Lect 16 - Acid-base homeostasis Flashcards
what buffering systems does the body have?
Haemoglobin Bicarbonate Phosphate Proteins Ammonia Misc organic acids
what is pH
-log [H+]
describe the Henderson-Hasselbalch Equation
pH = acid dissociation + log (base/acid).
shows what pH a weak acid will be.
what needs to be balanced if the body is to maintain [H+] homeostasis
H+ production and regeneration of HCO3-
what are the sites of Sites of Acid-base metabolism
Lungs
Kidneys
GI tract
Liver
how is Hb dependant on acid/base chemistry to dissociate oxygen?
(the same process works in reverse to allow loading of oxygen)
Co2 is broken down by enzymes within the cell to produce bicarbonate and a free H ion. this proton can acidify Hb, causing it to change its shape and release any loaded Oxygen.
what shifts a O2-Haemoglobin dissociation curve to the right?
with Increased:
2,3 diPG
Acidosis H+
Temperature
how does the kidney reclaim bicarb?
it uses a sodium hydrogen pump to take protons from the product of water and carbon dioxide: H2C03, and generate bicarb. (HCO3-)
why does the use of the hydrogen sodium pump in reclamation of bicarb not GENERATE new bicarb?
because the CO2 and water used to produce the H2CO3 came from the breakdown of bicarb in the first place - it is a cycle which is driven by the sodium pump.
How does the kidney generate new bicarb?
it unloads hydrogen from H2CO3 using sodium hydrogen pumps onto other molecules such as (HPO4)2- and NH3. The products of these reactions can be excreted, and essentially allows the conversion of CO2 and water into bicarb at the cost of energy and these proton accepting molecules.
what does Mineralocorticoid Action in the Kidney do?
K+ shares a common point of excretion with H+ in the nephron. Mineralocorticoids control the amount of acid in the body by controlling how much K+ or H+ is secreted.
these two tend to both run into problems together - too much H+ means it will be secreted and you can end up with too much K+ too.
how is the GI tract pH maintained?
Acid from the stomach is neutralised by alkali from the pancreas.
where is the dominant site of lactate metabolism?
the Liver. not it is also the only site of urea synthesis
does urea synthesis increase or reduce concentration of H+ in the body?
increase.
therefore urea synthesis is inhibited by acidosis.
if urea synthesis stops, what can you suffer from?
too much NH3
ammonia poisoning
