S/A Hormones

Question 1

Name three general classes of hormones and give an example of each.

Answer 1

(1) peptide (e.g., insulin, glucagon);
(2) catecholamine (e.g., epinephrine);
(3) steroid (e.g., testosterone, progesterone);
(4) eicosanoids (e.g., prostaglandins, thromboxanes).

Question 2

(1) peptide (e.g., insulin, glucagon); (2) catecholamine (e.g., epinephrine); (3) steroid (e.g., testosterone, progesterone); (4) eicosanoids (e.g., prostaglandins, thromboxanes).

Answer 2

Fast-acting hormones affect the activity of preexisting cellular enzymes. Slow-acting hormones alter gene expression thereby changing the levels of active cellular components.

Question 3

What distinguishes eicosanoids from other potent biological signaling molecules such as epinephrine

Answer 3

Eicosanoids are paracrine hormones: they generally do not move long distances between their points of release and their points of action.

Question 4

Which class of hormones acts via nuclear receptors? Give an example of this type of hormone and briefly describe its mode of action.

Answer 4

s: Steroid hormones. Examples are the sex hormones testosterone and estradiol. They pass through the plasma membrane and interact with receptor proteins in the nucleus. The hormone- receptor complex interacts with DNA and alters the expression of specific genes.

Question 5

How do hormonal cascades result in large amplification of the original signal?

Answer 5

At each level a small quantity of the signal molecule activates a larger number of molecules at the next level. When this occurs over several levels this multiplicative effect can result in several millionfold amplification of the original signal.

Question 6

Describe five possible fates for glucose 6-phosphate in the liver.

Answer 6

Possible answers include:

(1) conversion to liver glycogen;
(2) dephosphorylation and release of glucose into bloodstream;
(3) oxidation via the pentose phosphate pathway;
(4) oxidation via glycolysis and the citric acid cycle;
(5) oxidation to acetyl-CoA, which then serves as precursor for synthesis of triacylglycerols, phospholipids, and cholesterol.

Question 7

Describe five possible fates of amino acids arriving in the liver after intestinal uptake.

Answer 7

Possible answers include:

(1) synthesis of nucleotides;
(2) synthesis of hormones;
(3) synthesis of other nitrogenous products such as porphyrins; (
4) deamination, followed by oxidation of carbon skeleton for energy;
(5) synthesis of proteins for export to plasma;
(6) synthesis of proteins for liver;
(7) export of free amino acids to other tissues.

Question 8

Describe five possible fates for fatty acids in the liver.

Answer 8

(1) conversion to triacylglycerol or cholesterol esters for export in plasma lipoproteins;
(2) conversion into hepatocyte phospholipids;
(3) oxidation and conversion to ketone bodies for export to other tissues;
(4) β oxidation to acetyl-CoA, and further oxidation via citric acid cycle for ATP production;
(5) β oxidation to acetyl-CoA, followed by synthesis of cholesterol from acetyl-CoA;
(6) binding to serum albumin for transport to heart and skeleton.

Question 9

Compare in general terms the effects of epinephrine, glucagon, and insulin on glucose metabolism.

Answer 9

Epinephrine and glucagon cause an increase in the blood glucose level.
Epinephrine acts when a higher than normal level of glucose is required;
glucagon acts when the level is unusually low.
Both stimulate gluconeogenesis and glycogen breakdown and decrease glycolysis and glycogen synthesis.

Insulin causes a decrease in blood glucose levels; it acts by increasing glycogen synthesis, glycolysis, and glucose uptake by cells as well as by decreasing glycogen breakdown.

Question 10

Suppose you are responsible for formulating the diet for a 4-year-old boy with diabetes. How do you decide what kind and amount of carbohydrate and protein to include in the diet? What compounds would you monitor in blood and urine and why?

Answer 10

boy will need enough protein to furnish the essential amino acids for synthesis of new proteins and enough carbohydrate to provide for his energetic needs and to maintain a normal level of blood glucose. It is essential to

avoid excess carbohydrates and calories that might lead to ketoacidosis.

To find the correct balance between dietary intake and insulin, the levels of glucose and ketone bodies in blood and urine must be monitored.