A physiologist studies two hormones. Hormone X is a peptide, and its effect on the liver starts…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A physiologist studies two hormones. Hormone X is a peptide, and its effect on the liver starts within a few minutes. Hormone Y is a steroid, and its effect starts after several hours.
- Where is the receptor of X, and how does the message reach the inside of the cell?
- Where is the receptor of Y, and how does Y change the cell?
- Why is the effect of Y slower?
- Name one real hormone like X and one like Y.
Need a reminder? The key ideaShow
A hormone acts only through a specific receptor in the target tissue. Peptide hormones and adrenaline bind to receptors in the membrane and work through second messengers such as cyclic AMP. Steroid hormones and thyroid hormones pass into the cell, bind to receptors inside, and act on the genes. The fraction of receptors occupied is hormone divided by (Kd plus hormone).
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) The receptor of X is in the cell membrane. The message passes through the receptor, and a second messenger, for example cyclic AMP, carries it into the cell.
Step 2. (b) The receptor of Y is inside the cell. The hormone-receptor complex acts on the genome and regulates the expression of genes.
Step 3. (c) A change in gene expression needs new mRNA and new protein, which takes hours. The second messenger route changes enzymes that are already there.
Step 4. (d) X: glucagon (or insulin, or adrenaline). Y: cortisol (or testosterone, or thyroxine).
Answer: (a) membrane receptor and a second messenger; (b) an intracellular receptor and a change in gene expression; (c) new proteins must be made; (d) glucagon and cortisol.
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