Question 1

Which property of water is MOST responsible for its ability to dissolve a wide variety of biomolecules required for life?

Accepted Answer

Its polarity and ability to form hydrogen bonds

Question 2

Which of the following best describes a hydrogen bond?

Accepted Answer

A dipole-dipole interaction between a hydrogen atom bonded to an electronegative atom and another electronegative atom

Question 3

Why are weak interactions, such as hydrogen bonds and van der Waals forces, critical for biochemical processes?

Accepted Answer

They allow for dynamic binding and release of molecules, enabling regulation and function

Question 4

Which equation correctly relates the energy of an ionic interaction to the distance between charges?

Accepted Answer

$$E = \frac{q_1$ q_2$}{D r}$$

Question 5

A solution has $$[H^+] = 1 	imes 10$$^{-7}$$ M. What is the pH of this solution?

Accepted Answer

pH = 7

Question 6

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

Accepted Answer

It increases the entropy of water molecules when nonpolar molecules cluster together

Question 7

Which of the following is a consequence of the Second Law of Thermodynamics in biochemical systems?

Accepted Answer

The entropy of a system and its surroundings always increases

Question 8

What is the main reason why protein folding is powered by the hydrophobic effect?

Accepted Answer

It increases the entropy of water molecules by releasing ordered water from hydrophobic surfaces

Question 9

Which of the following best describes a buffer?

Accepted Answer

A solution of an acid-base conjugate pair that resists changes in pH upon addition of acid or base

Question 10

Given the Henderson-Hasselbalch equation $$pH = pK_a + \log \left( \frac{[A^-]}{[HA]} \right)$$, what happens to the pH if the concentration of $$[A^-] is $$doubled while $$[HA]$$ remains constant?

Accepted Answer

The pH increases by $$\log 2$$

Question 11

Which of the following is NOT a type of weak noncovalent interaction?

Accepted Answer

Covalent bonds

Question 12

Why do nonpolar molecules tend to cluster together in aqueous solutions?

Accepted Answer

Because clustering minimizes the disruption of hydrogen bonding among water molecules, increasing entropy

Question 13

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

Accepted Answer

They are strongest at the optimal van der Waals contact distance

Question 14

A weak acid, HA, has a $$K_a of$$ $$1 	imes 10$$^{-5}$$. What is the pK_a$?

Accepted Answer

p$$K_a = 5$$

Question 15

Which of the following functional groups is most likely to lose a proton at physiological pH?

Accepted Answer

Carboxyl group

Question 16

Which of the following best explains why water is an excellent solvent for ionic compounds?

Accepted Answer

Water molecules surround ions, stabilizing them through ion-dipole interactions

Question 17

Which of the following is the correct expression for the ionization equilibrium of a weak acid, HA?

Accepted Answer

$$K_a = \frac{[H^+][A^-]}{[HA]}$$

Question 18

Which of the following is a direct consequence of thermal motion in biological systems?

Accepted Answer

Molecules constantly move randomly, leading to frequent collisions and interactions

Question 19

Which of the following best describes the role of buffers in blood?

Accepted Answer

They resist changes in pH upon addition of acids or bases

Chapter 2: Water, Weak Interactions, and the Generation of Order out of Chaos

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