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Which of the following choices is a likely response to low blood glucose levels?
I. Phosphorylation of glycogen phosphorylase
II. Phosphorylation of glycogen synthase
III. Enhanced production of insulin
When blood glucose levels are low, the obvious bodily response is to create more free glucose. Glycogen phosphorylase is an enzyme that is responsible for freeing glucose monomers from glycogen (thus creating more free glucose and raising the blood glucose concentration). Phosphorylation of glycogen phosphorylase activates the enzyme to create more free glucose. Thus, statement I should appear in our answer.
Glycogen synthase is an enzyme that does just the opposite; it traps free-floating glucose monomers by adding them to glycogen chains. Phosphorylation of glycogen synthase inhibits the enzyme's function to create more free glucose. Thus, statement II should also appear in our answer.
Increasing the production of insulin would lower blood glucose levels even further (glucagon, another hormone, would help raise them). Thus, statement III should not appear in our answer.
The final answer is statements I and II.
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Antidiuretic hormone (ADH) is produced in the pituitary gland and then secreted into the blood stream. What is the function of ADH?
Antidiuretic hormone (ADH) binds the ADH receptors in the basolateral membrane of the collecting duct, which, through an ATP-dependent signaling cascade, synthesizes and relocates aquaporin-2 to the apical membrane of the collecting duct epithelial cells. The increase of aquaporin-2 at this membrane location facilitates increased water reabsorbtion into the bloodstream.
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Which of the following cellular processes is NOT stimulated by insulin?
Insulin is a hormone that can often be associated with post-meal metabolism. The body has just eaten a meal, and is sequestering all of the nutrients and vitamins in the food. As a result, insulin is often associated with anabolic processes: glycogenesis, cholesterol and protein synthesis, and lipogenesis. Lipolysis, or the breaking down of fatty acids, is observed in periods of starvation, and therefore would not be stimulated by insulin.
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Which enzyme would be inhibited in the body following a carbohydrate-heavy meal?
After eating a carbohydrate-heavy meal, the body is not going to have any problem getting access to glucose. As a result, the body is going to activate enzymes needed for bringing glucose into cells and storing/using it. This includes glucokinase, PFK-1, and glycogen synthase. Fructose-1,6-bisphosphatase is an enzyme used in gluconeogenesis. Since the body does not need to create glucose following the meal, this enzyme is inhibited.
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