SSC CGL 2024 Tier-I · 19 September 2024, Shift 3 · General Awareness · Question 4 of 99

Text as printed on a candidate's response sheet for this shift; answer per SSC's tentative key as marked on that sheet. Solution last reviewed 6 September 2026.

Where this paper and its answers come from

SSC does not publish CGL question papers or a public answer key. The questions and options here are reproduced as printed on a candidate's own response sheet for this shift — the Commission's text, unchanged. Each answer is SSC's tentative key as marked on that sheet; SSC allowed challenges to it and never publishes a final key. The solutions are written by UnlockIAS.

Which is the most important protein component in milk, both quantitatively and nutritionally, that accounts for about 80% of the total protein in bovine milk?

(a)Pepsin
(b)Casein
(c)Actin
(d)Albumin

Answer

Why

Correct — B. Casein is the dominant milk protein: it accounts for roughly the 80% the stem quotes, with the whey proteins making up the remaining fifth.

Casein is not one molecule but a family, carried in milk as micelles held together with calcium and phosphate. That is why milk is white and opaque.

It is also why acid or rennet curdles milk: the micelles come apart and the casein coagulates into curd, leaving whey behind.

Why the others are wrong

(a)
Pepsin — Pepsin is a digestive enzyme of the stomach, secreted as pepsinogen and activated by acid. It acts on proteins rather than being one of milk's own.
(c)
Actin — Actin is a cytoskeletal and muscle protein that forms filaments inside cells. It is not a nutritional protein of milk.
(d)
Albumin — Albumin really is present in milk, in the whey fraction along with alpha-lactalbumin. But whey is only about a fifth of milk protein, so it fails the 80% test.

Concept

Milk protein splits into two fractions by a simple test. Acidify milk to about pH 4.6, casein's isoelectric point, and the caseins precipitate while the whey proteins stay in solution.

The casein fraction is roughly four-fifths of bovine milk protein and carries much of milk's calcium and phosphorus. The whey fraction holds alpha-lactalbumin, beta-lactoglobulin, serum albumin and immunoglobulins.

Cheese-making is that separation done on purpose: rennet or acid coagulates the casein into curd and the whey is drained off.

The stem hands you the discriminator, "about 80% of the total protein". Albumin is genuinely present in milk, so it is the number and not mere presence that separates it from casein.

Key facts

Casein accounts for about 80% of the protein in bovine milk.
The whey fraction of milk protein includes alpha-lactalbumin, beta-lactoglobulin and serum albumin.
Casein is carried in milk as micelles that also hold calcium and phosphate.
Casein precipitates near pH 4.6, its isoelectric point, which is what curdling exploits.

Study next

Curdling of milk: rennet, lactic acid bacteria and the isoelectric point of caseinWhey proteins and their nutritional rolePepsin, trypsin and the enzymes of protein digestion

Common traps

Choosing albumin because it is a familiar protein name and is in fact present in milk.
Choosing pepsin because it is associated with digesting milk rather than with milk itself.

SSC also asks milk from the chemistry side. At 18 Sep 2024, 9:00, General Awareness Q.8 the question is why a milkman adds a very small amount of baking soda to fresh milk, keyed to raising the pH from about 6 to slightly alkaline.

Both items reward knowing that milk behaviour turns on acidity.

Related PYQs

No directly related past PYQ was found.