1.4b Hydrophobic signals and control of transcription NEED TO GO OVER

Question 1

Hydrophobic signalling molecules

Answer 1

Hydrophobic signalling molecules can 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

The receptors for hydrophobic signalling molecules are transcription factors. And transcription factors are proteins that when bound to DNA can either inhibit or stimulate initiation of transcription.

Question 3

Steroid hormones

Answer 3

Steroid hormones oestrogen and testosterone are examples of hydrophobic signalling molecules. Steroid hormones bind to specific receptors in the cytosol or the nucleus.

Question 4

Hormone-receptor complex

Answer 4

It moves to the nucleus where it 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.