1st Year Biology, where the intricacies of life’s fundamental building blocks come to life. In this engaging academic journey, we delve into the captivating Unit No. 6: Kingdom Prokaryotae. At the heart of the microscopic world, this unit unlocks the mysteries of prokaryotic organisms, shedding light on their remarkable diversity, essential roles, and profound impact on the broader biosphere. Join us as we embark on a fascinating exploration of these single-celled wonders, unraveling their unique characteristics and unveiling the intricate tapestry of life that they weave.
Unit 6 Biology of 1st Year Short Answers Questions
What does “Prokaryotae” refer to in the context of organisms?
“Prokaryotae” refers to organisms with prokaryotic cells, meaning they lack a true nucleus.
What is the Greek meaning of “Pro” in “Prokaryotae”?
In Greek, “Pro” means “before.”
What is the Greek meaning of “karyon” in “Prokaryotae”?
In Greek, “karyon” means “nucleus.”
How do microbiologists categorize bacteria based on the Greek terms?
Microbiologists categorize bacteria as “eubacteria” (true bacteria) and “archaeobacteria” (ancient bacteria).
Who was the first scientist to observe and describe microbes using a simple microscope?
The Dutch scientist Antonie van Leeuwenhoek was the first to observe and describe microbes using a simple microscope.
- 1st Year Biology Unit No.1 Introduction Notes
- 1st Year Biology Unit No. 2 Biological Molecules Notes
- 1st Year Biology Unit No. 3 Enzymes Notes
- 1st Year Biology Unit No. 4 The Cell Notes
- 1st Year Biology Unit No. 5 Variety of Life Notes
What term did Antonie van Leeuwenhoek use to describe the small creatures he observed?
Antonie van Leeuwenhoek called the small creatures he observed “animalcules.”
What did Louis Pasteur contribute to microbiology and medicine?
Louis Pasteur developed vaccines for diseases like anthrax, fowl cholera, and rabies. He also contributed to the development of pasteurization and fermentation industries.
What is the “germ theory of disease” formulated by Robert Koch?
The “germ theory of disease” formulated by Robert Koch states that specific microorganisms are the causal agents of certain diseases.
What are the four postulates of the germ theory of disease formulated by Robert Koch?
The four postulates are:
- A specific organism is always associated with a given disease.
- The organism can be isolated and grown in pure culture in the laboratory.
- The pure culture will produce the disease when inoculated into a susceptible animal.
- The organism can be recovered in pure culture from an experimentally infected animal.
What techniques did Koch and his colleagues contribute to microbiology?
Koch and his colleagues invented techniques related to inoculation, isolation, media preparation, maintenance of pure cultures, and preparation of specimens for microscopic examinations.
Where are bacteria found in their occurrence?
Bacteria are found almost everywhere, including air, land, water, oil deposits, food, decaying organic matter, plants, animals, and more.
How does the kind and number of bacteria vary?
The kind and number of bacteria vary according to locality and environmental conditions.
What are some specific environments where certain bacteria are present?
Some specific environments where bacteria are present include hot springs, alkaline/acidic soil, highly saline environments, highly polluted soils, and waters.
What are the common components of bacterial cells?
All bacterial cells have a cell membrane, cytoplasm, ribosomes, and chromatin bodies. Most also have a cell wall, while other structures like capsule, slime, flagella, pili, fimbriae, and granules are not found in all bacteria.
What is the range of sizes for bacteria?
Bacteria range in size from about 0.1 to 600 nm over a single dimension.
Describe the shape of Escherichia coli.
Escherichia coli is a bacillus with a width of 1.1 to 1.5 nm and a length of 2.0 to 6.0 nm.
How are bacteria classified based on their general shape?
Bacteria are classified into three categories based on their general shape: cocci (spherical or oval), bacilli (rod-shaped), and spiral.
What is the arrangement called when cocci occur in pairs?
The arrangement is called diplococcus.
What arrangement do cocci form when they occur in long chains of cells?
The arrangement is called streptococci.
What is the arrangement produced when cocci divide in two planes?
The arrangement produced is a tetrad arrangement, forming a square of 4 cocci.
