Lecture 19: Acid/Base Regulation

Question 1

What is a buffer?

Answer 1

Substance that can reversibly bind H+ (contains a weak acid)

Question 2

What are the 3 main buffer systems of the body and which is the most important extracellular buffer system?

Answer 2

Bicarbonate, Phosphate, and Proteins

*Bicarbonate most important

Question 3

How is the bicarbonate buffer system regulated?

Answer 3

By the kidneys, which excrete excess HCO3-

Question 4

Metabolic Acid-Base disorders

Answer 4

Due to change in extracellular [HCO3-]
Alkalosis: high [HCO3-]
Acidosis: low [HCO3-]

Question 5

Respiratory Acid-Base disorders

Answer 5

Due to change in pCO2
Acidosis: high pCO2
Alkalosis: low pCO2

Question 6

Why is the phosphate buffer system conducive to working in the renal tubular fluid?

Answer 6

Low pH of tubular fluid is optimal operating range because buffer is close to pK of the system

Question 7

Where are intercalated cells found?

Answer 7

Late distal renal tubules

Question 8

How does excess H+ secretion form new HCO3-?

Answer 8

H+ binds with buffers so that excess HCO3- can be returned to the blood as “new” bicarbonate ion

Question 9

How do the kidneys handle excess base/alkalosis?

Answer 9

Fail to reabsorb all filtered bicarbonate ion, lowering the pH

Question 10

What is metabolic acidosis and what is the compensatory response?

Answer 10

Decrease in HCO3-

*Compensatory: lungs increase ventilation rate (kidneys can also add more HCO3- to EC fluid)

Question 11

What is respiratory acidosis and what is the compensatory response?

Answer 11

Increase in CO2

*Compensatory: kidneys produce more HCO3-

Question 12

What is metabolic alkalosis and what is the compensatory response?

Answer 12

Increase in HCO3-

*Compensatory: decreased ventilation in lungs (less CO2 blown off), kidneys can also excrete HCO3-

Question 13

What is respiratory alkalosis and what is the compensatory response?

Answer 13

Decrease in CO2

*Compensatory: renal excretion of HCO3-

Question 14

Which of the following buffer systems is most important in buffering renal tubular fluid?

A. Phosphate buffer system
B. Carbonate buffer system
C. Bicarbonate buffer system
D. Hemoglobin buffer system

Answer 14

A. Phosphate buffer system

Question 15

Compounds that disassociate incompletely into hydrogen ions and a conjugate base are members of which of the following compounds?

A. Strong acids
B. Weak acids
C. Strong bases
D. Weak bases

Answer 15

B. Weak acids

Question 16

The bicarbonate buffer system consists of a bicarbonate salt and which of the following?

A. Weak acid
B. Strong acid
C. Weak base
D. Strong base

Answer 16

A. Weak acids

Question 17

Which of the following buffer systems is the most important buffer system?

A. Phosphate buffer system
B. Carbonate buffer system
C. Bicarbonate buffer system
D. Hemoglobin buffer system

Answer 17

C. Bicarbonate buffer system

Question 18

Primary active hydrogen secretion involves a hydrogen transporting ATPase. It occurs in which of the following parts of the renal tubules?

A. Descending limb of Henle
B. Ascending limb of Henle
C. Late distal tubules in intercalated cells
D. Early collecting tubules in principal cells

Answer 18

C. Late distal tubules in intercalated cells

Question 19

Most bicarbonate reabsorption occurs in which of the following parts of the renal tubule?

A. Proximal tubule
B. Descending limb of Henle
C. Ascending limb of Henle
D. Distal tubule

Answer 19

A. Proximal tubule

Question 20

Which of the following occurs when a decrease in bicarbonate ion results in a decrease in the ratio of bicarbonate ion to carbon dioxide in the extracellular fluid?

A. Respiratory acidosis
B. Respiratory alkalosis
C. Metabolic acidosis
D. Metabolic alkalosis

Answer 20

C. Metabolic acidosis

Question 21

Respiratory alkalosis due to a decrease in CO2 concentration caused by hyperventilation is compensated for by which of the following mechanisms?

A. Increased ventilation rate
B. Decreased ventilation rate
C. Renal excretion of bicarbonate ion
D. Renal addition of new bicarbonate ion to extracellular fluid

Answer 21

C. Renal excretion of bicarbonate ion