Glucose Metabolism

Question 1

What cells of the islets of langerhans produce insulin?

Answer 1

beta cells

Question 2

what type of signal is insulin?

Answer 2

the body’s most important anabolic signal

Question 3

how is insulin first produced?

Answer 3

it is first produced as a prohormone typical of a peptide hormone in the pancreas

Question 4

what does proinsulin consist of?

Answer 4

it consists of 3 domains

Question 5

what is the half life of insulin?

Answer 5

5-8 mins in the plasma and metabolised in kidney and liver

Question 6

what is secretion of insulin secreted by?

Answer 6

by a number of factors, mainly elevation of glucose and amino acid levels in plasma

Question 7

GLUT?

Answer 7

glucose transport protein

Question 8

Once GLUT detect the increase in glucose in blood what happens?

Answer 8

glucose is converted to … –> increase in ATP –> Voltage gated calcium channels –> influx of Ca –> secretion of insulin into the extracellular fluid by exocytosis

Question 9

what response does a glucose-stimulated secretion of insulin follow?

Answer 9

it follows a biphasic response

Question 10

Describe the biphasic of insulin secretion?

Answer 10

1st phase is release of pre-formed insulin (lasts 5-15mins elevation)
2nd phase is more prolonged due to the synthesis of new insulin

Question 11

GIP?

Answer 11

gastric inhibitory peptide

Question 12

what is insulin also secreted by?

Answer 12

by hormone produced in the intestinal tract - particularly GIP

Question 13

after eating, what happens regarding GIP?

Answer 13

the food in the intestines causes GIP release which travels through the circulation to the pancreas where the B cells are stimulated to secrete insulin

Question 14

What does an anticipatory release of GIP result in?

Answer 14

insulin response is much greater when glucose administered orally compared to systemically

Question 15

what does insulin have an effect on - regarding carbs?

Answer 15

has an effect on metabolism of carbs proteins and fats –> lowers glucose, AA and FA in the blood

Question 16

what does insulin promote?

Answer 16

intracellular conversion of glucose to storage forms –> target cells are hepatocytes, myocytes and adipocytes

Question 17

what are the metabolic actions of insulin?

Answer 17

cellular glucose uptake and glycogen synthesis
cellular amino acid uptake and protein synthesis
metabolism of glucose, amino acids and lipids

Question 18

when is insulin secretion enhanced?

Answer 18

after meals

Question 19

what does insulin inhibit?

Answer 19

inhibits gluconeogenesis

Question 20

hepatic gluconeogenesis requires?

Answer 20

amino acids

Question 21

how does insulin inhibit gluconeogenesis?

Answer 21

because hepatic gluconeogenesis requires AA and insulin increases cell uptake of AA
insulin also inhibits the enzymes required for gluconeogenesis

Question 22

insulin overall function

Answer 22

gets glucose and amino acids out of bloodstream and into cells
and creates stores of glucose

Question 23

where is glucagon secreted from?

Answer 23

alpha cells - first synthesised as a precursor molecule

Question 24

what type of hormone is glucagon?

Answer 24

single chain hormone

Question 24

what is the primary target organ of glucagon?

Answer 24

the liver and mobilises glucose from hepatic glycogen and gluconeogenesis

Question 25

what is glucagon release stimulated by?

Answer 25

by a decrease in plasma glucose (unlike insulin)

Question 26

where is glucagon metabolised?

Answer 26

in liver and kidney

Question 27

half life of glucagon?

Answer 27

half life of 5-6 mins

Question 28

other than a decrease in plasma glucose, what else stimulates release of glucagon?

Answer 28

an increase in plasma amino acids (like insulin) it needs to balance out glucose

Question 29

what effect does glucagon have on adipose tissue?

Answer 29

stimulates hormone - sensitive lipase increases ffa concentration in plasma

Question 30

how is glucose taken up by cells?

Answer 30

by using carrier proteins know as GLUTS particularly in skeletal muscle cells facilitated diffusion down conc gradient recruited by insulin

Question 31

what transport of glucose isn not dependant on insulin?

Answer 31

in neurones as brain needs constant energy

Question 32

where are pancreatic hormones released from?

Answer 32

from a small cluster of cells called the Islets of Langerhans which make up approx 2% of the gland

Question 33

what cells secrete glucagon?

Answer 33

α-cells from the islets of langerhans

Question 34

what cells secrete somatostatin?

Answer 34

δ-cells

Question 35

what cells secrete pancreatic polypeptide?

Answer 35

PP cells

Question 36

what are the endocrine functions of the pancreas?

Answer 36

produces hormones capillaries transport secreted hormones to the portal vein

Question 37

what are the exocrine functions of the pancreas?

Answer 37

pancreatic juice

Question 38

what are the 3 domains that proinsulin consists of?

Answer 38

-amino-terminal β-chain, carboxyterminal α-chain and the connecting inactive C-peptide

Question 39

what does the principal action of insulin involve?

Answer 39

it involves transport of glucose into certain tissue cells

Question 40

how does the autonomic nervous system stimulate secretion of insulin?

Answer 40

there is increased activity in the parasympathetic nerve fibres in the vagus nerve which stimulates secretion

Question 41

what insulin increase the synthesis of?

Answer 41

increases the synthesis of glycerol and FAs into triglycerides when entry of glucose into cells increases

Question 42

what insulin inhibit the breakdown of?

Answer 42

inhibits the breakdown of triglycerides and builds up fat stores