Nutrition
Plant and Animal Nutrition; Balanced Diet
---
Overview
Nutrition is the process by which living organisms obtain and utilize food for energy, growth, repair, and maintenance of life processes. This topic bridges biology fundamentals with practical health knowledge, making it a favourite in Assam TET Paper II science sections.
For the exam, you must understand two distinct nutritional modes—autotrophic (plants) and heterotrophic (animals)—along with the digestive system in humans, and the concept of a balanced diet. Questions typically test definitions, functions of nutrients, digestive organs, and deficiency diseases. Expect 2–4 questions directly from this topic, often combined with health and hygiene concepts.
Mastering nutrition requires clarity on photosynthesis mechanisms, the human digestive pathway, and the role of each nutrient class. Assam-specific elements like local food sources (rice, fish, leafy greens, bamboo shoots) occasionally appear in application-based questions.
---
Key Concepts
• **Autotrophic Nutrition**: Organisms (mainly green plants) synthesize their own food from inorganic substances using sunlight. Photosynthesis is the key process: carbon dioxide + water → glucose + oxygen in the presence of chlorophyll and light.
• **Heterotrophic Nutrition**: Organisms (animals, fungi, most bacteria) depend on other organisms for food. Types include holozoic (ingestion of solid food), saprophytic (feeding on dead matter), and parasitic (living on/in a host).
• **Photosynthesis Equation**: 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂. Chlorophyll in chloroplasts captures light; stomata allow gas exchange.
• **Human Digestive System**: A continuous alimentary canal—mouth → oesophagus → stomach → small intestine → large intestine → rectum → anus—with accessory glands (salivary glands, liver, pancreas).
• **Enzymes and Digestion**: Saliva contains amylase (starch → maltose); gastric juice contains pepsin (proteins → peptones); pancreatic juice contains lipase, trypsin, amylase; intestinal juice completes digestion.
• **Absorption and Assimilation**: Villi in the small intestine absorb nutrients into blood; absorbed food is used for energy or building body tissues.
• **Balanced Diet**: A diet containing carbohydrates, proteins, fats, vitamins, minerals, roughage, and water in correct proportions for age, sex, and activity level.
• **Deficiency Diseases**: Lack of specific nutrients causes diseases—scurvy (vitamin C), rickets (vitamin D), night blindness (vitamin A), anaemia (iron), goitre (iodine), kwashiorkor (protein), marasmus (protein-energy).
---
Formulas / Key Facts
| Nutrient | Main Function | Rich Sources | Deficiency Disease | |----------|---------------|--------------|-------------------| | Carbohydrates | Energy (4 kcal/g) | Rice, wheat, potato | Fatigue, weakness | | Proteins | Growth and repair (4 kcal/g) | Pulses, fish, eggs, milk | Kwashiorkor, marasmus | | Fats | Energy storage (9 kcal/g) | Oil, ghee, nuts | Weight loss, skin problems | | Vitamin A | Vision, immunity | Carrot, papaya, liver | Night blindness | | Vitamin B₁ | Nerve function | Whole grains | Beriberi | | Vitamin C | Wound healing, immunity | Citrus fruits, amla | Scurvy | | Vitamin D | Calcium absorption, bones | Sunlight, fish oil | Rickets (children), osteomalacia (adults) | | Calcium | Bones and teeth | Milk, green leafy vegetables | Weak bones | | Iron | Haemoglobin formation | Spinach, jaggery, meat | Anaemia | | Iodine | Thyroid hormone synthesis | Iodized salt, seafood | Goitre |