Hormones and gene expressionEdexcel International A Level Biology: Flashcards

What these 14 flashcards ask

What is a transcription factor?
Where does a transcription factor bind?
What does an activating transcription factor allow?
Why can every cell contain the same genes yet make different proteins?
Why can't peptide hormones enter cells?
Where do peptide hormones bind?
What is a second messenger?
Give two examples of peptide hormones.
Why can steroid hormones enter cells?
Where do steroid hormone receptors lie?
How does a steroid hormone change gene expression?
Give two examples of steroid hormones.
Which type of hormone usually has the faster effect?
What is a target cell?

Exam questions on Hormones and gene expression

A student compares how two hormones affect their target cells. Insulin is a peptide hormone released by the pancreas, and oestrogen is a steroid hormone released by the ovaries. Both hormones travel in the blood to all parts of the body.
Explain why only certain cells respond to insulin, even though every cell in the body is exposed to it.2 marks
In liver cells, a gene codes for an enzyme that is only made when the cell is exposed to a particular hormone. Researchers find that the gene is switched on only when a transcription factor is bound to a specific region of DNA next to the gene.
Explain how the binding of the transcription factor can result in the liver cell making more of the enzyme.2 marks
Researchers add radioactively labelled hormones to isolated liver cells. After a few minutes, labelled glucagon (a peptide hormone) is found only on the cell-surface membrane. Labelled cortisol (a steroid hormone) is found inside the nucleus. When the cells are also given a chemical that inhibits RNA polymerase, cortisol no longer causes the cells to make a new enzyme, but glucagon still causes the cells to release glucose within seconds.
Explain why labelled glucagon is found only on the cell-surface membrane but labelled cortisol is found in the nucleus.3 marks

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).