ACS CP ACS CP Biochemistry & Polymer Chemistry 2 — Questions and Answers
Question 1: Glass transition temperature (Tg) in polymers represents:
- The temperature at which a polymer melts and flows like a liquid
- The temperature below which amorphous polymer segments become rigid and glassy (Correct answer)
- The decomposition temperature of the polymer backbone
- The melting point of crystalline polymer domains
Correct answer: The temperature below which amorphous polymer segments become rigid and glassy
Tg is the temperature below which amorphous polymer chains lose segmental mobility and the material becomes hard and brittle (glassy state).
Question 2: Which coenzyme is essential for oxidation-reduction reactions and acts as an electron carrier in cellular respiration?
- Coenzyme A (CoA)
- NAD+/NADH (Correct answer)
- Pyridoxal phosphate (PLP)
- Thiamine pyrophosphate (TPP)
Correct answer: NAD+/NADH
NAD+ (nicotinamide adenine dinucleotide) is the primary electron carrier in cellular respiration, accepting electrons (becoming NADH) in glycolysis, the TCA cycle, and beta-oxidation.
Question 3: Free radical chain polymerization consists of which three fundamental steps?
- Initiation, condensation, termination
- Initiation, propagation, termination (Correct answer)
- Activation, chain transfer, deactivation
- Nucleation, growth, crystallization
Correct answer: Initiation, propagation, termination
Free radical chain polymerization proceeds through initiation (radical generation), propagation (chain growth), and termination (radical combination or disproportionation).
Question 4: DNA replication is described as semi-conservative, meaning:
- Only half of the DNA is replicated during each cell division
- Each new double helix contains one original strand and one newly synthesized strand (Correct answer)
- DNA is replicated conservatively in eukaryotes but dispersively in prokaryotes
- Replication is initiated at only one origin per chromosome
Correct answer: Each new double helix contains one original strand and one newly synthesized strand
Semi-conservative replication, confirmed by the Meselson-Stahl experiment, means each daughter DNA molecule contains one parental strand and one newly synthesized complementary strand.
Question 5: Which type of polymer exhibits both viscous and elastic behavior, behaving like a liquid at long time scales and a solid at short time scales?
- Crystalline thermoplastic
- Thermoset polymer
- Viscoelastic polymer (Correct answer)
- Liquid crystalline polymer
Correct answer: Viscoelastic polymer
Viscoelastic polymers exhibit both viscous (liquid-like, time-dependent) and elastic (solid-like, recoverable) deformation depending on the rate and duration of applied stress.
Question 6: The citric acid cycle (Krebs cycle) primarily functions to:
- Convert glucose to pyruvate for energy production
- Oxidize acetyl-CoA to CO2 while generating reduced electron carriers (NADH, FADH2) (Correct answer)
- Synthesize glucose from non-carbohydrate precursors
- Convert fatty acids to ketone bodies
Correct answer: Oxidize acetyl-CoA to CO2 while generating reduced electron carriers (NADH, FADH2)
The citric acid cycle oxidizes acetyl-CoA (from carbohydrates, fats, and proteins) to CO2, generating NADH and FADH2 that fuel the electron transport chain.
ACS CP ACS CP Biochemistry & Polymer Chemistry 2
Glass transition temperature (Tg) in polymers represents: