Question 1

Which of the following statements best describes a hydrogen bond?

Accepted Answer

It is an electrostatic attraction between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom.

Question 2

Which property of aqueous solutions allows them to dissolve ionic compounds efficiently?

Accepted Answer

High dielectric constant

Question 3

The pH scale is logarithmic. What does this mean in terms of hydrogen ion concentration?

Accepted Answer

Each unit increase in pH corresponds to a tenfold decrease in $$[H^+].$$

Question 4

Given equal concentrations of a strong acid and a weak acid, which will have the lower pH and why?

Accepted Answer

The strong acid, because it dissociates completely.

Question 5

A buffer is most effective when:

Accepted Answer

The concentrations of acid and conjugate base are approximately equal.

Question 6

Which equation is used to calculate the pH of a buffer solution?

Accepted Answer

The Henderson-Hasselbalch equation: $$\mathrm{pH} = \mathrm{p}K_a + \log \left( \frac{[	ext{A}^-]}{[	ext{HA}]} ight)$$

Question 7

Which of the following best describes the basic structure of an amino acid?

Accepted Answer

A central carbon ($$\alpha-$$carbon) bonded to an amino group, a carboxyl group, a hydrogen atom, and a variable R group.

Question 8

Which protein structure level is defined by the sequence of amino acids?

Accepted Answer

Primary structure

Question 9

At a pH equal to the pKa of a group, what is the ratio of protonated to deprotonated forms?

Accepted Answer

1:1

Question 10

Which amino acid is classified as positively charged at physiological pH?

Accepted Answer

Lysine (Lys)

Question 11

What is the point isoeléctrico (isoelectric point, $$pI) of a $$protein?

Accepted Answer

The pH at which the protein carries no net electrical charge.

Question 12

Which of the following best explains why RNA is more labile (prone to degradation) than DNA?

Accepted Answer

RNA has a 2' hydroxyl group on the ribose sugar, making it susceptible to hydrolysis.

Question 13

Which type of bond links nucleotides together in the backbone of DNA and RNA?

Accepted Answer

Phosphodiester bond

Question 14

Which DNA structure is most common under physiological conditions?

Accepted Answer

B-DNA

Question 15

How does the GC content of DNA affect its melting temperature ($$T_m$$)?

Accepted Answer

Higher GC content increases $$T_m$$ due to more hydrogen bonds.

Question 16

Which equation would you use to determine the pH of a solution containing a weak acid and its conjugate base?

Accepted Answer

Henderson-Hasselbalch equation: $$\mathrm{pH} = \mathrm{p}K_a + \log \left( \frac{[	ext{A}^-]}{[	ext{HA}]} ight)$$

Question 17

Which of the following best describes the role of chaperones in protein folding?

Accepted Answer

They assist proteins in achieving their correct three-dimensional structure.

Question 18

Which of the following is a motif commonly found in protein secondary structure?

Accepted Answer

Alpha helix

Question 19

Hemoglobin and myoglobin both bind oxygen reversibly. Which structural feature explains hemoglobin's cooperative binding?

Accepted Answer

Hemoglobin's quaternary structure allows subunit interactions.

Question 20

Which of the following bonds is strongest under physiological conditions?

Accepted Answer

Covalent bond

Biochemistry Exam 1 Study Guide – Step-by-Step Guidance

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