5.4.4 regulating blood glucose

Question 1

normal blood concentration of glucose

Answer 1

between 4-6 mmmol dm-3

Question 2

hypoglycaemia

Answer 2

blood glucose concentration drops below 4mmol dm-3 & remain low for long periods

Question 3

main problem caused by hypoglycaemia

Answer 3

inadequate delivery of glucose to body tissues & brain

Question 4

symptoms of mild hypoglycaemia

Answer 4

include:
- tiredness
- irritability

Question 5

symptoms of severe hypoglycaemia

Answer 5

include:
- impairment of brain function & confusion
- lead to seizures, unconsciousness & even death

Question 6

hyperglycaemia

Answer 6

blood glucose concentration allowed to rise too high for too long

Question 7

what can permanently high blood glucose lead to (hyperglycaemia)

Answer 7

significant organ damage

Question 8

diagnosis of diabetes mellitus

Answer 8

consistently higher blood glucose conc. exceeding 7 mmol dm-3

Question 9

which cells monitor concentration of glucose in blood

Answer 9

cells in islets of Langerhans

Question 10

what is released if blood glucose too high/low

Answer 10

too high = insulin
too low = glucagon

Question 11

what cells do insulin/glucagon act upon

Answer 11

hepatocytes (liver cells) - which store glucose in form of glycogen

Question 12

describe the process if blood glucose raises too high

Answer 12

1. detected by beta cells in islets of Langerhans
2. secrete insulin into blood
3. insulin travels via circulatory system
4. target cells are liver cells, muscle cells & some other body cells (eg. brain)

Question 13

describe human insulin

Answer 13

• small protein of 51 amino acids
  = unable to pass through cell surface membrane

Question 14

what do the target cells possess

Answer 14

specific membrane-bound receptors for insulin

Question 15

what happens when insulin binds to the insulin receptors on target cells

Answer 15

1. activates enzyme tyrosine kinase which is associated with receptor on inside of membrane
2. tyrosine kinase causes phosphorylation of inactive enzymes in cell
3. this activates enzymes leading to cascade of enzyme-controlled reactions inside cell

Question 16

effects of insulin on cell

Answer 16

• more transporter proteins specific to glucose placed into cell surface membrane = achieved by causing vesicles containing transporter proteins to fuse with membrane
• more glucose enters cell
• glucose in cell converted to glycogen for storage (glycogenesis)
• more glucose converted to fats
• more glucose used in respiration

Question 17

glycogenesis

Answer 17

glucose in cell converted to glycogen for storage

Question 18

what is a low blood glucose concentration detected by

Answer 18

alpha cells in islets of Langerhans

Question 19

what do the alpha cells secrete

Answer 19

glucagon into blood

Question 20

describe glucagon

Answer 20

small protein containing 29 animo acids

Question 21

target cell of glucagon

Answer 21

hepatocytes (liver cells) = possess receptor for glucagon

Question 22

what happens when glucagon reaches hepatocytes

Answer 22

1. glucagon binds to receptors
2. stimulates G protein inside membrane
3. activates adenyl cyclase inside cell
4. adenyl cyclase converts ATP to cAMP
5. activates series of enzme-controlled reactions in cells

Question 23

effects of glucagon on cells

Answer 23

• glycogen converted to glucose by phosphorylase A (one of enzymes activated) = glycogenolysis
• more fatty acids used in respiration
• amino acids & fats converted into additonal glucose = gluconeogenesis

Question 24

glycogenolysis

Answer 24

glycogen converted to glucose by phosphorylase A

Question 25

gluconeogenesis

Answer 25

amino acids & fats are converted into additional glucose

Question 26

what is the concentration of blood glucose controlled by

Answer 26

negative feedback

Question 27

how can the hormones insulin & glucagon be described

Answer 27

antagonistic