Biology 9201 | Paper 1 Mock 01 | Written Paper 1
Question 1 Report
Fig. 1 shows a section through a vein in a person’s leg. The person works at a desk and remains seated for long periods. Veins return blood to the heart at low pressure. Valves and contractions of nearby skeletal muscles help prevent blood collecting in the lower leg.
(a) What is the function of a valve in this vein? [1]
(b) Describe how contraction of leg muscles helps blood move towards the heart. [2]
(c) Give two features of veins that are different from arteries. [2]
Table 1 shows results from an investigation of blood flow in the fingers. A volunteer placed one hand in cool water and the other hand in warm water for two minutes. A sensor measured skin temperature and the time taken for colour to return after a fingernail was pressed. Blood vessels near the skin can change diameter to control heat transfer from the body.
| water temperature / degrees C | skin temperature after 2 minutes / degrees C | time for colour to return / s |
|---|---|---|
| 12 | 22 | 3.8 |
| 38 | 33 | 1.4 |
(a) Describe the difference in colour-return time between the two hands. [1]
(b) What change happens to skin arterioles in warm conditions? [1]
(c) Explain how this change affects heat loss from the body. [2]
Veins and valves
- A valve prevents backflow of blood, ensuring blood travels towards the heart. [1]
- When leg muscles contract, they squeeze the vein and force blood along it. Valves prevent reverse flow, so the blood is directed towards the heart. [2]
- Any two differences from arteries are accepted: veins have thinner walls, wider lumens, valves, and lower blood pressure. [2]
Blood flow near the skin
- Colour returned faster after warm water: it took 1.4 s rather than 3.8 s after cool water. [1]
- In warm conditions, skin arterioles dilate, meaning that they widen. [1]
- Dilation allows more blood to flow through capillaries close to the skin surface. More heat can then be transferred from the blood to the surroundings, increasing heat loss. [2]
Answer Details
Veins and valves
- A valve prevents backflow of blood, ensuring blood travels towards the heart. [1]
- When leg muscles contract, they squeeze the vein and force blood along it. Valves prevent reverse flow, so the blood is directed towards the heart. [2]
- Any two differences from arteries are accepted: veins have thinner walls, wider lumens, valves, and lower blood pressure. [2]
Blood flow near the skin
- Colour returned faster after warm water: it took 1.4 s rather than 3.8 s after cool water. [1]
- In warm conditions, skin arterioles dilate, meaning that they widen. [1]
- Dilation allows more blood to flow through capillaries close to the skin surface. More heat can then be transferred from the blood to the surroundings, increasing heat loss. [2]
Question 2 Report
Fig. 1 shows a fetus in the uterus at about 20 weeks of pregnancy. A midwife uses a similar diagram to explain the exchange between the pregnant person's blood and the fetus. The placenta has a large surface area and contains blood vessels from both the fetus and the mother. In a normal pregnancy, the two blood supplies remain separate. The umbilical cord carries blood between the fetus and the placenta. The fetus needs oxygen and glucose for respiration and growth, while carbon dioxide must be removed from its body.
(a) What is structure X? [1]
(b) Give two substances that move from the mother's blood into the fetal blood at Y. [2]
(c) Describe how carbon dioxide made by fetal cells is removed from the fetus. [2]
(d) Explain why the maternal and fetal blood do not normally mix directly. [2]
(e) When does implantation occur during human reproduction? [1]
(f) Give two health choices during pregnancy that reduce risks to fetal development. [2]
(a) Structure X is the placenta. [1]
(b) Accept any two substances moving from maternal to fetal blood at the placenta: oxygen, glucose, amino acids, or antibodies. [2]
(c) Carbon dioxide travels in fetal blood along the umbilical cord to the placenta [1]. It diffuses into the mother's blood and is removed by her lungs [1].
(d) The blood supplies do not normally mix directly because this prevents direct mixing of different blood groups [1], which could trigger an immune reaction or damage blood cells [1].
