions of blood in the human body.
Blood maintains colloid osmotic pressure, transports nutrients, hormones, gases (O2 and CO2), defends against diseases, provides immunity, produces interferon and antitoxins, buffers acid-base balance, regulates body temperature and homeostasis, facilitates material exchange between blood and body tissues, and aids in blood clotting.
What is leukemia, and what causes it?
Leukemia, also known as blood cancer, is a disorder characterized by the uncontrolled production of white blood cells (leucocytes). It is caused by a cancerous mutation of myelogenous or lymphogenous cells, resulting in greatly increased numbers of abnormal white blood cells in the bloodstream.
How does leukemia affect the production of white blood cells?
Leukemia leads to the production of undifferentiated and defective white blood cells at a faster rate than normal. Depending on the type of white blood cells affected, it can manifest as neutrophilic leukemia, eosinophilic leukemia, basophilic leukemia, monocytic leukemia, or lymphocytic leukemia.
What is the treatment for leukemia, and is it effective?
Leukemia can be treated by regular blood transfusions with normal blood from donors. Another treatment option is a bone marrow transplant, which is often effective but can be expensive.
What is thalassemia, and what are its key characteristics?
Thalassemia, also known as Cooley’s anemia, is a genetically transmitted hemoglobin abnormality. It is characterized by the presence of microcytes, enlargement of the spleen (spleenomegaly), and changes in the bones and skin. Thalassemia patients require regular blood replacement with normal blood.
Can thalassemia be cured, and what are the treatment options?
Thalassemia can be treated with a bone marrow transplant, although this treatment is expensive and does not guarantee a 100% cure rate. In many cases, thalassemia patients have hemoglobin molecules that lack beta chains, with fetal hemoglobin (F-chain) instead.
What is edema, and what are its causes?
Edema refers to the presence of excess fluid in the body’s tissues, either within or outside the cells. Intracellular edema is caused by osmosis of water into the cells, while extracellular edema can result from abnormal leakage of fluid from blood capillaries or failure of the lymphatic system to return fluid from the interstitial fluid. Renal retention of salts and water can also cause edema.
How does edema affect the body?
Edema can disrupt the exchange and concentration of minerals and ions in the blood and body cells, affecting blood pressure, increasing the load on the heart, and depressing metabolic systems due to the lack of nutrition and oxygen in the affected tissues.
What are the three layers of the heart’s wall, and what is the heart’s structure?
The heart’s wall consists of three layers: epicardium, myocardium, and endocardium. The myocardium is made up of specialized cardiac muscles with myofibrils containing myosin and actin. The heart has four chambers: two thin-walled atria and two thick-walled ventricles, functioning as a double pump responsible for pulmonary and systemic circulation.
How does blood flow through the heart, and what valves control its direction?
Deoxygenated blood enters the right atrium from the body, passes through the tricuspid valve to the right ventricle, and is then pumped to the lungs via the pulmonary trunk and semilunar valves. After oxygenation in the lungs, oxygenated blood returns to the left atrium and passes through the bicuspid valve to the left ventricle. The left ventricle pumps oxygenated blood through the aorta to the rest of the body. Valves like the tricuspid, bicuspid, and semilunar valves control the direction of blood flow.
What is the function of the aorta, and how does it supply blood to different parts of the body?
The aorta serves as the main artery that carries oxygenated blood from the left ventricle to all parts of the body except the lungs. It forms an arch and gives rise to various branches, supplying blood to the head, arms, shoulders, chest wall, abdominal region, alimentary canal, kidneys, and lower abdomen before bifurcating into iliac arteries that supply blood to the legs.
What is the cardiac cycle?
The cardiac cycle is the sequence of events that occur during one complete heartbeat.
What are the three distinct stages of a heart beat?
The three stages of a heart beat are diastole (relaxation phase), atrial systole (atria contraction), and ventricular systole (ventricles contraction).
What happens during diastole?
During diastole, the walls of the atria and ventricles are relaxed, and blood enters the atria. This is the relaxation phase of the heart chambers.
What occurs during atrial systole?
Atrial systole is when the muscles of the atria contract, pushing blood into the ventricles through the tricuspid and bicuspid valves.
What happens during ventricular systole?
Ventricular systole is when both ventricles contract, pumping blood into the pulmonary arteries and aorta. The tricuspid and bicuspid valves close during this phase, creating the ‘lubb’ sound.
How long does one complete heart beat last?
One complete heart beat, including one systole and one diastole, lasts for about 0.8 seconds.
