Insulin and Glucagon

Question 1

Glycolysis

Answer 1

Glucose –> Pyruvate (CO2, H2O), Lactate

Question 2

Glycogenolysis

Answer 2

Glycogen –> Glucose

Question 3

Gluconeogenesis

Answer 3

Glucose from AA, Glycerol, Lactate, Pyruvate in Liver

Question 4

Glucose Sparing

Answer 4

Switch off glucose. Use fat as energy.

Question 5

Lipolysis- Fat Mobilization

Answer 5

Breakdown of Triacylglycerol –> Glycerol & FA

Question 6

Hyperglycemia

Answer 6

Increase in plasma glucose

Question 7

Hypoglycemia

Answer 7

Decrease in plasma glucose

Question 8

Catabolism

Answer 8

Cellular breakdown of organic molecules (CHO, Fats, Proteins)

Question 9

Anabolism

Answer 9

Synthesis of organic molecules

Question 10

Fat Mobilization

Answer 10

Increase breakdown of triacylglycerol and release of glycerol and fatty acids

Question 11

What are the 3 major cell types in the regulation of plasma glucose? What do they do?

Answer 11

(1) Alpha cells- 25% of endocrine process; synthesize and secrete glucogon (increasing plasma glucose)
(2) Beta cells- 60%; synthesize and secrete insulin (decreasing plasma glucose)
(3) Delta cells- 10%; synthesize and secrete somatostatin (inhibits EVERYTHING)

Question 12

Where are the 3 major cell types in the regulation of plasma glucose located in the pancreas?

Answer 12

islets of Langerhans

Question 13

What is insulin?

Answer 13

A polypeptide hormone that consists of an A-chain and a B-chain held together by 2 disulfide bonds with a 3rd disulfide bond within the A-chain

Question 14

Insulin is derived from what?

Answer 14

Proinsulin

Question 15

What are the steps to insulin synthesis and release by the B-cell

Answer 15

(1) Pre-proinsulin in the RER
(2) Proinsulin
(3) Packaged into secretory vesicles
(4) Goes into the golgi body
(5) Becomes granules
- proinsulin is converted into insulin by proteolytic enzyme that clip the peptide into 2 places-
(6) Mature Granules and C-peptides that gets released into blood

Question 16

What is the complex that is stored in the mature granules?

Answer 16

Insulin-zinc complex

Question 17

What is the most important stimulus in secreting insulin?

Answer 17

An increase in plasma glucose

Question 18

When are plasma insulin concentrations generally highest?

Answer 18

Immediately following a meal

Question 19

What is the process of the role of insulin in the regulation of blood glucose concentration? (5)

Answer 19

(1) Increase Blood Glucose
(2) Increase insulin secretion; increase plasma insulin
(3) Increase glucose uptake into tissue
(4) Decrease blood glucose
(5) Restoration of blood glucose to normal

Question 20

What are the 3 major insulin sensitive tissues in the body?

Answer 20

(1) Adipose
(2) Liver
(3) Muscle

Question 21

Insulin Receptor

Answer 21

Actuates the signaling cascade which positions the insulin to mediate the transport of glucose across the plasma membrane

Question 22

What is lipoprotein lipase? What activates lipoprotein lipase?

Answer 22

An enzyme that promotes the uptake of lipoproteins from the blood; insulin

Question 23

What is the overall effect of insulin on adipose cell metabolism?

Answer 23

It promotes storage of excess fuel as tricylglycerols while inhibiting its breakdown

Question 24

What effect does insulin have on protein metabolism?

Answer 24

It stimulates active transport of amino acids from the blood into individual muscle cells allowing more AA to be available for protein synthesis (ribosomes) while inhibiting degradation

Question 25

What does insulin do to ribosomes in the muscle?

Answer 25

increases number in each muscle cell and increases the activity of individual ribosomes

Question 26

What is the overall effect of insulin on carbohydrate metabolism?

Answer 26

Stimulates glycogen synthesis while inhibiting gluconeogenesis (in the liver)

Question 27

What two tissues are readily permeable to glucose, even in the absence of insulin

Answer 27

Brain and Liver

Question 28

How does glucose enter into muscle/adipose tissue? What is it mediated by?

Answer 28

Facilitated diffusion; glucose transporters

Question 29

What is the effect of insulin to stimulate glucose uptake into cells

Answer 29

(1) Glucose transporters mainly inactive and inside the cytoplasm with very few transporters inside plasma membrane
(2) Stimulation of insulin provides translocation of transporters mostly into plasma membrane allowing more transportation of glucose inside the tissue

Question 30

What are the effects of insulin deficiency? (4)

Answer 30

(1) Increase glycogenolysis
(2) Increase gluconeogenesis
(3) Increase ketogenesis
(4) Increase Fatty Acids

Question 31

What are glucagon’s effects on metabolism?

Answer 31

OPPOSITE of insulin

Question 32

What happens in the plasma during insulin deficiency? (6)

Answer 32

Increase in

(1) glucose
(2) fatty acids
(3) ketoacids
(4) phospholipids
(5) cholesterol
(6) lipoproteins

Question 33

Glucose Tolerance Test (Normal vs. Diabetic)

Answer 33

• Normal person will have a transient increase in blood glucose that will trigger release of insulin so a very quick drop back to normal fasting glucose afterwards
• Diabetic person will have a larger increase in blood glucose that will have a fast response of insulin, the decrease is significantly slower depending on how bad the diabetes is; fasting glucose levels are higher as well