Respiration 3 Flashcards
What is Dalton’s Law?
Dalton’s Law states that the total pressure of a mixture of gases is the sum of their individual partial pressures.
what is partial pressure?
The pressure that a gas would exert if it alone occupied the volume of the mixture at the same temperature.
what can we use to calculate the amount of a gas dissolved in a solution
partial pressure
what law do we use to calculate the concentration of a gas dissolved in solution?
Henry’s law
What is Henry’s Law and how is it used to calculate gas concentration in solution?
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
key point is that plasma cannot carry much oxygen so it binds to haemoglobin in RBC
How much oxygen can plasma alone carry at 100mmHg PO2?
0.3ml O2 per 100mls of plasma, which is insufficient for body needs (requires 250ml O2/min)
What is the basic structure of haemoglobin?
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
how is foetal haemoglobin arrangement different?
It has 2 alpha and 2 GAMMA subunits
What are the two states of haemoglobin and how do they differ?
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)
what element does oxygen bind to? what state does it have to be in?
Iron in Fe2+ state
what happens when a single oxygen bind to haemoglobin in the tense state?
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
what factors change the oxygen-haemoglobin dissociation curve?
Temperature
pH (Bohr effect)
CO2
2,3 diphosphoglycerate (DPG)
what direction does the curve shift to when temperature is increased?
when temp is increased, oxygen binds off the haemoglobin shifting the curve to the right hand side
what direction does the curve shift to when pH is increased?
when pH is increased, the curve shifts to the right hand side
what direction does the curve shift to when CO2 is increased?
when CO2 is increased, the curve shifts to the right
what direction does the curve shift to when DPG is increased?
when DPG is increased, the curve shifts to the right
What is the significance of a right shift in the oxygen-haemoglobin dissociation curve?
A right shift results in decreased affinity for O2 on hemoglobin, leading to more O2 being released to the tissues.
How does foetal haemoglobin differ from adult haemoglobin?
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
why do foetuses have lots of myoglobin?
to store Oxygen
why is the regulation of CO2 and HCO-3 important?
For setting plasma pH
What does a right shift in the oxygen-hemoglobin dissociation curve mean?
- Decreased affinity of haemoglobin for oxygen
- More oxygen is released to the tissues
- Helps meet increased metabolic demands in active tissues
List the ways blood carries carbon dioxide (forms of carbon dioxide in the blood)?
- Dissolved carbon dioxide
- Carbonic acid
- Bicarbonate
- Carbonate
- Carbamino compounds
These are collectively referred to as ‘total CO2’
what is the majority of CO2 being carried as?
bicarbonate (HCO-3)
Where does the majority of CO2 enter?
90% into red blood cells
10% in plasma