What initiates the cardiac cycle?
The cardiac cycle begins when the sino-atrial node (pacemaker) in the upper end of the right atrium sends out electrical impulses, causing both atria to contract.
What is the role of the atrioventricular node in the cardiac cycle?
The atrioventricular node conducts regulatory impulses from the sino-atrial node to the ventricles, with a delay of approximately 0.15 seconds, allowing atrial systole to complete before ventricular systole begins.
What is an electrocardiogram (ECG)?
An electrocardiogram (ECG) is a recording of electrical potentials generated by the heart’s electrical currents as they spread through the body. It is used to diagnose abnormalities in the heart’s rhythmicity and conduction system.
How does an ECG help diagnose heart abnormalities?
An ECG can detect irregularities in the heart’s electrical activity, such as abnormal P waves, QRS waves, or T waves, which can indicate heart rhythm or conduction issues that may require treatment, such as an artificial pacemaker.
What is the role of an artificial pacemaker in the human body?
An artificial pacemaker is responsible for initiating electrical impulses that trigger the heart’s beating rate when there are issues with the natural impulse flow or when the impulses from the S.A. node are weak.
Why might an artificial pacemaker be used in a medical setting?
An artificial pacemaker is used when there is a block in the A-V pathway of the heart’s electrical system. It provides rhythmic impulses to take control of the ventricles and maintain a regular heartbeat, preventing potential death due to irregular heartbeats.
What is the medical condition known as “blue babies”?
“Blue babies” is a condition that results from the failure of the interatrial foramen or the ductus arteriosus to close completely in newborns. This leads to cyanosis, a blueness of the skin, due to the mixing of oxygen-rich and oxygen-poor blood in the body.
What are the three main types of blood vessels in the human circulatory system?
The three main types of blood vessels in the human circulatory system are arteries, capillaries, and veins.
What is the function of arteries in the circulatory system?
Arteries carry blood away from the heart to various parts of the body. They have three layers in their walls, including an outer layer made of connective tissue and elastic fibers, a middle layer made of thick muscular tissue and elastic fibers, and an inner endothelium.
How does the contraction of arterial muscles affect blood flow?
Contraction of arterial muscles leads to vasoconstriction, which reduces the flow of blood in the arteries. When the muscles relax, vasodilation occurs, allowing more blood to flow through the arteries.
What are capillaries, and how do they facilitate the exchange of materials between blood and body tissues?
Capillaries are the smallest blood vessels with walls only one cell thick. They facilitate the exchange of materials between blood and body tissues through three methods: active transport and diffusion through capillary wall cells, through intercellular spaces in the endothelial lining, and via materials passing through endocytosis and exocytosis.
How does atherosclerosis differ from arteriosclerosis, and what are their potential health consequences?
Atherosclerosis involves the deposition of hard yellow plaque of lipoid material in the innermost layer of arteries, often due to high cholesterol levels. Arteriosclerosis is a thickening of the middle layer of arteries and is usually associated with some degree of atheroma. Atherosclerosis can narrow and harden arteries, increasing the risk of thrombus formation, which can be fatal and is a major cause of heart attacks.
What do veins transport and in which direction?
Veins transport blood from body cells towards the heart.
How does the middle layer of veins compare to arteries?
The middle layer of veins is relatively thin and only slightly muscular, with few elastic fibers, similar to arteries.
What is the function of semilunar valves in veins?
Semilunar valves in veins prevent the backflow of blood as it moves towards the heart.
How do surrounding muscles assist the return of blood in veins?
When surrounding muscles contract, they exert pressure on the veins, helping to squeeze and push the blood towards the heart.
What do veins join to form ultimately?
Veins join to form larger veins, ultimately forming venae cavae (Inferior vena cava and superior vena cava), which pour blood into the right atrium of the heart.
Where is oxygenated blood from the lungs brought to in the heart?
Oxygenated blood from the lungs is brought to the left atrium of the heart by pulmonary veins.
What is interstitial fluid, and what does it consist of?
Interstitial fluid is a fluid that surrounds capillaries and tissues. It consists primarily of water, dissolved nutrients, hormones, gases, wastes, and small proteins from the blood.
Why do large proteins, red blood cells, and platelets remain within capillaries?
They cannot cross the intercellular spaces of the capillary wall.
What is the medium through which the exchange of materials between the blood and nearby cells occurs?
Interstitial fluid serves as the medium for the exchange of materials between the blood and nearby cells.
Do capillaries have valves like veins?
No, capillaries do not have valves.
