Q: Which formula correctly relates pH, $$pK_a$$, and the ratio of conjugate base to acid in the Henderson-Hasselbalch equation?

$$pH = pK_a + \log \left( \frac{[\text{conjugate base}]}{[\text{conjugate acid}]} \right )$$

Question 1

Which of the following statements best describes the relative strength of noncovalent interactions in biomolecules?

Accepted Answer

Charge-charge interactions are generally stronger than dipole-dipole and van der Waals interactions.

Question 2

A molecule with both hydrophilic and hydrophobic regions is called:

Accepted Answer

An amphipathic molecule

Question 3

Which equation is used to calculate the force between two charged particles in a vacuum?

Accepted Answer

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

Question 4

Which property of water is MOST responsible for its ability to dissolve ionic compounds?

Accepted Answer

High dielectric constant

Question 5

Which of the following is the correct definition of a conjugate base?

Accepted Answer

A chemical that can accept a proton after an acid has donated it

Question 6

Given the dissociation of acetic acid ($$\mathrm{CH_3COOH}) $$with $$pK_a = 4.76$$, what is the pH of a solution containing 0.9 M acetate ($$\mathrm{CH_3COO^-}) $$and 1.1 M acetic acid?

Accepted Answer

$$pH = 4.76 + \log \left( \frac{0.9}{1.1} \right )$$

Question 7

Which of the following best explains the 'hydrophobic effect' in protein folding?

Accepted Answer

Hydrophobic side chains aggregate to minimize the ordering of water molecules, increasing entropy.

Question 8

What is the isoelectric point ($$pI) of $$glycine if its $$pK_a$$ values are 2.3 and 9.6?

Accepted Answer

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

Question 9

Which of the following is NOT a class of biomolecule?

Accepted Answer

Enzymes

Question 10

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

Accepted Answer

The pH is close to the $$pK_a of $$the buffer

Question 11

Which formula correctly relates pH, $$pK_a$$, and the ratio of conjugate base to acid in the Henderson-Hasselbalch equation?

Accepted Answer

$$pH = pK_a + \log \left( \frac{[	ext{conjugate base}]}{[	ext{conjugate acid}]} ight )$$

Question 12

If the $$K_w of $$water at 25°C is $$1.0 	imes 10$$^{-14}$$, what is the concentration of $$[H^+]$$ in pure water?

Accepted Answer

$$1.0 	imes 10$$^{-7}$$ M

Question 13

Which of the following best describes a hydrophilic molecule in aqueous solution?

Accepted Answer

It interacts favorably with water through hydrogen bonding or ionic interactions.

Question 14

During agarose gel electrophoresis, which type of biomolecule is most effectively separated?

Accepted Answer

Large DNA fragments

Question 15

A solution contains 0.2 M formate ($$\mathrm{HCOO^-}) $$and 0.6 M formic acid ($$\mathrm{HCOOH}). If$$ $$pK_a = 3.75$$, what is the pH?

Accepted Answer

$$pH = 3.75 + \log \left( \frac{0.2}{0.6} \right )$$

Question 16

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

Accepted Answer

Purifying proteins using isoelectric focusing

Question 17

Which statement about buffers is TRUE?

Accepted Answer

Buffers resist changes in pH upon addition of small amounts of acid or base.

Question 18

Which of the following is a Bronsted-Lowry acid?

Accepted Answer

A molecule that donates a proton

Question 19

Which property of amino acid side chains is most important for protein-ligand binding?

Accepted Answer

Their ionic properties

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

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