Topic 2 Test B [40 marks]

Transcription

1 Topic 2 Test B [40 marks] 1. The graph shows the effect of increasing the substrate concentration on the rate of an enzyme-catalysed reaction. What is occurring during the phase indicated by section Y of the graph? A. The active site of the enzyme is saturated. B. The enzyme becomes denatured. C. The substrate concentration has risen too high. D. The optimum rate is reached. A 2. A polymer of alpha-d-glucose found in plants has mostly 1,4 linkages and some 1,6 linkages. Which molecule fits this description? A. Glycogen B. Cellulose C. Amylose D. Amylopectin D

2 3. Which molecule diagram corresponds to the name? B 4. Which molecule can be hydrolyzed? A. Glycerol B. Maltose C. Fructose D. Galactose B 5. Which molecule is a polysaccharide? A. Cellulose B. Fructose C. Maltose D. Sucrose

3 A 6. What is a consequence of the specific heat capacity for liquid water, ice and water vapour? A. Less energy is needed to warm water vapour than liquid water. B. Salt dissolves more readily in liquid water than in ice. C. Small insects can walk on liquid water. D. Ice floats on liquid water. A 7. What describes non-competitive inhibition? A. Inhibiting molecule does not resemble substrate and binds to an area other than active site B. Inhibiting molecule resembles substrate and binds to active site C. Inhibiting molecule does not resemble substrate and binds to active site D. Inhibiting molecule resembles substrate and binds to an area other than active site A 8. Which are functions of lipids? A. Hydrophilic solvent and energy storage B. Hydrophobic solvent and membrane potential C. Thermal insulation and energy storage D. Thermal insulation and hydrophilic solvent C 9. Which of the following is an organic compound made by all plants? A. Carbon dioxide B. DNA C. Lactose D. Oxygen B

4 Between which atoms do hydrogen bonds form in water? 10. A. Oxygen and hydrogen atoms in the same water molecule B. Oxygen and hydrogen atoms in different water molecules C. Hydrogen atoms in the same water molecule D. Oxygen atoms of different water molecules B Keratin is a protein found in hair, nails, wool, horns and feathers. The graphs show the relative keratinase activity obtained in experiments into keratin digestion at different ph values and different temperatures. Determine the optimum ph and temperature of keratinase. 11a. ph=8 AND temperature=46 C Both needed. Accept answers in the range of 7.8 to 8.5 ph and 44 to 48 C. Units required. Suggest two changes occurring in the reaction vessel that could be used to indicate keratinase activity. 11b. a. the amount of keratin measured OWTTE OR decrease in keratin mass OR size of keratin containing object b. the increase in peptides/amino acids/product c. changes in colour/absorbance/smell 11c. State two conditions that should be kept constant in both experiments.

5 a. amount/concentration of enzyme b. amount/concentration of keratin/substrate c. amount of buffer d. time/duration of experiment The image shows a nomogram. 12a. (i) Using the nomogram, state the lower weight limit for a woman with the height of 155 cm who is classified as overweight, giving the units. Lower weight limit:... (ii) State a major health problem of the circulatory system that is correlated with obesity. (i) 60 kg Units required. (ii) coronary heart disease or coronary artery disease or thrombosis or stroke or hypertension or high blood pressure or atheroma or fatty deposits in arteries or plaque «in arteries» or arteriosclerosis or atherosclerosis 12b. Draw the structure of a saturated fatty acid.

6 [CH 2] n / hydrocarbon chain with single bonds and at least four carbons COOH head at one end AND three hydrogens on other end The minimum of four carbons includes the end of the hydrocarbon chain and the COOH group. The following diagram shows the synthesis and regulation of some amino acids. 13a. State the type of inhibition shown in this diagram. end-product/non-competitive/(negative) feedback inhibition Explain how this type of regulation could affect the synthesis of an amino acid. 13b. amino acid/end product produced if used up/not enough present; production stops if amino acid/end product unused/accumulates/in excess; amino acid/end product changes active site of (first) enzyme of pathway; (this is an example of) negative feedback;

7 Obesity (excessive weight) is recognized as a global health problem and has been correlated with a large number of health issues, diseases and deaths. The increased consumption of fructose, now widely used as a sweetener, has been associated with the increase in obesity. In a study, mice were divided into four groups. Each group was given the same amount of food and either a soft drink with a different sweetener or water. 14a. Describe the overall trend in body fat accumulation for the four groups of mice. positive/direct relationship / correlation (in all four groups) / (all four groups) accumulated fat over time 14b. Compare the body fat accumulation between the four groups. a. body fat accumulation increased over time for all four groups; b. fructose caused the (significantly) greatest accumulation of fat and water the least; (both needed) c. sucrose and artificial sweetener/diet soft drink had the same increase; d. sucrose, artificial sweetener and water did not start accumulating fat until after 20 days while fructose increased from the beginning;

8 As it has been shown that high triglyceride levels correlate to obesity, another study was undertaken with humans. Over a ten-week period, one group was given glucose-sweetened drinks and the other fructose-sweetened drinks. Triglyceride levels in blood were measured throughout the study. 14c. Distinguish between the results for the two groups. a. glucose-fed group has no/little increase in triglycerides while fructose-fed group has a (large) increase; b. glucose-fed group has smaller variability than the fructose-fed group; c. more triglycerides in fructose-fed group than glucose-fed group (from week 2 to week 10); 14d. This study also showed a significant reduction in insulin sensitivity when participants were given fructose-sweetened drinks, but not when they were given glucose-sweetened drinks. Describe possible effects of the reduction of insulin sensitivity. a. raised blood glucose/sugar levels/higher glucose in the urine; b. decreased glycogen; c. excess glucose will be converted to fat/increase obesity; d. possibility of developing diabetes type II / late/adult onset diabetes; ( do not award this mark if answer refers to type 1 diabetes)

9 Studies investigated the role of glucose and fructose in the development of pancreatic cancer cells. Pancreatic cancer cells were grown in equal concentrations of each sugar and the uptake of each into ribose-producing pathways was measured. The graph shows the range of uptake of sugars and the mean value. 14e. Discuss whether the results provide clear evidence of a difference in uptake. a. glucose has a much greater range of uptake / vice versa; b. but a (much) lower mean/uptake / vice versa; c. there is no overlap (so there is clear evidence); 14f. Using all of the data, evaluate the evidence that suggests the consumption of large amounts of fructose poses a risk to human health. [3 marks] a. evidence that fructose causes (body) fat accumulation/obesity; b. evidence that fructose is related to increased (blood) triglycerides which are correlated with obesity/coronary heart disease; c. evidence that fructose is related to reduced insulin sensitivity/diabetes; d. evidence that fructose is used in ribose synthesis but no clear evidence that fructose causes pancreatic cancer; 15. Outline the differences between competitive and non-competitive inhibitors. [4 marks] Award marks for paired statements only. Answers do not need to be shown in a table format. 16. List two possible variants in the molecular structure of unsaturated fatty acids.

10 number of carbons (in the chain/length of chain); number of double bonds (in the chain) / may be monounsaturated/ polyunsaturated; cis/trans structure in unsaturated fatty acids / OWTTE; location of double bonds; counting inwards from opposite end of COOH group/omega 3/omega 7; International Baccalaureate Organization 2017 International Baccalaureate - Baccalauréat International - Bachillerato Internacional Printed for Dubai American Academy