Nutrition and Photosynthesis
NCERT Class 10 • Science • Chapter "Life Processes" | NCERT Class 7 • Science • Chapter "Nutrition in Plants"
Nutrition and Photosynthesis
Nutrition is the process of taking in food and using it for energy, growth and repair. Organisms that make their own food are autotrophs while those that depend on others are heterotrophs, and this single division separates plants from animals at the most basic level.
Photosynthesis
- Photosynthesis is the process by which green plants make food using carbon dioxide and water in the presence of sunlight and chlorophyll.
- The products are glucose and oxygen, and the oxygen released is what almost all aerobic life breathes.
- The essential conditions are sunlight, chlorophyll, carbon dioxide and water.
- Chlorophyll in the chloroplast traps light energy and converts it into chemical energy.
- Carbon dioxide enters through the stomata and water is drawn from the soil by the roots and carried up by xylem.
- The food made is stored as starch, which is why the iodine test turns a leaf blue black.
- Heterotrophic nutrition is of several kinds: holozoic as in humans, saprophytic as in fungi feeding on dead matter, and parasitic as in cuscuta and ticks.
Human Digestion
- Digestion begins in the mouth, where teeth break food down and saliva with its enzyme starts converting starch to sugar.
- The oesophagus carries food to the stomach by rhythmic muscular movement called peristalsis.
- The stomach releases hydrochloric acid, which kills germs and creates the acidic medium needed by pepsin to digest protein.
- The small intestine is the main site of digestion and absorption, and it receives bile from the liver and enzymes from the pancreas.
- Bile does not contain enzymes but breaks large fat droplets into small ones, a process called emulsification.
- Absorption takes place through finger like projections called villi, which greatly increase the surface area.
- The large intestine absorbs water and the remaining waste is expelled through the anus.
| Organ | Main Secretion | Main Action |
|---|---|---|
| Mouth | Saliva | Starts starch digestion |
| Stomach | Hydrochloric acid and pepsin | Protein digestion, kills germs |
| Liver | Bile | Emulsifies fat |
| Small intestine | Intestinal juice | Completes digestion and absorbs |
Photosynthesis — the process by which green plants make food from carbon dioxide and water using sunlight and chlorophyll.
Hindi me samjhein
पित्त में एंजाइम नहीं होता, फिर भी वह वसा के बड़े कणों को छोटे कणों में तोड़ देता है ताकि एंजाइम उन पर काम कर सकें। इसी को इमल्सीकरण कहते हैं।
Exam me kaise aata hai
- Photosynthesis takes place in which organelle — chloroplast
- Bile is secreted by the — liver
- Finger like projections in the small intestine are — villi
- Food made in photosynthesis is stored as — starch
UPSC/State PSC ke liye
- Bile has no enzyme yet is essential, because emulsification greatly increases the surface on which fat digesting enzymes can act.
- The small intestine is long and villus lined precisely because absorption depends on surface area, not on length alone.
Yahan confuse hote hain
✗ Bile contains digestive enzymes | Bile has no enzyme; it only emulsifies fat | ✓
✗ Digestion of protein begins in the mouth | Protein digestion begins in the stomach | ✓
✗ All plants are autotrophs | Cuscuta is a parasitic plant and is not autotrophic | ✓
Ek nazar me
- Autotrophs make food; heterotrophs depend on others.
- Photosynthesis needs sunlight, chlorophyll, carbon dioxide and water.
- Starch is the stored product; oxygen is released.
- Digestion completes in the small intestine and absorption happens through villi.