Biochemistry : Peptide Hormone Pathways
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Example Question #74 : Biochemical Signaling
When someone with type I diabetes mellitus fails to inject sufficient insulin, which one of the following will happen?
Fat cells hydrolyze more fat than normal and become depleted of triacylglycerol.
Glycogen synthesis in the liver increases and the liver becomes enlarged.
Ketone body production by the liver decreases and ketone levels in the blood become dangerously low.
Muscle cells take up more glucose than normal and store it as glycogen.
Fat cells hydrolyze more fat than normal and become depleted of triacylglycerol.
Type I diabetes occurs when the body is incapable of producing insulin, so after a meal it is necessary to inject it. Because insulin isn't being produced, the signal cascade following insulin secretion never occurs. Without insulin, when blood glucose is high it isn't taken up by the muscle cells. Glucagon release is still occurring, so fatty acids are being oxidized to provide energy. This depletes the supply of triacylglycerol. Ketone production is in fact too high in people with type I diabetes, leading to ketoacidosis, an acidification of the blood from excess ketone bodies. Glycogen synthesis would not be triggered, as glucagon would still be triggering glycogen breakdown.
Example Question #75 : Biochemical Signaling
Which polypeptide hormone stimulates the breakdown of glycogen and lipids?
Insulin
Somatostatin
Ghrelin
Glucagon
Epinephrine
Glucagon
The correct answer is glucagon. Epinephrine does stimulate the breakdown of glycogen and lipids, but it is an amino acid derivative, not a polypeptide. The rest are all polypeptide hormones, but with different functions. Somatostatin inhibits the release of insulin and glucagon from the pancreas. Insulin has the opposite effect of glucagon, reducing blood sugar levels by stimulating the synthesis of glycogen and fat. Ghrelin stimulates appetite.
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