Transport of oxygen in the blood

Question 1

What is special about erythrocytes shape?

Answer 1

biconcave shape -

increase surface area available for gas diffusion

help pass through narrow capillaries

Question 2

What other adaptation do erythrocytes have?

Answer 2

by the time they leave the red bone marrow they loose their nuclei, which maximises the amount of haemoglobin that fits into the cell, although it limits its lifespan to 120 days

Question 3

What is the structure of hemoglobin?

Answer 3

a red pigment that carries oxygen and give them their colour

large globular conjugated protein made of four peptide chains

each with an iron-containing haem prosthetic group

Question 4

What is the function of haemoblin?

Answer 4

carry oxygen molecules, can bind to four O2 molecules

O2 binds quite loosely to haemoglobin to form oxyheamoglobin

Hb + 4O2 -> Hb(O2)4

Question 5

How does haemoglobin gain oxygen?

Answer 5

erythrocytes entering the lungs have little O2 levels so there is a steep concentration between the inside of the erythrocytes and the air in the alveoli

Question 6

What is positive cooperativity in erythrocytes?

Answer 6

when O2 binds it changes it shape, making it easier for the next O2 molecules to bind

because the oxygen is bound to haemoglobin, the free oxygen concentration in the erythrocyte stays low

so a steep diffusion gradient is maintained until all of the haemoglobin is saturated

Question 7

What happens when the erythrocytes reach the body tissues?

Answer 7

the concentration of O2 inside the cytoplasm of the body cells is lower than the erythrocytes

so it moves down a concentration gradient

once a oxygen is released, the shape is changed so it is easier to remove the remaining molecules

a drop of oxygen partial pressure in tissues causes oxygen to be drawn in