Food & Nutrition
Food & Nutrition – Life Processes
Our food and components of food
Key idea: Our food comes from plant sources (cereals, pulses, vegetables, fruits, oils) and animal sources (milk, egg, meat, fish). Every item we eat contains one or more components of food needed for growth, energy and protection.
| Component of food | Main function | Common Indian sources |
|---|---|---|
| Carbohydrates | Give energy for daily activities like walking, reading, playing. | Rice, wheat, jowar, bajra, ragi, potato, sugar, jaggery. |
| Proteins | Body building, growth and repair of tissues. | Pulses (dal), beans, peas, soyabean, milk, curd, egg, meat, fish, groundnut. |
| Fats | Reserve source of energy, insulation, protection of organs. | Ghee, butter, oil (groundnut, sunflower, mustard, sesame), nuts and seeds. |
| Vitamins | Protective role, keep eyes, skin, bones and gums healthy; help in many body reactions. | Fresh fruits, green leafy vegetables, milk, egg, sprouts. |
| Minerals | Strong bones and teeth, formation of blood, working of muscles and nerves. | Milk, ragi, leafy vegetables, fruits, meat, egg, salt (iodised), whole grains. |
| Water | Dissolves nutrients, helps transport, regulates body temperature, removes waste. | Drinking water, buttermilk, soups, fruits and vegetables. |
| Roughage (dietary fibre) | Helps easy movement of food in intestine, prevents constipation. | Whole grains, unpolished rice, vegetables, fruits with peel, salads. |
Memory Line: Think of a complete Indian meal as “Energy (carb) + Body-building (protein) + Protection (vitamins & minerals) + Water & Fibre.”
Exam Tip: If the question asks “which food mainly gives energy?” – choose items rich in carbohydrates or fats. For growth and repair – choose protein-rich foods like pulses and milk.
Balanced diet, malnutrition and deficiency diseases
Balanced diet: A diet that contains all components of food (carbohydrates, proteins, fats, vitamins, minerals, water and roughage) in right amount as per age, work and health is called a balanced diet.
| Group | Role in balanced diet | Example (simple Indian meal) |
|---|---|---|
| Energy-giving foods | Provide energy for all activities and body functions. | Rice or roti or idli or dosa. |
| Body-building foods | Help growth of muscles and repair of body tissues. | Dal, sambar, rajma, milk, curd, egg. |
| Protective foods | Protect against diseases and keep body systems healthy. | Vegetable curry, leafy vegetables, fruits. |
| Fibre and water | Help in digestion, easy bowel movement and proper functioning of all systems. | Salads, fruit with peel, enough clean drinking water or buttermilk. |
Malnutrition: A condition in which a person does not get proper type or proper amount of food. It includes both undernutrition (too little) and overnutrition (too much of some components).
| Type of malnutrition | Cause | Effects |
|---|---|---|
| Undernutrition | Less food than required; lack of protein or calories. | Weakness, poor growth, underweight, frequent infections. |
| Overnutrition | Eating more energy-rich food and fats than needed. | Overweight, obesity, risk of diabetes and blood pressure in later life. |
| Imbalanced diet | Enough food but wrong proportion of components. | Can lead to deficiency of vitamins or minerals even when stomach is full. |
Deficiency diseases: Diseases caused by long-term lack of a particular vitamin, mineral or protein in the diet.
| Nutrient lacking | Deficiency disease / condition | Symptoms / Signs | Food sources for prevention |
|---|---|---|---|
| Protein | Kwashiorkor, Marasmus | Swollen abdomen, thin limbs, poor growth, dry hair, irritability. | Pulses, milk, curd, egg, fish, meat, groundnut, soybean. |
| Vitamin A | Night blindness | Poor vision in dim light, dry eyes, dry skin. | Carrot, papaya, mango, green leafy vegetables, milk, egg. |
| Vitamin C | Scurvy | Bleeding gums, loose teeth, slow wound healing. | Lemon, orange, amla, guava, fresh vegetables. |
| Vitamin D | Rickets (in children) | Soft, bent bones, bow legs. | Sunlight exposure, milk, egg yolk, fortified foods. |
| Iron | Anaemia | Pale skin, tiredness, breathlessness on slight work. | Green leafy vegetables, dates, jaggery, liver, ragi. |
| Iodine | Goitre | Swelling of neck (thyroid gland), mental dullness in severe cases. | Iodised salt, sea fish. |
Memory Line: “Full stomach ≠ full nutrition.” A child can eat daily but still have deficiency diseases if the diet lacks proteins, vitamins or minerals.
