Unit 1 - Topic 4 - Communication and signalling - Section B - Hydrophobic signals and control of transcription

Question 1

What can hydrophobic signalling molecules do

Answer 1

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

Question 2

What are the receptors for hydrophobic signalling molecules

Answer 2

Transcription factors

Question 3

What are transcription factors

Answer 3

Proteins that when bound to DNA can either stimulate or inhibit initiation of transcription.

Question 4

What are examples of hydrophobic signalling molecules

Answer 4

Steroid hormones oestrogen and testosterone

Question 5

What do steroid hormones bind to

Answer 5

Specific receptors in the cytosol or the nucleus

Question 6

What happens to the hormone-receptor complex

Answer 6

The hormone-receptor complex binds to specific DNA sequences called hormone response elements (HREs). Binding at these sites influences the rate of transcription, with each steroid hormone affecting the gene expression of many different genes.