Nutrition

• Nutrition — obtaining and using food for growth, repair, and energy.
• Autotrophic — synthesise food (plants: photosynthesis).
• Heterotrophic — depend on others (animals: holozoic, saprophytic, parasitic).
• Photosynthesis — 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (chlorophyll, sunlight).
• Human digestive system — mouth to intestines; enzymes; absorption.

1. Autotrophs — green plants, some bacteria; build organic food from inorganic sources.
2. Heterotrophs — animals, fungi; ingest or absorb ready-made food.
3. Photosynthesis site — chloroplasts; stomata exchange CO₂ and O₂.
4. Raw materials — CO₂ (air), H₂O (roots), sunlight, chlorophyll.
5. Holozoic nutrition — Amoeba (pseudopodia), Paramoecium (cilia), human (alimentary canal).
6. Saprotrophic — fungi secrete enzymes on dead matter, absorb digested food.
7. Parasitic — Cuscuta on host plant; tapeworm in intestine.
8. Digestive enzymes — salivary amylase (mouth), pepsin (stomach), trypsin/lipase (small intestine).
9. Villi — increase surface area for absorption in small intestine.
10. NCERT focus — nutrition modes + human digestion + photosynthesis equation.

Balanced equation and requirements for photosynthesis

6CO₂ + 6H₂O --sunlight/chlorophyll--> C₆H₁₂O₆ + 6O₂
Requirements: chlorophyll traps light; stomata take CO₂; roots absorb water.
Products: glucose (stored as starch); O₂ released — vital for aerobic respiration.
Test: iodine turns starch in leaf black-blue after destarching experiment.
Conclusion: plants autotrophic via photosynthesis.

• Writing C₆H₁₂O₆ + O₂ → CO₂ + H₂O for nutrition (that's respiration).
• Misconception: all plants photosynthesise all the time (also respire always).
• Confusing saprotrophs with parasites.
• Forgetting bile emulsifies fats (no enzyme).
• Assuming digestion ends in stomach (mainly small intestine).

• Distinguish autotrophic and heterotrophic nutrition.
• Write photosynthesis equation.
• Where does absorption of digested food mainly occur?
• Name enzyme in saliva and its substrate.

Open the Practice tab for graded questions on Nutrition.