Form 1:
Nutrition in Animals

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1. a) Name the bacteria found in the root nodules of leguminous plant. (1mk)

Rhizobium

b) State the association of the bacteria named in a) above with the leguminous plants. (1mk)

Symbiosis

2. a) State the function of co-factors in cell metabolism.

Activate enzymes

b) Give one example of metallic co-factor.

Magnesium/zinc

3. Name the disease in humans that is caused by lack of vitamin C. (1mk)

Scuvy

4. Name a disease caused by lack of each of the following in human diet;

Vitamin D (1mk)

Rickets

Iodine (1mk)

Goitre

5. Explain how birds of prey are adapted to obtaining their food. (2mks)

Sharp/ hooked/ strong beaks for killing/ripping off flesh from bones, sharp claws for grabbing/holding prey.

6. Explain biological principles behind the preservation of meat by;

i) Salting

This removes / absorbs water by osmosis from micro-organism cell which then die due to dehydration. Meat also becomes dehydrated and thus unsuitable for microbial growth.

ii) Refrigeration

Low temperature renders the micro-organism inactive(Enzymes do not work at low temperature).

iii) Canning

Boiling kills all micro-organism in the food. Sealing under pressure excludes all micro-organisms and ensures that growth takes place.

7. State one similarity and one difference between parasitic and predatory modes of feeding (3mks)

Similarity: Both are heterotrophic.
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)

Pancreatic juice containing digestive enzymes is prevented from reaching food. Insulin and glycogen hormones which regulate sugar are released directly into the blood stream.

9. Give a reason why lack of roughage in diet often leads to constipation.

Roughage provide grip needed for peristalsis/lack of roughage results in slow/no movement of food leading to constipation. (Accept: add bulk to peristalsis to take place)

10. a) What does the term digestion mean? (2mks)

Breakdown of (complex) food substance by enzymes to simpler compounds which can be absorbed.

b) Describe how the mammalian small intestine is adapted to its function. (18mks)

i)Small intestine is long/coiled to offer large surface area for digestion and absorption.
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)

i) Quicken healing of wounds.
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)

Homodont-Organism has same number of teeth, type of teeth and the same size.Heteredont-organism has teeth of different sizes and shapes that is incisors, canines, premolars and molars.

b) What is the function of carnasial teeth? (1mk)

Slice flesh and crush bones

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.

I=0/3, C =0/1, PM = 3/3, M= 3/3

13. a) State two functions of bile juice in the digestion of food.(2mks)

i)Has alkaline salts that help create alkaline media to neutralize acidic food from stomach.
ii)Enhance emulsification of fats into droplets.

b) How does substrate concentration affects the rate of enzyme action? (1mk)

As the substance concentration decreases the rate of enzyme action decreases.

14. Name the end-products of the light stage in photosynthesis. (2mks)

Hydrogen ions, ATP molecules andOxygen gas

15. The diagram below represents a section through a human tooth.

a) i) Name the type of tooth shown.

Premolar tooth

ii) Give a reason for your answer in (a) (i) above. (1mk)

i)Presence of two roots
ii)Presence of cusps on the crown.

16. a) Name a fat soluble vitamin manufactured by the human body. (1mk)

Vitamin D, Vitamin K

b) State two functions of potassium ions in the human body. (2mks)

i) Transmission of nerve impulses.
ii) Ionic balance/osmotic balance.
iii) Contraction of muscles.

17. a) The action of ptyalin stops at the stomach. Explain. (1mk)

In the stomach there is acid medium and ptyalin only acts at slightly alkaline medium.

b) State a factor that denatures enzymes. (1mk)

High temperatures above 400C.

c) Name the features that increase the surface area of small intestines.(2mks)

i) Villi
ii) Microvilli

18 Define the following terms (5mks)

a) Ingestion

Ingestion is the taking of food into the body.

b) Digestion

Digestion is the breakdown of large and insoluble molecules that can be absorbed.

c) Absorption

Absorption is the uptake of soluble food materials from lumen of digestive tract across the epithelial lining of the gut into blood stream.

d) Assimilation

Assimilation is the utilization of absorbed food molecules by the body to provide energy or the materials necessary for growth, repair and reproduction.

e) Egestion

Egestion in the elimination of undigested waste food materials from the body.

19 Explain the role of the following organs in the digestion of food in a mammal.

a) Salivary glands

They produce saliva. Saliva contains the enzyme salivary amylase(ptyalin) which begins the digestion of starch breaking it to maltose. It also lubricates food making it suitable for swallowing.

b) Pancrease

It produces pancreatic juice. Contains NaHCI3 which neutralizes the acid of chime and creates a PH of 7-8 which is the Optimum PH for the action of pancreatic juice are;
Trypsin which digests protein to peptides.
Amylase which digests starch to maltose.
Lipase which digests fats to fatty acids and glycerol.

c) Liver (3mks)

It produces bile.
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)

i) It lubricates food
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)

Hydrochloric acid in the stomach denatures salivary amylase stopping its activity.

22. Give an account of the adaptation of a named herbivore to its mode of feeding.(3mks)

A sheep has the following herbivorous adaptations.

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)

i) Pepsin-digests proteins to peptides
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)

This leads to lack of bile salts, which emulsify fats.

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
Vitamin A
Carrots, Liver, Egg yolk.
Synthesis of rhodopsin (for proper function of retinal).
Iron
Liver
Manufacture of hemoglobin
Iodine
Iodized salt, sea food
Manufacture thyroxin
Vitamin D
Fish, liver, plant oil, egg yolk
Aids assimilation of calcium phosphate for making teeth and bones.
Protein
Meat, milk seed of legumes, fish
Making new cells/growth and repair of tissues.
Introduction to Biology|Classification 1|The Cell |Cell physiology |Nutrition in Plants|Nutrition in Animals