Form 1:
Nutrition in Plants

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1. An experiment was carried out to investigate the rate of reaction shown below.

Sucrose → Fructose + Glucose

For the products; fructose and glucose to be formed, it was found that substance K was to be added and the temperature maintained at 370C. When another substance L was added, the reaction slowed down and eventually stopped.

a) Suggest the identity of substances K and L. (2mks)

K

Enzyme , sucrose, invertase

L

Inhibitor

b) Other than temperature state three ways by which the rate of reaction could be increased. (3mks)

Additional of sucrose/substance, Addition of enzyme, OptimumPH, Removal of products.

c) Explain how substance L slowed down the reaction. (1mk)

Compete with substrate for active site of the enzyme.

2. a) State the role of light in the process of photosynthesis. (2mks)

Split water molecules/photolysis

b) Name one product of dark reaction in Photosynthesis (1mk)

Glucose

3. State one effect of magnesium deficiency in green plants.

Yellowing of leaves/stunted growth/chlorosis/lack of chlorophyll.

4. The graph below shows the effect of substrate concentration on the rate of enzyme reaction.

a) Account for the shape of the graph between

i) A and B (3mks)

More active sites of enzymes available for a large number of molecules of substrate. There is increase in rate of reaction

ii) B and C (2mks)

Enzyme/substance are in equilibrium. All active sites are occupied hence rate of reaction is constant.

b) How can the rate of reaction be increased after point B? (1mk)

Raising concentration of enzymes

c) State two factors that affect the rate of enzyme reaction. (2mks)

PH, temperature, inhibitors/co-factors.

5. a) State the function of co-factors in cell metabolism. (1 mk)

Substances that activate enzymes.

b) Give one example of a metallic co-factor. (1 mk)

Iron/Magnesium/Zinc/Copper.

6. Name two mineral elements that are necessary in the synthesis of chlorophyll.(2mks)

Magnesium
Nitrogen
Iron

7. What is the role of the vascular bundles in plants nutrition? (3mks)

Xylem
Transport water to photosynthesizing cells from stem.
Offer support to the lamina for maximum exposure to sun-light.
Phloem
Transport manufactured food away from the leaf to create high concentration gradient.

8. Describe what happens during the light stage of photosynthesis. (3mks)

Takes place in the grana of the chloroplast. Light is absorbed and used to split water molecules into hydrogen ions and oxygen, photolysis. Energy is formed and is stored in form of ATP.

9. Photosynthesis takes place in two stages. Name the part of the chloroplast where

i) Light stage occurs

grana

ii) Dark stage occurs (2mks)

stroma

b) How is dark stage dependant on the light stage of photosynthesis? (2mks)

Uses the energy formed or produced during light stage.
Uses the hydrogen ions produced in light stage for carbon dioxide fixation.

10. A solution of sugarcane was boiled with hydrochloric acid; sodium carbonate was heated with Benedict’s solution. An orange precipitate was formed.

a) Why was the solution boiled with hydrochloric acid? (1mk)

To hydrolyse/break down the disaccharide (non-reducing sugar).

b) To which class of carbohydrates does sugarcane belong?

Non-reducing sugar

c) Name the type of reaction that takes place when:

i) Simple sugars combine to form complex sugar. (1mk)

Condensation

ii) A complex sugar is broken into simple sugar. (1mk)

Hydrolysis

d) State the form in which carbohydrates are stored in:

i) Plants

Starch

ii) Animals (2mks)

Glycogen

11. i) Name structural units of lipids (1mk)

Fatty acids and glycerol

ii) State three important functions of lipids in living organisms. (3mks)

i) Form part of the cell membrane .
ii) Provide insulation of bodies of animals.
iii) A source of metabolic water.
iv) Provide energy in absence of carbohydrates.

12. The diagram below shows an experiment carried out to investigate photosynthesis in a potted plant which has been kept in the dark for 48 hours.The setup was left in the sunshine for 6 hours. The leaf was tested for starch using iodine solution at the end of the experiment.

a) What would be the colours of the regions of the leaf marked L. M and N?(3mks)

L - Blue-black
M -Yellow
N - Blue Black

b) What is the function of the sodium hydroxide pellets? (1mk)

carbon (IV) oxide in the jar.
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