OxfordAQA International A Level Biology
OxfordAQA International A Level Biology 3.4.7 Hormones and the Control of Blood Glucose Concentration Exam Questions
Free OxfordAQA International A Level Biology revision for 3.4.7 Hormones and the Control of Blood Glucose Concentration: what you need to know, common mistakes and exam-style questions with answers. Covers glycogenesis, glycogenolysis and gluconeogenesis, insulin, glucagon and adrenaline, the second messenger model and type 1 and type 2 diabetes.
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About OxfordAQA International A Level Biology 3.4.7 Hormones and the Control of Blood Glucose Concentration
This Unit 4 topic applies homeostasis to blood glucose. You need to explain why blood glucose must be kept stable, describe glycogenesis, glycogenolysis and gluconeogenesis in the liver, and explain how insulin, glucagon and adrenaline act through receptors on target cells. The second messenger model for adrenaline and glucagon, involving adenylate cyclase, cyclic AMP and protein kinase, is required. You also need to explain the causes, symptoms, risk factors and control of type 1 and type 2 diabetes, and analyse data on risk factors. It links to negative feedback, membrane proteins and respiration, and appears often in longer answers.
What you need to know
- Why glucose is controlled Blood glucose must be stable to supply cells with respiratory substrate and because glucose affects the water potential of the blood.
- Liver processes Glycogenesis converts glucose to glycogen. Glycogenolysis converts glycogen to glucose. Gluconeogenesis makes glucose from non-carbohydrates such as glycerol and amino acids.
- Insulin Insulin is released by beta cells when glucose is high. It binds to receptors on target cells, increases the number of glucose channel proteins in the membrane and activates enzymes that convert glucose to glycogen.
- Glucagon and adrenaline Glucagon is released by alpha cells when glucose is low; it activates glycogenolysis and gluconeogenesis. Adrenaline also binds to receptors on liver cells and activates glycogenolysis.
- Second messenger model Adrenaline or glucagon binds to a receptor on the liver cell membrane, activating adenylate cyclase. This converts ATP to cyclic AMP, which activates protein kinase, which then activates enzymes for glycogenolysis.
- Diabetes In type 1 diabetes the body does not produce insulin and it is controlled by insulin injections. In type 2 diabetes receptors on target cells lose responsiveness to insulin; it is linked to obesity and controlled by diet, exercise and sometimes drugs.
Common mistakes in 3.4.7 Hormones and the Control of Blood Glucose Concentration
- Mixing up glycogen, glucagon and glycogenesis. Glycogen is the storage polysaccharide, glucagon is the hormone and glycogenesis is making glycogen.
- Saying insulin converts glucose into glycogen. Insulin activates enzymes that do the conversion.
- Saying the hormone enters the cell in the second messenger model. The hormone binds to a receptor on the membrane and cyclic AMP acts inside the cell.
- Saying type 2 diabetics produce no insulin. They often produce insulin, but cells respond less to it.
Try three 3.4.7 Hormones and the Control of Blood Glucose Concentration exam-style questions
1. Describe how insulin reduces blood glucose concentration. (3 marks)
Show the mark scheme answer
Insulin binds to specific receptors on target cell membranes; more glucose channel proteins are added to the membrane so more glucose enters cells; activates enzymes converting glucose to glycogen (glycogenesis).
2. Describe the second messenger model of glucagon action. (4 marks)
Show the mark scheme answer
Glucagon binds to receptor on liver cell membrane; activates adenylate cyclase; ATP converted to cyclic AMP; cAMP activates protein kinase, which activates enzymes that hydrolyse glycogen to glucose.
3. Explain why a person with type 2 diabetes can have high blood glucose even though they produce insulin. (2 marks)
Show the mark scheme answer
Receptors on target cells are less responsive to insulin; so less glucose is taken up by cells and less is converted to glycogen.
3.4.7 Hormones and the Control of Blood Glucose Concentration FAQs
What does OxfordAQA International A Level Biology 3.4.7 Hormones and the Control of Blood Glucose Concentration cover?
It covers glycogenesis, glycogenolysis and gluconeogenesis, insulin, glucagon and adrenaline, the second messenger model and type 1 and type 2 diabetes.
Which unit is 3.4.7 Hormones and the Control of Blood Glucose Concentration examined in?
It is part of Unit 4, Control, which is an International A2 paper. The Unit 5 synoptic paper can also draw on this content.
What does the specification say about adenyl cyclase?
The specification uses the term adenyl cyclase, which is the same enzyme as adenylate cyclase. Use it in the second messenger model with cyclic AMP and protein kinase.
