Control of blood glucose concentration (BIOL5)

Question 1

Factors that control blood glucose concentration

Answer 1

• Eating carbs inc conc
• Exercising dec conc - used in respiration
• Emotional stress - triggers release of adrenaline
• Pregnancy - goes up!

Question 2

Hormones that control blood glucose concentration

Answer 2

• Insulin - secreted by beta cells into blood
• Glucagon - secreted by alpha cells into blood
• Secreted by pancreas cells called islets of langerhans

Question 3

Role of insulin in controlling glucose concentration

Answer 3

Lowers glucose conc:

1. Pancreas detects glucose conc too high
2. B-cells secrete insulin; A-cells stop secreting glucagon
3. Insulin bind to spec receptors on cell memb of liver/muscle cells
4. Inc. permeability of cell memb to glucose, cells take up more glucose
5. Insulin activates enzymes to convert glucose –> glycogen, by glycogenesis

• Cells store glycogen in cytoplasm as energy source
• Insulin inc rate of respiration of glucose

Question 4

Action of insulin at the cellular level

Answer 4

1. Insulin binds to receptor on liver cell memb (chemical stimulation)
2. Vesicle in cytoplasm w/ memb rich in glucose carrier molecule, fuses w/ cell surface memb, inc. no. glucose carrier molecules in memb

Question 5

Role of glucagon in controlling glucose concentration

Answer 5

Raises glucose conc

1. Pancreas detects blood conc too low
2. A-cells secrete glucagon; B-cells stop secreting insulin
3. Glucagon binds to spec receptors on cell memb of liver cells
4. Activate enzymes that b/d glycogen –> glucose, by glycogenolysis

• Glucagon promotes formation of glucose fr fatty acids/amino acids
• Gluconeogenesis - forming glucose from non-carbs
• Glucagon dec. rate of respiration of glucose in cells

Question 6

Role of adrenaline in controlling glucose concentration

Answer 6

• Secreted when low glucose conc
• Binds to receptors in liver cell memb
• Activates glycogenolysis - b/d of glycogen –> glucose
• Inhibits glycogenesis - synthesis of glycose –> glycogen
• Gets body ready for action by making more glucose available for muscle respire

Question 7

How adrenaline/glucagon activate glycogenolysis inside cells

Second messenger model of adrenaline/glucagon action

Answer 7

1. Adrenaline/glucagon bind to spec receptors form hormone-receptor complex, activate enzyme adenylate cyclase
2. Activated adenylate cycle converts ATP into second messenger, cyclic AMP (cAMP) - activates enzymes that b/d glycogen –> glucose (glycogenolysis)

Question 8

Features of Type I diabetes

Answer 8

• B-cells in islets of langerhans don’t prod insulin
• After eating, glucose rises, stays high - hyperglycaemia
  
  • Kidneys can’t reabsorb glucose, so excreted in urine
• Treated by insulin shots

Question 9

Features of Type II diabetes

Answer 9

• B-cells don’t prod enough insulin or body doesn’t respond well to insulin
  
  • Cells don’t respond as insulin receptors on memb don’t work properly, so cells don’t uptake enough glucose
  • So blood glucose higher than normal!
• Treated by controlling carb intake