What is the function of arteries?
Arteries transport blood away from the heart to various parts of the body through capillaries.
What type of blood do pulmonary arteries carry?
Pulmonary arteries carry deoxygenated blood.
What is the main function of veins?
Veins collect blood from the body through capillaries and transport it towards the heart.
What is the role of valves in veins?
Valves in veins prevent the backflow of blood.
What is the difference in blood pressure between arteries and veins?
Arteries have high blood pressure, while veins have low blood pressure.
How does the rate of blood flow change from arteries to veins?
The rate of blood flow increases from smaller to larger veins.
What is the rate of blood flow in capillaries?
Blood flow in capillaries is the slowest, less than 1 mm per second.
How does the wall thickness of arteries, veins, and capillaries compare?
Arteries have a smaller bore and thick walls, veins have a larger bore and thin walls, and capillaries have a wall one cell in thickness.
What is the role of the thick muscle layer and elastic fibers in arteries?
The thick muscle layer and elastic fibers in arteries help accommodate the pulsating flow of blood.
What distinguishes capillaries in terms of their function?
Capillaries are responsible for the exchange of materials between the blood and nearby cells.
What is blood pressure, and how is it generated in the body?
Blood pressure is the measure of the force with which blood pushes against the walls of blood vessels. It is generated by the contraction of the ventricles during ventricular systole, and it is highest in the aorta, gradually reducing in arteries.
How is blood pressure related to the cardiac cycle?
Blood pressure is highest during systole (systolic pressure, around 120 mm Hg in normal individuals) when the heart contracts and lowest during diastole (diastolic pressure, ranging between 75-85 mm Hg in normal individuals) when the heart is in its relaxation phase.
What causes the variation in blood pressure along the systemic circuit of the circulatory system?
The decline in blood pressure as it moves through different parts of the systemic circuit is primarily due to friction between the flowing blood and the walls of blood vessels. Blood naturally moves from regions of higher pressure to lower pressure.
How does the difference between systolic and diastolic pressure change as blood flows through the circulatory system?
The difference between systolic and diastolic pressure diminishes as blood flows through the circulatory system until it disappears in the capillaries and veins.
How does the rate of blood flow change as it moves through the branching arteries and arterioles?
The rate of blood flow tends to decrease as blood moves through the branching arteries and arterioles, reaching its lowest point in the capillaries. It then increases again in the venules and veins due to changes in the total cross-sectional area of the vessel system.
How is blood flow maintained in veins, and what role do surrounding muscles and valves play?
Blood flow in veins is maintained by the contraction of surrounding muscles and the action of semilunar valves, which prevent the backflow of blood. Muscular activity, including breathing movements, also helps maintain normal blood flow in the body.
What is hypertension, and what are its potential consequences?
Hypertension is a condition characterized by high blood pressure. Prolonged high blood pressure can damage the lining of blood vessels and weaken heart muscles, leading to congestive heart failure, a potentially fatal condition.
What is thrombus formation, and what can it lead to?
Thrombus formation is the solid mass or clot of blood constituents in a blood vessel. If a thrombus blocks a blood vessel, it can lead to reduced blood flow or even embolism if it becomes dislodged and travels to another location in the circulatory system. Thromboembolism is a leading cause of death in western civilization.
What are some common causes of thrombus formation?
Thrombus formation can be due to irritation or infection of the lining of blood vessels, reduced blood flow due to prolonged inactivity, and certain medical conditions such as pneumonia, tuberculosis, and emphysema.
What is a heart attack, and what causes it?
A heart attack, technically known as myocardial infarction, occurs when a blood vessel in the heart becomes blocked by an embolus or locally formed thrombus, leading to the necrosis or damage of a portion of the heart muscle.
What can be done to avoid a heart attack?
To avoid a heart attack, you can:
i) Avoid consuming excessive fatty foods, especially those rich in cholesterol, and maintain a normal body weight.
ii) Control blood pressure through regular walking and exercise.
iii) Quit smoking.
What is a stroke, and what are its symptoms?
A stroke, also known as cerebral infarction, occurs when a blood vessel in the brain is blocked by an embolus or locally formed thrombus, leading to the death of surrounding neural tissue due to oxygen deprivation. The symptoms of a stroke vary depending on the affected part of the brain.
How can brain hemorrhage be prevented?
Brain hemorrhage, which results from the bursting of arteries supplying the brain due to high blood pressure, can be prevented by maintaining blood pressure within normal limits and ensuring that the arteries remain elastic.