Exam Tip: When you see a symptom like night blindness, bleeding gums or swollen neck in the question, first link it to the nutrient, then select the correct disease and food source option.
Types of nutrition
Nutrition is the process by which living organisms take in food and use it for energy, growth, repair and maintenance.
| Main type | Meaning | Examples |
|---|---|---|
| Autotrophic nutrition | Organisms prepare their own food from simple substances like CO₂ and water using sunlight. | Green plants, some algae, some bacteria (chemosynthetic bacteria use chemicals instead of light). |
| Heterotrophic nutrition | Organisms depend on other plants or animals for food. | Animals, non-green plants, most microorganisms. |
Heterotrophic nutrition can be further grouped:
| Heterotrophic type | Key feature | Example |
|---|---|---|
| Holozoic | Taking solid or liquid food inside body and digesting it. | Human beings, cow, dog, fish, Amoeba (unicellular holozoic). |
| Saprophytic | Feeding on dead and decaying organic matter outside the body. | Fungi like mushrooms, some bacteria. |
| Parasitic | Living on or inside another living organism (host) and taking ready-made food from it, often harming the host. | Cuscuta (amarbel) on plants, tapeworm in intestine, lice on scalp. |
| Symbiotic | Two different organisms live together and both get benefit. | Lichens (alga + fungus), Rhizobium in legume roots and plant. |
Memory Line: “Auto = self-food makers, Hetero = food-takers.” Under heterotrophs remember Holozoic, Saprophytic, Parasitic, Symbiotic.
Exam Tip: If the question mentions dead and decaying matter → saprophyte; living on host and causing harm → parasite; both partners benefit → symbiosis.
Nutrition in plants – Autotrophic, Parasitic, Saprophytic, Symbiosis, Insectivorous
Most plants show autotrophic nutrition, but some special plants show parasitic, saprophytic, symbioticinsectivorous
| Plant nutrition type | Key points | Examples with context |
|---|---|---|
| Autotrophic | Green plants use chlorophyll, sunlight, CO₂, water and minerals to prepare food (photosynthesis). | All green crops like paddy, wheat, sugarcane, leafy vegetables, trees. |
| Parasitic | Non-green plants (no chlorophyll) take food from host plant using sucking roots (haustoria). | Cuscuta (amarbel) growing on hedge plants or trees; it looks like yellow thread over host plant. |
| Saprophytic | Plants obtain food from dead and decayed organic matter. | Mushrooms on rotten wood, bracket fungi on dead tree trunks. |
| Symbiosis | Two different organisms live together and both are benefited. | Lichens (green alga + fungus), leguminous plants with Rhizobium bacteria in root nodules. |
| Insectivorous | Green plants that trap and digest insects to obtain extra nitrogen and minerals. | Nepenthes (pitcher plant), Drosera (sundew), Venus flytrap. |
| Plant | Special structure | How it helps in nutrition |
|---|---|---|
| Cuscuta | Haustoria (sucking roots) penetrating host tissues. | Directly absorbs prepared food from host plant; no leaves or chlorophyll. |
| Nepenthes (pitcher plant) | Leaf modified into pitcher with lid and digestive glands. | Insects fall into pitcher, get trapped and digested; plant absorbs nutrients. |
| Legume + Rhizobium | Root nodules containing nitrogen-fixing bacteria. | Bacteria fix atmospheric nitrogen; plant supplies food to bacteria; soil fertility improves. |
Memory Line: For nutrition in plants remember code: “A-P-S-S-I” – Autotrophic, Parasitic, Saprophytic, Symbiosis, Insectivorous.
