AH Biology - Unit 1 - KA4(b) - Hydrophobic Signals and Control of Transcription

What are key examples of hydrophobic signals?

Key examples of hydrophobic signals are steroid hormones, such as testosterone, oestrogen, thyroxine, and cortisol.

What can hydrophobic signalling molecules do?

Hydrophobic signalling molecules can diffuse directly through the phospholipid bilayer of membranes and so can bind to intracellular receptors (often found in the nucleus).

What kind of factor are hydrophobic signalling receptors?

Hydrophobic signalling receptors are transcription factors.

What is a transcription factor?

A transcription factor is a protein that can bind to DNA and either stimulate or inhibit the initiation of transcription.

What are steroid hormones?

Steroid hormones, such as testosterone, oestrogen, thyroxine, and cortisol, are extracellular hydrophobic signalling molecules. They can pass through the plasma membrane

What are the stages of steroid hormone signalling?

The stages of steroid hormone signalling are:

1. The steroid hormone diffuses through the phospholipid bilayer of the target cell’s plasma membrane.

2. It binds to the specific receptor in the cell’s cytosol or nucleus.

3. This forms a hormone-receptor complex.

4. The hormone-receptor complex moves into the nucleus and binds to specific DNA sequences called hormone response elements (HRE). These are sites which affect gene expression.

5. Binding at these sites influences the rate of transcription.

What is stage 1 of hormone signalling?

Stage 1 of hormone signalling is “The steroid hormone diffuses through the phospholipid bilayer of the target cell’s plasma membrane.”

What is stage 2 of hormone signalling?

Stage 2 of hormone signalling is “It binds to the specific receptor in the cell’s cytosol or nucleus.”

What is stage 3 of hormone signalling?

Stage 3 of hormone signalling is “This forms a hormone-receptor complex.”

What is stage 4 of hormone signalling?

Stage 4 of hormone signalling is “The hormone-receptor complex moves into the nucleus and binds to specific DNA sequences called hormone response elements (HRE). These are sites which affect gene expression.”

What is stage 5 of hormone signalling?

Stage 5 of hormone signalling is “Binding at these sites influences the rate of transcription.”

What does each steroid hormone affect?

Each steroid hormone affects gene expression of many different genes.