Biology HL
Receptors and Signal Transduction
- 1.
Compare how a water-soluble peptide hormone and a lipid-soluble steroid hormone can signal to target cells. Refer to membrane permeability, receptor location and the importance of receptor specificity.
[4 marks] · no calculator - 2.
Adrenaline binds to a G-protein-coupled receptor on a liver cell. Explain the roles of the receptor, G protein and cAMP in conveying and amplifying the signal, and predict the effect of a receptor that cannot activate its G protein.
[4 marks] · no calculator - 3.
In a hypothetical insulin-responsive muscle cell, insulin binds normally but the receptor's tyrosine kinase activity is blocked. Explain the normal sequence leading to increased glucose entry and predict the effect of the block. Assume the glucose gradient favours entry.
[4 marks] · no calculator - 4.
Two hypothetical cells are exposed to the same extracellular peptide signal. Cell A has its specific membrane receptor; cell B lacks it. Predict their initial responses and explain why the presence of a receptor does not imply that every responding cell must produce the same final response.
[3 marks] · no calculator - 5.
A hypothetical drug inhibits adenylyl cyclase without preventing adrenaline from binding its receptor. Predict the effect on cAMP production in a G-protein-linked pathway and explain how this illustrates the distinction between a first messenger and a second messenger.
[3 marks] · no calculator