Question 1

Which historical experiment provided the first evidence that organic molecules could be synthesized from inorganic precursors, challenging the doctrine of vitalism?

Accepted Answer

Friedrich Wöhler's synthesis of urea from ammonium cyanate

Question 2

Which of the following best describes the primary difference between biochemistry and molecular biology?

Accepted Answer

Biochemistry seeks to explain life at the molecular level, while molecular biology studies the overall function of biomolecules.

Question 3

Which of the following is NOT one of the four major classes of biological macromolecules?

Accepted Answer

Steroids

Question 4

What type of bond links nucleotide monomers together in DNA and RNA strands?

Accepted Answer

Phosphodiester bond

Question 5

Which property of water is primarily responsible for its high boiling point compared to other small molecules like ammonia or methane?

Accepted Answer

Its ability to form hydrogen bonds

Question 6

A solution contains 0.1 M acetic acid (Ka = $$1.76 	imes 10$$^{-5}$$). What is the approximate pH of this solution?

Accepted Answer

$$pH \approx 2.9$$

Question 7

Which of the following best explains why ice floats on liquid water?

Accepted Answer

Ice is less dense than liquid water because its hydrogen bonds form a tetrahedral lattice, maximizing distance between molecules.

Question 8

Which equation correctly relates the Gibbs free energy change ($$\Delta G) to $$enthalpy ($$\Delta H) $$and entropy ($$\Delta S$$)?

Accepted Answer

$$\Delta G = \Delta H - T\Delta S$$

Question 9

A reaction has $$\Delta H  0. $$What can you conclude about the spontaneity of the reaction at all temperatures?

Accepted Answer

The reaction is spontaneous at all temperatures.

Question 10

Which of the following statements about buffers is TRUE?

Accepted Answer

A buffer resists changes in pH when small amounts of strong acid or base are added.

Question 11

Which of the following best describes the hydrophobic effect?

Accepted Answer

The exclusion of nonpolar substances from aqueous solution, driven by increased entropy of water.

Question 12

Which of the following is a correct application of the Henderson-Hasselbalch equation?

Accepted Answer

Estimating the pH of a buffer solution made from a weak acid and its conjugate base.

Question 13

Which of the following is a property of amphipathic molecules?

Accepted Answer

They contain both hydrophilic and hydrophobic regions.

Question 14

Which of the following best explains why DNA with a higher GC content has a higher melting temperature (Tm)?

Accepted Answer

GC pairs form three hydrogen bonds, making the DNA more stable.

Question 15

Which experiment demonstrated that DNA replication is semiconservative?

Accepted Answer

Meselson-Stahl experiment

Question 16

Which of the following is TRUE regarding the structure of the DNA double helix?

Accepted Answer

The sugar-phosphate backbone is on the outside, and the bases are stacked inside.

Question 17

Which of the following best describes the role of topoisomerases in cells?

Accepted Answer

They modify the state of DNA supercoiling.

Question 18

Which of the following is the correct formula for the equilibrium constant ($$K_{eq}) $$for the reaction $$aA + bB \rightleftharpoons cC + dD$$?

Accepted Answer

$$K_{eq} = \frac{[C]^c [D]^d}{[A]^a [B]^b}$$

Question 19

Which of the following statements about coupled reactions in metabolism is CORRECT?

Accepted Answer

An unfavorable reaction can proceed if it is coupled to a favorable reaction with a sufficiently negative $$\Delta G.$$

Biochemistry Foundations: Structure, Water, pH, Thermodynamics, and Nucleic Acids

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