Acid-Base Balance

Question 1

what is the protein buffer system?

Answer 1

if pH rises (alkaline) then the carboxylic acid group of an amino group will dissociate into COO- and H+
acting like an acid

if pH falls (acidic) then the amine group will bind with excess protons
NH2 = NH3+
acting like a base

Question 2

describe the hemoglobin process with oxygen entering the tissue cells

Answer 2

H2O binds with CO2 that is entering the RBC from the cell (respiration product)
forms H2CO3 carbonic acid
Carbonic anhydrase breaks this down into H+ and HCO3-
the free H+ binds with Hbo2 to form HHb (reduced hemoglobin) and O2 which then enters the cell

Question 3

what buffer system is used in the urinary tract?

Answer 3

the phosphate buffer system

If pH falls, HPO42- (monohydrogen phosphate) can bind with excess H+ to form H2PO4- (dihydrogen phosphate)

and vice versa
dihydrogen phosphate binds with excess base to form water and monohydrogen phosphate

Question 4

describe the chloride shift

Answer 4

when CO2 enters the red blood cell as a byproduct of ATP production
it binds with water forming carbonic acid with the help of carbonic anhydrase
this dissociates into H+ and HCO3- (bicarbonate ion)

this bicarbonate ion exits the cell and into the plasma in exchange for a chloride ion (done via an anion exchanger)

the bicarbonate ion ultimately ends up in the lungs where again it is exchanged with chloride ions (bicarb ion into the blood and Cl- into the plasma) where carbonic anhydrase again converts it into CO2 and it is exhaled by the lungs

the bicarbonate ion at the lungs binds with the free H+ from the O2 from the lungs binding with HHb to form HbO2 and a free H+

Question 5

describe acid-base balance in the urinary system

Answer 5

CO2 as a product of cellular respiration in tubular cells of PCT and collecting duct go through the same process as other cells (carbonic anhydrase etc)
with the exception of when a H+ is formed, an ATPase actively pumps them out into the lumen of the tubule

to counteract the increased acidity of the tubule, NH3 that has been produced binds with H+ to form NH4+
and HPO4 2- (monohydrogen phosphate) binds also to form H2PO4-