Describe the sarcina arrangement.
The sarcina arrangement is produced when cocci divide in three planes, forming a cube of 8 cocci.
How are cocci arranged in a staphylococcus arrangement?
In a staphylococcus arrangement, cocci are arranged in irregular, often grape-like clusters.
What are bacilli?
Bacilli are rod-shaped bacteria that divide in one plane to produce bacillus, streptobacillus, or diplobacillus arrangements.
What is streptobacillus?
Streptobacillus is a chain of bacilli, which are rod-shaped bacteria.
What is diplobacilli?
Diplobacilli refers to the arrangement of rod-shaped bacteria occurring in pairs.
What are spiral shaped bacteria?
Spiral shaped bacteria are bacteria with spirally coiled forms, including vibrio, spirillum, and spirochete.
What is a vibrio?
A vibrio is a curved or comma-shaped rod among the spiral shaped bacteria.
What is a spirillum?
A spirillum is a thick and rigid spiral form of bacteria.
What is a spirochete?
A spirochete is a thin and flexible spiral-shaped bacteria.
What is the primary function of flagella?
The primary function of flagella is to aid in bacterial motility and movement.
How are bacteria with single polar lagellum classified?
Bacteria with a single polar lagellum are classified as monotrichous.
What is chemotaxis?
Chemotaxis is a type of behavior exhibited by lagellate bacteria, where they move in response to chemical signals.
What are pili and their primary function?
Pili are hollow, nonhelical appendages on bacteria.
They are involved in mating (conjugation) between cells.
Some pili help in bacterial attachment to surfaces.
What distinguishes true pili from flagella?
True pili are smaller than flagella.
True pili are present only in gram-negative bacteria.
True pili are involved in conjugation, not motility.
What is the composition of a bacterial capsule?
Capsule is made of repeating polysaccharide units and protein.
It is tightly bound to the bacterial cell.
Capsule contributes to pathogenicity and gives colonies a sticky character.
How does slime contribute to bacterial pathogenicity?
Slime is a soluble shield of macromolecules on some bacteria.
It enhances pathogenicity and protects against phagocytosis.
What is the role of a bacterial cell wall?
Cell wall is a rigid structure beneath the extracellular substances.
It determines the bacterium’s shape and prevents osmotic lysis.
Mycoplasmas are the only bacteria lacking a cell wall.
Who developed the gram staining technique?
Christian Gram developed the gram staining technique.
It divides bacteria into Gram-positive (purple) and Gram-negative (pink) groups.
Gram staining is based on differences in cell wall structure.
What is the unique macromolecule found in the cell walls of most bacteria?
The unique macromolecule is peptidoglycan.
What is the composition of peptidoglycan in bacterial cell walls?
Peptidoglycan is composed of long glycan chains cross-linked with peptide fragments.
What are the chemical constituents found in the intact bacterial cell wall?
The cell wall contains sugar molecules, teichoic acid, lipoproteins, and lipopolysaccharides.
How do the cell walls of archaeabacteria differ from eubacteria?
Archaeabacteria lack peptidoglycan and have cell walls composed of proteins, glycoproteins, and polysaccharides.
What is the function of the cell membrane or plasma membrane in bacteria?
The cell membrane regulates transport, surrounds the cytoplasm, and contains enzymes for respiratory metabolism.
How does the composition of bacterial membranes differ from eukaryotic membranes?
Bacterial membranes lack sterols like cholesterol found in eukaryotic membranes.
What is the cytoplasmic matrix in prokaryotic cells?
The cytoplasmic matrix is the gel-like substance between the plasma membrane and the nucleoid.
What is the major function of the cytoplasmic matrix?
The cytoplasmic matrix supports cellular processes and allows small molecules to move rapidly.
What is the term for the plasma membrane and everything present within it?
The term for this is protoplast.
What structures are absent in the cytoplasm of prokaryotic cells?
Prokaryotic cells lack membrane-bound organelles and a cytoskeleton (microtubules).
What is the structure of the nuclear material in bacterial cells?
