Protein Buffer Systems

Question 1

Protein buffer systems depend on

Answer 1

The ability of amino acids to respond to pH changes by accepting or releasing hydrogen, that is, by acting as a base or an acid.

Question 2

Molecules that act as a base or an acid are called

Answer 2

Amphoteric

Question 3

If pH increases in a solution

Answer 3

1. The carboxyl group of the amino acid can dissociate, acting as a weak acid and releasing a hydrogen ion.
2. The carboxyl group then becomes a carboxylate ion.
3. Some amino acid’s, notably histidine and cysteine, have R groups (side chains) that will donate hydrogen ions if the pH increases outside the normal range.
4. There buffering effects are very important in both the ECF and the ICF.

Question 4

In a neutral solution, and amino acid

Answer 4

Carries both positive and negative charges. This state is called a zwitterion (hybrid ion).

Question 5

If pH decreases in a solution

Answer 5

1. The carboxylate ion and the amino group (-NH2) can act as weak bases and except additional hydrogen ions, forming a carboxyl group (-COOH) and an amino ion (-NH3), respectively.
2. In free amino acids, both the main structural chain and the side chain can act as buffers.
3. In a protein, most of the carboxylic and amino groups in the main chain are tied up in peptide bonds.
4. Only the exposed amino group and carboxyl group at either end of a protein are available as buffers.
5. So most of the buffering capacity of proteins is provided by the R groups of amino acid’s.

Question 6

Plasma proteins contribute to the buffering capability of

Answer 6

Blood

Question 7

Interstitial fluid contains— and dissolved — that assist in regulating pH.

Answer 7

Extracellular protein fibers

Amino acids

Question 8

In the ICF, proteins provide buffering that prevents destructive changes in pH when

Answer 8

Cellular metabolism produces organic acids,

Such as lactic acid or pyruvic acid.

Question 9

How protein buffer system helps stabilize the pH of the ECF

Answer 9

1. When pH of ECF decreases, cells pumps out Hydrogen out of the ECF and into the ICF., where the intracellular proteins can buffer them.
2. When the pH of the ECF increases, pumps in plasma membranes move H out of the ICF and into the ECF.

Question 10

Why can’t the protein buffer system in most cells make rapid, large-scale adjustments in the pH of the ECF.

Answer 10

Hydrogen ions must be individually transported across the plasma membrane.

Question 11

Plasma proteins contribute to the buffering capability of

Answer 11

Blood

Question 12

Interstitial fluid contains— and dissolved — that assist in regulating pH.

Answer 12

Extracellular protein fibers

Amino acids

Question 13

In the ICF, proteins provide buffering that prevents destructive changes in pH when

Answer 13

Cellular metabolism produces organic acids,

Such as lactic acid or pyruvic acid.

Question 14

How protein buffer system helps stabilize the pH of the ECF

Answer 14

1. When pH of ECF decreases, cells pumps out Hydrogen out of the ECF and into the ICF., where the intracellular proteins can buffer them.
2. When the pH of the ECF increases, pumps in plasma membranes move H out of the ICF and into the ECF.

Question 15

Why can’t the protein buffer system in most cells make rapid, large-scale adjustments in the pH of the ECF.

Answer 15

Hydrogen ions must be individually transported across the plasma membrane.