Hormones

Question 1

Define hormone

Answer 1

A substance produced in minute amount at one site in a multicellular organism and transported to another site where it acts on target cells.

A chemical substance synthesised in small amounts by an endocrine tissue and carried in the blood to another tiddue, where it acts as a messenger to regulate the function of the tissue or organ

Question 2

Define circulating hormones

Answer 2

Secreted to blood to target organ

Question 3

Define autocrine hormones

Answer 3

hormones that bind to receptors on the same cell that secreted them

Question 4

Define paracrine hormones

Answer 4

Hormones that bind to receptors on nearby cells

Question 5

What is the endocrine system made of?

Answer 5

Hypothalamus
Anterior pituatory
posterior pituatory
thymus gland
pancreas (insulin, glucagon)
pineal gland
thyroid gland
parathyroid glands
adrenal glands
gonads

Question 6

What is hypoglycaemic?

Answer 6

Blood glucose is too low

Cause convulsions, coma

Mainly affects brain as it cannot metabolise fat

Question 7

What is hyperglycaemic?

Answer 7

Blood glucose is too high

Question 8

What is the normal blood glucose range?

Answer 8

3-5mM

Question 9

What hormones maintain blood glucose levels?

Answer 9

Insulin and Glucagon

Called homeostasis

Question 10

Outline how insulin works

Answer 10

Meal > Blood glucose rise > Insulin is released > return glucose levels to normal by glycogen storage and fat synthesis.

Question 11

Outline how glucagon works

Answer 11

Fasting state > Glucagon released > promote release of glucose via breakdown of glycogen by liver.

Question 12

Who discovered insulin?

Answer 12

1889, Oscar Monkowski

Question 13

How does release of insulin affect skeletal muscles?

Answer 13

Increase: Glucose uptake, Glycogen synthesis

Decrease: Glycogen breakdown

Question 14

How does release of insulin affect Fat cells?

Answer 14

Increase : Glucose uptake, Triacyglycerol synthesis

Question 15

How does release of insulin affect liver?

Answer 15

Increase: Glycogen synthesis, FA synthesis

Decrease: Glucose release, glycogen breakdown

Question 16

How does release of insulin affect the brain?

Answer 16

Stop eating

Question 17

What does the islets of langerhands produce?

Answer 17

Insulin, Glucagon and somatostatins

Beta cells secret insulin
alpha cells secrete glucagon
delta cells secrete somatostatins

Question 18

Outline insulin synthesis

Answer 18

Rough ER:

Preproinsulin > Proinsulin (Golgi) > Proteolytic cleavage > Insulin

Question 19

What is the cleavage site of insulin?

Answer 19

Between A and F

Question 20

How is preoproinsulin converted to proinsulin?

Answer 20

proteolytic cleavage of 23aa signal peptide
formation of 3 disulfide bonds

further cleavage removes the C peptide to produce mature insulin, composed of an A and B chain

Question 21

When are GLUT2 transporters used?

Answer 21

For Beta-cells
When blood glucose rises

Glucose converted into G6P and enters glycolysis, TCA, and oxidative phosphorylation

This closes the ATP-gated K+ channels

Membrane depolarises, this opens voltage sensitive Ca2+ channels and Ca2+ floods in

The influx of Ca triggers fusion of the secretory granules with the plasma membrane and insulin release

Question 22

How is insulin stored?

Answer 22

Secretory granules

Question 23

Who sequenced insulin?

Answer 23

Fred Sanger

consists of 2 polypeptide chains, A, B. linked together by disufide bonds

Question 24

What is the structure of insulin receptor?

Answer 24

2 units
alpha and B subunit linked by disulfide bond

a lie outside the cell, forming the binding site.

B has a transmembrane domain, and tyrosine kinase domain. Hence it phosphorylates tyrosine residues both itself and other proteins

Question 25

What other proteins do insulin receptors phosphorylate?

Answer 25

insulin receptor substrates (IRS) 1-4
phosphatidylinositol 3,4,5 triphosphate (PIP3)
PDK I
GLUT4

Increase glucose uptake

Question 26

What is the main role of insulin?

Answer 26

GLUT4 membrane translocation

other effects : proliferation via. MAP kinase cascade