What are some common preventive measures for various health problems mentioned?
Common preventive measures for various health problems include:
Reducing cholesterol intake in your diet.
Maintaining normal blood pressure.
Avoiding obesity.
Quitting smoking.
Engaging in regular exercise.
Managing stress and tension.
What is the lymphatic system responsible for?
The lymphatic system is responsible for transporting and returning materials from the body’s tissues to the blood. It includes lymph capillaries, lymph vessels, lymphoid masses, lymph nodes, and lymph fluid.
How does lymph form, and where does it flow?
Lymph forms when interstitial fluid or extracellular fluid is forced into lymph capillaries due to pressure in the body tissues. Lymph flows from lymph capillaries to larger lymph vessels, ultimately reaching the thoracic lymph duct, which opens into the subclavian vein. The flow of lymph is always towards the thoracic duct.
What is the role of lymph nodes in the lymphatic system?
Lymph nodes are points along the lymphatic system where lymphocytes are present. They filter lymph, and several afferent lymph vessels enter a lymph node, which is drained by a single efferent lymph vessel. Lymph nodes are present in various regions of the body, including the neck, axilla, and groin.
What functions does the lymphatic system perform?
The lymphatic system performs several functions, including:
i) Returning excess fluid, dissolved proteins, and substances to the blood.
ii) Absorbing large fat globules released by interstitial cells after digesting fats.
iii) Defending the body against foreign invaders by filtering lymph in lymph nodes and destroying bacteria and viruses.
iv) Filtering blood in the spleen, exposing it to macrophages and lymphocytes that destroy foreign particles and aged red blood cells.
What is immunity, and how is it defined?
Immunity is the capacity to recognize foreign materials in the body and mobilize cells and cell products to remove them efficiently.
What are the components of the immune system?
The components of the immune system include lymphocytes (B and T cells) and antibodies, which are specialized proteins.
How are antibodies produced, and what is their role in the immune system?
Antibodies are produced by B-lymphocytes in response to antigens, and they either immobilize or lead to the destruction of the antigens.
What are T-cells and B-cells, and how do they contribute to immunity?
T-cells combat microorganisms and reject foreign tissues, while B-cells form plasma cell clones that produce antibodies to neutralize toxins and speed up phagocytosis.
How does vaccination work to provide immunity?
Vaccination introduces antigens into the body, stimulating the production of antibodies and making a person immune to a specific disease.
What are the two types of immunity?
Active Immunity: Stimulated by vaccines or exposure to an infection, resulting in the production of antibodies.
Passive Immunity: Achieved by injecting antibodies (antisera) into the body to provide immediate but short-lived immunity.
Explain the difference between naturally induced immunity and artificially induced active immunity.
Naturally induced immunity occurs when a person survives an infection and develops immunity to that disease. Artificially induced active immunity is achieved by introducing antigens through vaccination.
How does passive immunity work, and when is it used?
Passive immunity involves injecting antibodies into the body to provide immediate protection against a disease. It is used in cases like tetanus, infectious hepatitis, rabies, and snakebite venom.
What is AIDS, and how does it affect the immune system?
AIDS (Acquired Immune Deficiency Syndrome) is caused by a virus and leads to a weakened immune system, making individuals susceptible to bacterial diseases and cancer. There is no known cure for AIDS.
How can AIDS spread, and what are the modes of transmission?
AIDS can spread through blood transfusion and sexual contact with infected individuals.
Long Question Answers Unit 14 Transport 1st Year Biology
Question: How are minerals and water taken up by roots? Draw the structures involved and the
pathways for water and minerals from soil water to xylem, and the transport processes at
each step.
The uptake of minerals and water by plant roots involves several structures and processes. Let’s break it down step by step:
Root Hairs: The process begins in the root hairs, which are tiny, finger-like extensions of root cells. Root hairs greatly increase the surface area of the roots available for absorption.
Cell Membrane: The outermost layer of root hair cells is the cell membrane, which is selectively permeable. It allows certain ions and water molecules to pass through.
Soil Solution: In the soil, minerals and water are present as a solution that surrounds the root hairs. This solution contains essential nutrients such as nitrate ions (NO3-), phosphate ions (PO4^3-), and water molecules (H2O).
Active Transport: Minerals, such as ions (e.g., K+, Ca2+, Mg2+), are taken up by the root hairs through active transport. Active transport requires energy (usually from ATP) and specific transport proteins (e.g., ion channels or pumps). The root cells actively pump ions against their concentration gradient into the root cells, leading to the accumulation of minerals in the root.
