Enzymes - Mechanism of Action & Clinical Importance is part of the Enzymes and Porphyrins section of Biochemistry. Practise 85 exam-style MCQs for NEET PG, FMGE, INI-CET and NEET SS, each with the correct answer and a detailed explanation.
Enzymes - Mechanism of Action & Clinical Importance MCQs move from cytosolic glycolytic enzymes and PFK-1 regulation to glutathione defence, selenocysteine enzymes such as deiodinase, and competitive inhibition patterns — high-yield NEET PG revision for FMGE and INI-CET.
All of the enzymes of glycolysis are found in the cytosol. Ref: Harper 28th edition, chapter 18.
Explanation: Phosphofructokinase-1 (PFK-1) is a key enzyme of glycolysis that catalyses the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate using ATP and is the main rate-limiting and regulatory step of the pathway. it is inhibited by ATP and citrate and activated by AMP and fructose-2,6-bisphosphate.
Ans. C. Deiodinase Selenocysteine is considered as 21 standard amino acid. It is present at the active site of some enzymes that catalyze redox reactions, e.g. thioredoxin reductase, glutathione peroxidase, and the deiodinase (converts thyroxin to triiodothyronine). Biosynthesis of selenocysteine requires cysteine, serine, ATP and a specific t-RNA. Serine provides the carbon skeleton of selenocysteine. Selenocysteine has a structure similar to cysteine, but containing the trace element selenium in place of sulfur atom of cysteine.
Glycine is converted to Serine by Serine Hydroxymethyl Transferase This is a reversible reaction Coenzymes required are Folic acid, Pyridoxal Phosphate Reference: Harper's 32 nd edition, page 284
Malic Enzyme converts Malate to Pyruvate by liberating CO 2 . Reference : Harper's illustrated biochemistry 32 nd edition, page 236
Functions of glutathione Free radical scavenging Transport of Amino acid across cell membrane Keep iron in the ferrous state, so prevent methemoglobin formation. Act as coenzyme for certain enzymes. Reference: Harper's 32 nd edition, page 23
Ans. is 'b' i.e., Competitive [Ref Essentials of Biochemistry p. 685] enzymes competitive inhibitors 1 Lactate dehydrogenase Oxamate 2 Aconitase Transaconitate 3 Succinate MalanateQ dehydrogenase 4 HMG-CoA reductase HMG, Lovastatin 5 Dihydrofolate reductase Amethopterin, Methotrexate 6 Xanthine oxidase Allopurinol 7 Alcohol dehydrogenase Ethanol 8 Carbonic anhydrase Acetazolamide 9 Digoxin Na-K ATPase 10 5 - Fluorouracil Thymidylate synthase
Functions of glutathione Glutathione is a tripeptide Free radical scavenging Transport of Amino acid across cell membrane Keep iron in the ferrous state, so prevent methemoglobin formation. Act as coenzyme for certain enzymes. Phase II Xenobiotic reaction in Conjugation Reference: Harper's 32 nd edition, page 23
Enzymes - Mechanism of Action & Clinical Importance MCQs move from cytosolic glycolytic enzymes and PFK-1 regulation to glutathione defence, selenocysteine enzymes such as deiodinase, and competitive inhibition patterns — high-yield NEET PG revision for FMGE and INI-CET.
MedLadder includes 85 curated MCQs for Enzymes - Mechanism of Action & Clinical Importance under Biochemistry (Enzymes and Porphyrins), covering NEET PG, FMGE, INI-CET and NEET SS preparation.
