Lecture 20: Renal Acid Base Regulation Flashcards Preview

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Flashcards in Lecture 20: Renal Acid Base Regulation Deck (8)
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1

Describe the terminology for acids and bases

Acids:
* Compounds that release H+ ions.
- Strong acids: Dissociate completely
- Weak acids (conjugate acid): Do not dissociate completely, but dissociate into: Hydrogen ions (H+), and Conjugate base

Bases:
* Compounds that accept H+ ions.

2

There are two types of acids produced by the body. Describe the volatile acid

Volatile Acid is excreted from the lungs
* Carbon dioxide
- Product of cellular aerobic metabolism
- CO2+ H2O ↔ H2CO3
- H2CO3 is a weak acid
- H2CO3 ↔ H++ HCO3−
- Carbonic anhydrase catalyzes the reversible reaction above.

3

There are two types of acids in the body. Describe the nonvolatile acid

Nonvolatile acids (fixed acids):
- Excreted from kidneys
- Sulfuric acid (product of protein catabolism)
- Phosphoric acid (product of phospholipid catabolism)
- Ketoacids, lactic acid, salicylic acid

4

Define pH

pH
* -log[H+]
* H2O ↔ H++ OH─
- Does not dissociate completely
- At equilibrium, [H+] = [OH─] = 10-7
- Therefore, pH = pOH= -log[H+] = 7.0
* pH of 0.1 M HCl= 1.0 (Strong acid)
- [H+] = 10-1
* The greater the hydrogen ion concentration, the lower the pH
- pH < 7 is acidic; pH > 7 is alkaline (basic)

- Arterial blood pH = 7.4
- Venous blood pH = 7.35

5

Describe the Henderson-Hasselbach equation

* Dissociation of a weak acid (conjugate acid):
HA ↔ H++ A-
- Ka is the equilibrium constant for the dissociation reaction.
Ka = [H+][A─]/[HA]
Ka = [H+][A─]/[HA] → Kax [HA] = [H+][A─]
[H+] = Ka x [HA]/[A─] → 1/[H+] = 1/Kax [HA]/[A─]
= -log [H+] = -log Ka -log ([HA]/[A─])

pH = pKa+ log ([A─]/[HA])

- See Slide 8

6

Describe Major Systems Regulating [H+]

- Chemical acid-base buffer systems of the body fluids.
- Respiratory center
- Kidneys

7

Describe buffers

* A buffer is a substance that can reversibly bind H+.
- A buffer consists of a weak acid (HA) = conjugate acid
- HA ↔ H++ A─
- Ka= [H+][A─]/[HA]
* Buffer systems:
- Bicarbonate buffer system
- Phosphate buffer system
- Proteins as buffers

8

Incomplete

Resume at slide 13