Question 1

Which form of glycine predominates at a pH equal to its isoelectric point (pI)?

Accepted Answer

The zwitterionic form with a protonated amino group and deprotonated carboxyl group

Question 2

A protein has an isoelectric point (pI) of 6.8. At pH 5, what is the net charge on the protein likely to be?

Accepted Answer

Positive

Question 3

Which equation is used to calculate the pH of a buffer solution containing a weak acid and its conjugate base?

Accepted Answer

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

Question 4

If the pKa of acetic acid is 4.76, what is the pH of a buffer solution where $$[CH_3COOH] = [CH_3COO^-]$$?

Accepted Answer

$$pH = 4.76$$

Question 5

A 0.100 M formic acid buffer (pKa = 3.75) is treated with a small amount of strong base. What happens to the pH?

Accepted Answer

The pH increases slightly

Question 6

Which of the following best describes the role of the bicarbonate buffer system in blood?

Accepted Answer

It maintains blood pH by interconverting $$H_2CO_3$$ and $$HCO_3$$^-$$

Question 7

Given the reaction $$CO_2 + H_2O$$ \rightleftharpoons H_2CO_3 \rightleftharpoons $$HCO_3^- + H$$^+$$, what happens when blood becomes more acidic?

Accepted Answer

The equilibrium shifts to produce more $$CO_2$$

Question 8

If a buffer is made by mixing 100 mL of 1.0 M acetic acid and 100 mL of 0.50 M sodium acetate, what is the ratio $$\frac{[A^-]}{[HA]}$$?

Accepted Answer

$$0.50$$

Question 9

A buffer solution is prepared with $$[CH_3COOH] = 2.00 M $$and $$[CH_3COO^-] = 2.00 M. $$What is the effect on pH after adding a small amount of strong acid?

Accepted Answer

The pH decreases slightly

Question 10

Which of the following is true about the isoelectric point (pI) of a protein?

Accepted Answer

It is the pH at which the protein has no net charge

Question 11

If the pKa of a carboxylic acid group is 4.2, at which pH would Ca$$^{2+}$$ bind most tightly to the protein surface?

Accepted Answer

pH 8

Question 12

Which of the following best explains why maintaining blood pH is critical for survival?

Accepted Answer

Blood pH affects enzyme structure and function

Question 13

Which of the following is the correct expression for the acid dissociation constant ($$K_a) $$for a weak acid $$HA$$?

Accepted Answer

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

Question 14

A buffer solution contains 0.30 M $$H_3PO_4$$ and 0.80 M $$KH_2PO_4. $$Which component acts as the conjugate base?

Accepted Answer

$$KH_2PO_4$$

Question 15

Which of the following best describes a buffer?

Accepted Answer

A solution that resists changes in pH when small amounts of acid or base are added

Question 16

Which of the following is a real-life consequence of blood pH falling below 6.8?

Accepted Answer

Denaturation of enzymes and loss of catalytic activity

Question 17

Which of the following is the correct relationship between pH and pKa when $$[A^-] = [HA] in a $$buffer solution?

Accepted Answer

$$pH = pK_a$$

Question 18

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

Accepted Answer

The buffer neutralizes the base, minimizing the pH increase

Question 19

Which of the following is the correct formula for calculating pH from $$[H^+]$$?

Accepted Answer

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

Buffer Systems and pH Regulation in Biochemistry

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