What are the three mechanisms that regulate the pH of body fluids?

Answer 1

1.Kidney excretion of H+

2.Exhalation of CO2 3. Buffer systems

1. The kidneys swap H+ for Na+ levels in the blood, controlled or in response to levels of H+, bicarbonate & partial pressure of CO2.

2.When carbon dioxide is dissolved in water or blood, it forms carbonic acid, H2CO3. Exhalation of CO2 allows the blood near your lungs to reduce their acid content.

3. Buffer Systems

Bicarbonate Buffer System

The bicarbonate buffer system is a mixture of carbonic acid (H2CO3) and its salt, sodium bicarbonate (NaHCO3, a weak base), in the same solution. Although it also buffers the ICF, it is the only important ECF buffer.

Carbonic acid, a weak acid, does not dissociate to any great extent in neutral or acidic solutions. When a strong acid such as HCl is added to this buffer system, the existing carbonic acid remains intact. However, the bicarbonate ions of the salt act as weak bases to tie up the H1 released by the stronger acid (HCl), forming more carbonic acid:

HCl 1 NaHCO3 S H2CO3 1 NaCl strong acid weak base weak acid salt

Phosphate Buffer System

The operation of the phosphate buffer system is nearly identical to that of the bicarbonate buffer. The components of the phosphate system are the sodium salts of dihydrogen phosphate (H2PO42) and monohydrogen phosphate (HPO422). NaH2PO4 acts as a weak acid. Na2HPO4, with one less hydrogen atom, acts as a weak base.

Again, H1 released by strong acids is tied up in weak acids:

HCl 1 Na2HPO4 S NaH2PO4 1 NaCl strong acid weak base weak acid salt

Protein Buffer System

Proteins in plasma and in cells are the body's protein buffer sys-

tem. In fact, at least three-quarters of all the buffering power of

body fluids resides in cells, and most of this reflects the powerful buffering activity of intracellular proteins.

As described in Chapter 2, proteins are polymers of amino acids. Some of the linked amino acids have exposed groups of atoms called carboxyl groups (---COOH), organic acid groups that release H1 when the pH begins to rise:

R---COOH S R---COO2 1 H1

(Note that R indicates the rest of the organic molecule, which contains many atoms.)

Other amino acids have exposed groups that can act as bases and accept H1. For example, an exposed ---NH2 group can bind with a hydrogen ion, becoming

---NH31:

R---NH2 1 H1 S R---NH31

Answer 2

the buffer system, respiratory mechanism, and the urinary mechanism

Answer 3

The buffer system.