Acid and Base Balance and Imbalance

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Acid and Base Balance and Imbalance

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Slide 2

pH Review

pH = - log [H+]

H+ is really a proton

Range is from 0 - 14

If [H+] is high, the solution is acidic; pH < 7

If [H+] is low, the solution is basic or alkaline ; pH > 7

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Acids are H+ donors.

Bases are H+ acceptors, or give up OH- in solution.

Acids and bases can be:

Strong – dissociate completely in solution

HCl, NaOH

Weak – dissociate only partially in solution

Lactic acid, carbonic acid

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Slide 6

The Body and pH

Homeostasis of pH is tightly controlled

Extracellular fluid = 7.4

Blood = 7.35 – 7.45

< 6.8 or > 8.0 death occurs

Acidosis (acidemia) below 7.35

Alkalosis (alkalemia) above 7.45

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Small changes in pH can produce major disturbances

Most enzymes function only with narrow pH ranges

Acid-base balance can also affect electrolytes (Na+, K+, Cl-)

Can also affect hormones

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Slide 9

The body produces more acids than bases

Acids take in with foods

Acids produced by metabolism of lipids and proteins

Cellular metabolism produces CO2.

CO2 + H20 ↔ H2CO3 ↔ H+ + HCO3-

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Slide 10

Control of Acids

Buffer systems

Take up H+ or release H+ as conditions change

Buffer pairs – weak acid and a base

Exchange a strong acid or base for a weak one

Results in a much smaller pH change

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Slide 11

Bicarbonate buffer

Sodium Bicarbonate (NaHCO3) and carbonic acid (H2CO3)

Maintain a 20:1 ratio : HCO3- : H2CO3

HCl + NaHCO3 ↔ H2CO3 + NaCl

NaOH + H2CO3 ↔ NaHCO3 + H2O

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Slide 12

Phosphate buffer