Answers · Homeostasis
Blood glucose — answer key
Check meaning, not exact wording. These are teaching points, not official Cambridge marks.
1. GQ1 · Practice
Model answer. Insulin decreases the blood glucose concentration: after the meal it brought the concentration back down from 140 to 90 mg per 100 cm³.
A full answer includes
- Insulin decreases the blood glucose concentration.
Also accept
- decreases it
Watch for
- “Insulin increases the blood glucose concentration.” — After insulin was released the trace fell. Insulin decreases blood glucose.
2. GQ2 · Practice
Model answer. The pancreas secretes insulin into the blood when the blood glucose concentration rises.
A full answer includes
- The pancreas.
Also accept
- pancreas
Watch for
- “The liver secretes insulin.” — The liver responds to insulin; the pancreas secretes it.
3. GQ3 · Practice
Model answer. (a) The highest point of the trace is at 150 mg per 100 cm³. (b) It is at 30 minutes on the time axis.
Checked automatically
- (a) Highest concentration (mg per 100 cm³): 150 (within ±2)
- Common wrong answer 30 : That is the time of the peak. Read its height on the vertical axis.
- (b) Time of the peak: 30 min (within ±2 min)
- Common wrong answer 150 : That is the height of the peak. Read its time on the time axis.
A full answer includes
- (a) 150 mg per 100 cm³.
- (b) 30 minutes.
Also accept
- (a) 150; (b) 30 minutes
Watch for
- “(b) 150 minutes.” — That is the end of the time axis. The peak is at 30 minutes.
4. GQ4 · Practice
Options as numbered on the pupil sheet: 1 — secreted when blood glucose falls; the liver breaks down glycogen and releases glucose; 2 — secreted when blood glucose rises; the liver takes up glucose and stores it as glycogen.
Model answer. Insulin is secreted when blood glucose rises; it causes the liver to take up glucose and store it as glycogen. Glucagon is secreted when blood glucose falls; it causes the liver to break down glycogen and release glucose.
A full answer includes
- insulin: when blood glucose rises, the liver takes up glucose and stores it as glycogen; glucagon: when blood glucose falls, the liver breaks down glycogen and releases glucose.
Also accept
- insulin rise, store; glucagon fall, release
Watch for
- “Glucagon makes the liver store glucose.” — Glucagon is secreted when glucose is low: it makes the liver release glucose.
5. GQ5 · Practice
Model answer. Glycogen is an insoluble storage carbohydrate made of many glucose molecules joined together. The liver stores glucose as glycogen.
A full answer includes
- A storage carbohydrate, made of many glucose molecules joined together, stored in the liver (and muscles).
Also accept
- a stored carbohydrate made from glucose
Watch for
- “Glycogen is a hormone from the pancreas.” — That is glucagon. Glycogen is the carbohydrate stored in the liver.
6. GQ6 · Practice
Model answer. In Type 1 diabetes the pancreas makes little or no insulin, so the blood glucose concentration is not brought back down after a meal.
A full answer includes
- The pancreas makes little or no insulin.
Also accept
- the pancreas makes little or no insulin
Watch for
- “The liver makes too much glucagon.” — In Type 1 diabetes the problem is that the pancreas makes little or no insulin.
7. GQ7 · Practice
Model answer. The concentration started at 85 and peaked at 150 mg per 100 cm³: the rise is 150 − 85 = 65 mg per 100 cm³.
Checked automatically
- Rise in blood glucose (mg per 100 cm³): 65 (within ±3)
- Common wrong answer 150 : That is the peak. Subtract the start: 150 − 85.
A full answer includes
- 150 − 85 = 65 mg per 100 cm³.
Also accept
- 65 mg per 100 cm³
Watch for
- “150.” — That is the peak itself. Subtract the starting value, 85.
8. GQ8 · Practice
Model answer. When the blood glucose concentration rose, the pancreas secreted insulin into the blood. Insulin decreases the blood glucose concentration, so it fell back towards 85 mg per 100 cm³.
A full answer includes
- The rise in blood glucose caused the pancreas to secrete insulin.
- Insulin decreases the blood glucose concentration.
Also accept
- the pancreas secreted insulin, which decreases blood glucose
Watch for
- “The glucose was all used up in respiration.” — Some is used in respiration, but the fall is brought about by insulin, which removes glucose from the blood.
