Question 1
1
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.
14 marks
Question 1(g)
1(g)
Suggest how sugar uptake might be related to pancreatic cancer.
Hardstructured2 marks
Answer
cancer is uncontrolled mitosis/cell division; sugar is an energy source/nutrient needed for mitosis/cell division; ribose is used to produce nucleic acids/DNA/RNA; production of nucleic acid is necessary for mitosis;
Question 1
1
Diabetes in Youth is a study that examined diabetes (type I and type II) among children and adolescents in the United States. The graphs show the rate per year of new cases of type I and type II diabetes among young people (aged less than 20 years) by ethnicity between 2002-2005.
15 marks
Question 1(e)
1(e)
State the relationship between plasma fatty acid level and enzyme activity.
Mediumdata_response1 marks
Answer
negative/inverse relationship/negative correlation/ as one variable increases the other decreases / as plasma fatty acid increases, enzyme activity decreases / vice versa
Question 1(f)
1(f)
Calculate the percentage change of enzyme activity after 5 hours exposure to lipids.
Mediumcalculation1 marks
Answer
(a decrease of) 45 (\%) (accept answers in the range of 44 (\%) to 47 (\%))
Question 1(g)
1(g)
Discuss, using the data, whether the effect of lipids on this enzyme is reversible.
Harddata_response2 marks
Answer
yes, effect is reversible as activity returns to (approximately) original level (when lipids/fatty acids decrease); when lipid/fatty acids washed out enzyme is more active/activity increases; difference between starting and final levels of enzyme activity is insignificant because of error bars; three hours/experimental time may be insufficient to reverse the effect;
Question 1
1
Isoprene is a chemical synthesized and emitted in large amounts by some plant species, especially oak (Quercus sp.) and poplar (Populus sp.) trees. It has been suggested that isoprene increases the tolerance of plants to high temperatures, which can cause a decrease in photosynthesis rates. Black poplar (Populus nigra) plants were subjected to two raised temperatures and to drought. Measurements of photosynthesis and isoprene emission were made during a 35-day-long drought stress (drought period) and 3 and 15 days after re-watering stressed plants (recovery period). The rate of photosynthesis was recorded as the carbon dioxide taken up per unit of leaf area per second.
18 marks
Question 1(g)
1(g)
Using the results in the graph, deduce the effect of the presence of fosmidomycin on the rate of photosynthesis in the leaves.
Mediumdata_response2 marks
Answer
no effect before (the first) heat treatment; lower rate/greater reduction in rate during heat treatments with fosmidomycin; lower photosynthesis/fosmidomycin reduces recovery after heat treatments; Ignore statements that fosmidomycin reduces the rate of photosynthesis if this is not related to heat treatments.
Question 1(h)
1(h)
Suggest possible conclusions for this experiment. To test the effect of isoprene on a plant that does not normally produce it, leaves of common beans (Phaseolus vulgaris) were treated with heat stress at 46^ C and were supplied with isoprene in the airstream. The percentage recovery compares the rate of photosynthesis before and after heat treatment. The data show the recovery of photosynthesis at different isoprene concentrations 1 hour and 24 hours after the heat treatment.
Harddata_response2 marks
Answer
high temperature/heat stress/treatment reduces rate of photosynthesis; repeated heat treatments cause greater reduction in photosynthesis; isoprene causes less change/less reduction in photosynthesis due to heat / 46^ C /higher rate of photosynthesis during heat treatment with isoprene (than without); isoprene helps photosynthesis to rise again after heat (treatments);
Question 1
1
The rate of hydrolysis of fish proteins using the enzymes papain and pancreatin was monitored using the apparatus shown. The pH decreased with the progress of hydrolysis, so alkali in the burette was added as necessary in order for the hydrolysis to proceed at constant pH . The rate of protein hydrolysis was measured as the amount of alkali added. Measurements were taken at constant conditions of temperature and pH for two enzyme concentrations, 1 % and 0.1 %.
0 marks
Question 1(a)
1(a)
State the effect of enzyme concentration on the hydrolysis of proteins.
Easystructured1 marks
Answer
positive correlation OR faster hydrolysis at higher concentration
Question 1(b)
1(b)
Sketch on the graph the curve expected if the hydrolysis were performed using papain 0.5 %.
Mediumstructured1 marks
Answer
curve with similar shape between papain 0.1 % and 1 % eg: Curve to start at 0. Allow a similar/same shaped curve to papain 1 \% to be anywhere within the shaded area shown on the graph.
Question 1(c)
1(c)
Explain what would happen to fish protein hydrolysis if no alkali were added to the reaction vessel.
Mediumstructured3 marks
Answer
a. hydrolysis of protein produces hydrogen ions/amino acids b. pH decreases / increased acidity c. causing denaturation of enzyme/pancreatin/papain d. decrease of reaction «rate»/no hydrolysis e. enzymes work best at the optimum pH / OWTTE 3 max
Question 1
1
Urease is an enzyme that breaks down urea into ammonia and carbon dioxide. The ammonia produced causes the pH of the solution to rise. This reaction can be followed using a pH indicator or a pH probe. In an experiment conducted by a student the time taken for the pH indicator, thymol blue, to change from yellow to blue was recorded at different temperatures.
7 marks
Question 1(a)
1(a)
Outline what the standard deviations reveal about the data from this experiment.
