Class 9th Biology Chapter 8 Nutrition Notes
Nutrition
Nutrition is the process of obtaining or preparing food, absorbing its nutrients, and converting them into body substances for growth and energy.
Nutrients
Nutrients are elements and compounds that organisms obtain and use for energy or to synthesize new materials.
Mineral Nutrition in Plants
Plants obtain carbon, hydrogen, and oxygen from carbon dioxide and water, but they also require mineral elements for various activities and structures.
Macronutrients are required in large quantities (e.g., carbohydrates, proteins, fats, cholesterol, fiber, and water.).
Micronutrients are needed in smaller quantities (e.g., iron, molybdenum, boron).
These nutrients play vital roles in plant growth and development.
Long Answer Question
Short Answer Question
Exercise and MCQ’s
Importance of Fertilizers
Fertilizers are added to the soil to provide essential nutrients to plants.
Inorganic fertilizers, like nitrogen fertilizers, are readily available to plants, while organic fertilizers take time to break down.
Excessive use of fertilizers can lead to environmental hazards like eutrophication and greenhouse gas emissions.
Components of Human Food
Human food includes carbohydrates, lipids, nucleic acids, proteins, minerals, vitamins, and water.
Carbohydrates are the primary source of energy and can be found in foods like bread, pasta, and potatoes.
Lipids provide energy and are found in butter, oils, and certain meats.
Proteins are essential for growth and can also be used for energy. They are present in meat, eggs, and dairy products.
Minerals, like calcium and iron, play vital roles in bodily functions and are obtained from various food sources.
Vitamins are chemical compounds required in small amounts for normal growth and metabolism.
Fat-Soluble Vitamins
Fat-soluble vitamins include A, D, E, and K.
Vitamin A is crucial for vision in dim light, cell differentiation, growth, and immunity. Its deficiency can cause poor growth and blindness.
Vitamin D maintains calcium and phosphorus concentrations in the body. Its deficiency can lead to rickets in children and osteomalacia in adults.
Water-Soluble Vitamins
Water-soluble vitamins include B complex vitamins and vitamin C.
Vitamin C is essential for collagen formation, wound healing, and immune system functioning. Its deficiency can cause scurvy, fatigue, and bleeding gums. Overall, proper nutrition is essential for the growth, development, and overall well-being of living organisms. Different organisms have different nutritional requirements, and maintaining a balanced diet is crucial for a healthy life.
Effects of Water and Dietary Fibre
Water
- Water constitutes approximately 60% of the adult human body and plays a vital role in life.
- Essential for life-sustaining chemical reactions as they require an aqueous environment.
- Functions as the medium for absorbing water-soluble food in the intestines and eliminating waste products in urine.
- Helps regulate body temperature through evaporation, such as sweating.
- Severe dehydration can lead to cardiovascular problems.
- The average adult requires about two liters of water per day.
- Important sources of water intake are natural water, milk, juicy fruits, and vegetables.
Dietary Fibre
- Dietary fibre (roughage) is found only in plant foods and is indigestible.
- Travels undigested through the stomach and small intestine into the colon.
- Insoluble dietary fibre moves quickly through the small intestines.
- Sources of insoluble dietary fibre include wheat bran, cereals, and skins of fruits and vegetables.
- Soluble dietary fibre breaks down as it passes through the alimentary canal.
- Sources of soluble dietary fibre include oats, beans, barley, and many fruits and vegetables.
- Fibre prevents and relieves constipation by stimulating intestinal muscle contraction.
- Avoiding constipation reduces the risk of many other diseases.
- Soluble fibre helps lower blood cholesterol and sugar levels.
- Insoluble fibre speeds up the movement of cancer-causing agents (carcinogens) from the intestine.
- Fibre supplements (like Ispaghol husk) should be used with a physician’s recommendation to help with constipation and lower cholesterol levels.
Balanced Diet
A balanced diet contains all the essential nutrients in the correct proportions for normal growth and development. It should be based on age, gender, and activity level. Different nutrients and energy requirements vary with age and lifestyle.
Stomach
- The stomach is a J-shaped, dilated part of the alimentary canal located on the left side of the abdomen, beneath the diaphragm.
- It has two main portions: the cardiac portion, which is immediately after the esophagus, and the pyloric portion, located beneath the cardiac portion.
- The stomach has two sphincters: the cardiac sphincter between the stomach and the esophagus, and the pyloric sphincter between the stomach and the small intestine.
- Gastric glands in the stomach wall secrete gastric juice when food enters the stomach. Gastric juice is composed of mucus, hydrochloric acid (HCl), and the inactive enzyme pepsinogen.
- HCl converts pepsinogen into its active form, pepsin, which partially digests proteins into polypeptides and shorter peptide chains.
The stomach wall is protected from digestion by pepsin due to the secretion of mucus, which neutralizes the HCl.
Small Intestine
- The small intestine is where most of the digestion process occurs and is divided into three parts: the duodenum, jejunum, and ileum.
- The duodenum, the first 10 inches of the small intestine, receives secretions from the liver and pancreas. Bile from the liver helps digest lipids, while pancreatic juice contains enzymes for digesting proteins, carbohydrates, and lipids.
- The jejunum is concerned with the further digestion of proteins, carbohydrates, and lipids.
- The ileum, the last 3.5 meters of the small intestine, is primarily responsible for the absorption of digested food. It contains villi with a rich supply of blood capillaries and lacteals to facilitate nutrient absorption.
Large Intestine
- The large intestine consists of the caecum, colon, and rectum. Water and salts are absorbed from the colon, leaving behind the solid remains of food, known as feces.
- The rectum temporarily stores feces until defecation occurs through the anus.
Liver
- The liver is the largest gland in the body, located beneath the diaphragm on the right side of the abdomen. It weighs about 1.5 kg and has multiple functions.
- The liver secretes bile, which is stored in the gallbladder and released into the duodenum to emulsify lipids.
- It also removes amino groups from amino acids, converts ammonia to urea, manufactures blood clotting proteins, and performs various metabolic processes.
- The liver stores fat-soluble vitamins and mineral ions and produces heat to maintain body temperature.
Disorders of the Gut
Diarrhea: Frequent watery, loose bowel movements caused by lack of water absorption in the colon or viral/bacterial infections of the large intestine. Treatment includes replacing lost fluids and nutrients.
Constipation: Difficulty passing hard feces, usually caused by excessive water absorption in the colon, insufficient dietary fiber, dehydration, or certain medications. Treatment involves dietary and lifestyle changes and the use of laxatives if necessary.
Ulcer (Peptic Ulcer): Sores in the inner wall of the gut caused by excess acid, infections, long-term use of anti-inflammatory medications, smoking, and certain dietary factors. Treatment includes medicines to neutralize stomach acid and avoiding triggers.
Overall, the digestive system plays a vital role in breaking down food and absorbing nutrients necessary for the body’s functioning and growth. It requires proper functioning and a balanced diet to maintain overall health.