Biomolecules MCQs

Which of the following statements regarding enzyme classification classes (EC 1 to EC 6) are correct?

Statement I: Enzymes are divided into 6 classes, each with 4–13 subclasses, designated by a 4-digit code.
Statement II: Class 1 enzymes are Oxidoreductases/Dehydrogenases.
Statement III: Class 2 enzymes are Transferases, which catalyze group transfer (other than hydrogen).
Statement IV: Class 3 enzymes are Lyases, which catalyze cleavage of bonds by hydrolysis.

Which of the following statements regarding metabolic pathways and glycolysis variations are correct?

Statement I: Glycolysis involves ten enzyme-catalyzed metabolic steps converting glucose to pyruvic acid.
Statement II: In human skeletal muscle under anaerobic conditions, pyruvic acid is converted to lactic acid.
Statement III: In yeast during fermentation, pyruvic acid is converted to ethanol under anaerobic conditions.
Statement IV: In human muscle cells under aerobic conditions, glucose is converted directly into chitin.

Which of the following statements regarding quaternary subunits of adult human haemoglobin are correct?

Statement I: Quaternary protein structure describes the spatial arrangement of individual folding subunits relative to each other.
Statement II: Adult human haemoglobin consists of four subunits: two α-subunits and two β-subunits.
Statement III: Each subunit of haemoglobin has its own primary, secondary, and tertiary structure.
Statement IV: Haemoglobin lacks quaternary structure because all four chains are fused covalently into a single unbranched loop.

Which of the following statements regarding the boundary between biomacromolecules and micromolecules are correct?

Statement I: Compounds in the acid-soluble pool have molecular weights between 18 and 800 Daltons.
Statement II: Biomacromolecules in the acid-insoluble fraction have molecular weights of 10,000 Daltons and above.
Statement III: Lipids are non-polymeric small molecules with molecular weights under 800 Daltons that form membrane vesicles during grinding.
Statement IV: All acid-insoluble biomolecules are true polymers composed of repeating monosaccharides only.

Which of the following statements regarding inulin, cellulose, and chitin complex polysaccharides are correct?

Statement I: Inulin is a fructan polymer made of fructose monomers.
Statement II: Plant cell walls are made of cellulose, which is an unbranched glucose homopolymer.
Statement III: Chitin is an amino-sugar polymer found in arthropod exoskeletons and fungal cell walls.
Statement IV: Cotton fibers are composed purely of chitin and inulin helices.

Which of the following statements regarding the thermal stability of biological enzymes are correct?

Statement I: Most enzymes isolated from mesophilic organisms denature at temperatures above 40°C.
Statement II: Thermophilic organisms isolated from hot vents and sulfur springs retain enzyme stability up to 80°–90°C.
Statement III: Thermal stability of thermophilic enzymes is an inherited trait reflecting structural adaptation.
Statement IV: Inorganic catalysts denature instantly at temperatures above 40°C while enzymes remain stable up to 500°C.

Which of the following statements comparing carbonic anhydrase catalysis and uncatalysed reaction rate are correct?

Statement I: In the absence of enzyme, CO₂ + H₂O → H₂CO₃ is a slow reaction producing about 200 molecules per hour.
Statement II: In the presence of carbonic anhydrase, the reaction forms about 600,000 molecules per second.
Statement III: Carbonic anhydrase accelerates the reaction rate by about 10 million times.
Statement IV: Carbonic anhydrase requires no active site and operates by consuming its own primary amino acid sequence.

Which of the following statements regarding polymer linkages (peptide, glycosidic, phosphodiester) are correct?

Statement I: Amino acids in proteins are joined by peptide bonds formed by dehydration synthesis between -COOH and -NH₂ groups.
Statement II: Monosaccharides in polysaccharides are joined by glycosidic bonds formed by dehydration synthesis.
Statement III: Nucleotides in nucleic acids are joined by phosphodiester bonds linking the 3'-carbon of one sugar to the 5'-carbon of the next.
Statement IV: All biological polymer bonds are broken by dehydration and synthesized by hydrolysis.

Which of the following statements regarding the dynamic state and non-equilibrium living state are correct?

Statement I: All biomolecules exist in a dynamic state of turnover, continuously being transformed via metabolic reactions.
Statement II: Living organisms exist in a non-equilibrium steady state to be able to perform continuous work.
Statement III: Systems at chemical equilibrium cannot perform work.
Statement IV: Metabolism provides a continuous mechanism for energy production to prevent living systems from reaching equilibrium.

Which of the following statements summarizing the core principles of biomolecules are correct?

Statement I: Primary metabolites have known physiological roles, while secondary metabolites (e.g., alkaloids, drugs, toxins) have ecological and economic importance.
Statement II: Collagen is the most abundant animal protein, and RuBisCO is the most abundant protein in the biosphere.
Statement III: B-DNA is a right-handed double helix with antiparallel strands, a pitch of 3.4 nm, and 10 base pairs per turn.
Statement IV: Enzymes lower the activation energy barrier without altering reaction equilibrium, and their activity depends on specific pH, temperature, and co-factors.