Acids and Bases

Question 1

pH

Answer 1

Power of hydrogen

Question 2

Normal animal plasma levels

Answer 2

• Normal plasma [H+] is ~40nmol
• Normal plasma pH is 7.38-7.44

pH = -log10[H+] by using norm plasma hydrogen concentration

Question 3

Importance of pH

Answer 3

Enzymes function within an optimal range of pH. If too basic or too acidic, then the protein will denature. Then altered activity results in a change of metabolic regulation and cell viability, which results in cell death

Exception: digestive enzymes are optimal at low pH

Question 4

Why does H+ fluctuate?

Answer 4

• Carbon dioxide diffuses freely out of cells into the blood. Then it reacts with water in the blood and forms carbonic acid (H2CO3). Since carbonic acid (H2CO3) is a weak acid, it dissociates into hydrogen (H+) and bicarbonate (HCO3-)
• This is considered a partial dissociation so it moves back and forth between carbonic acid and the hydrogen and bicarbonate

Question 5

pKa

Answer 5

A constant that determines which side the equilibrium shifts in a given environment.

Calculated using the equilibrium constant (Ka) (the ratio in equilibrium) and pKa=-log10(Ka)

Question 6

pKa of carbonic acid (H2CO3)

Answer 6

6.1

Question 7

1. pH < pKa
2. pH> pKa

Answer 7

1. More protonated; more acidic
2. More deprotonated; more basic

Question 8

Henderson-Hasselback Equation

Answer 8

Used to calculate pH of weak acids such as blood pH

Question 9

Factors that influence pH

Answer 9

• Metabolism- loss of hydrogen ions and bicarbonate in kidneys and stomach (stomach acid, urine)
• Respiratory component getting rid of CO2

Question 10

Type of acid-base disturbances

Answer 10

1. Respiratory disturbance- have an effect on P(CO2)
2. Metabolic Disturbance- have an effect on bicarbonate

Question 11

Abnormalities of pH

Answer 11

1. Acidemia
2. Alkalemia

Question 12

Processes causing abnormalities of pH

Answer 12

1. Acidosis
2. Alkalosis

Question 13

Normal HCO3- (bicarbonate) and PCO2 Ratio

Answer 13

The normal ratio between them is 20.

If less than 20, then acidemia. If greater than 20, then alkalemia.

Question 14

La Chatelliers Principle

Answer 14

Disturbance to a system in equilibrium shifts the equilibrium in the direction that counteracts the change.

CO2 + H2O <–> H2CO3 <–> H+ + HCO3-

Question 15

Respiratory Acidosis

Answer 15

• Caused by hypoventilation
• Less gas exchange, increase in CO2, causes a right shift towards H+ and HCO3-
• Higher P, less bicarbonate = acidic = Acidemia

Question 16

Renal compensation for respiratory acidosis

Answer 16

• Slow process
• Kidneys increase HCO3- reabsorption. Transporter in kidney cells move bicarbonate into capillaries so it can neutralize H+ ions and increase pH

Question 17

Respiratory Alkalosis

Answer 17

• Caused by hyperventilation
• Results in increase in gas exchange, so decrease in CO2 causing shift to left
• Decrease in P, small decrease in HCO3-, so increase in pH = Alkalemia

Question 18

Renal compensation for Respiratory alkalosis

Answer 18

• Slow process
• Kidneys reduce bicarbonate reabsorption

Question 19

Metabolic Acidosis

Answer 19

• Caused by overproduction of lactic acid from exercise. Causes an increase in H+ ions and a decrease of bicarbonate (due to saturation), so shift to left
• Acidemia

Question 20

Respiratory compensation for metabolic acidosis

Answer 20

• Hyperventilate. increase gas exchange, decrease CO2. Will cause a shift to left, decreasing H+
• Conducted through peripheral receptors (carotid and aortic chemoreceptors) which sense changes in O2, CO2, and H+. These sensors sent message to respiratory center of the medulla oblongata which tells motor neurons to get respiratory muscles and lungs to cause the animal to hyperventilate to decrease CO2

Question 21

Metabolic Alkalosis

Answer 21

• Caused by vomiting –> loss of stomach acid (decrease in H+) –> leads to increase in bicarbonate; causes a right shift

Question 22

Respiratory compensation for metabolic alkalosis

Answer 22

Chemoreceptors detect a drop in H+ ions, and send signal to supress respiration. This increases P and therefore causes the shift right to increase H+

Question 23

Factors hindering compensation responses

Answer 23

• Renal failure
• Pulmonary disease
• Depressant drugs of the respiratory center

Question 24

Mixed disturbances

Answer 24

Two or more acid-base disturbance together

Ex. unregulated diabetic animal
- Excess ketone leads to keto (metabolic) acidosis
- Vomiting leads to metabolic alkalosis
- Aspiration of vomit in lung leads to respiratory acidosis

Question 25

Anion Gap

Answer 25

Difference in concentration of major cations (Na+ and K+) and anions (Cl- and HCO3-). The gap is due to various organic cations, anions, and proteins

Question 26

Increase in anion gap

Answer 26

Indicates metabolic acidosis

Ex. Lactic acid in blood- an increase in H+, would mean that the HCO3- is used up

Question 27

Decrease in anion gap

Answer 27

Indicates a cation anomaly (hypercalcemia- overactive thyroid, or hypermagnesemia- renal failure) or metabolic alkalosis (increase in HCO3-)

Question 28

Metabolic acidosis and a normal anion gap

Answer 28

Ex. diarrhea causing HCO3- loss

Excess loss of HCO3- causes metabolic acidosis. Kidney compensation increases Cl- reabsorption to maintain a neutral charge. Metabolic acidosis but no change in anion gap