Science (Biology)

Revision for Mid year Examination

1) Biological Molecules (Nutrients)2) Enzymes3) Nutrition in Man4) Nutrition in Plants

Topics

What are the components of the

nutrients we need?

CarbohydrateFatsProtein

Biological Molecules (Nutrients)

What are the function of these

nutrients?

Biological Molecules (Nutrients)

How do we test for the nutrients?Food Test

Benedict’s Test Starch Test Emulsion Test Biuret’s Test

Biological Molecules (Nutrients)

What are enzymes?

Enzymes are biological catalysts that speed up the rate of reaction without themselves being chemically changed at the end of the reaction.

Enzymes

Describe the effects of temperature on enzyme action.

At low temperature, enzymes are inactive. Thus, little enzyme action. As temperature increases, enzyme action also

increases.

Enzymes

Enzymes work best at their optimum temperature

Beyond their optimum temperature, enzymes are denatured.

Thus, enzyme action decreases.

Enzymes

Describe the effects of pH on enzyme action.

Enzymes work best at their optimum pH.

At extreme changes in pH, enzymes are denatured.

Enzymes

Explain the effects of temperature on enzyme action.

At low temperature, enzymes have very little kinetic energy and are inactive.

They move slowly and collide less frequently with the substrate molecules.

Substrate molecules bind to enzymes’ active site less frequently little enzyme action

Enzymes

As temperature increases, enzymes gain more

kinetic energy and moves around faster.

Thus, enzymes collide with the substrate molecules more frequently .

Substrate molecules bind to enzymes’ active site more frequently enzyme action increases.

Enzymes

Enzymes work best at their optimum temperature.

Beyond their optimum temperature, active sites of the enzymes are physically altered.

Enzymes lose its specificity and can no longer

bind the substrate.

Enzymes are denatured enzyme action decreases.

Enzymes

Describe / Explain how enzymes work.

Enzymes work based on the lock and key hypothesis.

Enzymes are like the lock and substrates are the keys.

Enzymes have active sites which have a specific shape complementary to its substrate.

Enzymes

- Enzymes and substrate will collide.

Substrate will bind to the enzymes at the active site.

Products are then formed and released from the enzymes’ active site.

Enzymes

Enzymes remain chemically unchanged at the

end of the reaction.

- Enzymes can then be reused.

Enzymes

Describe / Explain the role of bile in digestion  bile is produced in the liver and secreted into the

duodenum

bile emulsifies fats by breaking up fat droplets into smaller droplets

this increases the fats surface area for lipase to digest into fatty acids and glycerol

Nutrition in Man

Describe the parts played in the digestion of food by (i) the pancreas (ii) the liver The pancreas:

pancreas secretes pancreatic juice into the duodenum pancreatic juice contains amylase, trysin and lipase for

digestion pancreatic amylase will digest starch to maltose trypsin digests proteins to polypeptides pancreatic lipase digests fats into fatty acids and glycerol

Nutrition in Man

(ii) the liver

the liver produces bile which aids in the digestion of fats

bile helps to emulsify the fats by breaking it up into smaller fat droplets

this increases the surface area for lipase to digest

Nutrition in Man

thus, lipase can digest fats faster

liver plays a part in assimilation of glucose and amino acids

excess glucose is converted into glycogen by the hormone insulin

Nutrition in Man

glycogen is stored in the liver

excess amino acids is deaminated whereby the amino group is removed

the remains of the amino acid is converted to glucose and excess glucose is converted to glycogen

Nutrition in Man

normal amounts of glucose and amino acids

will leave the liver via the hepatic vein

the glucose is used for respiration to produce energy

the amino acids is used for growth, repair of worn out tissues and synthesis of protoplasm

Nutrition in Man

Describe what happens to fats as they pass through the following regions of the alimentary canal:  the mouth cavity the duodenum the rest of the small intestine the mouth cavity

no fat digestion occurs in the mouth due to absence of lipase  

Nutrition in Man

(ii) the duodenum bile produced in the liver is secreted into the

duodenum bile emulsifies fats by breaking it up into

smaller fat droplets this increases the surface area for lipase to

digest into fatty acids and glycerol

Nutrition in Man

(ii) the rest of the small intestine

in the ileum, the fatty acids and glycerol would be absorbed into the lacteals in the villi

villi are minute finger-like projections of the walls of the small intestine in the lacteal, fatty acids and glycerol recombines to form fats

fats will then be carried away by the lymphatic vessels

Nutrition in Man

Describe / Explain how the small intestine is adapted to carry out absorption of nutrients 

The small intestine is adapted for absorption in three ways:

firstly, its inner walls are extensively folded to increase surface area for absorption

secondly, its wall bears numerous villivilli are minute finger-like projections that increases the surface area for absorption

thirdly, the small intestine is long and coiled to provide sufficient time for absorption

Describe / Explain how the villi is adapted to carry out its function/s

Main function of villi is absorption of digested food substances

Villi is richly supplied with blood capillaries and lacteals

Glucose and amino acids are absorbed into the blood capillaries

fats are absorbed into the lacteal

blood capillaries and lacteals carry away the absorbed food substances quickly

this maintains the concentration gradient for diffusion to occur

wall of the villi is also only one-cell thick

this provides a short diffusion distance for diffusion to occur faster