ICAR AIEEA-PG / PGS — Code 18 Food Science Technology · India · ICAR through the National Testing Agency
Original practice questions written to the published syllabus · not past papersThe structure of biomolecules and the metabolic pathways that turn food into energy and body tissue. Food chemistry (phase 2) describes how these molecules behave in a food; this subject explains how they behave in the body and in living raw materials such as respiring fruit and post-mortem muscle.
In the exams: ICAR AIEEA-PG Code 18 Unit I (metabolism of carbohydrates, lipids and protein; BV and PER)
How our questions for ICAR AIEEA-PG / PGS spread across the units of General Biochemistry & Metabolism. Difficulty: 19 easy, 43 medium, 7 hard.
| Biochemistry of post-harvest respiration and post-mortem muscle | 12 | |
| Coenzymes and vitamins as cofactors | 9 | |
| Protein and amino-acid metabolism and the urea cycle | 9 | |
| Carbohydrate metabolism: glycolysis, TCA cycle, gluconeogenesis and glycogen | 8 | |
| Lipid metabolism: beta-oxidation and fatty-acid synthesis | 7 | |
| Hormonal regulation of metabolism | 7 | |
| Biomolecules: carbohydrates, amino acids, proteins, lipids and nucleic acids | 5 | |
| Enzymes: classification, mechanism, Michaelis-Menten kinetics and inhibition | 5 | |
| Bioenergetics, ATP and the electron transport chain | 3 | |
| Biochemical laboratory techniques: centrifugation, electrophoresis and spectrophotometry | 3 | |
| Nucleic acids, replication, transcription and translation | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Which level of protein structure is held mainly by hydrogen bonds between backbone C=O and N–H groups?
B. Secondary structure
α-Helices and β-sheets are stabilised by hydrogen bonds between backbone carbonyl and amide groups. Primary structure is the covalent sequence; quaternary structure is the association of subunits through side-chain interactions.
Further reading: Lehninger Principles of Biochemistry; Berg et al., Biochemistry
Which coenzyme is derived from vitamin B6?
B. Pyridoxal phosphate
Pyridoxine, pyridoxal and pyridoxamine form pyridoxal phosphate, the coenzyme of transamination and amino-acid decarboxylation. TPP comes from B1, FAD from B2 and tetrahydrofolate from folate.
Further reading: Lehninger Principles of Biochemistry; Berg et al., Biochemistry
Which enzyme is the main regulatory step of glycolysis?
A. Phosphofructokinase-1
Phosphofructokinase-1 catalyses the committed, irreversible step and is regulated by ATP, AMP, citrate and fructose 2,6-bisphosphate. Aldolase, triose phosphate isomerase and enolase catalyse near-equilibrium reactions.
Further reading: Lehninger Principles of Biochemistry; Berg et al., Biochemistry
In yeast under anaerobic conditions, what are the end products of glucose fermentation?
C. Ethanol and carbon dioxide
Pyruvate decarboxylase gives acetaldehyde and CO₂; alcohol dehydrogenase reduces acetaldehyde to ethanol, regenerating NAD⁺. Lactic acid is the product in muscle and homofermentative lactic acid bacteria; acetic acid comes from oxidation of ethanol by aerobic bacteria.
Further reading: Lehninger Principles of Biochemistry; Berg et al., Biochemistry
In PCR, what happens during the annealing step?
B. Primers bind to complementary sequences on single-stranded templates
Annealing, at a temperature set by the primers, lets them hybridise to the template. Separation is denaturation; extension is the polymerase step; gel visualisation is after PCR.
Further reading: Lehninger Principles of Biochemistry; Berg et al., Biochemistry
Which hormone promotes glucose uptake into muscle and adipose tissue by moving GLUT4 to the cell surface?
B. Insulin
Insulin signals the translocation of GLUT4 transporters to the plasma membrane. Glucagon acts mainly on liver; adrenaline and cortisol raise blood glucose rather than promoting its uptake.
Further reading: Lehninger Principles of Biochemistry; Berg et al., Biochemistry
In the fasting state, which change occurs in the liver?
D. Gluconeogenesis and glycogen breakdown increase
Low insulin and high glucagon activate glycogenolysis and gluconeogenesis and increase fatty-acid oxidation and ketogenesis. Glycogen and fatty-acid synthesis are fed-state processes; GLUT4 is a muscle and fat transporter.
Further reading: Lehninger Principles of Biochemistry; Berg et al., Biochemistry
Which enzyme is usually rate-limiting in ethylene biosynthesis in ripening fruit?
A. ACC synthase
ACC synthase converts S-adenosylmethionine into ACC and is usually the controlling step; ACC oxidase then makes ethylene, using oxygen. Polygalacturonase and pectin methylesterase soften cell walls during ripening but do not make ethylene.
Further reading: Kays and Paull, Postharvest Biology; Lawrie's Meat Science
Which enzymes are chiefly responsible for the tenderisation of beef during ageing?
B. Calpains
Calcium-activated calpains degrade desmin, titin and other myofibrillar proteins in the first days after slaughter; cathepsins contribute less. Lipoxygenases and polyphenol oxidases act on lipids and phenols; amylases on starch.
Further reading: Kays and Paull, Postharvest Biology; Lawrie's Meat Science
What is the role of 2-mercaptoethanol or dithiothreitol in sample buffer for SDS-PAGE?
A. It reduces disulphide bonds so subunits separate
Reducing agents break S–S bonds so that disulphide-linked chains run as separate polypeptides. SDS supplies the charge; Coomassie or silver stains visualise; ammonium persulphate and TEMED polymerise the gel.
Further reading: Wilson and Walker, Principles and Techniques of Biochemistry and Molecular Biology
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