The nuclear material in bacterial cells is a single, circular, double-stranded DNA molecule located near the center of the cell, forming a region called the nucleoid.
What are plasmids and their function in bacteria?
Plasmids are circular, double-stranded DNA molecules found in many bacteria. They carry genes that are not essential for bacterial growth and metabolism, often including drug resistance and other advantageous traits.
What is the function of ribosomes in bacterial cells?
Ribosomes in bacterial cells are protein factories composed of RNA and proteins. They are involved in protein synthesis and are smaller than eukaryotic ribosomes.
What are mesosomes and their roles in bacterial cells?
Mesosomes are structures formed by the invagination of the cell membrane into the cytoplasm of bacterial cells. They are involved in processes like DNA replication, cell division, and the export of exocellular enzymes. Some mesosomes also contain respiratory enzymes.
Why do bacteria store granules and what are some examples?
Bacteria store granules as a way to store extra nutrients in environments with limited resources. Examples of stored materials include glycogen, sulfur, fat, phosphate, and waste products like alcohol and organic acids.
What are bacterial spores and their significance?
Bacterial spores are metabolically dormant bodies produced by certain bacteria. They are resistant to adverse environmental conditions like high temperatures, desiccation, and chemicals. Spores can germinate to form vegetative cells under favorable conditions.
What are the nutritional strategies of bacteria?
Most bacteria are heterotrophic, obtaining their energy from dead organic matter (saprophytic) or living organisms (parasitic). Some bacteria are autotrophic and can synthesize organic compounds from inorganic substances. Photosynthetic and chemosynthetic autotrophs are two categories of autotrophic bacteria.
How do photosynthetic autotrophic bacteria differ from green plants in terms of chlorophyll location?
Photosynthetic bacteria have dispersed chlorophyll in their cytoplasm, unlike green plants that contain chlorophyll in chloroplasts.
What is the primary hydrogen source for photosynthetic bacteria during photosynthesis?
Photosynthetic bacteria use hydrogen sulfide (H2S) as a hydrogen source during photosynthesis, producing sulfur instead of oxygen.
Name three types of photosynthetic bacteria.
Green sulfur bacteria, purple sulfur bacteria, and purple non-sulfur bacteria are types of photosynthetic bacteria.
What is respiration in bacteria?
Respiration in bacteria can be aerobic (requiring oxygen) or anaerobic (not requiring oxygen). Bacteria growing in the presence of oxygen are called aerobic, while those growing without oxygen are anaerobic.
Define facultative bacteria.
Facultative bacteria can grow either in the presence or absence of oxygen.
What is the process of bacterial growth called?
Bacterial growth refers to an increase in the number of bacterial cells through binary fission, an asexual means of reproduction.
Describe binary fission.
Binary fission involves the parent bacterial cell enlarging, duplicating its chromosome, and then dividing into two daughter cells by pinching its plasma membrane inward at the center.
What is the generation time?
The generation time is the interval of time between the completion of one bacterial division and the completion of the next division.
Name the phases of bacterial growth curve.
The phases of the bacterial growth curve are: Lag phase, Log phase, Stationary phase, and Death/Decline phase.
How does conjugation occur in bacteria?
Conjugation is a process where bacteria transfer genetic material from a donor to a recipient bacterium, often using specialized sex pili. This creates new genetic combinations.
What is the significance of conjugation in bacteria?
Conjugation allows bacteria to exchange genetic material, leading to the creation of new genetic combinations that enhance their survival under diverse conditions.
What is the ecological importance of bacteria?
Bacteria play a significant role in decomposing organic matter and completing cycles of nitrogen, phosphorus, sulfur, and carbon.
How are bacteria economically important?
Bacteria are utilized in various industries such as food, drugs (antibiotics and vaccines production), and biotechnology. They can also spoil food and cause agricultural losses.
What is the medical importance of bacteria?
Many bacterial species are pathogens causing diseases in humans. Some bacteria are normal inhabitants of human and animal bodies.
Why is controlling bacteria essential?
Microorganism control prevents and treats diseases, as well as inhibits spoilage of food and industrial products. Physical methods like heat, radiation, and filtration are used for control.