(e) Implantation occurs when the embryo attaches to or embeds in the lining of the uterus. [1]
(f) Accept any two: avoid alcohol; do not smoke; eat a balanced diet; attend antenatal appointments; avoid non-prescribed drugs. [2]
Answer Details
(a) Structure X is the placenta. [1]
(b) Accept any two substances moving from maternal to fetal blood at the placenta: oxygen, glucose, amino acids, or antibodies. [2]
(c) Carbon dioxide travels in fetal blood along the umbilical cord to the placenta [1]. It diffuses into the mother's blood and is removed by her lungs [1].
(d) The blood supplies do not normally mix directly because this prevents direct mixing of different blood groups [1], which could trigger an immune reaction or damage blood cells [1].
(e) Implantation occurs when the embryo attaches to or embeds in the lining of the uterus. [1]
(f) Accept any two: avoid alcohol; do not smoke; eat a balanced diet; attend antenatal appointments; avoid non-prescribed drugs. [2]
Question 3 Report
During a school rowing trial, a sports scientist records the pulse rate of a pupil who becomes breathless sooner than the rest of the team. The scientist uses Fig. 1 to discuss how the heart supplies the body cells with oxygen and glucose in the blood. The arrows show the direction of blood flow. The blood returning from the body has a lower oxygen concentration than blood leaving the lungs.
Fig. 1
(a) What is the name of the chamber labelled X? [1]
(b) What is the function of the structure labelled Y? [2]
(c) Describe the difference in oxygen concentration between the blood in vessel P and the blood in vessel Q. [2]
(d) Explain why a narrowed coronary artery can cause a person to stop exercising. [3]
(e) State two features of red blood cells that help them transport oxygen to body cells. [2]
(a) Chamber X is the left ventricle. [1]
(b) Structure Y is a valve. It prevents backflow of blood and ensures that blood flows in one direction through the heart. [2]
(c) Blood in vessel P has a lower oxygen concentration. Blood in vessel Q has a higher oxygen concentration because it has gained oxygen in the lungs. [2]
(d) A narrowed coronary artery means less blood reaches heart muscle. Less oxygen and glucose are supplied for aerobic respiration, so less energy is released for contraction. The person may become tired or breathless and have to stop exercising. [3]
(e) Red blood cells contain haemoglobin and have a biconcave shape that gives a large surface area. Other acceptable features are no nucleus, giving more space for haemoglobin, and flexibility to pass through narrow capillaries. Any two gain credit. [2]
Answer Details
(a) Chamber X is the left ventricle. [1]
(b) Structure Y is a valve. It prevents backflow of blood and ensures that blood flows in one direction through the heart. [2]
(c) Blood in vessel P has a lower oxygen concentration. Blood in vessel Q has a higher oxygen concentration because it has gained oxygen in the lungs. [2]
(d) A narrowed coronary artery means less blood reaches heart muscle. Less oxygen and glucose are supplied for aerobic respiration, so less energy is released for contraction. The person may become tired or breathless and have to stop exercising. [3]
(e) Red blood cells contain haemoglobin and have a biconcave shape that gives a large surface area. Other acceptable features are no nucleus, giving more space for haemoglobin, and flexibility to pass through narrow capillaries. Any two gain credit. [2]
Question 4 Report
The figure shows four possible tongue-rolling positions used in a classroom survey. Students recorded whether they could roll their tongue into a tube or could not do so. The teacher explained that this classroom characteristic is treated as a discontinuous category, although many human characteristics, such as height, vary continuously.
Table 1 shows the class results.
| tongue-rolling category | number of students |
|---|---|
| can roll | 21 |
| cannot roll | 15 |
(a) What type of variation is recorded in Table 1? [1]
(b) Give the percentage of students who can roll their tongue. [1]
(c) Describe why height would not be recorded using the same two boxes. [2]
(d) Give one precaution when collecting data about a human body characteristic. [1]
(e) Explain why this small class may not represent all students in the country. [1]
Variation that falls into separate categories is discontinuous; height is different because it can take many intermediate measured values.
