Macromolecules MCQs set 3 for BSN Nursing Entry Test Chemistry — 20 solved questions.
Q1. During a carbohydrate analysis, a student observes that most disaccharides reduce Fehling's solution, but one specific sugar fails to react. Identify it.
Answer: Sucrose
Explanation: Sucrose is non-reducing because its 1,2-glycosidic bond masks both anomeric carbons. Maltose is tempting but has a free hemiacetal group.
Q2. A chemist compares four different fats to determine their average molecular mass. Which fat will exhibit the highest saponification value during titration?
Answer: Tributyrin
Explanation: Higher saponification values indicate shorter fatty acid chains. Stearic acid is tempting but has a longer chain and lower value.
Q3. An industrial designer requires a polymer for electrical switches that will not soften or melt when exposed to high temperatures. Which material is best?
Answer: Bakelite
Explanation: Bakelite is thermosetting due to permanent cross-links formed during synthesis. Polyethylene is tempting but is a thermoplastic that melts on reheating.
Q4. In an electrophoresis experiment, an amino acid does not migrate toward either electrode at a specific pH. What is its structural state?
Answer: Zwitterion form
Explanation: At the isoelectric point, amino acids exist as dipolar zwitterions with zero net charge. The acidic form is tempting but occurs at low pH.
Q5. Biochemical reactions in the human body occur rapidly at 37°C. By what mechanism do enzymes allow these reactions to proceed at such low temperatures?
Answer: Lowering activation energy
Explanation: Enzymes lower the activation energy by stabilizing the transition state. Increasing total energy is tempting but enzymes only manipulate the barrier height.
Q6. A student attempts to dissolve starch in hot water and finds a portion remains insoluble. Which component is responsible for this lack of solubility?
Answer: Amylopectin
Explanation: Amylopectin is insoluble in water due to its highly branched alpha-1,6-glycosidic structure. Amylose is tempting but is actually the water-soluble component.
Q7. To determine the health benefits of various cooking oils, a nutritionist measures the amount of carbon-carbon double bonds. Which parameter is used?
Answer: Iodine value
Explanation: The iodine value measures the degree of unsaturation in a fat. Saponification value is tempting but it measures the chain length instead.
Q8. A synthetic fiber is produced by reacting adipic acid with hexamethylenediamine. What specific functional group links the repeating units in this polymer?
Answer: Amide linkage
Explanation: Nylon-6,6 contains amide linkages formed between carboxylic acid and amine groups. Terylene is tempting but contains ester linkages from alcohol groups.
Q9. Glucose is classified as an aldohexose. Which functional group is primarily responsible for its classification as an 'aldose' sugar?
Answer: Aldehyde group
Explanation: Glucose is an aldohexose because it contains an aldehyde group. Fructose is tempting because it is a hexose but contains a ketone group.
Q10. The alpha-helix of a protein is maintained by specific interactions between the backbone atoms. Identify the force responsible for this secondary structure.
Answer: Hydrogen bonds
Explanation: Secondary protein structures like alpha-helices are stabilized by hydrogen bonding between N-H and C=O groups. Peptide bonds are tempting but form primary structures.
Q11. A sample of butter is left at room temperature and develops an unpleasant odor. Which analytical value would increase as a result of this rancidity?
Answer: Acid value
Explanation: Acid value measures free fatty acids released by hydrolysis during rancidity. Iodine value is tempting but measures unsaturation loss during oxidation.
Q12. Polyvinyl chloride (PVC) is widely used for making water pipes. Which monomer is polymerized to produce this specific synthetic plastic?
Answer: Vinyl chloride
Explanation: PVC is formed from vinyl chloride (chloroethene). Tetrafluoroethene is tempting but it is the monomer for Teflon (PTFE).
Q13. When two amino acids react to form a dipeptide, a small molecule is released as a byproduct. What is this molecule?
Answer: Water
Explanation: Amino acids link via peptide bonds with the elimination of a water molecule. Ammonia is tempting but is not released during standard peptide formation.
Q14. After a meal, excess glucose in the human body is converted into a highly branched polymer for storage. Identify this polymer.
Answer: Glycogen
Explanation: Glycogen is the primary storage polysaccharide in animals, found mainly in the liver and muscles. Starch is tempting but is the plant equivalent.
Q15. A nutritionist advises a patient to consume specific proteins because the human body cannot synthesize ten particular amino acids. These are known as:
Answer: Essential amino acids
Explanation: Essential amino acids must be obtained from the diet as the body cannot synthesize them. Non-essential is tempting but they are body-produced.
Q16. Koshland proposed that the active site of an enzyme is flexible and adjusts its conformation upon substrate binding. This theory is the:
Answer: Induced fit model
Explanation: The induced fit model suggests the enzyme's active site changes shape to fit the substrate. Lock and key is tempting but implies rigidity.
Q17. Despite being a polymer of glucose, this substance is the main structural component of plant cell walls and is completely insoluble in water.
Answer: Cellulose
Explanation: Cellulose is insoluble in water due to high molecular weight and extensive hydrogen bonding. Glucose is tempting but it is a soluble monomer.
Q18. Vegetable oils like cottonseed oil are liquids at room temperature. What chemical feature distinguishes them from solid animal fats?
Answer: High unsaturation
Explanation: Oils are liquid at room temperature because they contain a higher proportion of unsaturated fatty acids. Saturated fats are tempting but are usually solid.
Q19. The production of polyethylene from ethene gas involves the repeated joining of monomers without the elimination of any byproduct. This is:
Answer: Addition polymerization
Explanation: Addition polymerization involves monomers with double bonds joining without losing any atoms. Condensation is tempting but requires the loss of small molecules.
Q20. An industrial chemist observes that the synthesis of Nylon-6,6 produces water as a byproduct, unlike the synthesis of polyethylene. How are these two classified?
Answer: Nylon-6,6 is a condensation polymer while polyethylene is an addition polymer
Explanation: Nylon-6,6 is a condensation polymer releasing water, whereas polyethylene is an addition polymer involving simple monomer unit stacking without byproduct loss.