Biology Practicals

Question 1

Effect of temperature on enzymes

Answer 1

Optimum temperature for enzymes is 37ºC (body temperature).
At cold temperatures, enzymes have little kinetic energy, the enzyme doesen’t collide.
At high temperatures, the enzymes get denatured(destroyed), their shape is changed.

Question 2

Effect of pH on enzymes.

Answer 2

If enzymes are not at their optimum pH they will become denatured.

Question 3

Effect of light on plant gas exchange (Hydrogen Carbonate)

Answer 3

• If light is pressent, the plant will photosynthesise and will absorb carbon dioxide. Hydrogen carbonate indicator will stay red.
• If no light is present, the plant will respire releasing carbon dioxide. Hydrogen carbonate indicator will turn orange/yellow.

Question 4

Effect of exercise on the release of carbon dioxide

Answer 4

By increasing exercise intesity or amount, breathing rate increases. Thus the amount of carbon dioxide released is higher.

Question 5

Investigate the energy content in a food sample

Answer 5

• The food sample is burned.
• After it finishes burning, temperature difference of water(end temp. - starting temp.) is measured.
• Energy content (J) = Mass (g) x temp rise(ºC) x specific heat capacity

Question 6

Test for glucose

Answer 6

Benedicts solution turns from blue to brick red.
- Add sample and water to test tube.
- Mix.
- Add bendicts solution and leave in water bath.

Question 7

Test for proteins

Answer 7

• Biruet solution(potassium hydroxide and copper sulphate) turns from blue to purple.
• Mix sample with biruet solution.

Question 8

Test for lipid

Answer 8

• Etanol and water solution turn from colourless to white cloudy
• Add sample and ethanol to test tube.
• Mix.
• Add solution to a test tube with cold wter.

Question 9

Test for starch

Answer 9

Iodine turns from orange to black.
Add iodine to starch.

Question 10

Rate of photosynthesis.

Answer 10

As temperature, light intesity or carbon dioxide increse; rate of photozynthesis also increases until it reaches a limit. Rate of photosynthesis is beign limited by another factor.

To measure rate of photosyntheis count numbe of bubbles produced by pondweed(any aquatic plant) in a fixed amount of time.

Question 11

Destarch a plant

Answer 11

Keep it in the dark

Question 12

Boil leaf in water

Answer 12

Remove waxy cuticle and soften

Question 13

Leaf in ethanol

Answer 13

Decolorise leaf