- Table 1 records discontinuous variation. [1]
- \[\frac{21}{36}\times100=58.3\%\]58.3%, or 58%. [1]
- Height has many possible intermediate values. It must be measured on a scale rather than placed into only two categories. [2]
- A suitable ethical precaution is to obtain consent, keep identities confidential, or avoid pressuring students to take part. [1]
- This small class may not represent all students because the sample is small or not random, and its allele frequencies may differ from those of the wider population. [1]
Answer Details
Variation that falls into separate categories is discontinuous; height is different because it can take many intermediate measured values.
- Table 1 records discontinuous variation. [1]
- \[\frac{21}{36}\times100=58.3\%\]58.3%, or 58%. [1]
- Height has many possible intermediate values. It must be measured on a scale rather than placed into only two categories. [2]
- A suitable ethical precaution is to obtain consent, keep identities confidential, or avoid pressuring students to take part. [1]
- This small class may not represent all students because the sample is small or not random, and its allele frequencies may differ from those of the wider population. [1]
Question 5 Report
Fig. 1 shows part of a family tree used by a cancer genetics team. Some people have developed breast or ovarian cancer linked to a changed BRCA1 allele. The changed allele increases risk but does not guarantee that cancer will develop, because cancer also involves further mutations in body cells and environmental factors. Individual III-2 is an adult who has not had cancer and is considering a test for the family allele.
(a) What type of allele is most consistent with the pattern in Fig. 1? [1]
(b) Describe two features of Fig. 1 that support your answer. [2]
(c) Give the probability that III-2 inherited the changed BRCA1 allele if their affected parent is heterozygous. [1]
(d) Explain why a positive BRCA1 result cannot predict with certainty that III-2 will develop cancer. [3]
(e) Describe two ways in which regular screening could help a person with a changed BRCA1 allele. [2]
(f) When a result is shared, give one reason why it may also be important to inform close blood relatives. [1]
(g) Give one ethical issue that a genetics team should consider before testing an adult for this allele. [2]
(a) The pattern is most consistent with a dominant allele. [1]
(b) Affected people occur in successive generations, and an affected parent has an affected child. The pedigree also shows that both males and females can inherit the allele. Any two relevant observations gain credit. [2]
(c) If the affected parent is heterozygous, there is a \(50\%\) probability that III-2 inherited the changed allele. [1]
(d) A changed BRCA1 allele increases susceptibility to cancer; it does not guarantee cancer. Further mutations in body cells may be needed before cancer develops, and environmental or lifestyle factors also affect risk. [3]
(e) Regular screening can detect a tumour at an early stage. Earlier treatment may improve the outcome or allow treatment before the tumour spreads. [2]
(f) Close blood relatives may also have inherited the changed allele, so informing them allows them to seek testing or screening. [1]
(g) The adult must give informed consent. A genetics team should also consider that a result may cause anxiety or affect insurance and family relationships. [2]
Answer Details
(a) The pattern is most consistent with a dominant allele. [1]
(b) Affected people occur in successive generations, and an affected parent has an affected child. The pedigree also shows that both males and females can inherit the allele. Any two relevant observations gain credit. [2]
(c) If the affected parent is heterozygous, there is a \(50\%\) probability that III-2 inherited the changed allele. [1]
(d) A changed BRCA1 allele increases susceptibility to cancer; it does not guarantee cancer. Further mutations in body cells may be needed before cancer develops, and environmental or lifestyle factors also affect risk. [3]
(e) Regular screening can detect a tumour at an early stage. Earlier treatment may improve the outcome or allow treatment before the tumour spreads. [2]
(f) Close blood relatives may also have inherited the changed allele, so informing them allows them to seek testing or screening. [1]
(g) The adult must give informed consent. A genetics team should also consider that a result may cause anxiety or affect insurance and family relationships. [2]
Question 6 Report
Fig. 1 shows a pedigree prepared by a clinic for a family affected by cystic fibrosis. Cystic fibrosis is caused by a recessive allele. Filled symbols show people with the disorder. A square represents a male and a circle represents a female. Individual IV-2 is expecting a baby with a partner who is known not to have cystic fibrosis.