Passive Water Uptake: Water is taken up by root hairs through a passive process called osmosis. Osmosis is the movement of water molecules from an area of higher water potential (in the soil solution) to an area of lower water potential (inside the root cells) through the cell membrane. This movement is driven by the concentration gradient of solutes (such as minerals) in the root cells.
Cortex: Once inside the root hair cells, minerals and water move radially inward through the root cortex, which is composed of multiple layers of cells. The movement of water and minerals through the cortex is facilitated by both apoplastic and symplastic pathways.
Apoplastic Pathway: In this pathway, water and minerals move through the cell walls and spaces between cells (apoplast). However, this route is blocked by a waxy, hydrophobic layer called the Casparian strip in the endodermis.
Symplastic Pathway: In this pathway, water and minerals move through the living cytoplasm of cells via plasmodesmata (small channels that connect neighboring plant cells). This pathway is not blocked by the Casparian strip.
Endodermis and Casparian Strip: The Casparian strip is a hydrophobic barrier located in the endodermal cells of the root. It forces water and minerals to cross the selectively permeable cell membranes of the endodermal cells, effectively regulating what enters the vascular cylinder (the core of the root).
Vascular Cylinder: The vascular cylinder contains the xylem and phloem. Water and minerals that have crossed the Casparian strip enter the xylem vessels, which are specialized for the transport of water and nutrients from roots to the rest of the plant. This movement is facilitated by the cohesive and adhesive properties of water, as well as transpiration pull (the loss of water from leaves through stomata creates a negative pressure, which pulls water up the xylem).
Transpiration: Water loss from the leaves (transpiration) creates a negative pressure in the xylem, which helps in the upward movement of water and minerals from the roots to the aerial parts of the plant.
Question: Describe the mechanism of opening and closing of stomata.
The opening and closing of stomata, tiny pores found on the surfaces of leaves and stems of plants, is a crucial process for regulating gas exchange, water loss, and photosynthesis. This mechanism is primarily controlled by changes in turgor pressure within specialized cells called guard cells, along with various environmental and internal factors. Here’s a detailed description of the mechanism:
Guard Cells: Stomata are typically composed of two specialized guard cells that surround the pore. These cells have a unique kidney or bean-like shape and are responsible for controlling the stomatal opening and closing.
Turgor Pressure: The key factor in regulating stomatal movement is the turgor pressure within the guard cells. Turgor pressure is the pressure exerted by the water inside the cell against the cell wall.
Stomatal Opening
Light: When light is available (usually during the day), photosynthesis occurs in the chloroplasts of the guard cells. This leads to the production of glucose and other sugars, increasing osmotic potential within the cells.
Water Uptake: As osmotic potential increases, water enters the guard cells through osmosis from surrounding epidermal cells, leading to an increase in turgor pressure.
Ion Transport: The accumulation of potassium ions (K+) inside the guard cells further increases the osmotic potential.
Cell Expansion: As water and ions enter the guard cells, they become turgid and swell. Due to their unique shape, this swelling causes the guard cells to bow outward, creating an opening or pore between them, allowing gas exchange (mainly CO2 intake) and transpiration (water loss) to occur.
Stomatal Closure
Lack of Light: During the night or in low light conditions, photosynthesis ceases, reducing the production of sugars and the osmotic potential within the guard cells.
Loss of Water: If the plant is experiencing water stress, guard cells will lose water through transpiration. As water exits the cells, turgor pressure decreases.
Ion Transport: The loss of turgor pressure is further facilitated by the active transport of potassium ions out of the guard cells.
Cell Contraction: As turgor pressure decreases, the guard cells become flaccid and shrink, closing the stomatal pore.
Environmental Factors: Various environmental factors influence stomatal movement, including humidity, temperature, and CO2 concentration. High humidity reduces water loss through transpiration and may keep stomata closed. Conversely, low humidity can promote stomatal opening. High temperatures can also lead to stomatal closure to conserve water.
Plant Hormones: Plant hormones like abscisic acid (ABA) play a crucial role in regulating stomatal closure, especially during water stress. ABA promotes the efflux of potassium ions from guard cells, leading to a decrease in turgor pressure and stomatal closure.
Other Factors: Factors like wind and mechanical stimuli can also influence stomatal behavior, with wind often leading to increased transpiration and stomatal opening.
Question: How does the pressure-low theory explain the movement of sugars through a plant?
