TMJC H2 Bio data response questions (Qn)

Tampines Meridian Junior College JC2 H2/9744 Biology Data Response Practice PRACTICE 1 Pyruvate dehydrogenase is a tetrameric enzyme found in the mitochondria that catalyses the conversion of pyruvate to acetyl CoA during cellular respiration. The activity of pyruvate dehydrogenase is inhibited by acetyl Co-A. Fig. 1 shows the relationship between the initial rate of reaction of pyruvate dehydrogenase activity and the concentration of pyruvate at the optimal temperature and pH of the enzyme. All other variables are kept constant. Fig 1

(a) Comment on the trend shown on the graph. [6] ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… (b) On Fig 1, sketch and label a curve to show the effect of adding acetyl Co-A on the initial rate of reaction of pyruvate dehydrogenase activity. [1]

PRACTICE 2 Fig. 2 shows the effect of increasing temperature on the activity of three protein -digesting enzymes: • thermitase from thermophilic Thermoactinomyces vulgaris • subtilisin from Bacillus subtilis • modified subtilisin Fig. 2 (a) Describe, with reference to Fig. 2, the effect of temperature on the rate of protein digestion by thermitase. [3] ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..…

(b) Modified subtilisin is similar to subtilisin, but had eight of its amino acids replaced with different amino acids. Describe and explain the effect of this modification on the activity of subtilisin. [4] ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… PRACTICE 3 In 1954, an article was published in the British Medical Journal entitled, The mortality of doctors in relation to their smoking habits. One aspect of the investigation studied a very large number of doctors in the UK aged 35 years and older. A survey established the quantity of tobacco smoked per day. Twenty-nine months later, the case of any deaths in the study group was recorded. Table 3 summarises the results obtained. Table 3 Cause of death Number of deaths Death rate per year per 1000 men in the study Non- smokers Smokers, tobacco smoked / g day-1 1-14 15-24 25 and above Coronary thrombosis (heart attack) 235 3.89 3.91 4.71 5.15 Lung cancer 36 0.00 0.48 0.67 1.14

(a) State which group in the study is most at risk from dying of lung cancer. [1] ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… (b) Using information from Table 3 to support your answer, discuss the evidence linking tobacco smoking to coronary thrombosis and early death. [4] ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… (c) Suggest a significant limitation of this study. [1] ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..…

PRACTICE 4 p53 is a tumor suppressor protein which plays an important role at cell cycle checkpoints. An experiment was carried out to investigate the effect of p53 on the cell cycle in human liver cells. Two types of cells were used in the investigation, one with normal p53 gene and the other with mutated p53 gene, resulting in p53-deficient cells. Both cell types were subjected to γ-radiation, which is a DNA damaging agent. Mitotic index of the cells were then measured and the results are shown in Fig. 4. Mitotic index reflects the percentage of cells in a population that are dividing. It is calculated by counting the number of cells with condensed chromosomes and dividing it by the total number of cells observed. Fig. 4 (a) With reference to Fig. 4, account for the difference in results obtained after 12 hours. [3] ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..…

PRACTICE 5 A chemical substance, 2 -carboxy-D-arabitinol 1-phosphate (also known as CA1P), is naturally found in plants and it is structurally similar (analogue) to ribulose bisphosphate (RuBP). Fig. 5 is a graph showing the effects of adding CA1P to a sample of purified chloroplasts. A control containing chloroplasts in the absence of CA1P was also set up. Light intensity, carbon dioxide concentration and temperature were kept constant. Fig. 5 (a) With reference to Fig. 5, describe and explain the effect of CA1P on carbon fixation. [4] ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..…

PRACTICE 6 A recent research study indicates that bed bugs have increased resistance to neonicotinoids, the most widely used insecticide in the world. Resistant strains were found to have elevated detoxifying enzymes. Scientists say non-chemical methods of control now need to be considered. Fig. 6 shows the volumetric units of insecticides used per thousand household per month, over a period of eleven years from 1984 to 1994. The figure also shows the percentage of infestations each year caused by resistant strains of Cimex lectularius. Fig. 6

(a) With reference to Fig. 6, (i) Describe and explain the trend in percentage of infestations each year caused by resistant strains of Cimex lectularius between 1986 and 1993. [3] ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..… (ii) Use evidence from the graph to suggest why the percentage of infestations each year caused by resistant strains of Cimex lectularius decreased in 1994 compared to previous years. [2] ………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..…