Question 1

Which of the following best explains why water is considered a polar molecule?

Accepted Answer

Because the oxygen atom is more electronegative than the hydrogen atoms, creating partial charges ($$\delta^- on O $$and $$\delta^+ on H).$$

Question 2

Which of the following interactions is primarily responsible for the base pairing in DNA?

Accepted Answer

Hydrogen bonds

Question 3

A solution has a hydrogen ion concentration of $$[H^+] = 1 	imes 10$$^{-5}$$ M. What is the pH of this solution?

Accepted Answer

$$pH = 5$$

Question 4

Which of the following best describes the hydrophobic effect in biological systems?

Accepted Answer

It is the association of nonpolar molecules with each other, increasing the entropy of water.

Question 5

Which equation correctly relates pH and hydrogen ion concentration?

Accepted Answer

$$pH = -\log[H^+]$$

Question 6

Which scenario would maximize the strength of an ionic interaction between two charged groups?

Accepted Answer

In a vacuum at a small distance

Question 7

Which of the following statements about van der Waals interactions is TRUE?

Accepted Answer

They are weak, transient interactions due to temporary charge asymmetry.

Question 8

A buffer is most effective at resisting changes in pH when:

Accepted Answer

The pH is close to the pKa of the acid.

Question 9

Which of the following is a consequence of altering the pH of a biological system away from its optimal range?

Accepted Answer

Ionic interactions may weaken or disappear, leading to loss of function.

Question 10

Which of the following best describes the role of water in the formation of biological membranes?

Accepted Answer

Water drives the hydrophobic effect, causing lipid tails to cluster away from water and form bilayers.

Question 11

Which of the following is TRUE regarding the timescale of biochemical interactions?

Accepted Answer

Biochemical interactions occur on the order of picoseconds ($$10^{-12} s) to $$microseconds ($$10^{-6} s).$$

Question 12

Which of the following functional groups is LEAST likely to participate in hydrogen bonding?

Accepted Answer

Methyl group ($$-CH_3$)

Question 13

A weak acid, HA, has a $$pK_a of 4.75. At $$what pH will the concentrations of HA and its conjugate base A$$^- be $$equal?

Accepted Answer

$$pH = 4.75$$

Question 14

Which of the following best explains why protein folding is spontaneous despite a decrease in entropy of the protein itself?

Accepted Answer

The entropy of water increases due to the hydrophobic effect, compensating for the decrease in protein entropy.

Question 15

Which of the following is the correct relationship between pH and pOH in aqueous solution at 25°C?

Accepted Answer

$$pH + pOH = 14$$

Question 16

Which of the following is a real-life example of the importance of weak, reversible interactions in biology?

Accepted Answer

The binding and release of a hormone to its receptor

Question 17

Which of the following statements about the dielectric constant (D) in the Coulomb energy equation is correct?

Accepted Answer

A lower dielectric constant increases the strength of ionic interactions.

Question 18

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

Accepted Answer

Buffers resist changes in pH when small amounts of acid or base are added.

Question 19

Which of the following is TRUE about the mobility of molecules in water?

Accepted Answer

Water renders molecules mobile and permits thermal-motion-powered interactions.

Water, Weak Interactions, and the Generation of Order in Biochemistry

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