The pressure-flow theory, also known as the pressure-flow hypothesis or the mass flow hypothesis, is an explanation for the movement of sugars (primarily sucrose) through a plant’s phloem tissue. This theory was developed to describe how plants transport the products of photosynthesis, such as sugars, from their source (usually the leaves) to various parts of the plant, including the roots, stems, and other growing tissues. Here’s how the pressure-flow theory explains this process:
Source and Sink: In a plant, there are regions called “sources” and “sinks.” Sources are the areas where sugars are produced or stored, primarily the leaves where photosynthesis takes place. Sinks are the areas of the plant where sugars are needed for growth, energy, or storage, such as the roots, fruits, or growing shoots.
Sugar Loading: In the source tissues (usually leaves), sugars produced during photosynthesis, mainly sucrose, are actively transported into the phloem cells. This process is known as sugar loading and involves the active transport of sucrose molecules from the source cells into the sieve-tube elements of the phloem.
Increased Pressure: As more and more sucrose is actively transported into the sieve-tube elements, the concentration of sugars within the phloem increases. This creates a higher osmotic pressure within the phloem sap compared to the surrounding cells. Osmotic pressure is the pressure exerted by water molecules moving from an area of low solute concentration (outside the phloem) to an area of high solute concentration (inside the phloem) through osmosis.
Water Influx: Due to the high solute concentration within the phloem, water from adjacent xylem vessels and surrounding cells moves into the phloem by osmosis. This influx of water creates a positive pressure gradient, known as turgor pressure, within the phloem cells.
Pressure Gradient: The turgor pressure generated by the influx of water pushes the sugary phloem sap in the direction of the sink tissues, where it’s needed. This positive pressure gradient, created by the accumulation of solutes and the influx of water, drives the flow of phloem sap from source to sink.
Sugar Unloading: At the sink tissues, where sugars are needed, sucrose is actively transported out of the phloem and into the surrounding cells for use in growth, energy, or storage. This process is called sugar unloading.
Return of Water: After sugar unloading, water returns to the adjacent xylem vessels, completing the cycle. The water is ultimately drawn up from the roots by transpiration, maintaining a continuous flow of water and nutrients throughout the plant.
Question: Describe cohesion-tension theory of water movement in xylem. What supplies the cohesion, and what is the source of tension? How do these two forces interact to move water through plant.
The cohesion-tension theory is a widely accepted explanation for the movement of water in the xylem of plants. It describes how water is transported from the roots to the leaves in a continuous column, against gravity, in vascular plants. This theory relies on two key forces: cohesion and tension.
Cohesion: Cohesion refers to the attractive forces between water molecules. Water molecules are polar, with a positive and a negative end, due to the unequal sharing of electrons. This polarity results in hydrogen bonding between adjacent water molecules, creating a cohesive force that holds them together.
Tension: Tension, in the context of the cohesion-tension theory, is essentially a negative pressure or a suction force. It is created by the transpiration process, which is the loss of water vapor from the stomata (small openings) in the leaves. As water molecules evaporate from the leaves and exit the plant through these openings, it creates a partial vacuum or negative pressure within the leaf’s air spaces.
Now, let’s understand how these two forces interact to move water through the plant:
Transpiration: Water is constantly evaporating from the moist surfaces inside the leaf into the surrounding air spaces through small openings called stomata. This loss of water vapor creates a continuous flow of water molecules from the leaf’s cells into the air spaces.
Cohesion: As water molecules evaporate from the leaf, the cohesive forces between water molecules cause neighboring water molecules to be pulled along. This creates a continuous, unbroken column of water from the leaf’s cells all the way down to the roots.
Tension: The negative pressure created by transpiration acts like a ‘pulling force’ on the water column. This tension is transmitted down the plant from the leaves to the roots through the xylem, thanks to the cohesive forces holding the water molecules together. It’s as if the plant is “sucking” water up from the roots.
Root Uptake: The roots of the plant absorb water and minerals from the soil through osmosis and active transport. As water is taken up by the roots and moved into the xylem, it replenishes the water lost through transpiration and maintains the cohesion-tension system.
Question: Explain, apoplast, symplast and vacuolar pathways, and describe the movement of water and dissolved minerals, through them.
In plant biology, the movement of water and dissolved minerals from the soil into the plant’s roots and then throughout the plant involves several pathways, including the apoplast, symplast, and vacuolar pathways. These pathways collectively contribute to the process of water and nutrient uptake and transport in plants.
Apoplast Pathway
The apoplast is the space outside the plant cells, including cell walls and the intercellular spaces.
