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une ch 26
basic concepts in the regulation of fuel metabolism
Question | Answer |
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What is the effect of insulin on the following metabolic pathways? The storage of glucose in glycogen. | Insulin increases the rate of the pathway for converting glucose to glycogen. (This is an example of anabolism.) |
The mobilization of glucose from glycogen. | Insulin inhibits glycogenolysis.(Insulin is an anabolic hormone. This is an example of catabolism.) |
The synthesis of fatty acids from glucose in the liver. | Insulin increases the rate of the pathway of fatty acid synthesis from glucose. |
The synthesis of triacylglycerols in liver and adipose tissue. | Insulin increases the rate of the pathway of the synthesis of triacylglycerols in liver and adipose tissue. (This is an example of anabolism.) |
The mobilization of free fatty acids from adipose tissue (breakdown of TG & FA). | Insulin inhibits the mobilization (breakdown) of free fatty acids from adipose tissue. (Insulin is an anabolic hormone. This is an example of catabolism.) |
The synthesis of proteins in most tissues. | Insulin increases the rate of protein synthesis in most tissues. (This is an example of anabolism.) |
The mobilization of amino acids from proteins for gluconeogenesis. | Insulin inhibits the mobilization (breakdown) of amino acids from proteins. |
Would you expect this insulin effect after a high carbohydrate meal, after an overnight fast, during times of stress? | High carb meal: Yes Overnight Fast: No Insulin low bc the glucose levels low. Stressful Times: No During stressful times, insulin is low because glucagon and epinephrine are high to raise blood glucose to cope with the stress. |
What is the effect of glucagon upon the following metabolic pathways? The storage of glucose in glycogen. | Glucagon inhibits the storage of glucose in glycogen. |
The mobilization of glucose from glycogen. | Glucagon increases the rate of glycogenolysis (mobilization of glucose FROM glycogen) |
The synthesis of fatty acids from glucose in the liver. | Glucagon inhibits the synthesis of fatty acids from glucose in the liver. |
The synthesis of triacylglycerols in liver and adipose tissue. | Glucagon inhibits the synthesis of triacylglycerols in liver and adipose tissue. |
The mobilization of free fatty acids from adipose tissue. | Glucagon increases the rate of lipolysis (mobilization of free fatty acids from lipids) |
The mobilization of amino acids from proteins for gluconeogenesis. | Glucagon increases the rate of amino acid mobilization from proteins for gluconeogenesis. However, in the skeletal muscle there is no effect because skeletal muscles lack glucagon receptors. |
Would you expect this glucagon effect after a high carbohydrate meal, after an overnight fast, during times of stress? | HC Meal:N(inc glucose= increase of Insulin->inhibits glucagon release.) ON Fast:Y(Both glucose n insulin levels drop after meal.allows glucagon release->cont thru overnight fast.) Stress:Y(Cortisol same effect as glucagon- inc catabolic reactions) |
What is the effect of stress hormones as a group upon the following metabolic pathways? The storage of glucose in glycogen. | No. It is inhibited except by cortisol which stimulates glycogen synthesis. |
The mobilization of glucose from glycogen. | Yes. It is activated/increased. |
The synthesis of fatty acids from glucose in the liver. | No. It is inhibited. |
The synthesis of triacylglycerols in liver and adipose tissue. | No. It is inhibited. |
The mobilization of free fatty acids from adipose tissue. | Yes. It is activated/increased. |
The synthesis of proteins in most tissues. | It is inhibited in most tissues. Some proteins must still be synthesized in order to maintain body functions. However, protein degradation happens at a much more rapid pace than synthesis. |
The mobilization of amino acids from proteins for gluconeogenesis. | Yes. It is activated/increased. |
Cortisol stimulates both | glycogen synthesis and gluconeogenesis. |
What is the effect of the following upon insulin release and what is the hormone or metabolite directly affecting the B-cells?: (1) A high carbohydrate meal: | Inc glucose/insulin=inhibit glucagon. Inc glucose= inc glycolysis n ATP. Inc ATP acting on Beta cells=inc insulin secretion.Blood carrying secreted insulin from Beta cells. insulin binds to alpha cells, where glucagon secretion is suppressed. |
What is the effect of the following upon insulin release and what is the hormone or metabolite directly affecting the B-cells?: (2) A high protein meal: | protein meals secrete less insulin compared to a carb meal. Insulin inc following a high protein diet that inc concentrations of AA Beta cells not inhibited by protein meals and inc glucagon caused by protein meal does not bind to Beta receptors. |
What is the effect of the following upon insulin release and what is the hormone or metabolite directly affecting the B-cells?: | Insulin inhibited due to increased epinephrine and norepinephrine, which bind to Beta cell receptors. Epinephrine and norepinephrine released during times of stress such as sickness, exercise and starvation. |
how does glucose directly affect the beta cells? | Glucose directly affects the B-cells. An increase in glucose causes an increase in ATP generated (from glycolysis, TCA cycle) which increases the amount of insulin secreted. |
What is the effect of the following upon glucagon release and what is the hormone or metabolite directly affecting the a-cells? (1) A high carbohydrate meal: | Insulin up, glucagon down. Glucose will rise in response to the high intake of carbohydrate. Once there is a rise in glucose, insulin hormone is triggered and released, causing a suppression of glucagon as a result. |
What is the effect of the following upon glucagon release and what is the hormone or metabolite directly affecting the a-cells? (2) A high protein meal: | AA up. Glucagon up. Glucagon made of AA,AA will form and trigger glucagon release. AA induce insulin secretion,just not as much as glucose. Glucagon will stimulate GNG from AA following a high protein, low carb (Atkins diet) meal. |
What is the effect of the following upon glucagon release and what is the hormone or metabolite directly affecting the a-cells? (3) Starvation, trauma, or vigorous exercise: | Inc epinephrine & cortisol leads to inc glucagon. (epi has a bigger effect because it inhibits insulin release). In cases of stress and trauma, insulin secretion is not matched to glucagon release and blood glucose present. (looksliketype2diabetes) |
how does insulin affect the alpha cells? | Insulin directly affects the a-cells. Increased insulin release causes an inhibition of glucagon release from a-cells. |
To the extent that it is known, explain the series of events following an increase in insulin that results in more glucose transporters in muscle and adipose tissue cell membranes. | insulin binds to alpha subunits->tyrosine kinase region of beta subunit autophosphorylates->beat subunit activated n binds IRS proteins-> binds PI3-kinase (has SH2)->becomes activated protein kinase B-> PKB puts GLUT-4 in membrane-> inc glucose uptake |
Be able to list all the intermediates in the signal transduction of glucagon from the binding of the ligand to the activation of a protein by phosphorylation. | Glucagon Binds --> Activates heterotrimeric G protein and releases--> GDP for GTP --> alpha subunit binds Adenylate Cyclase --> produces cAMP --> cAMP takes Protein Kinase A apart-> catalytic subunit phosphorylates phosphorylase kinase-> glycogen degraded |