Biochemistry : Other Hormone Pathways

Study concepts, example questions & explanations for Biochemistry

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Example Questions

Example Question #1 : Other Hormone Pathways

Which of the following statements about adrenergic receptors is true?

Possible Answers:

Phentolamine is a beta-antagonist.

Isoproterenol is a beta-agonist.

Propranolol is an alpha-agonist.

Norepinephrine/noradrenaline is the methylated form of epinephrine/adrenaline.

Correct answer:

Isoproterenol is a beta-agonist.

Explanation:

Phentolamine is an alpha-antagonist. Propranolol is an beta-agonist. Epinephrine/adrenaline is the methylated form of norepinephrine/noradrenaline.

 

Example Question #116 : Biochemical Signaling

Which of the following statements about pancreatic hormones is not true?

Possible Answers:

Beta cells secrete insulin.

Insulin stimulates muscle and fat cells to store glucose.

Delta cells secrete somatostatin.

Glucagon is secreted in response to high blood glucose levels.

Correct answer:

Glucagon is secreted in response to high blood glucose levels.

Explanation:

Insulin is secreted in response to high blood glucose levels, which increases cell uptake of glucose. Glycogen has the opposite effect - it stimulates glycogenolysis and lipolysis to release glucose into the bloodstream during times of fasting/starvation.

Example Question #117 : Biochemical Signaling

Which of the following does not lead to an increase in the secretion of insulin?

I. Gastric inhibitory polypeptide (GIP)

II. Cholecystokinin (CCK)

III. Closing of the voltage gated potassium channels

IV. Decreased arginine levels

Possible Answers:

I and II

I, II, and IV

III only

IV only

Correct answer:

IV only

Explanation:

Elevated arginine leads to an increase in secretion of insulin, not decreased. GIP, CCK and closing of the voltage gated potassium channels lead to an increase in secretion of insulin. 

Example Question #2 : Other Hormone Pathways

During a fasting state, the brain reduces its need for serum glucose by using which of the following substances as an alternate energy source?

Possible Answers:

Beta-hydroxybutyrate and acetoacetate

Beta-carotene and apoprotein B

Beta-hydroxybutyrate only

Beta-hydroxybutyrate and apoprotein B

Correct answer:

Beta-hydroxybutyrate and acetoacetate

Explanation:

Ketone bodies, which include acetoacetate, beta-hydroxybutyrate, and acetone, are produced by the liver in the fasting state by beta-oxidation of fatty acids. They are then released into the blood stream, where they can be used as alternative energy sources for other organs, such as muscle, kidney, and brain. Apoprotein B is one of the proteins that hold lipoproteins together. Beta-carotene is a vitamin with antioxidant properties. 

Example Question #119 : Biochemical Signaling

Which of the following is not a step in the signal transduction pathway when epinephrine acts on its receptor?

Possible Answers:

Activation of diacylglycerol and IP3

Activation of adenylate cyclase

Activation of a G protein

Increase in the quantity of cAMP

Activation of protein kinase A

Correct answer:

Activation of diacylglycerol and IP3

Explanation:

Epinephrine first binds to an adrenergic receptor. The activated receptor works via a G protein, and so GDP is exchanged for GTP and the protein is activated. This then causes activation of adenylate cyclase and subsequent conversion of ATP to cAMP. cAMP acts upon protein kinase A and several other effector molecules. Diacylglycerol and IP3 are second messengers that are uninvolved in this process.

Example Question #120 : Biochemical Signaling

Erythropoietin is an important glycoprotein in the human body. What is the function of erythropoietin?

Possible Answers:

Stimulates red blood cell destruction

Stimulates production of red blood cells

Stimulates white blood cell activity

Stimulates secretion in the tubules of the nephron

Stimulates filtering in the kidney

Correct answer:

Stimulates production of red blood cells

Explanation:

Erythropoietin is a glycoprotein hormone produced in the kidney that stimulates the production of red blood cells in the bone marrow.

Example Question #3 : Other Hormone Pathways

Which hormone below would result in an increase in cAMP?

Possible Answers:

Epidermal growth factor

None of these

Insulin

Human growth hormone

Epinephrine

Correct answer:

Epinephrine

Explanation:

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 #122 : Biochemical Signaling

Which of the following hormones crosses the plasma membrane in order to affect its target cell?

Possible Answers:

None of these hormones act by crossing the plasma membrane

Insulin

Glucagon

Thyroxine

Epinephrine

Correct answer:

Thyroxine

Explanation:

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 #4 : Other Hormone Pathways

Which of the following is a polypeptide?

Possible Answers:

Epinephrine

Glucagon

Biotin

Pyridoxal phosphate

Correct answer:

Glucagon

Explanation:

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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