(a) What is the genotype of individual II-2? Use C for the normal allele and c for the cystic fibrosis allele. [1]
(b) Describe the evidence in Fig. 1 that shows cystic fibrosis is recessive. [2]
(c) Complete a genetic diagram to show the possible genotypes of children produced by two carriers of cystic fibrosis. [3]
(d) Give the percentage chance that a child of two carriers will have cystic fibrosis. [1]
(e) When a couple are considering a genetic test, give one reason why a trained counsellor should discuss the result with them. [1]
(a) Individual II-2 is affected and cystic fibrosis is recessive, so their genotype is \(cc\). [1]
(b) The parents in generation I are unaffected but have an affected child. This shows that they can carry the cystic fibrosis allele without having the disorder, so the allele is recessive. [2]
(c) Two carriers are \(Cc\) and \(Cc\). Each produces gametes carrying \(C\) or \(c\).
| \(C\) | \(c\) | |
|---|---|---|
| \(C\) | \(CC\) | \(Cc\) |
| \(c\) | \(Cc\) | \(cc\) |
Parents \(Cc\) and \(Cc\), correct gametes, and offspring \(CC\), \(Cc\), \(Cc\), \(cc\) each gain a marking point. [3]
(d) One of the four equally likely genotypes is \(cc\), so the probability of cystic fibrosis is \(\frac14=25\%\). [1]
(e) Genetic counselling is important because a result may cause anxiety, may affect relatives, and can help the couple understand their reproductive choices. Any one of these is creditworthy. [1]
Answer Details
(a) Individual II-2 is affected and cystic fibrosis is recessive, so their genotype is \(cc\). [1]
(b) The parents in generation I are unaffected but have an affected child. This shows that they can carry the cystic fibrosis allele without having the disorder, so the allele is recessive. [2]
(c) Two carriers are \(Cc\) and \(Cc\). Each produces gametes carrying \(C\) or \(c\).
| \(C\) | \(c\) | |
|---|---|---|
| \(C\) | \(CC\) | \(Cc\) |
| \(c\) | \(Cc\) | \(cc\) |
Parents \(Cc\) and \(Cc\), correct gametes, and offspring \(CC\), \(Cc\), \(Cc\), \(cc\) each gain a marking point. [3]
(d) One of the four equally likely genotypes is \(cc\), so the probability of cystic fibrosis is \(\frac14=25\%\). [1]
(e) Genetic counselling is important because a result may cause anxiety, may affect relatives, and can help the couple understand their reproductive choices. Any one of these is creditworthy. [1]
Question 7 Report
Fig. 1 shows a glucose sensor trace for a cyclist who ate a meal containing bread and fruit at 08:00. The sensor measures glucose concentration in the blood every few minutes. The cyclist is healthy and did not eat again before 11:00. The rise after the meal is followed by a return towards the starting concentration. This control prevents body cells from being exposed to a very high glucose concentration for a long time.
