Which is the fastest-acting known enzyme? Explain the concept of turnover number.

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Different enzymes vary enormously in how quickly they can process substrate, and this speed is captured by the turnover number: the number of substrate molecules that one molecule of enzyme, working at full (saturating) substrate concentration, can convert into product in one second. A high turnover number therefore means the enzyme completes its catalytic cycle - substrate binding, conversion, and product release - extremely rapidly and repeatedly. Carbonic anhydrase, the enzyme that rapidly interconverts carbon dioxide, water and bicarbonate ion, is generally cited in textbooks as having one of the highest turnover numbers of any known enzyme, capable of converting several hundred thousand substrate molecules per second. This extraordinary speed is physiologically important because it allows the rapid loading and unloading of carbon dioxide that respiration and blood gas tra …

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CBSE 2026Set ANNUAL2 marks
$Q. Name two amino acids in which sulphur is present.$
›Reveal solutionSolution
The sulphur-containing amino acids are cysteine and methionine.

Amino acids are the building blocks of proteins and enzymes. Of the twenty standard amino acids, only two contain sulphur in their molecule:

Cysteine: contains a thiol (-SH) group. Two cysteine residues can be joined by a disulphide (-S-S-) bond, which is important for maintaining the three-dimensional (tertiary) structure of proteins and enzymes. …
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$Q. Name any two industrially important enzymes.$
›Reveal solutionSolution

Enzymes are widely used in industry as efficient, specific biocatalysts; amylase and protease are two classic industrially important examples.

Enzymes are used on an industrial scale because they are highly specific, work under mild conditions, and speed up reactions enormously compared to uncatalysed processes. Two commonly cited industrially important enzymes are:

1. Amylase — hydrolyses starch into simpler sugars (maltose, glucose). It is used in the food industry (baking, brewing, fruit-juice/starch processing), the textile industry (desizing fabric), and is a key component of many detergents to remove starchy food stains.

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CBSE 2019Set ANNUAL2 marks
$Q. Name two amino acids in which sulphur is present.$
›Reveal solutionSolution

Cysteine and methionine are the two standard amino acids that contain sulphur; cysteine's –SH group forms disulphide bonds that stabilise protein structure.

Proteins are polymers of amino acids, and out of the 20 standard amino acids only two carry a sulphur atom in their structure. This topic is part of the biomolecules/enzymes portion of the TS Intermediate botany course, which follows the NCERT/CBSE curriculum.

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Q.Which is the fastest-acting known enzyme? Explain the concept of turnover number.

Concept understanding — Enzymes as Biological Catalysts

Q.Which is the fastest-acting known enzyme? Explain the concept of turnover number.

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