What is sterilization?
Sterilization is a process that uses physical agents like heat, radiation, and filtration to destroy all life forms, including microorganisms.
How does heat control bacteria?
Both dry heat and moist heat can effectively control bacteria. Moist heat causes protein coagulation, while dry heat leads to the oxidation of microbial components.
Which type of radiation is used for sterilization?
Gamma rays, a type of electromagnetic radiation below 300 nm, are commonly used for the sterilization process.
How can heat-sensitive compounds be sterilized?
Heat-sensitive substances like antibiotics and hormones can be sterilized using membrane filters.
What are antiseptics?
Antiseptics are chemical substances used on living tissues that inhibit the growth of microorganisms.
Give examples of chemical agents used for disinfection.
Examples of chemical agents used for disinfection include halogens, phenols, hydrogen peroxide, potassium permanganate, alcohol, and formaldehyde.
How do chemotherapeutic agents work?
Chemotherapeutic agents work by stopping the growth of bacteria and other microbes in living tissues. Examples include sulfonamides, tetracycline, and penicillin.
What is the difference between microbicidal and microbistatic effects?
Microbicidal effects immediately kill microbes, while microbistatic effects inhibit their reproductive capacities, maintaining a constant population size.
What did Pasteur discover about bacterial attenuation?
Pasteur discovered that bacteria could lose their virulence after aging, but still stimulate the host to produce protective antibodies. This principle led to vaccination.
How did Edward Jenner contribute to vaccination?
Edward Jenner successfully vaccinated a boy against smallpox in 1796, using cowpox to protect against smallpox, leading to the term “vaccination.”
What disease did Pasteur create a vaccine for?
Pasteur created a vaccine for hydrophobia (rabies), a disease transmitted by bites from rabid animals like dogs and cats.
What is the etymology of the term “antibiotics”?
Antibiotics comes from the Greek words “Anti” (against) and “Bios” (life).
Which microorganisms are responsible for synthesizing antibiotics?
Bacteria, actinomycetes, and fungi synthesize and secrete antibiotics.
Can antibiotics be produced in a laboratory?
Yes, some antibiotics are synthesized in the laboratory, but their origins are in living cells.
Why is it important to know a drug’s mode of action and potential side effects?
Knowing a drug’s mode of action helps determine its effectiveness, while awareness of side effects is crucial for patient safety.
What is the consequence of widespread antibiotic use?
Overuse of antibiotics leads to drug resistance in microorganisms, reducing the effectiveness of disease treatments.
How can misused antibiotics impact human health?
Misused antibiotics can interact with metabolism, leading to severe consequences, including death. Allergic reactions and other adverse effects are also possible.
What is an example of a negative effect caused by misusing penicillin?
Misuse of penicillin can result in allergic reactions in individuals.
What auditory issue can arise from misusing streptomycin?
Misuse of streptomycin can damage the auditory nerve, potentially causing deafness.
What adverse effect can tetracycline have on children?
Tetracycline and related compounds can cause permanent tooth discoloration in young children.
What are cyanobacteria commonly known as?
Cyanobacteria are commonly known as ‘blue-green algae’.
Are cyanobacteria prokaryotic or eukaryotic?
Cyanobacteria are true prokaryotes.
What is the diameter range of cyanobacteria?
Cyanobacteria range in diameter from about 1-10 micrometers (um).
How do cyanobacteria move in water?
Cyanobacteria often use gas vesicles for movement in water, and some filamentous species have gliding motility.
What type of photosynthesis do cyanobacteria carry out?
Cyanobacteria carry out oxygenic photosynthesis, using water as an electron donor and generating oxygen.
Which pigment is predominant in cyanobacteria’s accessory pigments?
The predominant phycobilin pigment in cyanobacteria is phycocyanin (blue).
How do cyanobacteria assimilate CO2?
Cyanobacteria assimilate CO2 through the Calvin cycle.
What is the reserve food material in cyanobacteria?
The reserve food material in cyanobacteria is glycogen.
How do cyanobacteria reproduce?
Cyanobacteria reproduce by binary fission and fragmentation.
