Glucose Homeostasis

Question 1

For a healthy adult, the basal blood glucose is…

Answer 1

4-5mM

Question 2

Why does the body regulate blood-glucose within a narrow range?

Answer 2

The body defends against low blood-glucose concentrations, hypoglycaemia

and high blood-glucose concentrations, hyperglycaemia

Question 3

Beta-cells release…

Answer 3

Insulin to prevent hyperglycaemia

Question 4

Alpha-cells release…

Answer 4

Glucagon to prevent hypoglycaemia

Question 5

What mechanisms are responsible for maintaining such tight regulation of blood glucose?

Answer 5

While plasma glucose remains consistent, there is a robust increase in insulin concentrations with each meal.

Insulin acts to immediately lower blood glucose by promoting its up-take in cells.

Question 6

Glucagon is constantly being degraded in the…

Answer 6

Post-absorptive state

Question 7

Glucagon is maintained….

Answer 7

Between meals

*Important in preventing blood-glucose decline between meals

Question 8

Glucose molecules are stored as…

Answer 8

Glycogen, readily available in the liver and muscles

Question 9

When exercising, glycogen is catabolised to provide energy for contraction. T/F

Answer 9

True

Question 10

Neurons can store glycogen. T/F

Answer 10

False.

Neurons cannot store glycogen

Question 11

When glucose is limited, the brain switches to…

Answer 11

ketone-bodies; utilised for starvation

Question 12

Exocrine cells:

Answer 12

• Arranged in lobules that secrete a range of digestive enzymes, sodium bicarbonate, and other electrolytes into the duodenum.

Question 13

Endocrine cells:

Answer 13

Secrete hormones into systemic blood

Question 14

Alpha cells:

Answer 14

release glucagon –> catabolic, mobilise glucose, fatty and amino acids for energy production

Question 15

Beta cells:

Answer 15

releases insulin –> anabolic, storage of glucose, fatty, and amino acids

Question 16

Gamma cells:

Answer 16

releases somatostatin –> local to the pancreas to inhibit insulin and glucagon secretion

Question 17

The prime blood-glucose lowering hormone in the body is…

Answer 17

Insulin

Question 18

Excess glucagon production causes a _____ , a tumour of the pancreatic alpha cells that hyper-secretes glucagon.

Answer 18

gucagonoma

Question 19

C-peptide is secreted via…

Answer 19

Insulin and pancreatic beta-cells

Question 20

C-peptide is biologically inactive as a metabolic hormone. T/F

Answer 20

True

Question 21

A person with elevated blood glucose levels will likely exhibit increased secretion of _____ from their pancreatic beta-cells within the islet of Langerhans.

Answer 21

insulin

Question 22

Insulin receptor substrates (IRS) are….

Answer 22

downstream and act as cytoplasmic protein scaffolds to organise signalling complexes

Question 23

*IRS1 and IRS2 are ubiquitously expressed; primary mediators of insulin-dependant regulation of glucose metabolism. T/F

Answer 23

True

Question 24

Glucose is hydro…

Answer 24

Hydrophillic

Question 25

GLUT1 is found at:

Answer 25

1. Blood 2. Blood Brain Barrier 3. Heart **Insulin dependant

Question 26

GLUT1-4 are insulin dependent. T/F

Answer 26

True

Question 27

GLUT2 is found at:

Answer 27

1. Liver 2. Pancreas 3. Small intestine **Low affinity

Question 28

GLUT3 is found at:

Answer 28

1. Brain 2. Neurons 3. Sperm **High affinity

Question 29

GLUT4 is found at:

Answer 29

1. Skeletal muscle 2. Adipose tissue 3. Heart **Moderate affinity

Question 30

GLUT5 is found at:

Answer 30

Enterocyte of interstitial epithilium (Luminal side)

Question 31

GLUT5 is insulin INdependant and a transporter of...

Answer 31

Fructose

Question 32

GLUTS are...

Answer 32

Sodium and ATP-dependant | Ubiquitous

Question 33

SGLTs stand for:

Answer 33

Sodium-Glucose Transport Systems

Question 34

SGLTs are...

Answer 34

Sodium dependant | Require ATP for a sodium gradient

Question 35

SLGT1 is found at:

Answer 35

Enterocyte of interstitial epithelium **Glucose absorption

Question 36

SLGT2 is found at:

Answer 36

Proximal tubule of nephron in the kidney

Question 37

MAPK pathway:

Answer 37

Promotes cell growth.

Question 38

PI3K/PKB pathway:

Answer 38

Activated through IRS; promotes glucose transporters (GLUT4) translocation to cell surface.

Question 39

PI3K/mTOR pathway:

Answer 39

Activated through IRS; promotes protein synthesis, inhibits proteolysis, cell growth. 

Question 40

GLUT1 →

Answer 40

Basal glucose uptake | Expressed in all tissue, Important in glucose crossing the blood brain barrier

Question 41

GLUT2 → 

Answer 41

Important in pancreatic beta cells and liver hepatocytes

Question 42

GLUT3 →

Answer 42

Basal glucose uptake, expressed in all tissue, important in CNS neurons

Question 43

GLUT4 →

Answer 43

Insulin stimulated glucose uptake | Expressed in muscle (skeletal and cardiac) and fat adipocytes

Question 44

GLUT5 → 

Answer 44

Fructose transport in small intestine

Question 45

Which of the following pathways are activated by insulin signal transduction?

Answer 45

MAPK: promotion of cell growth P13K/MTOR: Promotion of protein synthesis, inhibits proteolysis and cell growth P13K/PKB - promotion of movement of GLUT4 to the cell surface in muscle and adipose cells

Question 46

How does the body ensure that insulin is secreted in response to digested nutrients.

Answer 46

The anatomical arrangement that allows nutrient rich blood from the GI-tract travels via the pancreas --> liver via the hepatic portal vein

Question 47

How does insulin promote glucose uptake in the liver after a meal?

Answer 47

- Via expression and activation of enzymes that promote storage and utilisation of glucose. - Insulin maintains a concentration gradient in hepatocytes that favours glucose intake via GLUT2 (and other GLUTs) transporters (glucose movement is down the concentration gradient). This occurs after a meal, when the blood glucose concentration is high.

Question 48

Insulin binds to its receptor and activates the...

Answer 48

Tyrosine kinase domain

Question 49

Insulin Receptor Substrates are phosphorylated by receptor kinases on tyrosine residues. T/F

Answer 49

True

Question 50

Within hepatocytes, insulin...

Answer 50

Promotes Glycogenesis (storage of glycogen) and inhibits Glycogenolysis (breakdown of glycogen to glucose)