- Present in skeletal and cardiac muscle - One haem group per molecule (1:1 ratio) - No cooperative effect - Provides short term storage of oxygen for anaerobic conditions

Physiology 3: Gas Transport (L-4&5) Flashcards by Lucas Findlay

Describe how PO2 change as oxygen travels from the lungs to the systemic capillaries

It decreases

How well did you know this?

Not at all

Perfectly

What is the effect of partial pressure on gas solubility?

Henry’s Law

The amount of gas dissolved in a given type and volume of a liquid is proportional to the partial pressure of the gas in equilibrium with the liquid

(At a constant temp.)

How well did you know this?

Not at all

Perfectly

What are the 2 mechanisms by which oxygen is transported in the blood?

Dissolved oxygen (1.5%)

- Oxygen bound to haemoglobin (98.5%)

How well did you know this?

Not at all

Perfectly

Describe the structure of haemoglobin (Hb)

4 haem groups (1 per subunit)
2 Beta chains
2 Alpha helices

How well did you know this?

Not at all

Perfectly

Describe the binding of oxygen to Hb

Each Hb group reversibly binds to one oxygen molecule
PO2 is the primary factor determining %O2 saturation of Hb
Binding of oxygen to one subunit increases the other subunits oxygen affinity (Co-operativity)

How well did you know this?

Not at all

Perfectly

Describe the oxygen delivery index (DO2I)

Oxygen delivery to tissue depends on the oxygen content of arterial blood and the cardiac output

DO2I = (Arterial O2 conc.) X (Cardiac Index)

How well did you know this?

Not at all

Perfectly

Describe the factors that determine the oxygen content of arterial blood

Hb concentration

- Saturation of Hb with oxygen

How well did you know this?

Not at all

Perfectly

What factors affect the partial pressure of inspired oxygen?

Total pressure

- Proportion of oxygen in the air

How well did you know this?

Not at all

Perfectly

Give examples of ways that oxygen delivery to tissue can be impaired

Decreased partial pressure of inspired oxygen
Respiratory disease (Less oxygen can bind to Hb)
Anaemia (Less Hb so less oxygen)
Heart failure
Infarction/vessel occlusion

How well did you know this?

Not at all

Perfectly

Describe co-operativity in Hb with regards to oxygen binding

When oxygen binds to one Hb subunit, the affinity of the other subunits for Hb increases

(This is positive cooperativity)

How well did you know this?

Not at all

Perfectly

What is the reason for the sigmoid shape of the oxygen binding curve?

The positive cooperativity of Hb due to oxygen binding

How well did you know this?

Not at all

Perfectly

Describe the effect of a change in PO2 on %Hb saturation at high PO2 values (e.g. in pulmonary capillaries), and lower PO2 values (systemic capillaries)

At a high PO2:

A change in PO2 will have a small impact on the %Hb saturation. (Graph is flat)

At lower PO2:

A change in PO2 will have a larger impact on the %Hb saturation. (Graph is steeper)

How well did you know this?

Not at all

Perfectly

Explain the significance of the fact that, at a lower PO2, a change in PO2 will have a larger impact on the %Hb saturation

PO2 lower at peripheral tissues

- Smaller change in PO2 required to release the same amount of oxygen from the Hb into the tissues

How well did you know this?

Not at all

Perfectly

Describe myoglobin

Present in skeletal and cardiac muscle
One haem group per molecule (1:1 ratio)
No cooperative effect
Provides short term storage of oxygen for anaerobic conditions

How well did you know this?

Not at all

Perfectly

Does myoglobin exhibit a cooperative effect?

Only has one subunit

How well did you know this?

Not at all

Perfectly

Compare the oxygen association/dissociation curves of haemoglobin and myoglobin

Haemoglobin:

Sigmoid (due to cooperativity)

Myoglobin:

Hyperbolic (due to no cooperativity)

Describe the structure of foetal haemoglobin (HbF)

2 alpha subunits

- 2 Gamma subunits

Compare the interactions of HbF and Hb with 2,3-Bisphosphoglycerate (2,3-BPG)

What does this cause?

