transport of oxygen and carbon dioxide

What are the main 3 adapatiatiosn of erythrocytes

• biconcave disc shape

• No nuclei

• HAEMOGLOBIN ( each can bind to 4 oxygens)

What is the structure of HAEMOGLOBIN

It gives RBC its red colour

As it contains 4 haem prosthetic group that contain fe2+

Large globular protein

What is made when HAEMOGLOBIN binds to oxygen

Oxyhaemoglobin

Hb(02)4

How is oxygen carried and moves into the RBC from the lungs

What happens when one oxygen molecule becomes attached

Erythrocytes in capillaries in lungs have lower oxygen that in alveoli

Concentration gradient

Oxygen moves into the erythrocytes and binds to HAEMOGLOBIN

Hameoglobin has higher affinity

As one oxygen molecule binds the hg shape changes to make it easier to bind to the others and join the haem groups

How is oxygen carried into the tissues from the capillaries

Blood reaches the tissues and the conc of o2 in cytoplasm is lower

Concentration gradient

Oxygen moves out

Once first is released the HAEMOGLOBIN changes shape to make it easier to remove the rest

Label a graphh showing how oxygen is transported and explain the graph

At first the partial pressure doesn’t cause an immediate increase as the HAEMOGLOBIN needs to slowly change shape to then quickly be able to gain the other oxygen molecules (Which is where the line increases and becomes more steep)

It cuts off when the hg is saturated and no more o2 can load

What is te Bohr effect

Where the line shifts to the right

As there is an incrweae in CO2 pp = decrease in O2 pp

It occurs when exercising

Tissues have high CO2 and need O2 so Hg has lower affinity for O2 as the conc gradient causes O2 to be unloaded to tissues

What causes the hg to change shape

There is a decrease in pH

What is the graph like for fetal hg and why

It shifts to the left

Foetus gets 02 from mother and the mothers blood is already low of O2 due to it BEINg in the placenta

Foetus adapts to have higher affinity for O2

It then is able to get the 02 it needs

What percentage is co2 transported by dissolving directly into blood plasma

5%

What percentage is CO2 transported by combining with Hg

20%

How is 75% of CO2 transported by

As hydrogencarbonate ion in plasma

Describe how co2 is transported with hg

One molecule of hg can react with 4 molecules of c02

C02 + hg (reversible arrow) - carboaminohaemoglobin

The reaction is forward in respiring tissue to quickly remove c02 From cells

The reaction is backward to quickly get co2 out of the lungs

Describe how co2 is transported by water? What are the 2 equations

Co2 + H20 (reversible arrows) H2CO3

The reaction occurs when CO2 is high

It uses carbonic a hydrate as an enzyme in RBC

H2CO3 (reversible arrows) HCO3- + H+

What happens after the 2nd equation when carbon is trying to be transported by combing with water

The chloride shift

• HCO3- diffuses out RBC to plasma

• Causes charge imbalance in RBC

• Chlorine molecules enter to balance the charge

H+ ions could cause pH to fall

But it bind to hg which acts as a buffer if binds to form HAEMOGLOBIN if acid

WHAT happens when co2 levels are low

Hydrogen carbonate ions move diffuse back into BC and combine with H+ to reform H2CO3 and broken down by carbonic anyhrdase into co2 and diffuses out RBC and into plasma and CO2 exhaled from lungs when breathed out