In the apoplast pathway, water and dissolved minerals move through the non-living components of the plant, primarily the cell walls.
Water enters the root through the root hairs and moves along the cell walls of root cells, facilitated by capillary action and the cohesive and adhesive properties of water molecules.
As water moves through the apoplast, it can bypass the cell membrane and reach the endodermis, which is a critical layer of cells that surrounds the vascular tissue in roots.
However, the endodermis has a Casparian strip, which is a hydrophobic barrier made of suberin. This strip prevents water and minerals from freely entering the vascular tissue via the apoplast pathway. Instead, they must enter the symplast.
Symplast Pathway
The symplast consists of the living protoplasts (living parts of plant cells) and their interconnected cytoplasm through plasmodesmata, which are microscopic channels that connect adjacent plant cells.
Water and dissolved minerals can move through the symplast by crossing cell membranes and passing through plasmodesmata.
Once water reaches the endodermis with the Casparian strip, it must enter the symplast to progress further into the plant.
In the symplast pathway, water and nutrients are subject to more selective control by the plant, as they must be actively transported across cell membranes.
Vacuolar Pathway
The vacuole is a large, membrane-bound organelle found in plant cells. It can also play a role in water and mineral storage and transport.
Water can be actively transported into the vacuole, creating a concentration gradient that can drive water movement within the plant.
The vacuole can store excess water and nutrients, helping the plant regulate its water balance.
Movement of Water and Dissolved Minerals
Root Uptake: Water and dissolved minerals enter the plant primarily through root hairs, which are extensions of root epidermal cells. These structures increase the surface area for absorption.
Apoplast to Symplast Transition: As water and minerals move through the root, they typically follow the apoplast pathway initially. When they reach the endodermis, they are forced to enter the symplast due to the Casparian strip.
Symplast Transport: Within the symplast, water and minerals can move from cell to cell through plasmodesmata, allowing for symplastic transport. This pathway involves crossing cell membranes and can be regulated by the plant.
Vacuolar Storage: Some water and minerals may be stored in vacuoles within root cells, contributing to the plant’s water and nutrient storage capacity.
Transpiration: Once water and minerals reach the xylem, they are transported upwards through the plant via a process called transpiration. Transpiration is the loss of water vapor from the plant’s aerial parts, primarily through tiny openings called stomata on leaves. This loss of water creates a negative pressure in the xylem, which pulls water and minerals up from the roots.
Question: Explain water potential. What is the relationship of water potential with solute potential and pressure potential?
Water potential is a critical concept in plant biology and physiology that helps explain the movement of water within plants and across cell membranes. It is denoted by the Greek letter Ψ (psi) and is measured in units of pressure, typically megapascals (MPa) in the metric system. Water potential is a representation of the potential energy of water in a system, which drives the movement of water from areas of higher water potential to areas of lower water potential.
Water potential is affected by two main components: solute potential (Ψs) and pressure potential (Ψp). These components are combined to determine the overall water potential of a system:
Solute Potential (Ψs):
Solute potential, also known as osmotic potential, is a measure of the effect of solute concentration on water potential. It represents the tendency of water molecules to move away from areas with a high solute concentration to areas with a lower solute concentration. In other words, the more solutes (such as salts or sugars) a solution contains, the lower its water potential becomes. Pure water has the highest water potential, and as solute concentration increases, Ψs becomes more negative.
The formula for solute potential is typically expressed as: Ψs = -iCRT
Ψs represents solute potential.
i is the ionization constant (usually 1 for most solutes).
C is the molar concentration of the solute.
R is the pressure constant (0.0831 liter bar per mole per Kelvin).
T is the absolute temperature in Kelvin (usually around 273 + °C).
Pressure Potential (Ψp):
Pressure potential, also known as turgor pressure, is the physical pressure exerted by the cell contents (cytoplasm and vacuole) against the cell wall in plant cells. It is a positive component of water potential and can counteract the negative effects of solute potential. When a plant cell is turgid (fully inflated), it has a high pressure potential. When it becomes flaccid (loses water), pressure potential decreases.
Pressure potential can be influenced by factors like the rigidity of the cell wall and the amount of water in the central vacuole.
The relationship between these two components and water potential can be summarized with the following formula:
Ψ = Ψs + Ψp
Ψ represents the overall water potential.
Ψs represents solute potential.
Ψp represents pressure potential.
By understanding water potential, scientists and researchers can explain and predict the movement of water in plants. Water moves from regions of higher water potential to regions of lower water potential, and this movement is essential for various physiological processes in plants, including water uptake from the soil, cell expansion, and overall plant growth. The balance between solute potential and pressure potential helps maintain the turgor pressure necessary for plant support and proper functioning.
