1. Pyruvate produced by glycolysis in the cytosol a. is small enough to cross th
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1. Pyruvate produced by glycolysis in the cytosol a. is small enough to cross the inner mitochondrial membrane by simple diffusion b. is always converted to lactate before it can enter other pathways c. must first be transported into mitochondria if it is to be consumed by pyruvate dehydrogenase d. is consumed by pyruvate dehydrogenase, which is also found in tho cytosol 2. Coenzyme A forms esters with rclatively small standard free energies of hydrolysis b. a. forms thiocsters with acyl groups can have pyruvate linked to it through an ester linkage c. d. bas lipoic acid as one of its components 3. PDH complex a. Has thiamine pyrophosphate as its only required cofactor b. Uses an amide bond between the acctyl group between active sites of the complex Is a hetcxtrimcr c. d. Consists of multiple copies of three enzymes 4. Which statement is not true regarding substrate channeling? a. It prevents intermediates from diffusing away from the active sites. b. It makes the kinetics of the complex so rapid as to prevent it from being c. d. the ratc-limiting step(s) of a pathway. It prevents intermediates from feeding into other pathways. It increases the local concentration of substrates. 5. Which statement regarding isocitrate dchydrogenase is false? a. It catalyzes a reversible reaction under physiological conditions. b. It has a Mn cofactor c. In eukaryotes, there is an NAD+ -dependent form found in mitochondria and an NADP+ -dependent form found in both mitochondria and the cytosol. It catalyzes an oxidative decarboxylation d. 6. a-Kctoglutarate dehydrogenase a. b. c. is nearly identical to PDH in terms of mechanism and cofactors catalyzes an unusual reductive decarboxylation is an example of convergent evolution when compared to the complex that degrades branched-chain a-kcte acids catalyzes a reaction with a standard free energy change near zero d.Explanation / Answer
1. Option C is correct.
Pyruvate is a charged molecule. So, it can not cross the inner mitochondrial membrane. It must be transported into the mitochondria for it to be acted by pyruvate dehydrogenase.
2. Option B is correct.
Coenzyme A forms a thioester linkage with acyl groups.
3. Option D is correct.
PDH complex contains multiple copies of three different enzymes.
4. Option B is correct.
The nature of a rate-limiting step of a metabolic pathway is not dependent on substrate channeling.
5. Option C is correct.
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