(a) Describe the change in blood glucose concentration between the meal and 10:00. [2]
(b) What substance is released by the pancreas when the blood glucose concentration rises? [1]
(c) Give one way in which this substance causes the blood glucose concentration to fall. [1]
(a) Blood glucose concentration rises after the meal [1] and then falls towards its starting or normal concentration by 10:00. [1]
(b) The pancreas releases insulin when blood glucose concentration rises. [1]
(c) Insulin can cause liver or other body cells to take up glucose from the blood, or cause glucose to be converted to glycogen for storage. Either process lowers blood glucose concentration. [1]
Answer Details
(a) Blood glucose concentration rises after the meal [1] and then falls towards its starting or normal concentration by 10:00. [1]
(b) The pancreas releases insulin when blood glucose concentration rises. [1]
(c) Insulin can cause liver or other body cells to take up glucose from the blood, or cause glucose to be converted to glycogen for storage. Either process lowers blood glucose concentration. [1]
Question 8 Report
Fig. 1 shows cells from a sample of an unknown organism collected from a pond. The cells have a cell membrane, cytoplasm, a nucleus and a cell wall. They do not have chloroplasts. The sample was later identified as yeast, a fungus used by bakers. When yeast has glucose and warm water, it releases carbon dioxide. The gas causes bread dough to rise. A baker asks why yeast is not classed as a plant even though its cells have a wall.
(a) What is structure B? [1]
(b) Give one structure shown in Fig. 1 that is also found in an animal cell. [1]
(c) Describe why yeast cells cannot make their own food by photosynthesis. [1]
(d) Complete the word equation for anaerobic respiration in yeast: glucose → ethanol + ______. [1]
Fig. 1 shows cells from the leaf of a Venus flytrap plant. When an insect touches sensitive hairs, the two halves of the leaf close. Digestive enzymes are then released and the plant absorbs mineral ions from the insect. The cells shown are from a green part of the trap and contain chloroplasts. The plant still needs photosynthesis to make glucose, although it gains nitrogen-containing compounds from captured food.
(a) What is structure A? [1]
(b) Give the name of the process that uses chloroplasts to make glucose. [1]
(c) Describe why the Venus flytrap gains an advantage from digesting insects even though its cells can make food. [2]
(d) Give one other structure present in these plant cells but not in animal cells. [1]
Yeast cells, (a) Structure B is the nucleus. [1]
Yeast cells, (b) A structure shown that is also found in animal cells is the cell membrane, cytoplasm, or nucleus. [1]
Yeast cells, (c) Yeast cannot photosynthesise because it has no chloroplasts. [1]
Yeast cells, (d) Anaerobic respiration in yeast is:
glucose → ethanol + carbon dioxide. [1]
Venus flytrap cells, (a) Structure A is a sensitive hair, also called a trigger hair. [1]
Venus flytrap cells, (b) The process using chloroplasts to make glucose is photosynthesis. [1]
Venus flytrap cells, (c) Digesting insects provides mineral ions or nitrogen-containing compounds. These are needed to make proteins and support healthy growth, even though photosynthesis supplies glucose. [2]
Venus flytrap cells, (d) A structure in these plant cells but not animal cells is a cell wall, chloroplast, or large permanent vacuole. [1]
Answer Details
Yeast cells, (a) Structure B is the nucleus. [1]
Yeast cells, (b) A structure shown that is also found in animal cells is the cell membrane, cytoplasm, or nucleus. [1]
Yeast cells, (c) Yeast cannot photosynthesise because it has no chloroplasts. [1]
Yeast cells, (d) Anaerobic respiration in yeast is:
glucose → ethanol + carbon dioxide. [1]
Venus flytrap cells, (a) Structure A is a sensitive hair, also called a trigger hair. [1]
Venus flytrap cells, (b) The process using chloroplasts to make glucose is photosynthesis. [1]
Venus flytrap cells, (c) Digesting insects provides mineral ions or nitrogen-containing compounds. These are needed to make proteins and support healthy growth, even though photosynthesis supplies glucose. [2]
Venus flytrap cells, (d) A structure in these plant cells but not animal cells is a cell wall, chloroplast, or large permanent vacuole. [1]
Question 9 Report
The table below shows plant cover measured along a transect from a woodland path into the woodland. Fig. 1 shows a student placing a quadrat beside the tape. The path is used by walkers and dogs. Trampling compacts the soil and can damage plant shoots. Each percentage is the mean cover from five quadrats of the same size.
