Question 1
1
Stem cells in the bone marrow can be forced into blood vessels in a process called mobilization. Mobilization of stem cells from the bone marrow into the blood vessels represents the basis for modern bone marrow transplantation procedures. To test the effect of light on the mobilization of stem cells, mice were subjected to a simulated "jet lag" by advancing the light-dark cycle by 12 hours. This was done by subjecting mice to a 24 -hour light period before the results shown in the graph were recorded. The results were compared to the stem cells in control mice under normal conditions of 12 hours of light ( □ ) and 12 hours of darkness ( ). ) and 12 hours of darkness ( ). > Nature by Nature Publishing Group. Reproduced with permission of Nature Publishing Group in the format Journal via Copyright Clearance Center.
13 marks
Question 1(a)
1(a)
2 marks
Question 1(a)(i)
1(a)(i)
State the maximum number of stem cells per ml blood in the control mice.
Easystructured1 marks
Answer
83 (allow whole number answers in the range of 82 to 84)
Question 1(a)(ii)
1(a)(ii)
Determine the number of hours of light needed to release the maximum number of stem cells in blood in control mice.
Easystructured1 marks
Answer
5 (allow 4) Do not allow answers with two different numbers.
Question 1(b)
1(b)
Distinguish between the trends shown in the number of stem cells per ml blood by the mice subjected to jet lag and the control mice.
Mediumstructured2 marks
Answer
more stem cells are formed in control / jet lag reduces the release of stem cells into blood stream / greater range in control; graph is rhythmic in control / control has more regular pattern; greater number of stem cells produced in light period in control, whereas greater number in dark period in jet lag; graph is shifted to the right in jet lag / stem cells are released later in time in jet lag;
Question 1(c)
1(c)
Other studies suggest that a greater number of blood stem cells for transplantation may be obtained if they are harvested during darkness. Evaluate this hypothesis.
Mediumstructured2 marks
Answer
(hypothesis supported in control) if stem cells are harvested towards the end of the dark period / (hypothesis supported) as stem cells start increasing in dark period; (hypothesis not supported) in control as peak of stem cells occurs during light period/lowest number during dark period; (hypothesis supported) if patient is jet-lagged as more stem cells are produced in dark period;
Question 1
1
Cells in the alveolus wall produce a surfactant. Its function is to prevent alveoli collapse at the end of expiration. Surfactants are used in the treatment of respiratory system disease in premature babies. The table shows some of the components of different surfactant preparations.
structured0 marks
Question 1(a)
1(a)
State the surfactant that contains the least amount of phospholipids.
Easystructured1 marks
Answer
natural human (surfactant)
Question 1(b)
1(b)
Compare the composition of natural human surfactant with synthetic surfactants.
Mediumstructured2 marks
Answer
main component of all surfactants is phospholipids; (natural human surfactant ) has less phospholipids (than synthetic surfactants); (natural human surfactant) has more cholesterol (than (synthetic surfactant) A); (natural human surfactant) has more free fatty acids than (synthetic surfactant) A and less than (comparison with both synthetic (synthetic surfactant) B; ʃsurfactants required) (natural human surfactant) has more proteins (than synthetic surfactants);
Question 1
1
What happens to the cell surface area to volume ratio as a cell grows? A. It decreases, so production of waste material is reduced. B. It increases, so mineral ion absorption is increased. C. It increases, so osmosis is reduced. D. It decreases, so rate of gas exchange is too low.
Easymcq1 marks
Answer
D
Question 1
1
Type I diabetes is a leading cause of death in advanced countries and is associated with various severe or fatal complications, including blindness, kidney failure, heart disease, stroke, neuropathy, and amputations. Embryonic stem cells are considered to be a powerful tool in the treatment of diabetes. In a study, embryonic stem cells were grown in culture and tested for insulin mRNA. A drug was injected into two groups of healthy mice in order to simulate type I diabetes 15 days prior to the transplant of embryonic stem cells. The mice in the transplant group received embryonic stem cells that produce insulin mRNA. The control group did not receive the transplant. The graph shows the blood glucose concentration in both groups.
18 marks
Question 1(i)
1(i)
Suggest an ethical advantage of using this type of therapy over embryonic stem cell therapy.
Mediumstructured1 marks
Answer
umbilical cord «stem» cells are discarded/die if not harvested OR harvesting umbilical cord cells does not harm the baby OR taking «stem» cells from an embryo may harm/kill it Do not accept answers relating to consent. 1 max Question Answers Notes Total
Question 1
1
Hypoxia is a condition in which tissues of the body are deprived of an adequate oxygen supply. A study was carried out in rats to examine the effects of continuing hypoxia on the structure of the diaphragm, and to determine whether nitric oxide is implicated in adaptation of the diaphragm to hypoxia. The diaphragm helps to supply oxygen to tissues and organs in the body by ventilating the lungs. A group of 36 adult male rats were kept for 6 weeks in low oxygen while 36 adult male rats were kept in normal oxygen levels.
