Lecture 11- Cell communication: hormone signalling pathways

Question 1

What is a precursor of a range of steroid hormones?

Answer 1

Cholesterol

Question 2

Describe some properties of steroid hormones

Answer 2

1. Both hydrophilic and hydrophobic properties

2. Able to penetrate through cell membranes and BBB

Question 3

What are the 2 classes of steroid hormones?

Answer 3

1. Corticosteroids

2. Sex steroids

Question 4

What are the 5 subtypes of steroid hormones?

Answer 4

1. Glucocorticoids
2. Mineralocorticoids
3. Androgens
4. Oestrogens
5. Progestogens

Question 5

What is a zinc finger?

Answer 5

Contains 4x cysteine residues which co-ordinate with a zinc atom to form a looped structure that is able to access the major groove of the DNA double helix

Question 6

Describe the early phase response to steroid hormones

Answer 6

1. Steroid hormone binds to the steroid hormone receptor
2. The receptor-steroid hormone complexes activate primary response genes
3. This induces the synthesis of primary response proteins

Question 7

Describe the delayed response to steroid hormone

Answer 7

1. The primary response proteins shuts off primary response genes
2. And turn on secondary response genes

Question 8

Give an example of a disease caused by too much cortisol

Answer 8

Cushing’s syndrome

Question 9

Give an example of a disease caused by too little cortical

Answer 9

Addison’s disease

Question 10

State the 3 major biochemical steps in insulin signalling

Answer 10

1. Tyrosine phosphorylation of the receptors and its direct substrate
2. Activation of the lipid kinase PI3K
3. Activation of multiple serine/threonine kinases (most importantly AKT)

Question 11

What happens following insulin binding

Answer 11

1. The insulin receptor tyrosine kinase is activated
2. Causing tyrosine phosphorylation of insulin receptor and the insulin receptor substrate protein
3. P-tyrosine sites on IRS allow the binding of PI3K which synthesised PIP3 at the PM
4. PIP3 recruit PDK which directly phosphorylates the Thr308 residue of AKT
5. Activated AKT goes on to phosphorylate a number of substrates at Ser/Thr residues

Question 12

Give 2 diseases associated with lack of insulin

Answer 12

1. Type 1 diabetes

2. Type 2 diabetes

Question 13

Give a treatment of type 2 diabetes

Answer 13

Metformin

Question 14

How does metformin treat type 2 diabetes?

Answer 14

• Decreases insulin resistance

* Reduces plasma fasting insulin levels

Question 15

How does metformin treat diabetes at a molecular level?

Answer 15

1. Drug is positive so accumulated in mitochondria
2. Inhibits the mitochondrial complex I and prevents ATP production
3. This activated AMPK which is an enzyme that helps regulate glucose metabolism

Question 16

What processes are triggered by insulin binding?

Answer 16

1. Glucose production
2. Lipid synthesis
3. Protein synthesis
4. Glycogen synthesis
5. Glucose uptake