| Distance from path / m | Mean plant cover / % |
|---|---|
| 0 | 12 |
| 2 | 35 |
| 5 | 68 |
| 10 | 74 |
(a) Describe the pattern in plant cover shown in Table 1. [2]
(b) Give one reason for using five quadrats at each distance. [1]
(c) What effect does trampling have on competition between plants near the path? [1]
The table below shows the percentage of snowshoe hares with brown or white fur at two times of year. Fig. 1 shows a hare in winter. In this region, foxes hunt hares by sight. Snow cover normally lasts from November to March, but recent warm years have shortened the period of snow cover.
| Month | Hares with white fur / % | Ground covered by snow / % |
|---|---|---|
| January | 96 | 92 |
| April | 38 | 21 |
| July | 2 | 0 |
(a) Describe the relationship between white fur and snow cover in Table 1. [2]
(b) Explain how white fur is an adaptation in January. [2]
(c) What may happen to a white hare on brown ground? [1]
Labelled answer diagram:
Woodland transect
- (a) Mean plant cover increases with distance from the path, rising from 12% at 0 m to 74% at 10 m. [2]
- (b) Using five quadrats allows a mean to be calculated and reduces the effect of anomalous results. [1]
- (c) Trampling damages plants, so they are less able to compete for resources such as light, space or water. [1]
Snowshoe hares
- (a) The percentage of hares with white fur and the percentage of ground covered by snow follow the same pattern: both are highest in January and decrease towards July. [2]
- (b) In January, white fur camouflages a hare against snow. Foxes are less likely to see and catch it, increasing its chance of survival. [2]
- (c) A white hare on brown ground is more visible to predators and is more likely to be eaten. [1]
Answer Details
Labelled answer diagram:
Woodland transect
- (a) Mean plant cover increases with distance from the path, rising from 12% at 0 m to 74% at 10 m. [2]
- (b) Using five quadrats allows a mean to be calculated and reduces the effect of anomalous results. [1]
- (c) Trampling damages plants, so they are less able to compete for resources such as light, space or water. [1]
Snowshoe hares
- (a) The percentage of hares with white fur and the percentage of ground covered by snow follow the same pattern: both are highest in January and decrease towards July. [2]
- (b) In January, white fur camouflages a hare against snow. Foxes are less likely to see and catch it, increasing its chance of survival. [2]
- (c) A white hare on brown ground is more visible to predators and is more likely to be eaten. [1]
Question 10 Report
Fig. 1 shows an island forest where native fruit-eating birds disperse seeds from a tree. Goats were introduced for farming and now eat young plants. Conservation workers counted tree seedlings in fenced and unfenced squares of equal area. The table shows the mean number of seedlings after one year. Each square had similar soil, light and water conditions.
| Square type | Mean tree seedlings per m2 | Mean goat droppings per m2 |
|---|---|---|
| Fenced | 18 | 0 |
| Unfenced | 3 | 11 |
(a) Describe the effect of fencing on the number of tree seedlings. [1]
(b) Give one variable that was controlled in this investigation. [1]
(c) Explain how goats can reduce the population of native birds over several years. [2]
The figure shows a coastal village that uses wind turbines and diesel generators to supply electricity. Engineers recorded the percentage of electricity generated by each source over four months. The village also measures carbon dioxide released from fuel use. Wind energy does not require diesel to be burned.
