1. a) Name the bacteria found in the root nodules of leguminous plant. (1mk)
b) State the association of the bacteria named in a) above with the leguminous plants. (1mk)
2. a) State the function of co-factors in cell metabolism.
b) Give one example of metallic co-factor.
3. Name the disease in humans that is caused by lack of vitamin C. (1mk)
4. Name a disease caused by lack of each of the following in human diet;
Vitamin D (1mk)
5. Explain how birds of prey are adapted to obtaining their food. (2mks)
6. Explain biological principles behind the preservation of meat by;
7. State one similarity and one difference between parasitic and predatory modes of feeding (3mks)
Difference: Predators kill to get food while parasites obtain foods without killing the host.
8. In an investigation, the pancreatic duct of a mammal was blocked. It was found that the blood sugar regulation remained normal while food digestion was impaired. Explain these observations. (3mks)
9. Give a reason why lack of roughage in diet often leads to constipation.
10. a) What does the term digestion mean? (2mks)
b) Describe how the mammalian small intestine is adapted to its function. (18mks)
ii) The walls are muscular for peristalsis.
iii)Inner walls posses mucus glands, goblet cell; that secret mucus for lubrication and protection of the walls from digestive enzymes.
iv)The inner walls have digestive glands that secrete digestive senzymes.
v) The inner walls has villi to increase surface area for absorption.
vi)The villi have numerous blood vessels for transport of the end products of digestion.
vii)The villi also have lacteal vessels, for transport of fats/lipids.
11. State the role of vitamin C in humans. (2mks)
ii) Forms connective tissues of the teeth and jaws.
iii) Provides resistance to body infections.
12. a) Distinguish between the terms homodont and heterodont. (1mk)
b) What is the function of carnasial teeth? (1mk)
c) A certain animal has no incisors, no canines, 6 premolars and 6molars in its upper jaw, in the lower jaw there are 6 incisors, 2 canines, 6 premolars and 6 molars. Write its dental formula.
13. a) State two functions of bile juice in the digestion of food.(2mks)
ii)Enhance emulsification of fats into droplets.
b) How does substrate concentration affects the rate of enzyme action? (1mk)
14. Name the end-products of the light stage in photosynthesis. (2mks)
15. The diagram below represents a section through a human tooth.
a) i) Name the type of tooth shown.
ii) Give a reason for your answer in (a) (i) above. (1mk)
ii)Presence of cusps on the crown.
16. a) Name a fat soluble vitamin manufactured by the human body. (1mk)
b) State two functions of potassium ions in the human body. (2mks)
ii) Ionic balance/osmotic balance.
iii) Contraction of muscles.
17. a) The action of ptyalin stops at the stomach. Explain. (1mk)
b) State a factor that denatures enzymes. (1mk)
c) Name the features that increase the surface area of small intestines.(2mks)
18 Define the following terms (5mks)
19 Explain the role of the following organs in the digestion of food in a mammal.
a) Salivary glands
Trypsin which digests protein to peptides.
Amylase which digests starch to maltose.
Lipase which digests fats to fatty acids and glycerol.
c) Liver (3mks)
Bile salts help in the breakdown of fat globules in the duodenum into tiny droplets, which provides a larger surface area on which the enzyme pancreatic lipase can act to digest the fats into fatty acids and glycerol.
20 State any three functions of the mucus, which is secreted along the wall of the alimentary canal. (3mks)
ii) It prevents digestion of the gut wall by proteolytic enzymes
iii) It makes food particles to adhere to one another during swallowing and during gestation.
21. Explain why the digestion of starch stops after food enters the stomach. (3mks)
22. Give an account of the adaptation of a named herbivore to its mode of feeding.(3mks)
i) It has a thick horny pad on the upper jaw over which vegetation is pressed by chisel-like incisors and canines on the lower jaw during feedings.
ii) It has a diastema which provides space for tongue movements that separate grass which is being chewed by teeth and grass that is newly gathered by front teeth.
iii) Its premolars and molars have large top surface, which is worn out unevenly forming cusps which help in crushing and grinding of vegetation.
iv) The joints of the jawbones are loose allowing up and down as well as sideways movement of the lower jaw, which aids in the grinding of vegetation.
v) Its rumen contains microorganisms that ferment cellulose releasing simple fatty acids that are absorbed by the animal.
23. What are the contents of gastric juice and what is their role in digestion. (6mks)
ii) Rennin-Coagulation of milk proteins to peptides
iii) Hcl-converts pepsinogen to pepsin
Kills bacteria in food
Provides an acidic pH (pH 1.5-2.5) which is the optimum pH foraction of Pepsin
Unfolds proteins enabling pepsin to work on them.
24. Liver damage leads to impaired digestion of fats . Explain the statement. (3mks)
25. For each of the following nutrients give one example of a good source and one example of its role in the body.
|Nutrient||Food source||Role in the body|
Carrots, Liver, Egg yolk.
Synthesis of rhodopsin (for proper function of retinal).
Manufacture of hemoglobin
Iodized salt, sea food
Fish, liver, plant oil, egg yolk
Aids assimilation of calcium phosphate for making teeth and bones.
Meat, milk seed of legumes, fish
Making new cells/growth and repair of tissues.