Question 1

Which of the following best explains why water is an effective solvent for polar and charged molecules in biological systems?

Accepted Answer

Water's ability to form extensive hydrogen bonds enables it to surround and stabilize polar and charged molecules.

Question 2

A researcher is purifying a His-tagged enzyme using Ni-NTA affinity chromatography. Which principle allows the enzyme to be selectively retained on the column?

Accepted Answer

The His-tag binds specifically to nickel ions immobilized on the resin.

Question 3

Which of the following statements about the Henderson-Hasselbalch equation is correct?

Accepted Answer

It relates the pH of a solution to the pKa and the ratio of base to acid concentrations.

Question 4

A protein has a pI (isoelectric point) of 6.0. In which buffer would it be least soluble?

Accepted Answer

pH 6.0

Question 5

Which of the following best describes the difference between prokaryotic and eukaryotic cells?

Accepted Answer

Eukaryotic cells have a nucleus, while prokaryotic cells lack a nucleus.

Question 6

A solution contains a weak acid (HA) and its conjugate base (A-). If the concentration of HA is 0.1 M and A- is 0.2 M, and the pKa of HA is 5.0, what is the pH of the solution? Use the Henderson-Hasselbalch equation: $$ \mathrm{pH} = \mathrm{p}K_a + \log_{10} \left( \frac{[A^-]}{[HA]} \right) $$

Accepted Answer

pH = 5.3

Question 7

Which of the following amino acids is most likely to be found on the surface of a soluble, globular protein?

Accepted Answer

Aspartic acid

Question 8

During SDS-PAGE, proteins are separated primarily based on which property?

Accepted Answer

Molecular weight (size)

Question 9

Which of the following statements about DNA replication fidelity is correct?

Accepted Answer

Hydrogen bonding and complementary base pairing ensure accurate replication.

Question 10

A buffer is prepared using acetic acid (pKa = 4.76) and sodium acetate. Which of the following pH values would this buffer be most effective at resisting changes in pH?

Accepted Answer

pH 4.8

Question 11

Which of the following best describes the dynamic steady state in living cells?

Accepted Answer

Cells maintain constant concentrations of molecules far from equilibrium by continuous energy input.

Question 12

Which of the following is a correct statement about the stereochemistry of amino acids in proteins?

Accepted Answer

All amino acids in proteins are L-isomers except glycine.

Question 13

A scientist wants to separate a mixture of proteins based on their net charge at a specific pH. Which technique should they use?

Accepted Answer

Ion-exchange chromatography

Question 14

Which of the following functional groups is present in all amino acids?

Accepted Answer

Carboxyl

Question 15

A peptide bond is formed by which type of reaction?

Accepted Answer

Condensation (dehydration synthesis)

Question 16

Which of the following best explains the hydrophobic effect in protein folding?

Accepted Answer

Hydrophobic side chains aggregate to minimize disruption of water's hydrogen bonding network.

Question 17

A protein sample is analyzed by mass spectrometry (MS). Which information can be directly obtained from the MS data?

Accepted Answer

Molecular weight of the protein or peptide

Question 18

Which of the following statements about actin, microtubules, and intermediate filaments is correct?

Accepted Answer

They are dynamic cytoskeletal elements involved in cell shape and movement.

Question 19

A solution contains a mixture of proteins. Which method would best separate them based on differences in size?

Accepted Answer

Gel filtration (size-exclusion) chromatography

Question 20

Which of the following best describes the role of phosphate buffers in biological systems?

Accepted Answer

They maintain pH near physiological values due to their pKa close to 7.

Biochemistry Study Guide: Foundations, Chemical Principles, Genetics, and Protein Analysis (Lectures 1–7)

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