Question 1

Which of the following best explains why the hydrolysis of ATP is considered a highly favorable reaction in cells?

Accepted Answer

Because the products of hydrolysis (ADP and Pi) are more stable due to resonance stabilization and reduced electrostatic repulsion.

Question 2

Which of the following statements about the hydrophobic effect is CORRECT?

Accepted Answer

It is driven primarily by an increase in entropy of water molecules when nonpolar substances aggregate.

Question 3

Which of the following best describes the difference between DNA and RNA at the level of their sugar components?

Accepted Answer

DNA contains 2'-deoxyribose, which lacks a hydroxyl group at the 2' carbon, while RNA contains ribose with a hydroxyl group at the 2' carbon.

Question 4

Which of the following amino acids is NOT chiral?

Accepted Answer

Glycine

Question 5

Which of the following best explains why DNA denaturation (melting) temperature ($$T_m) $$increases with higher GC content?

Accepted Answer

GC base pairs form three hydrogen bonds, compared to two in AT pairs, increasing the stability of the double helix.

Question 6

Which of the following is a correct statement about the role of BPG (2,3-bisphosphoglycerate) in hemoglobin function?

Accepted Answer

BPG binds to deoxyhemoglobin, stabilizing the T state and decreasing hemoglobin's affinity for oxygen.

Question 7

Which of the following best describes the difference between competitive and allosteric inhibition of enzymes?

Accepted Answer

Competitive inhibitors bind to the active site and can be overcome by increasing substrate concentration, while allosteric inhibitors bind to a separate site and alter enzyme activity regardless of substrate concentration.

Question 8

Which of the following best explains why RNA is more susceptible to alkaline hydrolysis than DNA?

Accepted Answer

RNA contains a 2'-hydroxyl group that can act as a nucleophile, attacking the phosphodiester bond under basic conditions.

Question 9

Which of the following is a correct description of the Bohr effect in hemoglobin?

Accepted Answer

A decrease in pH (increase in $$[H^+]) $$reduces hemoglobin's affinity for oxygen, facilitating oxygen release in tissues.

Question 10

Which of the following best describes the function of the Na$$^+/K$^+$$ ATPase in animal cells?

Accepted Answer

It uses the energy from ATP hydrolysis to pump 3 Na$$^+$$ ions out of the cell and 2 K$$^+$$ ions into the cell, maintaining electrochemical gradients.

Question 11

Which of the following statements about the electron transport chain (ETC) is CORRECT?

Accepted Answer

Electrons from NADH enter the ETC at Complex I, while electrons from FADH$$_2$$ enter at Complex II.

Question 12

Which of the following best explains why the structure of double-stranded DNA is stabilized by non-covalent forces only?

Accepted Answer

Non-covalent forces allow the strands to separate during replication and transcription.

Question 13

Which of the following is a correct statement about the amphipathic nature of phospholipids?

Accepted Answer

They contain both hydrophobic fatty acid tails and a hydrophilic phosphate-containing head group.

Question 14

Which of the following best describes the role of anapleurotic reactions in the citric acid cycle (CAC)?

Accepted Answer

They replenish intermediates of the CAC that are withdrawn for biosynthetic purposes.

Question 15

Which of the following is a correct equation for the reduction of NAD$$^+ in a $$redox reaction?

Accepted Answer

$$ \mathrm{NAD}^+ + 2\,\mathrm{H}^+ + 2\,e^- \rightarrow \mathrm{NADH} + \mathrm{H}^+ $$

Question 16

Which of the following best explains why the net yield of ATP from glycolysis is 2 molecules per glucose, even though 4 ATP are produced?

Accepted Answer

Two ATP are consumed in the early steps of glycolysis, so the net yield is 2 ATP.

Question 17

Which of the following best describes the function of the F$$_0$$ and F$$_1$$ components of ATP synthase?

Accepted Answer

F$$_0$$ forms a proton channel in the membrane, and F$$_1$$ catalyzes the synthesis of ATP from ADP and Pi.

Question 18

Which of the following best explains why oxygen consumption increases in the presence of an uncoupler?

Accepted Answer

Uncouplers dissipate the proton gradient, causing the electron transport chain to work harder to restore it, thus increasing oxygen consumption.

Question 19

Which of the following is a correct description of the role of histidine residues in hemoglobin function?

Accepted Answer

They participate in oxygen binding, stabilize the T state via salt bridges, and contribute to the Bohr effect by accepting or donating protons.

Comprehensive Study Guide: Foundations of Biochemistry (BIOCH 200)

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