| Month | Electricity from wind / % | Diesel used / dm3 | Carbon dioxide released / tonnes |
|---|---|---|---|
| January | 64 | 920 | 2.5 |
| February | 52 | 1210 | 3.3 |
| March | 71 | 690 | 1.9 |
| April | 43 | 1510 | 4.1 |
(a) Which month had the greatest percentage of electricity from wind? [1]
(b) Describe the relationship between wind electricity and diesel use. [1]
(c) Explain why replacing diesel with wind energy can reduce global warming. [2]
Labelled answer diagram:
Island seedlings
- (a) Fencing increases the number of tree seedlings: fenced squares had 18 seedlings per \(\text{m}^2\), compared with 3 in unfenced squares. [1]
- (b) One controlled variable was soil conditions. Other acceptable controls include square area, light intensity, water availability, or the time left for growth. Controlling these means fencing is the main difference being tested. [1]
- (c) Goats eat seedlings, so fewer seedlings survive to become mature trees. Over several years, birds have less fruit for food, and possibly fewer nesting sites; this reduces bird survival and reproduction. [2]
Wind and diesel electricity
- (a) March had the greatest wind-generated electricity, at 71%. [1]
- (b) Higher wind electricity is associated with lower diesel use. For example, March has the highest wind percentage and the lowest diesel use, whereas April has the lowest wind percentage and the highest diesel use. [1]
- (c) Replacing diesel means less fossil fuel is burned. Therefore less carbon dioxide is released, reducing the enhanced greenhouse effect and hence global warming. [2]
Answer Details
Labelled answer diagram:
Island seedlings
- (a) Fencing increases the number of tree seedlings: fenced squares had 18 seedlings per \(\text{m}^2\), compared with 3 in unfenced squares. [1]
- (b) One controlled variable was soil conditions. Other acceptable controls include square area, light intensity, water availability, or the time left for growth. Controlling these means fencing is the main difference being tested. [1]
- (c) Goats eat seedlings, so fewer seedlings survive to become mature trees. Over several years, birds have less fruit for food, and possibly fewer nesting sites; this reduces bird survival and reproduction. [2]
Wind and diesel electricity
- (a) March had the greatest wind-generated electricity, at 71%. [1]
- (b) Higher wind electricity is associated with lower diesel use. For example, March has the highest wind percentage and the lowest diesel use, whereas April has the lowest wind percentage and the highest diesel use. [1]
- (c) Replacing diesel means less fossil fuel is burned. Therefore less carbon dioxide is released, reducing the enhanced greenhouse effect and hence global warming. [2]
Question 11 Report
Fig. 1 shows a simplified liver cell from a person who has not eaten since the previous evening. The person’s blood glucose concentration began to decrease during the night. The liver stores carbohydrate as glycogen, shown as many small granules. A hormone released by the pancreas can cause the liver cell to break down glycogen and release glucose into the blood. This is one part of keeping the concentration of glucose available for brain cells and other body cells.
(a) What is the name of the stored carbohydrate shown by the granules labelled X? [1]
(b) When blood glucose concentration falls, give the name of the pancreatic hormone that acts on liver cells. [1]
(c) Describe what happens to glycogen in the liver cell after this hormone acts. [2]
(d) Explain how the response shown helps body cells during the night. [4]
(a) The carbohydrate stored in liver-cell granules is glycogen. It is a large storage carbohydrate that can be converted back to glucose when needed. [1]
(b) The pancreatic hormone released when blood glucose falls is glucagon. [1]
(c) Glucagon causes glycogen to be broken down to glucose [1]. The glucose is then released from the liver cell into the blood [1].
(d) During the night, no new glucose is being absorbed from food, so blood glucose concentration would otherwise fall [1]. Glucagon causes the liver to release glucose into the blood [1], which raises or maintains blood glucose concentration [1]. Cells, including brain cells, can therefore carry out respiration and release energy [1]. This is negative feedback because the response opposes the original fall in glucose concentration.
Answer Details
(a) The carbohydrate stored in liver-cell granules is glycogen. It is a large storage carbohydrate that can be converted back to glucose when needed. [1]
(b) The pancreatic hormone released when blood glucose falls is glucagon. [1]
(c) Glucagon causes glycogen to be broken down to glucose [1]. The glucose is then released from the liver cell into the blood [1].
(d) During the night, no new glucose is being absorbed from food, so blood glucose concentration would otherwise fall [1]. Glucagon causes the liver to release glucose into the blood [1], which raises or maintains blood glucose concentration [1]. Cells, including brain cells, can therefore carry out respiration and release energy [1]. This is negative feedback because the response opposes the original fall in glucose concentration.
