Physiology 5

Question 1

Plasma buffer system equation?

Answer 1

HCO3- + H+ H2CO3

Question 2

What is the first line of defence in terms of protecting against acidosis/alkalosis?

Answer 2

Buffers

Question 3

What are the relative concentrations of bicarbonate and carbonic acid?

Answer 3

26mM 3uM

Question 4

what is the equation which controls the amount of carbonic acid in the blood?

Answer 4

CO2 + H2O H2CO3 Equalibirum is far towards CO2 Very slow reaction Needs carbonic anhydrase Particularly high in RBCs

Question 5

What enzyme converts carbonic acid?

Answer 5

Carbonic anhydrase

Question 6

What is the effective buffer system between?

Answer 6

Bicarbonate and carbon dioxide (dray out equation)

Question 7

What is the pK of CO2 and HCO3-?

Answer 7

6.1

Question 8

What would be the ideal pK of a buffer?

Answer 8

7.4

Question 9

What organ controls bicarbonate?

Answer 9

Kidneys

Question 10

Henderson-Hasselbalch equation:

Answer 10

pH = pK + log {[base]/ [acid]}

Question 11

What is the role of the lungs in altering pH?

Answer 11

Alter pCO2 through changes in ventilation

Question 12

What is the role of the kidneys in altering pH?

Answer 12

–Alter HCO3- by changes in production & excretion –Alter pH by changes in H+ excretion

Question 13

Aside from buffers what else can buffer the blood?

Answer 13

Plasma proteins

Phosphate (HPO4/H2PO4)

Heamoglobin (very high buffering ability)

Buffering is just a temporary solution

Question 14

What reaction takes place with CO2 in the RBC?

Answer 14

CO2 + H2O H2CO3 (Carbonic anhydrase)

Question 15

What acids to the kidneys deal with?

Answer 15

Sulphuric and phosphoric acids from proteins and lipids.

Lactic acid from anaerobic metabolism

Keto acids from fatty acids

Question 16

Why does the kidney need to deal with acids?

Answer 16

There are a number of non-volatile acids (i.e. cannot breath them out). Relatively a lot less than CO2

Question 17

How much acid to the kidneys deal with each day?

Answer 17

70 mmol of strong acid per day

Question 18

What is the hallmark of a metabolic acidosis?

Answer 18

Decrease in a bicarbonate level

Question 19

What happens with regard to pH with prolonged diarrhoea?

Answer 19

Metabolic acidosis due to loss of bicarbonate

Question 20

What happens with vomiting with regard to pH?

Answer 20

Metabolic alkalosis

Question 21

What is the anion gap?

Answer 21

If we add Na and K HCO3 and Cl It is found that the gap is about 10mmol

Question 22

What is the most important contribution to the anion gap?

Answer 22

Proteins

Question 23

What causes a high anion gap?

Answer 23

• Lactic acidosis (lactic acid) • Diabetic ketoacidosis (keto-acids) • Renal failure

Question 24

What are the renal compensations in an alkalosis?

Answer 24

Reduced acid excretion Excretion of bicarbonate

Question 25

What is the renal response to acidosis?

Answer 25

Increased acid secretion Increased HCO3 re-absorption and production

Question 26

How is bicarbonate reabsorbed?

Answer 26

Proton secretion into the tubule

Question 27

Where are hydorgen ions secreted?

Answer 27

Proximal tubule Distal tubule Collecting duct

Question 28

Steps bicarbonate reabsorption and acid excretion

Answer 28

Na+/H+ antiport secretes H+

H+ in filtrate combines with filtered HCO3- to form CO2

CO2 diffuses into cell and combines with water to from H+ and HCO3-

H+ is secreted again and excreted

HCO3- is reabsorbed

Glutamate is metabolized to ammonium ion and HCO3-

NH4+ is secreted and excreted

HCO3- is reabsorbed

Question 29

What happens to secreted hydrogen ions?

Answer 29

There is a lot of carbonic anhydrase and will convert it into water and produce a CO2