Fluid compartments and pH regulation

Question 1

Where is most of the fluid in the body found?

Answer 1

Intracellular (body cells and red blood cells)

Question 2

What ion is in the highest concentration in the intracellular compartment?

Answer 2

Potassium ions

Question 3

If the conc inside and outside the cell is the same, but the charge inside the cell is more positive, will ions move out of the cell or stay?

Answer 3

Move out of the cell down the electrochemical gradient. The concentration gradient is therefore not the only gradient that ions move down but also the charge gradient.

Question 4

What is the normal intracellular pH in skeletal muscle?

Answer 4

6.8-7.10
(Produces lots of hydrogen ions as it is very active hence the lower pH).
This also shows that different fluid compartments are a different mixture of ions resulting in varying pHs.

Question 5

What are the 2 main sources of acid?

Answer 5

Volatile- acid that results from CO2 dissolving in water (carbonic acid)- most common
Non- volatile- Acid that results from the breakdown of proteins and accumulation of organic acids such as lactate

Question 6

How does carbonic acid pass across the epithelial membrane in the Proximal convoluted tubule to be reabsorbed?

Answer 6

HCO3- (is charged so can’t diffuse across the membrane) combines with H+ ions to form CO2 and H2O. CO2 is then lipid soluble and can pass across the membrane.
In the epithelial membrane, CO2 then reacts with water to reform HCO3- which moves into the blood via co-transport with a sodium ion.

Question 7

Where are H+ ions dealt with in the nephron?

Answer 7

In the distal convoluted tubule

Question 8

What are 2 urinary buffers?

Answer 8

Phosphoric acid- H+ combines with HPO42- to form H2PO4- which decreases the H+ conc in the DCT so ore H+ ions move into the DCT down a concentration gradient.
Ammonia- NH3 combines with H+ to form NH4+