Steroid Hormones

Question 1

Steroid Hormones bind to which class of receptors?

Answer 1

Intracellular

Steroid hormones can easily exit and enter the cell due to lipophillic nature

Question 2

Which enzyme is responsible for cleaving off carbon 20 to generate ketone?

Answer 2

CYP11A1

Question 3

Cholesterol is used to derived steroids. A steroid with a double bond between which two carbons is ALWAYS innactive?

Answer 3

Delta 5

i.e. Between carbons 5 and 6

Question 4

Which enzyme is responsible for changing a delta5 to a delta4 double bond? Where is this enzyme located?

Answer 4

3(Beta)HSD located in the SER

Question 5

Fast Response of Hormones

Answer 5

1. Increase release of cholesterol from cholesterol esters
2. Increase steroidogenic enzymes
3. Increase LDL receptor and HDL receptor SR-B1

Question 6

Long Term Response of Hormones

Answer 6

1. Increase cell number

2. Increase Organ size

Question 7

Mechanism of Steroid Receptors

Answer 7

1. Steroid diffuses through cell membrane
2. Steroid binds to chaperon protein (often heat shock protein)
3. Steroid+ HSP bind to DNA normally in dimer
4. SH+HSP bind to Hormone Response Element (HSE)
5. HSE recruits co-regulatory molecules to change chromatin conformation