Exam Tip: Questions often give picture of Cuscuta or pitcher plant. Even without name, if the plant has no green leaves but many host connections → parasite; if it has pitcher-like leaves trapping insects → insectivorous.
Nutrition in animals – Different ways of taking food & digestion in humans
Nutrition in animals includes different ways of taking food and the process of digestion in the alimentary canal.
| Animal type | Way of taking food | Example |
|---|---|---|
| Herbivores | Eat plant parts (leaves, grass, grains, fruits). | Cow, goat, deer, rabbit. |
| Carnivores | Eat other animals. | Lion, tiger, frog, snake. |
| Omnivores | Eat both plants and animals. | Human beings, bear, crow. |
| Filter feeders | Filter tiny food particles from water. | Some fishes, oysters. |
| Fluid feeders | Suck liquid food from host. | Mosquito, bed bug, leech. |
Digestion in humans: Digestion is the process of breaking down complex food into simple, absorbable form.
| Part of digestive system | Action on food | Important point |
|---|---|---|
| Mouth (buccal cavity) | Teeth cut, tear and grind food (mastication); saliva mixes with food. | Saliva contains amylase which starts digestion of starch. |
| Oesophagus (food pipe) | Food pushed down by muscular movements (peristalsis). | No digestion; only passage of food to stomach. |
| Stomach | Food is churned; gastric juice acts on proteins. | Contains HCl (kills germs, creates acidic medium), pepsin (digests proteins partly). |
| Small intestine | Most digestion and absorption. | Receives bile (from liver) and pancreatic juice; villi absorb digested food into blood. |
| Large intestine | Absorbs water and some salts. | Undigested waste is formed into faeces. |
| Anus | Removal of faeces from body. | Process called egestion. |
Memory Line: Flow of food in human body: Mouth → Oesophagus → Stomach → Small intestine → Large intestine → Anus.
Exam Tip: Many questions mix up organs and functions. Always match: starch → mouth & small intestine, proteins → stomach & small intestine, fats → small intestine with bile and pancreatic enzymes.
Digestion in grass eating animals
Grass-eating animals like cow, buffalo, goat are called ruminants. They eat large amount of grass quickly and complete digestion in a special stomach with four chambers.
| Feature | Explanation | Exam use |
|---|---|---|
| Four-chambered stomach | Rumen, reticulum, omasum, abomasum. | Rumen acts as fermentation chamber where microbes digest cellulose. |
| Rumination | After first swallowing, partially digested food (cud) is brought back to mouth, chewed again and swallowed. | Animals seen “chewing cud” even when not grazing. |
| Cellulose digestion | Special bacteria in rumen break cellulose of plant cell wall. | Humans cannot digest cellulose; this is often asked as comparison. |
Memory Line: “Ruminants ruminate.” They have a four-part stomach and bring back cud to chew again.
Exam Tip: If question mentions cud, rumen or chewing again, the answer is related to grass eating ruminant animals like cow and buffalo.
Feeding and digestion in Amoeba
Amoeba is a unicellular organism living in pond water. It shows holozoic nutrition and performs feeding and digestion in the same cell.
| Step | What happens | Key term |
|---|---|---|
| Food capture | Amoeba moves towards food particle and sends out finger-like projections of cytoplasm. | Pseudopodia (“false feet”). |
| Ingestion | Pseudopodia surround food particle and fuse to form a sac. | Food vacuole is formed. |
| Digestion | Digestive enzymes are released into food vacuole; complex food breaks into simple substances. | Intracellular digestion. |
| Absorption | Simple substances pass from vacuole into cytoplasm. | Nutrients used for energy and growth. |
| Egestion | Undigested material is thrown out by opening the vacuole at cell surface. | Waste removal. |
Memory Line: Feeding steps in Amoeba: “Pseudopodia → Food vacuole → Digestion → Absorption → Egestion.”
Exam Tip: If diagram shows irregular shape cell with pseudopodia and food vacuole, it is Amoeba. Questions may ask sequence of events or meaning of pseudopodia.