Question: Name and describe the general functions of the three major type of cells or cell like bodies found in blood of humans. Which of these cell types is found predominantly in lymph?
In human blood, there are three major types of cells or cell-like bodies, which are collectively referred to as blood cells or blood components. These three types are:
Red Blood Cells (RBCs or Erythrocytes)
Description: Red blood cells are the most numerous type of blood cells. They are small, biconcave, disc-shaped cells that lack a nucleus in mature form in humans. This absence of a nucleus allows them to have more space for hemoglobin, a protein responsible for transporting oxygen.
Function: The primary function of red blood cells is to transport oxygen from the lungs to all the body’s tissues and organs and to carry carbon dioxide back to the lungs for exhalation. Hemoglobin, the iron-containing molecule within RBCs, binds to oxygen in the lungs and releases it in tissues.
White Blood Cells (WBCs or Leukocytes)
Description: White blood cells are larger than red blood cells and have a nucleus. There are different types of white blood cells, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils, each with specific functions and characteristics.
Function: White blood cells are a crucial part of the immune system. They play a vital role in defending the body against infections, bacteria, viruses, and other foreign invaders. Each type of white blood cell has its specific function within the immune response.
Platelets (Thrombocytes):
Description: Platelets are small, colorless cell fragments rather than complete cells. They lack a nucleus and are much smaller than both red and white blood cells.
Function: Platelets are essential for blood clotting and wound healing. When a blood vessel is damaged, platelets adhere to the site and release chemicals that trigger the formation of a blood clot, sealing the injury and preventing excessive bleeding.
Lymph predominantly contains a specific type of white blood cell called lymphocytes. Lymphocytes are a crucial component of the immune system and play a central role in the body’s defense against infections. They are responsible for producing antibodies, recognizing and destroying infected or abnormal cells, and regulating immune responses. Lymphocytes are found in lymph nodes, spleen, thymus, and other lymphoid tissues and organs, and they circulate within the lymphatic system.
Question: Write a note on immunity and its types.
Immunity is a crucial component of the human body’s defense system against infections, diseases, and foreign invaders. It is the ability of the body to recognize and respond to various pathogens, such as bacteria, viruses, fungi, and parasites, as well as abnormal cells like cancerous ones. Immunity is a complex and highly coordinated system involving various cells, tissues, and molecules, and it plays a fundamental role in maintaining overall health.
There are two primary types of immunity in the human body:
Innate Immunity
Innate immunity, also known as natural or nonspecific immunity, is the first line of defense against pathogens and is present from birth. It provides immediate protection without prior exposure to specific pathogens. Key features of innate immunity include:
Physical Barriers: The skin and mucous membranes serve as physical barriers that prevent pathogens from entering the body.
Cellular Components: Phagocytes (such as neutrophils and macrophages) are white blood cells that engulf and destroy pathogens. Natural killer (NK) cells are responsible for recognizing and killing infected or abnormal cells.
Inflammatory Response: When tissue is damaged or invaded by pathogens, the body initiates an inflammatory response, characterized by redness, swelling, heat, and pain. This response helps to contain and eliminate the threat.
Complement System: A group of proteins that enhance the immune response by promoting inflammation, opsonization (coating pathogens for easier recognition), and cell lysis (breaking down pathogen cell membranes).
Adaptive Immunity
Adaptive immunity, also known as acquired or specific immunity, is a highly specialized defense mechanism that develops over time as the body encounters and recognizes specific pathogens. It is characterized by its ability to remember and respond more effectively upon subsequent exposures to the same pathogen. Key features of adaptive immunity include:
Lymphocytes: Adaptive immunity primarily involves two types of white blood cells, B lymphocytes (B cells) and T lymphocytes (T cells). B cells produce antibodies, while T cells have various functions, including killing infected cells (cytotoxic T cells) and coordinating immune responses (helper T cells).
Antigen Recognition: B and T cells can recognize specific antigens, which are unique molecules found on the surface of pathogens. This recognition is highly specific and allows the immune system to target and neutralize specific invaders.
Immunological Memory: After an initial encounter with a pathogen, memory B and T cells are formed. These cells “remember” the pathogen, allowing for a faster and more effective response if the same pathogen is encountered in the future. This forms the basis for vaccination, where a controlled exposure to a weakened or inactivated pathogen stimulates the immune system to create memory cells without causing the disease.