Respiration 3

Question 1

What is Dalton’s Law?

Answer 1

Dalton’s Law states that the total pressure of a mixture of gases is the sum of their individual partial pressures.

Question 2

what is partial pressure?

Answer 2

The pressure that a gas would exert if it alone occupied the volume of the mixture at the same temperature.

Question 3

what can we use to calculate the amount of a gas dissolved in a solution

Answer 3

partial pressure

Question 4

what law do we use to calculate the concentration of a gas dissolved in solution?

Answer 4

Henry’s law

Question 5

What is Henry’s Law and how is it used to calculate gas concentration in solution?

Answer 5

Henry’s Law states that the concentration of a dissolved gas is determined by:
- Formula: [Gas]dis = s × Pgas
- s = solubility coefficient (mM/mmHg)
- Pgas = partial pressure of the gas

• Example for Oxygen: s = 0.0013 mM/mmHg
• Arterial blood (PO2 = 100 mmHg): [O2]dis = 0.13 mM
• Venous blood (PO2 = 40 mmHg): [O2]dis = 0.05 mM

Question 6

key point is that plasma cannot carry much oxygen so it binds to haemoglobin in RBC

Question 7

How much oxygen can plasma alone carry at 100mmHg PO2?

Answer 7

0.3ml O2 per 100mls of plasma, which is insufficient for body needs (requires 250ml O2/min)

Question 8

What is the basic structure of haemoglobin?

Answer 8

Tetrameric structure with molecular weight of 68 kD

• 4 subunits: 2 α-chains and 2 β-chains
• Each unit contains:
• A Haem unit (porphyrin ring with iron atom)
• A globin chain
• Iron must be in Fe2+ state to bind oxygen

Question 9

how is foetal haemoglobin arrangement different?

Answer 9

It has 2 alpha and 2 GAMMA subunits

Question 10

What are the two states of haemoglobin and how do they differ?

Answer 10

Tense state: low affinity for O2 (hard for oxygen to bind to haemoglobin)
Relaxed state: high affinity for O2 (easy for oxygen to bind to haemoglobin)

Enzyme methaemoglobin reductase helps convert Fe3+ (tense) back to Fe2+ (relaxed)

Question 11

what element does oxygen bind to? what state does it have to be in?

Answer 11

Iron in Fe2+ state

Question 12

what happens when a single oxygen bind to haemoglobin in the tense state?

Answer 12

the first oxygen is hard to bind in the tense state, however once the first oxygen binds, it flips all 4 units into the relaxed state making it easier for future oxygens to bind

Question 13

what factors change the oxygen-haemoglobin dissociation curve?

Answer 13

Temperature
pH (Bohr effect)
CO2
2,3 diphosphoglycerate (DPG)

Question 14

what direction does the curve shift to when temperature is increased?

Answer 14

when temp is increased, oxygen binds off the haemoglobin shifting the curve to the right hand side

Question 15

what direction does the curve shift to when pH is increased?

Answer 15

when pH is increased, the curve shifts to the right hand side

Question 16

what direction does the curve shift to when CO2 is increased?

Answer 16

when CO2 is increased, the curve shifts to the right

Question 17

what direction does the curve shift to when DPG is increased?

Answer 17

when DPG is increased, the curve shifts to the right

Question 18

What is the significance of a right shift in the oxygen-haemoglobin dissociation curve?

Answer 18

A right shift results in decreased affinity for O2 on hemoglobin, leading to more O2 being released to the tissues.

Question 19

How does foetal haemoglobin differ from adult haemoglobin?

Answer 19

Has γ-chains (gamma) instead of β-chains
Shows a leftward shift in the O2 dissociation curve
Has higher affinity for O2

What does this mean?
the foetus can efficiently get O2 from the mothers circulation

Question 20

why do foetuses have lots of myoglobin?

Answer 20

to store Oxygen

Question 21

why is the regulation of CO2 and HCO-3 important?

Answer 21

For setting plasma pH

Question 22

What does a right shift in the oxygen-hemoglobin dissociation curve mean?

Answer 22

• Decreased affinity of haemoglobin for oxygen
• More oxygen is released to the tissues
• Helps meet increased metabolic demands in active tissues

Question 23

List the ways blood carries carbon dioxide (forms of carbon dioxide in the blood)?

Answer 23

• Dissolved carbon dioxide
• Carbonic acid
• Bicarbonate
• Carbonate
• Carbamino compounds

These are collectively referred to as ‘total CO2’

Question 24

what is the majority of CO2 being carried as?

Answer 24

bicarbonate (HCO-3)

Question 25

Where does the majority of CO2 enter?

Answer 25

90% into red blood cells
10% in plasma