What are some specialized structures present in cyanobacteria?
Cyanobacteria have hormogonia, akinetes, and heterocysts.
What is the economic importance of cyanobacteria?
Cyanobacteria help reclaim alkaline soils, fix atmospheric nitrogen, and release oxygen. Some are used as pollution indicators, and they form symbiotic associations with various organisms.
What issues can cyanobacteria blooms cause in water bodies?
Cyanobacteria blooms can lead to unpleasant smell, suspended organic matter, and toxin production that can harm livestock and animals.
What is Nostoc’s habitat and distribution?
Nostoc is a common terrestrial and subaerial cyanobacterium found in alkaline soils and on moist rocks and cliffs.
How do Nostoc trichomes appear?
Nostoc trichomes are unbranched and beaded, with occasional larger cells called heterocysts.
How does Nostoc reproduce asexually?
Nostoc reproduces asexually through hormogonia formation, fragmentation, and akinete formation.
Unit 6 Biology of 1st Year Long Answer Questions
Describe in detail the structure of bacterial cell wall, emphasizing Gram positive and Gram negative properties.
Answer: Bacterial Cell Wall Structure: Gram Positive and Gram Negative Properties
The bacterial cell wall is a crucial structural component that not only provides shape and rigidity to the cell but also protects it from osmotic lysis. Two major types of bacterial cell walls exist: Gram-positive and Gram-negative, each exhibiting distinct structural properties.
Gram-Positive Bacteria
Gram-positive bacteria have a thick peptidoglycan layer that forms a substantial part of their cell wall. Peptidoglycan is a mesh-like structure composed of repeating units of sugar chains cross-linked by short peptide chains. In Gram-positive bacteria, these layers are dense and extensive, making the cell wall appear homogeneous under a microscope. Teichoic acids, which are unique to Gram-positive bacteria, are also embedded within the peptidoglycan layer. These molecules aid in ion exchange and play a role in bacterial adhesion to surfaces.
Gram-Negative Bacteria
The cell walls of Gram-negative bacteria consist of a thinner peptidoglycan layer sandwiched between two lipid bilayers – the inner and outer membranes. The outer membrane contains lipopolysaccharides (LPS), which confer structural integrity and provide a barrier against certain chemicals and host immune responses. The periplasmic space between the inner and outer membranes houses various enzymes and transport proteins.
The key distinction between Gram-positive and Gram-negative bacteria lies in their response to the Gram staining method. Gram-positive bacteria retain the crystal violet stain and appear purple under the microscope, while Gram-negative bacteria do not retain the stain and appear pink after counterstaining.
Write an account of diferent methods used for controlling microbes.
Answer: Methods for Controlling Microbes
Various methods are employed to control microbial growth and prevent their proliferation:
Physical Methods: Heat, radiation (UV and ionizing), and filtration are used to destroy or inhibit microbes by damaging their DNA, proteins, or cell structures.
Chemical Methods: Disinfectants, antiseptics, and preservatives disrupt microbial structures and metabolic processes. They can be used on surfaces, inanimate objects, and living tissues.
Antibiotics: These are specific chemicals that inhibit the growth of or kill bacteria by targeting essential cellular processes unique to bacteria.
Antimicrobial Drugs: These include antiviral, antifungal, and antiparasitic medications that target specific pathogens.
Vaccination: Immunization stimulates the immune system to produce antibodies against specific pathogens, providing immunity and preventing infections.
Hand Hygiene: Regular handwashing with soap and water is a simple yet effective method to reduce the transmission of harmful microbes.
Quarantine and Isolation: These practices prevent the spread of contagious diseases by restricting the movement of infected individuals.
Discuss the role of antibiotics and immunization in controlling bacterial diseases.
Answer: Role of Antibiotics and Immunization
Antibiotics: Antibiotics are potent tools against bacterial infections. They inhibit bacterial growth or kill bacteria by targeting processes like cell wall synthesis, protein synthesis, DNA replication, and metabolism. However, misuse and overuse of antibiotics can lead to antibiotic resistance, where bacteria evolve to withstand the effects of antibiotics, rendering them ineffective. This can result in difficult-to-treat infections and compromised medical treatments.
