Question 1

Which of the following best explains why water is an excellent solvent for polar and ionic substances?

Accepted Answer

Water's polarity allows it to form hydrogen bonds and electrostatic interactions with solutes.

Question 2

A mutation changes a glutamic acid residue to valine in the β-chain of hemoglobin. Which disease is most likely to result, and what is the molecular basis for the symptoms?

Accepted Answer

Sickle cell disease; the mutation introduces a hydrophobic residue, leading to aggregation of hemoglobin.

Question 3

Which of the following statements about the central dogma of molecular biology is correct?

Accepted Answer

Information flows from DNA to RNA to protein.

Question 4

Which of the following best describes the difference between DNA and RNA?

Accepted Answer

DNA contains deoxyribose sugar, while RNA contains ribose sugar.

Question 5

A reaction has a negative $$\Delta G$$ and a positive $$\Delta H. $$Which of the following must be true about the entropy change $$\Delta S$$?

Accepted Answer

$$\Delta S$$ must be positive and large enough to outweigh $$\Delta H.$$

Question 6

Which of the following best describes the role of enzymes in biochemical reactions?

Accepted Answer

Enzymes lower the activation energy $$E_a$$ without affecting $$\Delta G.$$

Question 7

Which of the following is a correct statement about the Michaelis-Menten constant $$K_m$$?

Accepted Answer

$$K_m is $$the substrate concentration at which the reaction rate is half-maximal.

Question 8

Which of the following best explains why phospholipids form bilayers in aqueous environments?

Accepted Answer

Phospholipids have both hydrophilic heads and hydrophobic tails, leading to spontaneous bilayer formation.

Question 9

A patient is found to have a deficiency in an essential amino acid. Which of the following best explains why this is problematic?

Accepted Answer

Essential amino acids must be obtained from the diet because the body cannot synthesize them.

Question 10

Which of the following best describes the difference between facilitated diffusion and active transport across cell membranes?

Accepted Answer

Facilitated diffusion uses membrane proteins to move substances down their concentration gradient without energy input.

Question 11

Which of the following is a correct statement about the secondary structure of proteins?

Accepted Answer

Secondary structure includes $$\alpha-$$helices and $$\beta-$$sheets stabilized by hydrogen bonds between backbone atoms.

Question 12

Which of the following best describes the function of antibodies?

Accepted Answer

Antibodies bind specifically to antigens using shape and charge complementarity.

Question 13

Which of the following statements about enzyme inhibition is correct?

Accepted Answer

Competitive inhibitors bind to the active site and increase $$K_m$$ without affecting $$V_{max}.$$

Question 14

Which of the following is a correct statement about the fluid mosaic model of cell membranes?

Accepted Answer

Membrane proteins and lipids can move laterally within the bilayer, giving the membrane fluidity.

Question 15

Which of the following best describes the difference between anomeric and epimeric forms of carbohydrates?

Accepted Answer

Anomers differ at the carbonyl carbon after cyclization, while epimers differ at any single chiral center except the anomeric carbon.

Question 16

A solution has a pH of 3. What is the concentration of hydrogen ions $$[H^+] in $$the solution?

Accepted Answer

$$[H^+] = 1 	imes 10$$^{-3}$$ \ \mathrm{M}$$

Question 17

Which of the following best explains why triacylglycerols are efficient energy storage molecules?

Accepted Answer

They are hydrophobic and can be stored without water, providing more energy per gram.

Question 18

Which of the following best describes the function of second messengers in signal transduction?

Accepted Answer

Second messengers relay signals from receptors to target molecules inside the cell.

Question 19

Which of the following statements about the first and second laws of thermodynamics is correct?

Accepted Answer

The first law states that energy is conserved, and the second law states that entropy tends to increase.

Question 20

Which of the following best describes the difference between nucleosides and nucleotides?

Accepted Answer

Nucleosides contain a nitrogenous base and a sugar, while nucleotides also contain one or more phosphate groups.

Comprehensive Biochemistry Midterm Review Guide

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