nutrition

• The process of acquiring food that is needed for nourishment and sustainance of the organism i.e. to grow, develop, synthesize protein and other substances required by the body is called nutrition.
• There are 2 modes of nutrition: autotrophic and heterotrophic.
• If an organism can make it's own food using inorganic materials from the environment, and convert it into stored forms of energy, such a mode of nutrition is called autotrophic nutrition.
• The process by which green plants make their own food with the help of carbon dioxide and water in the presence of chlorophyll and sunlight is called photosynthesis.
• what is the site of photosynthesis and why?

  chloroplast in the leaf because it contains chlorophyll.
• steps/events of photosynthesis:

  I. absorption of light energy by chlorophyll.

  II. conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.

  III. reduction of carbon dioxide to carbohydrates.
• equation of photosynthesis

  6CO2 + 12H2O - C6H12O6 + 6O2 + 6H2O
• Stomata are tiny pores present on the surface of the leaves that help in exchange of gases.
• Each stoma is guarded by a pair of guard cells, which control the opening and closing of the pore.
• How do guard cells control the opening and closing of the stomata?

  The guard cells swell when water flows into them, causing the stomatal pore to open. Similarly, the pore closes if the guard cells shrink.
• Heterotrophic organisms are directly or indirectly dependent on autotrophs for food.
• 3 types of heterotrophic nutrition: holozoic nutrition, saprophytism, and parasitism
• Amoeba feeds through holozoic mode of nutrition.
• What is phagocytosis?

  Phagocytosis is the process by which the amoeba engulfs and digests food particles.
• Human alimentary canal consists of:

  Mouth, buccal cavity, oesophagus, stomach, small intestine and large intestine.
• Saliva contains an enzyme salivary amylase which breaks down starch into simple sugar.
• Buccal cavity consists of two jaws bearing teeth and three pairs of salivary gland (that secretes saliva) and a tongue.
• What is peristaltic movement?

  The rhythmic contraction and relaxation of the oesaphagus to push down partially digested food is called peristaltic movement.
• Gastric glands are present in the walls of stomach that release HCl, pepsin and mucus.
• Small intestine is the site for complete digestion of carbohydrates proteins and fats.
• Liver produces bile juice which creates an alkaline environment in the small intestine to facilitate the action of the pancreatic enzymes.
• Bile juice helps in emulsification of fats.
• Pancreas secrete trypsin (protein digesting enzyme), lipase (fat digesting enzyme), and amylase (starch digesting enzyme).
• What are villi?

  They are small finger-like projections present in the inner wall of intestine.
• Villi increase the internal surface area of the intestinal walls making available a greater surface area for absorption and is richly supplied with blood vessels which takes the absorbed food to each and every cell of the body.