CB7.2 — Blood glucose regulation (Edexcel 1SC0)

Regulation mechanism (negative feedback)

Blood glucose rises (after a meal) → pancreas detects rise → beta cells secrete insulin → target cells (liver, muscle) absorb glucose → glucose converted to glycogen (insoluble store) → blood glucose falls.

Blood glucose falls (after exercise) → pancreas detects fall → alpha cells secrete glucagon → liver breaks down glycogen to glucose (glycogenolysis) → glucose released into blood → blood glucose rises.

This is negative feedback — the response opposes the change.

Diabetes

Type 1 diabetes

• Pancreatic beta cells destroyed (autoimmune response) → no insulin produced.
• Blood glucose rises dangerously after meals.
• Treatment: insulin injections (genetically engineered human insulin); blood glucose monitoring; controlled diet.

Type 2 diabetes

• Body cells become resistant to insulin → reduced response.
• Associated with obesity and poor diet (high sugar/fat).
• Treatment: diet and exercise; oral medication (e.g. metformin); sometimes insulin injections.

Worked calculation

If blood glucose is 5 mmol/L and rises to 8 mmol/L after eating, insulin is released. If target is 5 mmol/L, the percentage increase = (8-5)/5 × 100 = 60%.