W1 Glucose Metabolism

Question 1

pancreatic hormones are produced by which combination of glands?

Answer 1

endocrine and exocrine glands

Question 2

a small cluster of cells called the islets of langerhans make up approximately what percentage of the gland?

Answer 2

2%

Question 3

which type of cells stimulates the release of insulin?

Answer 3

beta cells

Question 4

which type of cells stimulate the secretion of glucagon?

Answer 4

alpha cells

Question 5

which type of cells secrete somatostatin?

Answer 5

delta cells

Question 6

what are PP cells?

Answer 6

pancreatic polypeptide cells

Question 7

what are the endocrine functions of the pancreas?

Answer 7

• produces hormones
• capillaries transport secreted hormones to the portal vein

Question 8

what are the exocrine functions of the pancreas?

Answer 8

formation of pancreatic juice

Question 9

what is the body’s most important anabolic signal?

Answer 9

insulin

Question 10

what is insulin first produced as?

Answer 10

a prohormone typical of a peptide hormone in the pancreas

Question 11

proinsulin consists of what 3 domains?

Answer 11

amino-terminal beta-chains
carboxyterminal alpha-chains
and connecting inactive C-peptide

Question 12

what is the principle action of insulin?

Answer 12

transporting glucose into certain tissues

Question 13

what is the half life of insulin in plasma?

Answer 13

5-8 minutes

Question 14

where is insulin metabolised?

Answer 14

the kidney and liver

Question 15

what is secretion of insulin mainly stimulated by?

Answer 15

the elevation of glucose and amino acid levels in plasma

Question 16

what happens to allow the increased secretion of insulin?

Answer 16

voltage gated calcium channels allow and influx of calcium causing a secretion of insulin into the extracellular fluid by exocytosis

Question 17

what is GLUT?

Answer 17

a glucose transport protein

Question 18

glucose stimulated secretion of insulin follows a biphasic response, briefly describe stage 1 and 2:

Answer 18

1 - a spike due to the release of pre-formed insulin (from 5-15 mins)
2 - a gentle curve which is more prolonged due to synthesis of new insulin

Question 19

insulin is also secreted by hormones produced in the GIT particularly GIP, what does GIP stand for?

Answer 19

gastric inhibitory peptide

Question 20

what effects does food in the intestines have on insulin?

Answer 20

it causes GIP release which travels to the pancreas where beta-cells are stimulated to secrete insulin

Question 21

insulin response is much greater when glucose is administered orally or systematically?

Answer 21

orally (anticipatory release of GIP)

Question 22

how does the autonomic nervous system effect insylin secretion?

Answer 22

increased activity in parasympathetic nerve fibres in the vagus nerve stimulates insulin secretion

Question 23

does insulin increase or decrease levels of glucose, amino acids and fatty acids in the blood?

Answer 23

decrease

Question 24

insulin promotes intracellular conversion of glucose to storage forms, what are the target cells for this?

Answer 24

hepatocytes, myocytes and adipocytes

Question 25

metabolic actions of insulin occur through its effects on membrane transport causing what?

Answer 25

1. cellular glucose uptake and glycogen synthesis
2. cellular amino acid uptake and protein synthesis
3. metabolism of glucose, amino acids and lipids

Question 26

in secretion of insulin enhanced before or after meals?

Answer 26

after

Question 27

insulin causes gluconeogenesis inhibition, what are the reasons why?

Answer 27

it requires amino acids and insulin increases cell uptake of amino acids, it also inhibits enzymes required for gluconeogenesis

Question 28

insulin increases synthesis of glycerol and fatty acids due to an increase of what substance?

Answer 28

triglycerides (when glucose entry increases)

Question 29

how does insulin build up fat stores?

Answer 29

by inhibiting the breakdown of triglycerides

Question 30

glucagon is first synthesised as what?

Answer 30

a precursor molecule

Question 31

is glucagon a single or double chain peptide hormones?

Answer 31

single

Question 32

what is glucagon’s primary target organ?

Answer 32

the liver

Question 33

glucagon mobilises glucose from hepatic glycogen and what?

Answer 33

gluconeogenesis

Question 34

what is glucagon stimulated by?

Answer 34

a decrease in plasma glucose (opposite of insulin)
and/or an increase in plasma amino acids (like insulin)

Question 35

where is glucagon metabolised?

Answer 35

in the liver and kidney

Question 36

what is glucagon’s half life?

Answer 36

5-6 mins

Question 37

glucose is taken up by cells using carrier proteins know as what?

Answer 37

glucose transporters/GLUTs

Question 38

how do GLUTs transport glucose?

Answer 38

allow facilitated diffusion down concentration gradients