HbF interacts less with 2,3-Bisphosphoglycerate in red blood cells

Thus HbF has a higher oxygen affinity than Hb

Compare the sigmoid curves of Hb and HbF

HbF has a sigmoid curve that is shifted to the LEFT

This means it has a higher oxygen saturation at a lower PO2

Give an example of the significance of the differing oxygen affinities of Hb and HbF

Allows maternal Hb to lose oxygen to foetal HbF

List changes in environment that would increase the release of oxygen at the tissues (i.e. decrease Hb% saturation)

PCO2 increase
pH decrease ([hydrogen ion] increase)
Temp increase
2,3-Bisphosphoglycerate increase

List changes in environment that would decrease the release of oxygen at the tissues (i.e. increase Hb% saturation)

PCO2 decrease
pH increase ([hydrogen ion] decrease)
Temp decrease
2,3-Bisphosphoglycerate decrease

What term describes the shift in Hb oxygen affinity under different environmental conditions?

Bohr Shift

due to the Bohr Effect

List the 3 ways carbon dioxide is transported in the blood

And give their relative proportions

Dissolved (10%)
Bicarbonate (60%)
Carbamino compounds (30%)

What determines the amount of carbon dioxide that is dissolved in the blood?

The partial pressure of the carbon dioxide gas (PCO2) in equilibrium with the solution (Henry's Law)

Which is more soluble carbon dioxide or oxygen?

Carbon dioxide is roughly 20 times more soluble

By which method is the majority of carbon dioxide transported in the blood?

As bicarbonate (HCO3)

Describe the how bicarbonate is formed in the blood

- In red blood cells - Water and carbon dioxide react to form carbonic acid - This is catalysed by Carbonic Anhydrase - Carbonic acid dissociates into bicarbonate and a proton

Which enzyme catalyses the production of carbonic acid as part of the formation of bicarbonate?

Carbonic anhydrase

Describe the Chloride shift

- In order for more CO2 to diffuse into the cell the equilibrium of bicarbonate formation must shifted - By facilitated diffusion bicarbonate ions move out of the RBC into the plasma in exchange for chloride ions - Occurs at tissue, the reverse happens at the alveoli

Describe how carbamino compounds are formed

- Carbon dioxide reacts with the terminal amine group in blood proteins - Especially globin of haemoglobin (forming carbamino-haemoglobin) - Very rapid even without enzyme action

Describe how is carbamino-haemoglobin HbCO2 formed

- Carbon dioxide reacts with the terminal amine group in the globins (subunits) in haemoglobin

How many carbon dioxide molecules can each haemoglobin molecules bind to?

4 One for each subunit

Describe the Haldane Effect

HbO2 --> Hb Increases the ability of Hb to bind to carbon dioxide and hydrogen ions (O2 availability governs the binding of CO2 and H+ to Hb)

Which 2 effects work together to ensure: O2 liberation and uptake of CO2 & H+ at tissues

- Bohr Effect | - Haldane Effect

Why at the lungs does: HbCO2 --> Hb + CO2 HbH --> Hb + Hydrogen ion

The Hb binds to oxygen with a higher affinity | Haldane Effect

Provide an overview of the exchange of oxygen and carbon dioxide at tissue

- Some CO2 is dissolves in plasma, some in the RBC - Oxyhaemoglobin releases oxygen, freeing up Hb - CO2 binds to form carbaminos (e.g. Carbamino-haemoglobin) - Bicarbonate ion formed - Bicarbonate ion is moved to the blood plasma during Chloride Shift - Free Hb binds to hydrogen ions making HbH

Provide an overview of the exchange of oxygen and carbon dioxide at the alveoli

- Carbaminos release their Hb and intracellular dissolved CO2 - HbH releases its Hb and hydrogen ions - Free Hb binds to oxygen, forming oxyhaemoglobin - The chloride shift is reversed - Bicarbonate ions and freed hydrogen ions form carbonic acid - Carbonic acid released CO2 - Intracellular and extracellular dissolved CO2 --> Alveoli