The factors that influence blood glucose concentration.

The idea

Blood glucose concentration is influenced by diet, exercise, hormones and body mass. Glucose rises after a carbohydrate meal as gut enzymes hydrolyse starch and disaccharides and the products are absorbed from the small intestine. It falls when cells respire glucose, especially during exercise, and when the liver and muscle cells convert glucose to glycogen (glycogenesis) under the influence of insulin. During fasting, the liver breaks down glycogen to glucose (glycogenolysis) and can synthesise glucose from non-carbohydrate sources such as glycerol and amino acids (gluconeogenesis). Glucagon stimulates both glycogenolysis and gluconeogenesis, while adrenaline stimulates glycogenolysis. Body mass is a risk factor for type 2 diabetes rather than an acute control factor.

What earns the marks

• Absorption of glucose from the small intestine after a carbohydrate meal raises blood glucose concentration.
• Respiration of glucose by cells lowers blood glucose concentration, particularly during exercise.
• Glycogenesis in liver and muscle cells lowers blood glucose concentration by storing glucose as glycogen; insulin promotes this.
• Glycogenolysis in the liver raises blood glucose concentration by breaking down glycogen to glucose; both glucagon and adrenaline stimulate this process.
• Gluconeogenesis raises blood glucose concentration by making glucose from non-carbohydrate sources such as glycerol and amino acids; glucagon stimulates this process.
• Body mass is a risk factor for type 2 diabetes, not an acute factor controlling blood glucose concentration.

Common mistakes and how to put them right

• Listing only hormones and omitting diet and exercise.

  Put it right: Include absorption of glucose from the gut and respiration of glucose by cells.

• Confusing glycogenesis and glycogenolysis.

  Put it right: Genesis means making glycogen; lysis means splitting glycogen.

• Stating that adrenaline drives gluconeogenesis.

  Put it right: Adrenaline primarily stimulates glycogenolysis; glucagon stimulates both glycogenolysis and gluconeogenesis.

• Treating body mass as a direct acute control of blood glucose.

  Put it right: Body mass is a risk factor for type 2 diabetes, not an acute regulator.

Exam tips

• Split your answer into factors that raise blood glucose concentration and factors that lower it.
• Distinguish the hormones carefully: insulin lowers glucose; glucagon raises glucose via glycogenolysis and gluconeogenesis; adrenaline raises glucose via glycogenolysis.
• Mention body mass only as a risk factor for type 2 diabetes, not as an acute control mechanism.