9. GQ9 · Practice
Model answer. (a) After a meal the blood glucose rises and the pancreas secretes insulin: the liver takes up glucose and converts it to glycogen. (b) During the walk the blood glucose falls and the pancreas secretes glucagon: the liver breaks down glycogen into glucose and releases it into the blood.
A full answer includes
- (a) Insulin: the liver takes up glucose and stores it as glycogen.
- (b) Glucagon: the liver breaks down glycogen and releases glucose into the blood.
Also accept
- (a) insulin, store as glycogen; (b) glucagon, break down glycogen and release glucose
Watch for
- “(b) Insulin makes the liver release glucose.” — Insulin decreases blood glucose. Glucagon causes the liver to release glucose.
10. GQ10 · Practice
Model answer. Glycogen, not glucagon, is stored in the liver: it is a carbohydrate made of many glucose molecules. Glucagon is a hormone secreted by the pancreas when the blood glucose concentration falls; it causes the liver to break glycogen down and release glucose.
A full answer includes
- Glycogen is the carbohydrate stored in the liver.
- Glucagon is a hormone secreted by the pancreas; it causes the liver to break glycogen down.
Also accept
- glycogen is stored; glucagon is a pancreas hormone
Watch for
- “Glucagon and glycogen are two names for the same thing.” — They are different: glucagon is a hormone, glycogen a stored carbohydrate.
11. GQ11 · Practice
Model answer. Type 1 diabetes is treated by measuring the blood glucose concentration regularly, injecting insulin, and planning meals and exercise around the insulin, because food raises the blood glucose concentration and exercise lowers it.
A full answer includes
- Measuring the blood glucose concentration regularly.
- Injecting insulin.
- Planning meals and exercise around the insulin.
Also accept
- measure glucose; inject insulin; plan meals and exercise
Watch for
- “It is treated by injecting glucose.” — The missing substance is insulin. Injected insulin brings the blood glucose concentration down.
12. GQ12 · Practice
Model answer. In Type 1 diabetes the pancreas makes little or no insulin. Without insulin, the liver and muscles do not take up glucose after a meal, so the blood glucose concentration stays high. Injected insulin does the job the pancreas cannot.
A full answer includes
- The pancreas makes little or no insulin.
- Without insulin, the liver and muscles do not take up glucose, so the concentration stays high after a meal.
Also accept
- pancreas makes little or no insulin; glucose not taken up
Watch for
- “Because the person ate too much sugar.” — Type 1 diabetes is not caused by what a person ate. The pancreas makes little or no insulin.
13. GT1 · Apply
Model answer. Glucose from the digested lunch was absorbed, so the blood glucose concentration rose. The pancreas secreted insulin, which decreases blood glucose: it caused the liver to take up glucose and convert it into glycogen, so the liver's glycogen store increased.
A full answer includes
- After the lunch the blood glucose concentration rose.
- The pancreas secreted insulin.
- Insulin caused the liver to take up glucose and store it as glycogen.
Also accept
- glucose rose; insulin; liver stored glucose as glycogen
Watch for
- “Glucagon made the liver store the glucose.” — Glucagon is secreted when glucose falls and causes glycogen to be broken down. Storing is insulin's effect.
14. GT2 · Apply
Model answer. Respiration in the leg muscles uses glucose, so the blood glucose concentration falls. The pancreas secretes glucagon, which causes the liver to break down its glycogen store into glucose and release it into the blood, keeping the concentration up.
A full answer includes
- As the cyclist uses glucose, the blood glucose concentration falls.
- The pancreas secretes glucagon.
- Glucagon causes the liver to break down glycogen and release glucose into the blood.
Also accept
- falls; glucagon; liver releases glucose from glycogen
Watch for
- “Insulin releases glucose from the liver.” — Insulin decreases blood glucose. Glucagon causes the liver to release glucose.
15. GT3 · Apply
Model answer. Exercise uses glucose in respiration, so it lowers the blood glucose concentration. Injected insulin lowers it too. Without planning, the two together could make the concentration fall too low, so meals, insulin and exercise are planned together.
A full answer includes
- Exercise uses glucose, so it lowers the blood glucose concentration.
- Insulin also lowers it, so the two together could make it fall too low.
- So the insulin and food are planned around the exercise.
Also accept
- exercise and insulin both lower blood glucose
Watch for
- “Exercise raises blood glucose, so more insulin is needed.” — Exercise uses glucose in respiration and lowers the blood glucose concentration.