Hormones and gene expressionEdexcel International A Level Biology: Mind map

Exam questions on Hormones and gene expression

1. 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
2. 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
3. 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