Week 4 - Lecture 2 - Acid-Base Imbalance Flashcards Preview

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Flashcards in Week 4 - Lecture 2 - Acid-Base Imbalance Deck (12):

Acid base balance

pH affects all functional proteins and biochemical reactions, so it is tightly regulated


what is normal pH of the arterial blood



what is normal pH of the venous blood and interstitial fluid



what is the normal pH of intracellular fluid



what is alkalosis or alkalemia

arterial pH >7.45


what is acidosis or acidemia

arterial pH < 7.35


acid base balance cont'

acids are substances that donate H+ ions
Bases are substances that accept H+ ions

Most H+ produced by metabolism

1. phosphorous containing protein breakdown releases phosphoric acid into the extracellular fluid

2. lactic acid from anaerobe respiration of glucose

3. fatty acids and ketone bodies from fat metabolism

4. H+ liberated when O2 converted to bicarbonate (HCO3- ) in blood

CO2+H2O - H2CO3 - H+ + HCO3-


concentration of hydrogen ions regulated sequentially by

1 plasma (chemical) buffer systems
rapid ; first line of defence
- bicarbonate buyer system
- protein buffer system

2. physiological buffer system
- brain stem respirator centres : act within 1-3 mins
- renal mechanisms : most potent, but require hours to days to effect pH changes


chemical buffer

system of one or more compounds that act to resist pH changes when strong acid or base is added
- bind H+ if pH drops
- release H+ if pH rises


bicarbonate buffer system

mixture of H2CO3 (weak acid) and salts of HCO3- )eg. NaHCO3 a weak base)

It is the primary buffer in the extracellular fluid


if strong acid is added

HCO3- ties up H+ and forms H2CO3
pH decreases only slightly, unless all available HCO3- (alkaline reserve) used up

HCO3- concentration closely regulated by kidneys


if strong base added (NaOH)

it cases H2CO3 to dissociate and donate H+
H+ ties up the base

PH rises only slightly

H2CO3 supply is almost limitless (from Co2 released by respiration and subject to respiratory controls