1. Which process is not a goal of biochemical regulatory mechanisms? a) slowing
ID: 203635 • Letter: 1
Question
1. Which process is not a goal of biochemical regulatory mechanisms?
a) slowing down biosynthetic pathways when their products accumulate
b) maintaining most biochemical reactions far from their equilibrium states
c) maximizing efficiency of fuel utilization
d) partitioning of metabolites between alternative pathways
2. Gycogenesis____
a) involves the action of glycogen debranching enzyme
b) involves transfer of glucose from CDP-glucose to a nonreducing end of a glycogen chain
c) occurs only in the liver and muscle
d) begins the production of a new glycogen molecule with the reactions of glycogen
3. Glycogenolysis____
a) is used by muscle to increase blood glucose levels
b) produces mostly glucose 1-phosphate from the reducing ends of glycogen molecules
c) releases glucose 1-phosphate from the reducing ends of glycogen molecules
d) is mostly the result of the actions of glycogen hydrolase
4. Which statement regarding glycogen phosphorylase is false?
a) In muscle, Ca2 stimulates dephosphorylation of glycogen phosphorylase.
b) In muscle, epinephrine indirectly stimulates glycogen phosphorylase activity.
c) In the liver, glucagon indirectly stimulates glycogen phosphorylase activity.
d) Glycogen phosphorylase b is less active than glycogen phosphorylase a.
5. Glycogen synthase kinase 3 __________.
a) is indirectly stimulated by insulin
b) functions only in regulation of glycogen synthase
c) phosphorylates glycogen synthase only after glycogen synthase has been phosphorylated by another kinase
d) phosphorylates casein kinase II
6. Hormonal regulation of glycogen metabolism in muscle __________.
a) involves phosphorylation and dephosphorylation of GM
b) does not involve the actions of cAMP
c) results in stimulation of glycogen synthesis when blood glucose levels are low
d) is primarily through the actions of insulin and glucagon
Explanation / Answer
1. Answer is b. Biochemical regulatory mechanism try to maintain reactions in equilibrium. E.g. enzyme regulation which speed up the reactions within body but also maintain an equilibrium state by positive and negative feedback inhibition. When substrate is high enzyme acclerates the reaction to form product but when product concentration is more negative feedback loop stops the product to form by inhibition of enzyme catalysis.
2.c. Glycogenesis occurs in liver and muscle. Liver can store 100 gm and muscle store 250 gm of glycogen. When Blood glucose level is high insulin promotes glycogen biosynthesis. Glycogen synthase enzyme starts condensation reaction between existing glycogen and UDP glucose.
3.c.In glycogenolysis glycogen phosphorylase promotes breakdown of glycogen and releases glucose 1 phosphate from the reducing end of the glycogen molecules.
4. a. In muscle calcium binds with calmodulin and this complex activates CAM kinase which phosphorylates glycogen phosphorylase enzyme and dephosphorylate glycogen synthase.
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