Oxygen transport

Question 1

Why is haemoglobin critical to O2 transport?

Answer 1

-Oxygen has low solubility
-Hb enables O2 to be concentrated, hence increasing capacity and then released at respiring tissues

Question 2

What are the 3 ways that oxygen content of blood measured/defined?

Answer 2

1. O2 partial pressure, expressed as kPa
2. Total O2 content(CaO2), expressed as mL of O2 per L of blood (ml/L)
3. O2 saturation

Question 3

What is O2 partial pressure?

Answer 3

the partial pressure of O2 within a gas phase (at a gas-liquid
interface) that would yield this much O2 in the plasma at equilibrium”

Question 4

What is the total O2 content (CaO2)?

Answer 4

“the volume of O2 carried in each litre of blood, including O2
dissolved in the plasma and O2 bound to Hb”

Question 5

What is the total O2 saturation?

Answer 5

the % of total available haemoglobin binding sites that are occupied
by oxygen

Question 6

What does the gradient of the oxygen-haemoglobin dissociation curve mean?

Answer 6

It means the cooperative binding of O2 to Hb

Question 7

What does the plateau mean in the oxygen-haemoglobin dissociation curve?

Answer 7

It means the saturation of O2 binding sites

Question 8

Why is hemoglobin so effective at transporting oxygen within the body?

Answer 8

The structure of Hb produces high O2 affinity, therefore a high level
of Hb-O2 binding (and saturation) is achieved at relatively low PO2.

Question 9

What does the oxygen-haemoglobin binding curve shift to in order to provide effective transport of oxygen?

Answer 9

The oxygen-haemoglobin binding curve
shifts to offload oxygen to demanding tissues

Question 10

What does a leftward shift of the oxygen-haemoglobin binding curve mean?

Answer 10

-Higher Hb-O2 affinity therefore Hb binds more O2 at a given PO2

Question 11

What does a rightwards shift of the oxygen-haemoglobin binding curve mean?

Answer 11

-Lower Hb-O2 affinity therefore Hb binds less O2 at a given PO2

Question 12

What is the bohr effect?

Answer 12

Effect of CO2 & pH on Hb-O2
affinity

Question 13

What happens in a leftward shift to CO2, pH, 2,3 DPG and temperature?

Answer 13

-Decreased CO2
-Increased pH(alkalosis)
-Decreased 2,3 DPG
-Decreased temperature

Question 14

What happens in a rightward shift to CO2, pH, 2,3 DPG and temperature?

Answer 14

-Increased CO2
-Decreased pH(acidosis)
-Increased 2,3 DPG
-Increased temperature

Question 15

When does O2 affinity change and what does this enable?

Answer 15

Hb O2 affinity changes depending on the local
environment, enabling O2 delivery to be coupled to demand

Question 16

How is O2 affinity like in lungs?

Answer 16

-Increased PO2
-Decreased PCO2
-Increased pH
therefore increased O2 saturation

Question 17

How is O2 affinity like in resting tissue?

Answer 17

-Decreased PO2
therefore decreased O2 saturation and O2 moves from Hb to tissue

Question 18

How is O2 affinity like in working tissue?

Answer 18

-Decreased PO2
-Anaerobic respiration and hypoxia produce lactic acid(H+), CO2 and 2,3 DPG
-Therefore O2 demand increases, CO2 increases, pH decreases and 2,3 DPG increases
-This means that Hb-O2 affinity and binding decreases
-Therefore O2 saturation decreases and there’s an increase in O2 movement from Hb to tissue

Question 19

What does oxyhaemoglobin appear as?

Answer 19

Appears as red

Question 20

What does deoxyhemoglobin appear as?

Answer 20

Blue

Question 21

What is cyanosis?

Answer 21

purple discoloration of the skin
and tissue that occurs when the
[deoxyhaemoglobin] becomes excessive.

Question 22

What are the symptoms of central cyanosis?

Answer 22

Bluish discoloration of core, mucous
membranes and extremities

Question 23

What causes central cyanosis?

Answer 23

Inadequate oxygenation of blood
E.g. hypoventilation, V/Q mismatch

Question 24

What are the symptoms of peripheral cyanosis?

Answer 24

Bluish coloration confined to
extremities (e.g. fingers)

Question 25

What are the causes of peropheral cyanosis?

Answer 25

Inadequate O2 supply to extremities
* E.g. small vessel circulation issues

Question 26

What are the causes of anaemia?

Answer 26

-Iron deficiency(decreases production)
-Haemorrhage(increases loss)

Question 27

HB Affinity comparison of CO and O2

Answer 27

Hb has >200x affinity for carbon monoxide (CO) than O2 and
competes for the same binding site.

Question 28

What happens in carbon monoxide poisoning?

Answer 28

-Increased CO-Hb
-therefore decreased O2 capacity

Question 29

What pigmentation does carboxyhemoglobin have and hence when does hypoxia occur?

Answer 29

Carboxyhaemoglobin has cherry red pigmentation, hence hypoxia
occurs in the absence of cyanosis

Question 30

What are the clinical aspects of Hb and O2 transport in anaemia ?

Answer 30

-Decreased O2 content
-Normal saturation
-Normal PaO2(the same amount is dissolved in the plasma)
-Decreased concentration of Hb and decreased concentration of O2-Hb

Question 31

What are the clinical aspects of Hb and O2 transport in carbon monoxide poisoning?

Answer 31

-CO inhibits glycolysis in RBCs, hence decreases DPG
-This shifts curve to the left and this decreases unloading