Unit 1 Part 4b (Hydrophobic Signals And Control Of Transcription)

Question 1

What can hydrophobic signalling molecules do?

Answer 1

Diffuse directly through the phospholipid bilayer of membranes, and so bind to intracellular receptors

Question 2

Give examples of hydrophobic signalling molecules

Answer 2

Steroid hormones like oestrogen and testosterone

Question 3

What are the receptors for hydrophobic signalling molecules?

Answer 3

Transcription factors - proteins that when bound to DNA can either stimulate or inhibit initiation of transcription

Question 4

How do steroid hormones affect the rate of transcription?

Answer 4

1. Steroid hormones bind to specific receptors in the cytosol or nucleus
2. Hormone-receptor complex binds to specific DNA sequences called hormone response elements
3. Binding at these sites influences the rate of transcription, with each steroid hormone affecting the gene expression of many different genes.