Mediumstructured2 marks
Answer
a. standard deviation indicates the degree of variation in the data OR the spread of data around the mean b. high standard deviation at \(30^{\circ} \mathrm{C}\) «in proportion to the average» indicates less reliable data c. Iow standard deviation for results from 40 to \(70^{\circ} \mathrm{C}\) indicates more reliable data 2 max
Question 1(c)
1(c)
Outline the effect of temperature on the activity of urease enzyme.
Easystructured2 marks
Answer
a. the reaction / activity increases with temperature b. rate slows from \(60^{\circ} \mathrm{C}\) to \(70^{\circ} \mathrm{C}\) c. fastest increase in activity is between \(30^{\circ} \mathrm{C}-40^{\circ} \mathrm{C} \) d. optimum temperature is \(60^{\circ} \mathrm{C}\)
Question 1(d)
1(d)
State one factor that would need to be controlled in this experiment.
Easystructured1 marks
Answer
a. concentration / volume of urea «solution» b. concentration / volume of urease «solution» c. concentration / volume of indicator d. lighting conditions / background «to test tubes» 1 max
Question 1
1
A study was carried out on the activity of catalase in bacteria living in extreme environments. Catalase decomposes hydrogen peroxide \(\left(\mathrm{H}_{2} \mathrm{O}_{2}\right)\). The data were obtained for a strain of bacteria called Vibrio rumoiensis which exhibits high catalase activity.
0 marks
Question 1(a)
1(a)
Describe the relationship between increasing \(\mathrm{H}_{2} \mathrm{O}_{2}\) concentration and catalase activity.
Mediumstructured2 marks
Answer
a. as \(\mathrm{H}_{2} \mathrm{O}_{2}\) concentration increases catalase activity increases / positive correlation (up to 70 mM ) b. peak activity at approximately 70 mM c. activity decreases after the peak 2 max
Question 1(b)
1(b)
Identify two factors that would need to be controlled in generating these data.
Mediumstructured1 marks
Answer
temperature / pH / enzyme concentration / enzyme volume / quantity of bacteria 2 answers for 1 mark.
Question 1(c)
1(c)
Evaluate the claim that, based on the data, the optimum \(\mathrm{H}_{2} \mathrm{O}_{2}\) concentration for catalase is 70 mM .
Mediumstructured2 marks
Answer
a. maximum peak / optimum around 70 mM b. but overlapping error bars around 70 mM c. no clear optimum / range between 60-90 mM d. may only be true for this strain Vibrio rumoiensis / other variables not reported (e.g. another form of catalase) 2 max
Question 1
1
Two models of plasma membrane structure are shown.
0 marks
Question 1(c)
1(c)
Phospholipase C is an enzyme that digests the polar heads of phospholipids. Scientists used phospholipase C to test these models of membrane structure. They found that the enzyme could digest the heads of phospholipids in the plasma membranes of red blood cells.
0 marks
Question 1(c)(ii)
1(c)(ii)
Suggest one reason for maintaining a pH of 7.5 throughout the experiment.
Mediumstructured2 marks
Answer
a. pH values away from optimum pH affect enzyme OR so enzyme can function properly OR pH 7.5 is the optimum pH for the enzyme b. sketch of enzyme activity versus pH c. change in pH affects 3D structure of protein/active site OR change in pH denatures the enzyme / protein d. substrate does not fit in active site OR interaction of substrate and active site affected Sketch of enzyme activity needs labels.
Question 1
1
Lipase was extracted from the fungus Aspergillus niger and used to hydrolyse one of its substrates. This was repeated for an immobilized form of lipase. The graph shows how the enzyme activity varied at different pH and temperature levels.
0 marks
Question 1(b)
1(b)
The graph of the effect of pH on immobilized lipase activity does not allow for the determination of optimum pH precisely. Explain how a more exact value for the optimum pH could be determined.
Mediumstructured2 marks
Answer
a. the experiment is repeated with smaller increments of pH b. «repeated» within the range of the optimum pH OR between pH 6/7 and 8 c. the pH that gives the highest enzyme activity is optimum 2 max
Question 1(c)
1(c)
Based on these experimental results, suggest one advantage of immobilizing lipase.
Mediumstructured1 marks
Answer
a. a. it increases the range of temperature/pH that give high activity b. allows for commercial use in detergents 1 max
Question 1
1
The biodiversity of insects worldwide is in decline. Destruction of habitats, pollution and climate change have contributed to the decline in global insect populations and to the extinction of insect species. A comprehensive literature review was carried out to determine the annual global rate of decline in insect species. The graph shows the results for three major orders of terrestrial insects and the total decline in insect biomass worldwide.
0 marks
Question 1(g)
1(g)
Suggest a reason that the mass of protein and lipid mixture eaten at 25: 1 is lower than at 50:1.
Hardstructured1 marks
Answer
a. the mixture was closer to what the bees ate naturally; b. the bees like the taste better/prefer sucrose; c. there was more lipid in the 25:1 mixture so they achieved their daily lipid/energy requirement with less mass of food; d. the bees eating 50:1 diet ate more to reach their daily lipid requirement; e. prefer the higher proportion of protein (in the 50:1) 1 max
Question 1
1
Cell metabolism involves anabolic and catabolic reactions. Which process directly involves anabolism? Active transport of ions Release of energy from glucose Production of intracellular enzymes Breakdown of worn-out cell organelles by lysosomes
Easymcq1 marks
Answer
C