Question 1
Define the term denature.
Answer
Denatutre - Change in protein structure so that some of its original properties /configuration stop functioning.
Question 2
In an experiment to investigate the action of pepsin on egg albumen, equal amounts of pepsin were added to equal amounts of egg albumen in different test-tubes. The test tubes were placed in water baths at different temperatures.
The graph below shows time taken for the enzyme to digest protein in each.
a) What is the optimum temperature for the enzyme?
b) Account for the time taken to digest egg albumen at 45oC.
c) In which form is the enzyme pepsin secreted.
d) Give a reason for your answer in (c) above.
e) Name four plant tissues which lack chloroplast.
f) State the function of the pad of gum in herbivorous feeding.
Answer
a) Optimum temperature 36 ± 1
b) At 45o C time taken is more than at 35oC because enzyme pepsin is being denatured.
c) Pepsinogen
d) Digest stomach /digest lumen in its active form (pepsin) in absence of protein food.
e)
b) At 45o C time taken is more than at 35oC because enzyme pepsin is being denatured.
c) Pepsinogen
d) Digest stomach /digest lumen in its active form (pepsin) in absence of protein food.
e)
- Epidermal tissue
- Parenchyma
- Schlerenchyma
- Xylem tissue
- Collenchyma
Question 3
During ecological study, students collected and marked 120 ants and released them. After 48 hours, the students captured another 90 ants, 20 of which had been marked previously.
(i) How many ants were there in the compound? Show your working.
(ii) What are the limitations of this method in sampling animal populations?
(iii) State two other methods which could be used to determine the population?
Answer
i)
ii)
iii) - Quadrant method
- Belt transect method
ii)
- Does not consider migration of organisms into and out of study area
- Does not consider the effects of paint used on the animals behavior
- Released animals may not mix freely with the remaining population
- Marked organisms may not have adequate time to mix with the rest
- Does not consider the effects of weather on the organisms behavior
iii) - Quadrant method
- Belt transect method
Question 4
The experiment below was set-up to investigate some physiological processes. The glucose solution was first boiled then cooled. The set-up was left for 24 hrs.
(a) Suggest two aims of the experiment
(b) (i) State the expected observations after 24 hours
(ii) Explain your observations in b (i) above
(iii) Why was glucose solution boiled then cooled?
(c) Suggest a control for the above experiment.
Answer
(a) - To find out whether energy or heat is released in anaerobic respiration /fermentation
- To investigate the gas produced during fermentation/anaerobic respiration.
(b) (i) - significant rise in temperature
- color of bicarbonate indicator turns yellow.
(ii) Yeast will respire aerobically releasing energy /and carbon dioxide gas that turn indicator yellow.
(iii) Expel /drive out oxygen
(c) Use glucose solution without yeast cells/killed yeast cells.
- To investigate the gas produced during fermentation/anaerobic respiration.
(b) (i) - significant rise in temperature
- color of bicarbonate indicator turns yellow.
(ii) Yeast will respire aerobically releasing energy /and carbon dioxide gas that turn indicator yellow.
(iii) Expel /drive out oxygen
(c) Use glucose solution without yeast cells/killed yeast cells.
Question 5
The diagram below shows an experimental set up to investigate an aspect of germination
(a) Why are the following used in this experiment?
(i) Potassium hydroxide pellets?
(ii) Moist cotton wool?
(b) With reference to points x and y state the direction the dye would move towards during the experiment.
(c) Give reasons for your answer in (b)
Answer
(a) Why the following used in this experiment;
(i) Potassium hydroxide pellets - Absorb carbon (IV)oxide produced by germinating seedlings.
(ii) Moist cotton wool - Provide moisture /water for seeds to germinate
(b) Towards Y; / X → Y
(c) Seeds use up oxygen in flask for respiration during germination creating a vacuum in the flask, air is drawn in the tube at point A (causing the red dye to move towards Y).
(i) Potassium hydroxide pellets - Absorb carbon (IV)oxide produced by germinating seedlings.
(ii) Moist cotton wool - Provide moisture /water for seeds to germinate
(b) Towards Y; / X → Y
(c) Seeds use up oxygen in flask for respiration during germination creating a vacuum in the flask, air is drawn in the tube at point A (causing the red dye to move towards Y).