10 marks
Question 1(a)
1(a)
Outline the effect of hypoxia on body mass and erythrocyte percentage.
Mediumstructured1 marks
Answer
erythrocyte percentage increased AND body mass reduced/smaller increase in mass \(\boldsymbol{}\)
Question 1(e)
1(e)
Skeletal muscle contractions can take two different forms: if they are stimulated by a single action potential they take the form of a twitch and if they are stimulated by a series of action potentials the contraction is longer lasting (tetanic). The table shows the effects of hypoxia on the force of twitch and peak tetanic contraction in the diaphragm.
0 marks
Question 1(e)(ii)
1(e)(ii)
Hypoxia caused a 13 % increase in the surface area to volume ratio of the diaphragm. Suggest a reason for this change.
Mediumstructured1 marks
Answer
a. decrease in volume/atrophy/loss of cells/less muscle fibres/less tissue in the diaphragm b. SA to volume ratio increased to make oxygen uptake into muscle/cells faster Do not accept reduction in area of diaphragm 1 max
Question 1
1
The larval stage of the fly Eurosta solidaginis develops in the plant Solidago altissima. The larva secretes a chemical which causes plant tissue to grow around it forming a swelling called a gall. The gall provides the developing insect with protection from predators. The E. solidaginis fly is preyed upon by the parasitic wasp Eurytoma gigantea. The graph shows the relationship between gall diameter and the percentage of flies that avoid predation by E. gigantea.
0 marks
Question 1(a)
1(a)
In order to form galls, the insects choose a location where cell division occurs at a high rate. State the term for a region of rapid cell division within a plant.
Easystructured1 marks
Answer
«apical» meristem/shoot apex
Question 1
1
Measurements of the lung capacity of a student were recorded using a spirometer and displayed with a data logger. Initially the student was at rest, then changed to carrying out strenuous exercise. The results are displayed in the graph.
0 marks
Question 1(d)
1(d)
Outline the function of pneumocytes in the lungs.
Mediumstructured2 marks
Answer
a. type I pneumocytes carry out gas exchange b. type II pneumocytes secrete surfactant/fluid OR type II pneumocytes create a moist surface inside the alveoli OR type II pneumocytes reduce surface tension between alveoli OR type II pneumocytes prevent the sides of the alveolus adhering to each other OWTTE OWTTE
Question 1
1
When compared to other body cells, which characteristic of stem cells is the most important for therapeutic uses? A. Less differentiation B. Less excretion C. Lower rate of reproduction D. Lower rate of metabolism
Mediummcq1 marks
Answer
A
Question 1
1
Arabidopsis is a small flowering plant in the mustard family (Brassicaceae) that is widely used in basic research. It has a short life cycle, flowers quickly producing a large number of seeds and is easy to cultivate. It forms a circle of leaves known as a rosette that lies close to the soil. Flowers form at the end of short stems. A study was carried out of differences in development between Arabidopsis plants grown in long days ( 16 hours light, 8 hours dark) or short days ( 8 hours light, 16 hours dark). The sixth leaf (L6) to emerge in the rosette of each plant was used in all investigations. New leaves are initiated by the meristem and go through four stages as they develop. - Stage 1 (S1) - rapid cell division - Stage 2 (S2) - cell division has ceased, cell expansion continues - Stage 3 (S3) - decreasing cell expansion rate - Stage 4 (S4) - leaf growth complete The start of each stage of leaf development for plants grown in long days and short days is shown above the first graph.
0 marks
Question 1(a)
1(a)
0 marks
Question 1(a)(i)
1(a)(i)
Calculate the difference in the mean leaf area of L6 at the start of stage 4 between the leaves of plants grown in long days and short days. \(\mathrm{mm}^{2}\)
Mediumstructured1 marks
Answer
« 130-85 » =45 « \(\mathrm{mm}^{2}\) » Allow answers in the range of 40 to 50 « \(\mathrm{mm}^{2}\) »
Question 1(a)(ii)
1(a)(ii)
Distinguish between plants grown in long days and short days in the timing of the four stages of leaf development.
Mediumstructured2 marks
Answer
a. S 1 / S 2 is longer in short day plants OR the stages in long day plants are more variable in length b. leaves of plants grown in long day reach S2 / S3 /S4 stages sooner OR S1/S2/S3 completed earlier in plants grown in long days c. leaves of plants grown in long day reach S1 later than plants grown in short days Accept vice versa. 2 max
Question 1
1
Which graph represents the change in cell surface area to volume ratio with increasing cell diameter?
Mediummcq1 marks
Answer
B