Haemoglobin

What is haemoglobin

globular protein in RBC that transports O2 by binding with it to form oxyhaemoglobin

Describe the role of haemoglobin in transporting oxygen around the body.

1. (haemoglobin has) high affinity for oxygen

2. oxygen binds to haemoglobin in lungs

3. oxygen released in tissues

How many oxygen molecules can one haemoglobin carry

4 oxygen molecules (one per haem group)

What is oxyhaemoglobin

Haemoglobin bound to oxygen

What happens to oxyhaemoglobin in tissues

It dissociates releasing oxygen into respiring cells

What is partial pressure of oxygen

concentration of oxygen in a gas or solution

(measured in kPa)

How does pO2 affect haemoglobin saturation

High pO2 increases oxygen binding

low pO2 causes oxygen release

What is haemoglobin affinity for oxygen

How strongly haemoglobin binds to oxygen

What happens in lungs where pO2 is high

Haemoglobin has high affinity and binds oxygen to form oxyhaemoglobin

What happens in tissues where pO2 is low

Haemoglobin releases oxygen due to low affinity

What is cooperative binding

When binding of one oxygen makes it easier for more oxygen molecules to bind

What is fetal haemoglobin

Haemoglobin in the fetus with a higher affinity for oxygen than adult haemoglobin

Why does fetal haemoglobin have higher oxygen affinity

To allow oxygen transfer from maternal blood to fetal blood

What is the Bohr effect

Haemoglobin has a lower affinity for oxygen at higher (pCO₂).

How does high pCO2 affect haemoglobin

It causes haemoglobin to release oxygen more readily

Why is the Bohr effect important

It increases oxygen delivery to respiring tissues producing CO2

What is carbaminohaemoglobin

Haemoglobin bound to carbon dioxide

How is most CO2 transported in blood

As HCO3 ions in plasma after conversion in red blood cells

What is carbonic acid formation

CO2 reacts with H2O

forming carbonic acid

catalysed by carbonic anhydrase

What happens to carbonic acid

It dissociates into hydrogen ions and hydrogen carbonate ions

What is the chloride shift

Movement of chloride ions into red blood cells to maintain charge balance when hydrogen carbonate leaves

What happens in tissues for CO2 transport

CO2 enters red blood cells forms carbonic acid and promotes oxygen release

What happens in lungs for CO2 transport

HCO3 and H convert back to CO2 which diffuses out during expiration

State one difference between fetal haemoglobin and adult haemoglobin and give one reason why this difference is essential to the fetus. [2 marks]

higher affinity for oxygen

must be able to bind to oxygen, in lower partial pressure

Erythrocytes are full of haemoglobin.

Describe the role of haemoglobin in transporting oxygen around the body. [3 marks]

1 (haemoglobin has) high affinity for oxygen

2 oxygen binds to haemoglobin in alveoli

3 oxyhaemoglobin

4 oxygen released respiring tissues

High concentrations of carbon dioxide in the blood reduce the amount of oxygen transported by haemoglobin.

Name this effect and explain why it occurs. [3 marks]

Bohr effect

reduces affinitiy of haemoglobin for oxygen

alters shape of Hb

Dotted line represents fetal haemoglobin.

Explain why the fetal haemoglobin curve is to the left of the adult haemoglobin curve. [3 marks]

1 placenta has low pO2

2 fetal Hb has higher affinity for oxygen

3 so fetal Hb is still able to take up some oxygen in placenta