6.4.2 Blood glucose regulation

Why is it important to maintain a stable blood glucose concentration?

• maintain constant water potential

• maintain constant concentration of respiratory substrate

What factors affect blood glucose concentration?

• digestion of carbohydrates

• exercise

Define glycogenesis

liver converts excess glucose into glycogen

Define glycogenolysis

liver hydrolyses glycogen into glucose

Define gluconeogenesis

liver synthesises gluocse from non-carbohydrate sources (amino acids, glycerol)

What are islets of Langerhans?

cells in the pancreas which detect blood glucose levels and release hormones

What is the role of alpha cells?

• detect low glucose concentration

• release glucagon

What is the role of beta cells?

• detect high glucose concentration

• release insulin

How insulin lowers blood glucose concentration?

• binds to complementary receptors

• (vesicles contaning glucose channel proteins fuse with cell membrame and increase permeability to glucose)

• stimulated uptake (facilitated diffusion) of glucose by channel proteins

• activates enzymes that catalyse glycogenesis

How does glucagon increase blood glucose concentration?

• glucagon binds to complementary receptors (on liver cells)

• activates enzymes which catalyse glycogenolysis and gluconeogenesis

How does adrenaline increase blood glucose concentration?

• adrenaline binds to complementary receptors in the liver cells

• activates enzymes that catalyse glycogenolysis

Explain the role of the second messenger model in glycogenolysis

• hormone (primary messenger) binds to complementary receptor

• causes adenyl cyclase (which undergoes conformational change) to be activated

• catalyses conversion of ATP → cyclic AMP (secondary messenger)

• cAMP activates enzyme protein kinase (which catalyses glycogenolysis)

What causes type 1 diabetes?

cannot produce insulin (e.g caused by autoimmune disease destroying beta cells)

How can you treat type 1 diabetes?

• insulin injections

• controlling diet (sugat intake)

What causes type 2 diabetes?

• poor diet and obesity

• glycoprotein receptors are damaged and lose responsiveness to insulin

How to treat type 2 diabetes?

• regulating diet (e.g carb intake)

• increasing exercise