In regard to acid excretion by the body, which of the following ...

[karen]

In regard to acid excretion by the body, which of the following statements are true?
 
  1. If one system fails, the other can help compensate.
  2. The kidneys can only remove fixed acids.
  3. The kidneys can quickly remove acid.
  4. The lungs can quickly remove acid.
  a. 1, 2, and 4 only
  b. 2 and 3 only
  c. 4 only
  d. 1 and 4 only

Question 2

A patient has a PCO2 of 80 mm Hg. What is the concentration of dissolved CO2 (in mmol/L) in the blood?
 
  a. 1.2 mmol/L
  b. 2.4 mmol/L
  c. 24 mmol/L
  d. 40 mmol/L

[Ahernandez18]

Answer to Question 1

ANS: A
Bicarbonate buffers effectively buffer the H+ originating from fixed acid, converting it to H2CO3 and, in turn, to CO2 and H2O. By eliminating the CO2, the lungs can rapidly remove large quanti-ties of fixed acid from the blood. The kidneys also remove fixed acids, but at a relatively slow pace. In healthy individuals, the acid excretion mechanisms of lungs and kidneys are delicately balanced. In diseased individuals, failure of one system can be partially offset by a compensatory response of the other.

Answer to Question 2

ANS: B
Because dissolved CO2 (PCO2  0.03) is in equilibrium with and directly proportional to blood H2CO3, and because blood PCO2 is more easily measured than H2CO3, dissolved CO2 is used in the denominator of the Henderson-Hasselbalch equation.