Biochemistry : Biochemical Signaling
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Example Questions
Example Question #7 : Other Hormone Pathways
Which hormone below would result in an increase in cAMP?
Epinephrine
Insulin
Epidermal growth factor
None of these
Human growth hormone
Epinephrine
Epinephrine and glucagon are examples of hormones that affect G protein-coupled receptors like adenylate cyclase and increase levels of cAMP. The other hormones listed affect receptor tyrosine kinases and non-receptor tyrosine kinases.
Example Question #8 : Other Hormone Pathways
Which of the following hormones crosses the plasma membrane in order to affect its target cell?
Glucagon
Insulin
Thyroxine
None of these hormones act by crossing the plasma membrane
Epinephrine
Thyroxine
This question is asking us to identify a hormone that passes through the target cell's plasma membrane in order to affect that cell.
When looking at hormones, there are three general types: amine, peptide, and steroid. Out of these, steroid hormones are all capable of crossing the plasma membrane. In fact, the receptors for steroid hormones are often found in the cytoplasm or nucleus of the target cell. Generally, amine and peptide hormones act by binding to a receptor on the outer surface of the target cell's plasma membrane. However, thyroxine is an exception. Thyroxine is an amine hormone based off of the amino acid tyrosine. Normally, amine-derived hormones do not cross the plasma membrane, but the largely hydrophobic nature of thyroxine allows it to cross the plasma membrane and bind with its intracellular receptor.
Of the other answer choices shown, none of them cross the cell membrane. Epinephrine is an amine-derived hormone, utilizing tyrptophan as the starting material. Insulin, glucagon, and growth hormones are all peptide hormones.
Example Question #9 : Other Hormone Pathways
Which of the following is a polypeptide?
Glucagon
Epinephrine
Biotin
Pyridoxal phosphate
Glucagon
Glucagon is a short peptide hormone involved in triggering signal cascades in response to low blood glucose. Biotin, also known as vitamin B7, is a cofactor in fatty acid synthesis. Pyridoxal phosphate, the activated form of vitamin B6, is a cofactor in transamination reactions, among others. Epinephrine is a steroid hormone involved in the fight or flight response.
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