6.4.2 Control of blood glucose concentration

Question 1

Glucose concentration

Answer 1

Concentration measured by the pancreas. Rises after eating carbs, falls after exercise

Question 2

Hormonal controls

Answer 2

Insulin and glucagon secreted by clusters of cells in pancreas called islets of Langerhans. Islets contain both beta and alpha cells

Question 3

Insulin

Answer 3

Secreted by beta cells, lowers blood glucose concentration. Binds to receptors on muscle and liver cells, increases permeability of muscle-cell membranes to glucose by increasing the number of channel proteins. Also activates glycogenesis

Question 4

Glucagon

Answer 4

Secreted by alpha cells, raises glucose concentration when it’s too low. Binds to specific receptors on cell membrane of liver cells, activates glycogenolysis and gluconeogenesis. Also increases rate of respiration

Question 5

Glycogenesis

Answer 5

Glucose to glycogen, activated by insulin

Question 6

Glycogenolysis

Answer 6

Glycogen to glucose, activated by glucagon

Question 7

Gluconeogenesis

Answer 7

Glycerol and amino acids (non-carbs) to glucose, activated by glucagon

Question 8

Hormone responses vs Nervous impulses

Answer 8

Travel in blood, slower than nervous impulses. Responses to hormones can occur all over the body if widespread target cells, nervous impulses are localised. Hormones are not broken down as quickly as neurotransmitters, effects last longer

Question 9

Glucose transporters

Answer 9

Channel proteins allow glucose to be transported across a cell membrane by facilitated diffusion. Insulin triggers movement of carrier protein holding vesicles to cell membrane

Question 10

Adrenaline

Answer 10

Hormone secreted from adrenal glands. Secreted when low concentration of glucose, stressed or exercising. Binds to receptors on liver cells. Activates glycogenolysis, inhibits glycogenesis

Question 11

Adrenaline effects on hormones

Answer 11

Activates glucagon secretion, inhibits insulin secretion

Question 12

Second messengers

Answer 12

Binding of hormone to receptors activates an enzyme inside cell membrane, produces a second messenger chemical. Second messenger activates other enzymes in cell to bring about response

Question 13

Adrenaline and glucagon second messenger

Answer 13

Activate an enzyme called adenylate cyclase, converts ATP into cyclic AMP (second messenger). Cyclic AMP activates protein kinase A enzyme, which activates a cascade that breaks down glycogen to glucose

Question 14

Type 1 diabetes

Answer 14

Immune system attack beta cells in islets of Langerhans, can’t produce insulin. Kidney can’t reabsorb all insulin, some excreted in urine.

Question 15

Type 2 diabetes

Answer 15

Beta cells don’t produce enough insulin or body’s cells don’t respond properly to insulin