Question 1

Which of the following best distinguishes science from nonscience?

Accepted Answer

Science relies on empirical evidence and testable hypotheses, while nonscience does not require evidence or testability.

Question 2

Why is reproducibility considered a cornerstone of scientific research?

Accepted Answer

It ensures that experimental results can be independently verified, increasing confidence in the findings.

Question 3

Which of the following lists the three domains of life correctly?

Accepted Answer

Bacteria, Archaea, Eukarya

Question 4

A gene is best defined as:

Accepted Answer

A segment of DNA that encodes a functional product, usually a protein or RNA.

Question 5

Which equation correctly relates the change in free energy ($$\Delta G) to $$the equilibrium constant ($$K_{eq}) at $$temperature $$T$$?

Accepted Answer

$$\Delta G = -RT \ln K_{eq}$$

Question 6

Which of the following is a real-world example of how weak interactions stabilize aqueous solutions in biological systems?

Accepted Answer

Hydrogen bonds between water molecules and the polar side chains of proteins help maintain protein solubility.

Question 7

A solution contains a weak acid with a $$pK_a of 4.8. If $$the pH of the solution is 5.8, what is the ratio of deprotonated (A$$^-) to $$protonated (HA) forms? (Use the Henderson-Hasselbalch equation: $$pH = pK_a + \log \left( \frac{[A^-]}{[HA]} \right))$$

Accepted Answer

10:1

Question 8

During a titration experiment, 25 mL of 0.1 M NaOH is required to neutralize 50 mL of a monoprotic acid solution. What is the concentration of the acid?

Accepted Answer

0.05 M

Question 9

Why are buffers crucial in biological systems?

Accepted Answer

They maintain a stable pH, which is essential for enzyme activity and cellular processes.

Question 10

Which amino acid has a side chain that can form disulfide bonds, and what is its one-letter code?

Accepted Answer

Cysteine, C

Question 11

A protein sample is analyzed by SDS-PAGE and shows two bands at 25 kDa and 50 kDa. What can you infer about the protein's quaternary structure?

Accepted Answer

The protein likely consists of two different subunits, one of 25 kDa and one of 50 kDa.

Question 12

Which method is most commonly used to determine the three-dimensional structure of large proteins at atomic resolution?

Accepted Answer

X-ray crystallography

Question 13

Which of the following best describes the relationship between protein structure and function?

Accepted Answer

The specific three-dimensional structure of a protein determines its biological function.

Question 14

A patient has a genetic mutation that leads to improper folding of a key enzyme, resulting in disease. This is most directly an example of disruption in:

Accepted Answer

Proteostasis

Question 15

Which of the following interactions is NOT a major contributor to the tertiary structure of proteins?

Accepted Answer

Phosphodiester bonds

Question 16

Which of the following best explains how a protein adopts its native conformation?

Accepted Answer

The amino acid sequence determines the folding pathway, leading to the most thermodynamically stable structure.

Question 17

Which of the following is a correct application of the concept of entropy in biological systems?

Accepted Answer

The hydrophobic effect, where nonpolar molecules aggregate in water, increases the entropy of the surrounding water molecules.

Question 18

You are given a mixture of two proteins: one with a pI of 4.5 and another with a pI of 9.0. Which purification method would best separate them at pH 7.0?

Accepted Answer

Ion-exchange chromatography

Question 19

Which of the following is a widely accessible resource for both scientists and laypersons to access products of biochemical research?

Accepted Answer

PubMed

Question 20

Given the following peptide sequence: Ala-Glu-Lys-Ser, which of the following statements is correct about its net charge at pH 7.0? (Assume N-terminus and C-terminus are free.)

Accepted Answer

The net charge is +1.

Core Biochemistry Learning Outcomes: Foundations, Biomolecules, and Protein Structure

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