Lecture 26 - Acid/Base Physiology 1

Question 1

Acid production - Oxidative metabolism?

Answer 1

vast majority of production, water + CO2 H2CO3 H+ + HCO3-, carbonic acid is in equilibrium with CO2 it is a volatile acid

Question 2

Acid production - Protein catabolism?

Answer 2

vast minority, oxidation of sulphur containing amino acid residues to produce sulphuric acid, non-volatile acid, increased in ischaemia (lactic acid) and diabetes (

Question 3

Dealing w acid?

Answer 3

buffer and excrete: lungs excrete CO2, kidneys remove protein metabolism acid

Question 4

Buffering non-volatile acid?

Answer 4

bicarbonate system; blood and ECF give quick and short term buffering (RBC); H+ combines with intracellular proteins and organic phosphates, H+ transported across membrane in exchange for Na and K

Question 5

Isohydric Principle?

Answer 5

pH can be evaluated from the status of any buffer system, accurate for blood and interstitial phases but not necessarily for intracellular phases, making them harder to measure

Question 6

Buffering volatile acid?

Answer 6

CO2 in RBC is converted into H2CO3 and binds Hb, making it acidic, HCO3- promotes a chloride shift into the scell, H+ is buffered by histidine

Question 7

Carbamino-Hb?

Answer 7

30% of exhaled CO2, in capillaries O2 falls, Hb becomes reduced (deoxy Hb), becomes more basic and better buffer

Question 8

deoxy-Hb?

Answer 8

more effective than oxy in forming carbamino-, better buffer also therefore better CO2 carraige

Question 9

Base excess (and deficit) definition?

Answer 9

measure by the titration of a blood sample with a strong acid(base/NaOH) to pH 7.4 at a PCO2 of 40mmHg at 37 degrees C (in practice, use Henderson-Hesselbalch equation)