QUESTION 2
a.Complete the table below.
Element |
Function in plants |
Effects of deficiency in plants |
Iron |
|
|
Molybdenum |
|
|
Potassium |
|
|
Copper |
|
|
Nitrogen |
|
|
[10 marks]
b. Name three classes of organic foods which are essential constituents in the diet of a mammal. [3 marks]
c. State two roles each of the following structures of the digestive system in humans:
- buccal cavity;
- duodenum;
- stomach. [6 marks]
d. Name the end product of adding dilute hydrochloric acid to sucrose. [1 mark]
Few candidates attempted this question.
In question 2(a), Some candidates gave correct response to the functions and deficiency effects of the listed mineral elements. The function of molybdenum i.e. converts nitrogen to amino acids, could not be correctly stated by many candidates.
Most candidates gave correct answers in question 2(b).
Some candidates wrote wrong answers in question 2(c)(i), (ii) and (iii). They mention the function of the buccal cavity as helping to mix food with saliva and in swallowing and the function of duodenum as site for digestion of all food.
Many candidates on
The expected answers include:
(a) Table
Element |
Functions in plants |
Effect of deficiency in plants |
Iron |
Necessary for the synthesis of chlorophyll/protein |
Chlorosis/yellowing of leaves/poor growth; |
Molybdenum |
Converts nitrogen to amino acids |
Stunted growth/pale leaves; |
Potassium |
Protein synthesis/formation of cell membrane/crop maturation/activates respiration/ photosynthesis |
Premature death of plant/leaf margin turns yellow/brown; |
Copper |
Activates enzymes for respiration/carbohydrate metabolism/photosynthesis |
Pale/wilted/spotted leaves; |
Nitrogen |
Necessary for the formation of chlorophyll/amino acids/protein |
Poor/stunted growth/yellowing of leaves/poor flower formation. |
(b) Classes of organic food in diet of mammals
- Carbohydrate;
- Protein;
- Lipids/fats and oil;
- Vitamin.
(c) Roles of structures of digestion in humans
(i) Buccal cavity
- Takes in/receives food;
- Contains the teeth that chew/masticate the food; to increase the surface area of food particles;
- Contains salivary gland that secretes saliva that moistens the food; it also secretes the enzyme ptyalin which breaks down starch to maltose;
- Contains the tongue which tastes /rolls the food into bolus for swallowing.
(ii) Duodenum
- Receives the food as chyme from the stomach;
- Receives pancreatic juice from pancreas;
- Receives bile from the liver which reduces surface tension/emulsifies fats and oil;
- Contains amylase in pancreatic juice which hydrolyses starch to maltose;
- Contains trypsin which breaks down proteins to polypeptides;
- Contains lipase which breaks down fats and oil to carboxyl acid and glycerol;
- Provides large surface area for absorption of some digested food/vitamins and nutrients
(iii) Stomach
- Temporarily stores food;
- Secretes dilute HCl/hydrochloric acid which destroys bacteria;
- Churns food;
- Contains enzymes which start the digestion of protein.
(d) End product of adding dilute hydrochloric acid to sucrose
Glucose and fructose are produced.