Question 1

Which of the following noncovalent interactions is generally the strongest in biological systems?

Accepted Answer

Charge-charge interaction

Question 2

A solution contains 0.1 M acetic acid (pKa = 4.76) and 0.1 M sodium acetate. What is the pH of the solution? Use the Henderson-Hasselbalch equation.

Accepted Answer

$$pH = 4.76 + \log \frac{0.1}{0.1} = 4.76$$

Question 3

Which property of water is primarily responsible for its high boiling point compared to other molecules of similar size?

Accepted Answer

Its ability to form hydrogen bonds

Question 4

Given the following pKa values for glycine: $$pK_{COOH} = 2.3$$ and $$pK_{NH_3$^+} = 9.6$$, calculate the isoelectric point (pI) of glycine.

Accepted Answer

$$pI = \frac{2.3 + 9.6}{2} = 5.95$$

Question 5

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

Accepted Answer

Hydrophobic side chains aggregate to minimize ordered water structure, increasing entropy

Question 6

A buffer is made by mixing 0.2 M formic acid (pKa = 3.75) and 0.1 M sodium formate. What is the pH of the buffer?

Accepted Answer

$$pH = 3.75 + \log \frac{0.1}{0.2} = 3.75 + \log 0.5 = 3.45$$

Question 7

Which equation correctly represents the force between two charges in water, considering the dielectric constant?

Accepted Answer

$$F = k \frac{q_1$ q_2$}{\varepsilon r^2$}$$

Question 8

Which of the following molecules is amphipathic and can form micelles in water?

Accepted Answer

Phospholipid

Question 9

A solution has $$[OH^-] = 1 	imes 10$$^{-3}$$ M. What is the pH of the solution at 25°C?

Accepted Answer

$$pH = 14 - 3 = 11$$

Question 10

Which of the following statements about conjugate acids and bases is correct?

Accepted Answer

A conjugate acid can donate a proton, and a conjugate base can accept a proton

Question 11

Which property of water allows it to dissolve ionic compounds such as NaCl?

Accepted Answer

High dielectric constant

Question 12

Which of the following best describes a hydrogen bond in biomolecules?

Accepted Answer

An interaction between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom

Question 13

Which of the following interactions is most sensitive to changes in distance between interacting particles?

Accepted Answer

van der Waals interaction

Question 14

If the pH of a solution is 2 units higher than the pKa of an acid, what is the ratio of conjugate base to acid?

Accepted Answer

$$[A^-]/[HA] = 100$$

Question 15

Which of the following best explains why proteins are least soluble at their isoelectric point (pI)?

Accepted Answer

Proteins have no net charge at pI, reducing electrostatic repulsion

Question 16

Which of the following is a real-life application of the isoelectric point (pI) in biochemistry?

Accepted Answer

Separating proteins by isoelectric focusing

Question 17

Which of the following best describes the effect of adding a strong acid to a buffer solution?

Accepted Answer

The buffer resists pH change within about ±1 pH unit of its pKa

Question 18

Which of the following is the correct Henderson-Hasselbalch equation for a weak acid?

Accepted Answer

$$pH = pK_a + \log \frac{[A^-]}{[HA]}$$

Question 19

Which of the following best explains why water is a good solvent for salts?

Accepted Answer

Water's high dielectric constant reduces the force between ions, allowing them to separate

Chapter 2: The Chemical Foundation of Life – Weak Interactions in an Aqueous Environment

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