Immunization: Immunization, also known as vaccination, is a proactive strategy to prevent infectious diseases. Vaccines contain weakened or inactivated forms of pathogens or their antigens. When administered, they stimulate the immune system to produce antibodies and memory cells that provide protection against future infections. Immunization has played a pivotal role in controlling and eradicating diseases like smallpox, polio, and measles.
What problem can arise due to misuse of antibiotics.
Answer: The misuse of antibiotics can lead to a range of significant problems, both on an individual and a global scale. Some of the key issues that arise due to the inappropriate use of antibiotics include:
Antibiotic Resistance: Perhaps the most concerning consequence of antibiotic misuse is the development of antibiotic resistance. Bacteria can evolve and adapt to the antibiotics used against them, leading to the emergence of drug-resistant strains. When antibiotics are used improperly, such as not completing a full course of treatment or using them for non-bacterial infections, bacteria can survive and develop resistance mechanisms. This renders antibiotics less effective, making infections harder to treat and potentially causing prolonged illness, increased healthcare costs, and even death.
Difficult-to-Treat Infections: As antibiotic-resistant strains of bacteria become more prevalent, infections caused by these strains can become extremely challenging to treat. This can lead to longer hospital stays, more invasive treatments, and higher mortality rates. Certain infections, like drug-resistant tuberculosis, have limited treatment options, making them particularly dangerous.
Compromised Medical Procedures: Antibiotics are essential for various medical procedures, including surgeries, chemotherapy, and organ transplants. If antibiotic resistance becomes widespread, these procedures could become riskier or even impossible due to the increased risk of infection.
Increased Healthcare Costs: The emergence of antibiotic-resistant infections requires more complex and expensive treatment regimens, which can strain healthcare systems and lead to higher medical costs for individuals and society as a whole.
Public Health Threat: Antibiotic resistance doesn’t respect borders. Resistant bacteria can spread globally, making it a public health threat that requires international cooperation to address effectively.
Loss of Effective Treatment: If the development of new antibiotics doesn’t keep pace with the emergence of resistant bacteria, we could eventually face a situation where common infections become untreatable. This would have a significant impact on public health and could lead to increased morbidity and mortality rates.
Disruption of Microbial Balance: Antibiotics not only target harmful bacteria but also affect beneficial bacteria in the body, such as those in the gut. This can disrupt the natural balance of the microbiome, potentially leading to issues like gastrointestinal problems, weakened immune function, and susceptibility to other infections.
To mitigate these problems, it’s crucial to use antibiotics responsibly and only as prescribed by healthcare professionals. Completing the full course of antibiotics as directed, not sharing antibiotics with others, and avoiding the use of antibiotics for viral infections (where they are ineffective) are all important steps to help combat antibiotic resistance and its associated consequences.
Describe general characteristics of Cyanobacteria with special reference to Nostoc.
Answer: General Characteristics of Cyanobacteria with Special Reference to Nostoc
Cyanobacteria, often referred to as blue-green algae, are a group of photosynthetic prokaryotic microorganisms. They play a crucial role in aquatic ecosystems and have significant ecological and economic importance. General characteristics of cyanobacteria include:
Photosynthesis: Cyanobacteria are capable of oxygenic photosynthesis, producing oxygen as a byproduct. They contain pigments such as chlorophyll-a and phycobilins.
Cell Structure: Cyanobacteria have a prokaryotic cell structure without membrane-bound organelles. Their DNA is located in the nucleoid region.
Reproduction: Reproduction occurs through binary fission, akinetes (thick-walled resting cells), and heterocysts (nitrogen-fixing cells).
Habitat: They thrive in various habitats, including freshwater, marine environments, and even extreme conditions like hot springs and deserts.
Nostoc: Nostoc is a genus of cyanobacteria known for its filamentous growth pattern. It forms colonies consisting of intertwined filaments. Nostoc colonies can fix atmospheric nitrogen, making them important contributors to nitrogen availability in ecosystems. These colonies are found in soil, moist rocks, and aquatic environments, forming gelatinous masses.