The Citric Acid Cycle Quiz All of question 1 and question 2 with associated part
ID: 214359 • Letter: T
Question
The Citric Acid Cycle Quiz
All of question 1 and question 2 with associated parts to the answers please.
1. Match the function from the list on the right with each of the items below on the left. Please write the letter of your choice in the blank space. Each function may be used only once or not at all Biochemical functions A. Generation of NADH and FADH2 B.Allows conversion of fats to glucose 0.6 pts.) 0.6 pts.) 0.6 pts.) (0.6 pts) . (0.6 pts.) pyruvate dehydrogenase in bacteria and plants C. Enzymatic cofactor D. Replenishes the pool of tricarboxylic citric acid cycle acids E. Generate ATP F. Prepare glycolytic products for entry -_ pyruvate carboxylase NADH into the citric acid cycle glyoxylate cycle G. Allow conversion of fats to glucose n mammals H. Regulate the citric acid cycle 2. Write the reaction catalyzed by ONE of the three REGULATED enzymes WITHIN the citric acid cycle itself (i.e., not leading into or feeding from the cycle), including (1 pt.) Substrate name and chemical structure (1 pt.) Enzyme name (1 pt.) Cofactor name(s) (1 pt.) Product name and chemical structure (1 pt.) Effector name(s) and impact on enzyme activityExplanation / Answer
Q1.
Pyruvate dehydrogenate -----F----- prepare glycolytic product for entry into citric acid cycle
Pyruvate carboxylase -----D ------replanish the pool of tricarboxylic acids
citric acid cycle ------- A -------generates NADH And FADH2
NADH --- C------ enzymatic cofactor
glyoxylate cycle ----B------ covertes the fat into glucose in bacteria and plant
Q2. CITRIC ACID CYCLE is regulated at three steps
1. pyruvate dehydrogenase
2. isocitrate dehydrogenase
3. alpha keto glutarate dehydrogenase
1. The formation of acetyl CoA from pyruvate is an irreversible step thus they are unable to convert acetyl CoA back into glucose. The activity of the pyruvate dehydrogenase complex is stringently controlled by several means
High concentrations of reaction products of the complex inhibit the reaction:
i. acetyl CoA inhibits the transacetylase component (E2),
ii. NADH inhibits the dihydrolipoyl dehydrogenase (E3).
covalent modification of the pyruvate dehydrogenase by a specific kinase switches off the activity of pyruvate dehydrogenase complex. Deactivation is reversed by the action of a specific phosphatase.
Increasing the NADH/NAD+, acetyl CoA/CoA, or ATP/ADP ratio promotes phosphorylation and, hence, deactivation of the complex. In other words, high concentrations of immediate (acetyl CoA and NADH) and ultimate (ATP) products inhibit the activity. The pyruvate dehydrogenase is switched off when the energy charge is high and biosynthetic intermediates are abundant.
On the other hand, pyruvate as well as ADP (a signal of low energy charge) activate the dehydrogenase by inhibiting the kinase.
1-adrenergic agonists and hormones such as vasopressin stimulate pyruvate dehydrogenase and triger the cytosolic Ca2+ level. The rise in mitochondrial Ca2+ activates the pyruvate dehydrogenase complex by stimulating the phosphatase.
Insulin also accelerates the conversion of pyruvate into acetyl CoA by stimulating the dephosphorylation of the complex.
2. allosteric regulation of enzymes isocitrate dehydrogenase
isocitrate dehydrogenase is allosterically stimulated by ADP, which enhances the enzyme's affinity for substrates.
NADH inhibits iso-citrate dehydrogenase by directly displacing NAD+. ATP, is also inhibitory.
3. -ketoglutarate dehydrogenase
next control site in the citric acid cycle is -ketoglutarate dehydrogenase. it is inhibited by succinyl CoA and NADH, the products of the reaction that it catalyzes. I
-ketoglutarate dehydrogenase is inhibited by a high energy charge. Thus, the rate of the cycle is reduced when the cell has a high level of ATP.