12. As catalysts, enzymes are; a) significantly less effective than non-enzymati
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12. As catalysts, enzymes are; a) significantly less effective than non-enzymatic catalysts. b) slightly less effective than non-enzymatic catalysts. c) significantly more effective than non-enzymatic catalysts. d) slightly more effective than non-enzymatic catalysts. 13. Which of the following is not true concerning enzymes? a) they exhibit great specificity in the reaction they catalyze. reaction substrate. of substrate and the catalysis. b) they increase the rate of reaction many fold compared to the uncatalyzed c) they do not distinguish between the L-isomer and the D-isomer of their d) the amino acids in the active site are important for determining the specificity 14. The common catabolic pathway consists of the citric acid cycle and glucose metabolism. b) oxidative phosphorylation the the chemiosmotic pump. c) electron and H transport. d) the citric acid cycle and oxidative phosphorylation 15. The enzymes of the citric acid cycle are in the; a) cytosol b) nucleus matrix of the mitochondria d) cristae of the mitochondria 16. The N in NADH stands for; a) nicotine b) nicotinic acid nicotinamide d) neomycinExplanation / Answer
Ans. #12. Correct option C. significantly more effective than non-enzymatic catalysts.
Enzymes are biocatalysts – i.e. catalyst of the living system. Because of substrate binding as well as bonding-guided orientation and proximity of the substrate at the active site and further induced conformational change always ensures the conversion of substrate into the product. Moreover, the same enzyme can binding two or more substrate in the specific orientation to enhance catalysis.
However, binding of reactants to a non-enzymatic catalyst does not ensure spontaneous orientation and proximity of groups. Above that, the binding of two or more reactants to the non-enzymatic catalyst also reduces the probability of correct orientation and proximity of groups because there is NO active site (where the substrates are brought in correct orientation and proximity by numerous amino acid residues around the active site).
Therefore, as catalyst, enzymes are significantly more effective than non-enzymatic catalyst.
#13. Correct option. C. They don’t distinguish between L- and D-isomers.
Enzymes also exhibit stereospecificity, i.e. they generally catalyze one stereoisomer but not the other. For example, most of proteolytic enzymes in biological system are specific to L-amino acids but not to D-amino acids.
#14. Correct option. C.
# Option A. The citric acid cycle and oxidative phosphorylation.
Catabolism is the breakdown of biomolecules in simpler molecules.
Anabolism is the synthesis of biomolecules.
Catabolism and Anabolism are together called metabolism.
So, the term glucose metabolism also include anabolic pathways simultaneously with catabolic pathways. Therefore, option A is NOT purely catabolic.
# Option B. Oxidative phosphorylation (don’t confuse with ETC) produces ATP. So, it is an anabolic process.
# Option C. There is transfer of electrons (that forms NADH and FADH2) and H+ (during ETC).
Though electron transfer also occurs during all the reactions (both catabolic and anabolic), there option C does not presents a direct example of synthesis of any biomolecule like those indicated by the process oxidative phosphorylation.
Therefore option C is most appropriate one.
# Option D. Oxidative phosphorylation is an anabolic process.
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