Carriage of O2 and CO2 in the blood

Question 1

What are the two ways oxygen is carried in the blood?

Answer 1

Dissolved or combined with Hb

Question 2

Does more gas dissolve in a solution at a high or low temperature?

Answer 2

Low

Question 3

What is a normal O2 saturation of Hb?

Answer 3

> 94%

Question 4

How do you work out the volume of O2 in the blood?

Answer 4

O2 saturation x Hb concentration x Hufner constant (1.39ml/g)

Question 5

How many moles of O2 are carried by 1 mol Hb?

Answer 5

4

Question 6

What is the quaternary structure of adult Hb?

Answer 6

2 alpha chains and 2 beta chains

Question 7

Is Hb in the tense state when it is oxygenated or deoxygenated?

Answer 7

Deoxygenated

Question 8

What is the effect of the first O2 molecule binding?

Answer 8

It alters the Hb molecule’s structure to allow the next 3 O2 molecules to bind more easily- co-operativity

Question 9

What does the oxygen saturation of venous blood tend to be?

Answer 9

75%

Question 10

What is the Bohr effect?

Answer 10

Decreased pH (more acidic) makes the Hb-O2 dissociation curve shift to the right and decreases Hb’s affinity for O2

Question 11

Why is the Bohr effect beneficial?

Answer 11

In CO2 rich tissues the pH is lower, so Hb’s affinity for O2 is reduced meaning that O2 is released into the tissues that need it.

Question 12

What three things can increase Hb’s affinity for O2?

Answer 12

1. High pH
2. Low temperature
3. Low 2,3 DPG

Question 13

What is thalassaemia?

Answer 13

One globin chain is missing- only apparent when start getting adult Hb as foetal Hb (gamma and alpha) unchanged.

Question 14

What is the cause of sickle cell anaemia?

Answer 14

A single amino acid defect

Question 15

What is methaemoglobin?

Answer 15

Drug induced defective Fe atom forming methaemoglobin which does not carry O2- like being anaemic.

Question 16

Why is carbon monoxide exposure dangerous?

Answer 16

It has 230 x more affinity for Hb than O2 does so blocks the O2 binding sites.

Question 17

What shape is the Hb-oxygen dissociation curve?

Answer 17

Sigmoidal

Question 18

What is a buffer made of?

Answer 18

A weak acid and its base in equilibrium

Question 19

What is the range of safe blood pH?

Answer 19

7.35-7.45

Question 20

What is p50?

Answer 20

The PO2 at which O2 sat is 50% (normally 3.5 kPa)

Question 21

Which of the 4 O2 molecules binds the most easily?

Answer 21

The fourth one

Question 22

What are the four buffer systems in the blood?

Answer 22

Bicarbonate
Plasma proteins
Hb
Phosphate

Question 23

Which buffer systems in the blood do most of the work?

Answer 23

Bicarbonate and Hb (bicarbonate does most)

Question 24

What are the three ways CO2 can be carried in the blood?

Answer 24

1. Dissolved (3ml/dl)
2. Carbamino compounds (4ml/dl)- binds to amino group on proteins e.g. Hb
3. As bicarbonate (45ml/dl)
   (CO2 + H2O H2CO3 H+ + HCO3-)

Question 25

Which enzyme is used in the carriage of CO2 as bicarbonate?

Answer 25

Carbonic anhydrase in the RBCs- conversion of CO2 + H2O to H2CO3. Contains zinc. Extremely efficient.

Question 26

What is the Hamburger shift?

Answer 26

HCO3- ions pumped out of RBC in exchange for a Cl- ion

Question 27

What shape is the CO2 dissociation curve?

Answer 27

Curved, not sigmoidal.

Question 28

What is the Haldane effect?

Answer 28

The oxygenation level of the blood affects how easily CO2 is dissociated. Deoxygenated can carry more CO2.

Question 29

Is oxygenated or deoxygenated blood a better buffer?

Answer 29

Deoxygenated

Question 30

What is the implication of the Henderson-Hasselbalch equation?

Answer 30

If pH, [HCO3-] or [CO2] change, the other two will change predictably

Question 31

Which two systems compensate for changes in blood pH?

Answer 31

Renal and respiratory

Question 32

What are the four pH abnormalities that can occur in the blood?

Answer 32

1. metabolic acidosis
2. metabolic alkalosis
3. respiratory acidosis (chronic or acute)
4. respiratory alkalosis

Question 33

What is the body’s reaction to acidosis or alkalosis?

Answer 33

Compensation e.g. by kidneys producing more HCO3- if respiratory acidosis

Question 34

What might cause respiratory alkalosis?

Answer 34

Hyperventilation

Question 35

What might cause metabolic alkalosis?

Answer 35

Vomiting, too much antacid medication

Question 36

What might cause respiratory acidosis?

Answer 36

Ventilatory failure

Question 37

What might cause metabolic acidosis?

Answer 37

Renal failure, diabetic ketoacidosis, shock (poor tissue perfusion)