ICAR AIEEA-PG: Dairy Science (group 16) and Dairy Technology (group 17) · India · NTA for ICAR
Original practice questions written to the published syllabus · not past papersCarbohydrates, proteins, lipids, enzymes and metabolism at the level a dairy chemist and microbiologist needs before studying milk itself.
In the exams: Background for ICAR AICE subject 34 Units 1–3 and GATE XL-Q/XL-U Section 1
How our questions for ICAR AIEEA-PG spread across the units of Biochemistry for Dairy Science. Difficulty: 12 easy, 61 medium, 0 hard.
| Carbohydrate structure and reactions | 8 | |
| Enzymes: classification and Michaelis-Menten kinetics | 8 | |
| Lipid and amino acid metabolism | 8 | |
| Nucleic acids and protein synthesis | 8 | |
| Vitamins as coenzymes and minerals | 8 | |
| Amino acids, peptides and protein structure | 7 | |
| Lipid classes and fatty acids | 7 | |
| Enzyme inhibition and regulation | 7 | |
| Glycolysis, TCA cycle and oxidative phosphorylation | 7 | |
| Water, pH and buffers | 5 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
The interconversion of α- and β-anomers of lactose in solution until equilibrium is reached is called:
C. Mutarotation
Through the open-chain form the anomers interconvert, changing optical rotation until equilibrium (about 37% α, 63% β for lactose at room temperature).
Further reading: Fox et al., Dairy Chemistry and Biochemistry
In the Kjeldahl method, milk protein is calculated from total nitrogen using the factor:
D. 6.38
Milk proteins contain about 15.7% nitrogen, so the factor is 100/15.7 ≈ 6.38. 6.25 is the general factor for proteins with 16% N; 5.70 is used for wheat.
Further reading: ISO 8968 | IDF 20 Milk — Determination of nitrogen content
Glycine has pKa values of 2.34 (carboxyl) and 9.60 (amino). What is its isoelectric point?
A. 5.97
pI = (2.34 + 9.60)/2 = 5.97. 11.94 is the sum without halving.
Further reading: Nelson and Cox, Lehninger Principles of Biochemistry
An α-helix contains how many amino acid residues per turn?
A. 3.6
The right-handed α-helix has 3.6 residues per turn and a rise of 0.54 nm per turn. 10.5 is the number of base pairs per turn of B-DNA.
Further reading: Nelson and Cox, Lehninger Principles of Biochemistry
Which pair are the essential fatty acids for humans?
B. Linoleic (18:2 n-6) and α-linolenic (18:3 n-3)
Humans cannot introduce double bonds beyond Δ9, so n-6 and n-3 parents must come from the diet.
Further reading: Nelson and Cox, Lehninger Principles of Biochemistry
β-Galactosidase hydrolysing lactose in milk slows down as the reaction proceeds partly because:
C. Galactose, a product, competitively inhibits the enzyme
Galactose resembles the galactosyl part of lactose and competes for the active site of many β-galactosidases. Substrate depletion also reduces the rate.
Further reading: Fox et al., Dairy Chemistry and Biochemistry
Why must lactic acid bacteria reduce pyruvate to lactate rather than simply accumulate pyruvate?
C. To regenerate NAD⁺ so that glycolysis can continue
Glyceraldehyde 3-phosphate dehydrogenase needs NAD⁺; without respiration, reducing pyruvate is the way to reoxidise NADH. The LDH step itself makes no ATP.
Further reading: Nelson and Cox, Lehninger Principles of Biochemistry
Antibiotics such as tetracyclines inhibit bacteria selectively because they act on:
A. Bacterial 70S ribosomes, which differ from 80S ones
Structural differences between 70S and 80S ribosomes allow selective inhibition of bacterial protein synthesis.
Further reading: Nelson and Cox, Lehninger Principles of Biochemistry
Biotin acts as the coenzyme of which type of reaction?
D. Carboxylation
Biotin carries activated CO₂ in carboxylases such as acetyl-CoA carboxylase and pyruvate carboxylase.
Further reading: Nelson and Cox, Lehninger Principles of Biochemistry
Magnesium is required by virtually every enzyme that uses ATP because:
C. The true substrate is the magnesium–ATP complex
Mg²⁺ binds the phosphates of ATP, shielding charge and positioning it for catalysis.
Further reading: Nelson and Cox, Lehninger Principles of Biochemistry
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