Which of the following statement/s is/are correct ?
a. Enzymes are organic catalyst that accelerate biochemical reaction.
b. Enzymes are made up from proteins.
c. Enzyme activity is not depends upon t

Question

Which of the following statement/s is/are correct ?
a. Enzymes are organic catalyst that accelerate biochemical reaction.
b. Enzymes are made up from proteins.
c. Enzyme activity is not depends upon temperature.
d. Amylase is an enzyme that act on starch.

UnlockIAS · Accepted Answer

Correct — option (3). The stem is positive: it asks which statements are correct, and the safe procedure on a list of this kind is to mark each statement true or false on its own before looking at the options at all. Statement a says enzymes are organic catalysts that accelerate biochemical reactions, and that is the standard definition — enzymes are organic molecules produced by living cells which speed up reactions by lowering the activation energy, and which emerge from the reaction unconsumed and unchanged, so that a very small quantity can process a great deal of substrate. Statement b says enzymes are made up from proteins, and that too is correct: enzymes are proteins, chains of amino acids folded into a specific three-dimensional shape whose active site accommodates the substrate, and it is the dependence of function on that folded shape which explains almost everything else about enzyme behaviour. Statement d says amylase is an enzyme that acts on starch, which is correct — amylase hydrolyses starch to smaller sugars, and in the human body it is secreted twice, as salivary amylase which begins the digestion of starch in the mouth and as pancreatic amylase which continues it in the small intestine. Statement c is the one that fails. It asserts that enzyme activity is not dependent upon temperature, and the opposite is true: temperature is among the strongest influences on enzyme activity. As temperature rises from low values the rate increases, because molecules move faster and collide more often, up to an optimum which for human enzymes is about the normal body temperature of 37 °C. Beyond that the rate does not keep rising but falls away sharply, because heat disrupts the weak bonds holding the protein in its folded shape; the enzyme is denatured, the active site loses its geometry, and the catalytic power is destroyed. The asymmetry is worth noting — cooling slows an enzyme without destroying it, and activity returns on warming, whereas heating past the denaturation point is irreversible. Statement c is therefore incorrect, and the correct statements are a, b and d, which is option (3). One warning about statement c: it is itself phrased negatively, so a candidate who is also mis-reading the stem as negative can double back on themselves and count it as correct. The stem here is positive, and statement c is simply false.

Why the other options are wrong — (a) This option correctly excludes the false statement c but also drops statement d, which is true, and an option that omits a correct statement is as wrong as one that includes an incorrect one. Amylase does act on starch: it is the starch-splitting enzyme of the digestive system, secreted in the saliva by the salivary glands, where it begins breaking starch down into maltose and shorter dextrin chains, and again by the pancreas into the small intestine, where the work is completed. A candidate may hesitate over statement d because the printed English is faulty — the paper prints 'Amylase is an enzyme that act on starch' — but a grammatical slip in the printing is not a factual error, and this paper carries several. The lesson is procedural: having identified the false statement, do not stop, because the option list still requires every true statement to be accounted for.  (b) This option includes statement c, which is the one false item in the list, and that alone disqualifies it whatever else it contains. Enzyme activity depends very strongly on temperature: the rate rises with temperature up to an optimum, around 37 °C for most human enzymes, and then falls steeply as the heat breaks the weak bonds that maintain the enzyme's folded shape and denatures the protein. The same option also omits statement b, so it is doubly wrong. This is the option that catches the candidate who has misread the direction of the stem, since a and d are true while c is false, making the selection an incoherent mixture rather than the answer to either the positive or the negative version of the question — a useful reminder that a wrong reading of the stem does not usually produce a self-consistent wrong answer, and that noticing the incoherence is a way back.  (d) 'All the above' requires every one of the four statements to be correct, and statement c is not. Enzyme activity is dependent upon temperature in the most direct way, which is why the body maintains a stable internal temperature and why a high fever is dangerous, and why enzyme preparations are refrigerated rather than warmed. Escape options of this kind appear ten times across this paper, and being offered is no evidence of being keyed; the discipline they demand is to verify each statement individually and select the escape only when all of them survive. Here the item can in fact be reduced very quickly, because statement c is the only one making a claim that is easy to test against ordinary experience, and once it falls, both this option and option (2) fall with it, leaving only two options to choose between.

Concept: Enzymes are protein catalysts made by living cells. They speed up biochemical reactions, often by many orders of magnitude, by binding the substrate at an active site and lowering the activation energy the reaction must overcome; they are not consumed in the process and are free to act again, so a small quantity turns over a large amount of substrate. The active site is a pocket whose shape and chemistry complement the substrate, which accounts for the high specificity of enzyme action — an idea first expressed as the lock-and-key model and refined into the induced-fit model, in which the active site adjusts its shape as the substrate binds. Because catalytic power depends on that three-dimensional shape, and the shape is held together by weak bonds, enzymes are sensitive to their physical conditions. Activity rises with temperature to an optimum, near 37 °C for human enzymes, and falls sharply above it as the protein denatures; the fall is irreversible, whereas the loss of activity at low temperature is not, since cooling merely slows molecular motion. Each enzyme also has an optimum pH, and these differ widely according to where the enzyme works: pepsin acts in the strong acid of the stomach at a pH of about 2, whereas trypsin acts in the alkaline conditions of the small intestine at a pH near 8, and salivary amylase near neutrality. Activity also rises with substrate concentration until every active site is occupied, after which the rate levels off. Enzymes are named and classified by the reaction they catalyse, and the digestive enzymes illustrate the pattern of specificity plainly — amylase on starch, protease on protein, lipase on fats, each acting on one class of substrate and no other. The one important qualification to the statement that enzymes are proteins is the existence of ribozymes, catalytic RNA molecules, which is a recognised exception rather than a challenge to the general rule.

State PCS 2023 Q70 — Science & Technology PYQ with Answer

State PCS 2023 Q70 — Science & Technology PYQ with Answer