Acid-base Balance

Question 1

Acid-Base Homeostasis

Answer 1

Maintains body’s pH.
The acid-base balance affects the body’s chemistry. The structure and function of proteins are dependent on the amount of H+ ions present. Alterations of the body’s pH will cause the denaturation and digestion of proteins as well as enzymes to lose their ability to function.

Question 2

If enzymes lose their ability to function…

Answer 2

Neuromuscular excitability will be altered thereby changing enzymatically controlled metabolic activity. This will cause a K+ imbalance which can lead to cardiac arythmias and thus leading to death.

Question 3

Acid

Answer 3

Any substance that can yield a hydrogen ion when dissolved in water. It releases free H+ ions and anions.

Question 4

Base

Answer 4

Any substance that can yield hydroxyl ions. It accepts free H+ ions and protons

Question 5

pH

Answer 5

The negative log of the hydrogen ion concentration.
pH = -log(1/[H+])
Represents the hydrogen concentration.

Question 6

pH in body fluids

Answer 6

pH=7.4 in most mammals
The concentration of hydrogen ions are kept relatively constant.
Regulation of the concentration of hydrogen ions, makes the fluid more acidic, whilst regulation of hydroxide makes the fluid more basic.

Question 7

Acidosis

Answer 7

Increase in the concentration of hydrogen ions which causes a decrease in pH.
Acidosis occurs when the blood pH is less than 7.35 (pH of the venous blood).

Question 8

Alkalosis

Answer 8

Decrease in hydrogen ions results in an increase in pH.

Alkalosis occurs when the blood pH is greater than 7.45 (pH of the arterial blood).

Question 9

Every unit of change in pH is…

Answer 9

Equal to a 10 fold change in the concentration of hydrogen ions.

Question 10

pH in non-mammalian species

Answer 10

Depends on temperature.
A thermoconformer in a warm habitat will have a pH of approximately 7.4.
A thermoconformer in a cold habitat will have a pH of approximately 8.0.

Question 11

Metabolic activities which add hydrogen ions to the body fluids

Answer 11

Carbonic acid formation.
Inorganic acids produced during the catabolism of food.
Organic acids resulting from intermediary metabolism.

Question 12

Mechanisms which compensate for increase hydrogen ions

Answer 12

Chemical buffer systems
Respiratory adjustment of blood
Excretion of hydrogen ions or HCO3 by the kidney.

Question 13

First line of defense against a pH shift

Answer 13

Chemical buffer system.

The bicarbonate, phosphate and protein buffer systems. These respond immediately and in small quantities.

Question 14

Second line of defense against pH shift

Answer 14

Physiological buffers.
The respiratory mechanism (CO2 excretion), takes a few minutes and occur in limited quantities.
Renal mechanism (H+ excretion), takes hours to days and occurs in large quantities.

Question 15

Chemical buffer systems

Answer 15

A pair of chemical substances involved in a reversible reaction that minimizes pH changes.
A substance can either yield free H+ ions, when the H+ concentration decreases, or a substance can bind with free H+ ions, when the concentration of H+ ions increase.

Question 16

Bicarbonate-carbonic acid Buffer system

Answer 16

Maintains the extra cellular fluids pH.

H+ + HCO3- H2CO3 H2O + CO2

Question 17

Protein buffer systems

Answer 17

Maintains the pH of the plasma and the intracellular pH.
For amino acids, a carboxyl group gives up a H+ ion and an amino group accepts the H+ ion.
The hemoglobin buffer system involves the buffering of H+ ions generated from the metabolism produced CO2.
H+ + Hb HHb+

Question 18

Phosphate buffer system

Answer 18

Maintains the pH of the intracellular fluid and the urine.

NaHPO4 + H+ NaH2PO4 + Na

Question 19

Physiological buffers

Answer 19

The respiratory adjustment of blood by regulating the concentration of CO2. A decrease in the bloods pH, causes an increase in the rate and depth of breathing which causes an increase in CO2 expired thus increasing the bloods pH.
Excretion by the kidney can eliminate large amounts of acid as well as excretion of bases. It can conserve and produce bicarbonate ions.