Which of the following statements about enzymes is/are correct ?
1. They are biocatalysts.
2. They perform their action on the site where they are produced.
Select the correct answer from the codes gi

Question

Which of the following statements about enzymes is/are correct ?
1. They are biocatalysts.
2. They perform their action on the site where they are produced.
Select the correct answer from the codes given below :
Codes :

UnlockIAS · Accepted Answer

Correct — C, both 1 and 2. Statement 1 is beyond argument: enzymes are biological catalysts. They speed up a reaction by lowering its activation energy, are not consumed or permanently changed by it, act in very small amounts, and are almost all globular proteins (the exceptions are ribozymes, which are catalytic RNA). Statement 2 is the one the commission's key treats as true, and it holds for the largest classes of enzymes a student meets. Intracellular enzymes — the glycolytic enzymes of the cytoplasm, the respiratory enzymes of the mitochondrion, the hydrolases of the lysosome — act inside the very cell that synthesised them. The intestinal brush-border enzymes (maltase, sucrase, lactase) are made by intestinal epithelial cells and act on the surface of those same cells. Salivary amylase acts in the mouth, into which the salivary glands empty; pepsin acts in the stomach lumen, where the gastric chief cells that make it discharge it. HONEST NOTE, because this item is a known key conflict: statement 2 is broadly true rather than universally true. The standard exception is the pancreatic digestive enzymes — trypsin, chymotrypsin, pancreatic amylase and lipase are synthesised in the acinar cells of the pancreas but do their work in the duodenum, a different organ altogether. On a strict reading of 'the site where they are produced', that exception makes option (a) defensible, and many candidates argued for it. The official UPPSC SET-D key marks (c), and the key is what decides marks — so (c) is the answer to carry into the exam, while the pancreatic exception is the fact to carry into your notes.

Why the other options are wrong — (a) This is the defensible dissent, not a careless error: if you insist that statement 2 must hold for EVERY enzyme, the pancreatic enzymes (made in pancreatic acinar cells, active in the duodenum) break it. The commission nevertheless marked statement 2 correct, reading it in the looser textbook sense that an enzyme acts at or around its site of secretion. Marks follow the key, so (a) scores zero — but understand why it was argued rather than dismissing it.  (b) Rejects statement 1, which is the single least controversial claim in the whole question. 'Biocatalyst' is the textbook one-word definition of an enzyme. No reading of enzyme biology makes statement 1 false.  (d) A blanket rejection cannot stand, because statement 1 is definitionally true. This option only attracts candidates who spot the pancreatic problem in statement 2 and then over-correct by discarding both statements.

Concept: Enzymes are biological catalysts — overwhelmingly proteins, plus a small class of catalytic RNAs called ribozymes — that accelerate specific biochemical reactions by lowering the activation energy, without themselves being used up. Each enzyme is highly specific to its substrate (the lock-and-key idea, refined into the induced-fit model), works only within a narrow band of temperature and pH, and is often dependent on a cofactor or coenzyme (many of which are vitamin derivatives). Where an enzyme acts is a separate question from what it does: some enzymes never leave the cell that made them, while others are secreted and travel to their site of action.

State PCS 2019 Q91 — Science & Technology PYQ with Answer

State PCS 2019 Q91 — Science & Technology PYQ with Answer