8.3 Haemoglobin

Question 1

composition

Answer 1

2 alpha polypeptide chains
2 beta polypeptide chains
each chain has a prosthetic haem group attached to it

Question 2

arrangement of polypeptide chains

Answer 2

hydrophobic R groups facing inwards; hydrophilic R groups facing outwards

Question 3

why can Hb bind with O2?

Answer 3

presence of Fe2+ in Haem group

Question 4

reaction between Hb & O2

Answer 4

Hb + 4O2 –> HbO8

reversible reaction

Question 5

benefit of being soluble

Answer 5

can dissolve in blood plasma; transported easily

Question 6

benefit of having small surface area: volume ratio

Answer 6

can be transported in large concentrations through narrow vessels

Question 7

cooperative binding: meaning

Answer 7

every time a polypeptide chain binds with O2 the molecule undergoes a conformational change that makes subsequent binding easier

Question 8

cooperative binding: impact

Answer 8

Hb has a high affinity for binding with O2

Question 9

why does Hb unload O2 in the muscles? (3)

Answer 9

1. low pO2; oxygen diffuses into tissue cells
2. protons compete with O2 for Hb
3. CO2 competes with O2 for Hb

Question 10

reaction for formation of carbonic acid

Answer 10

CO2 + H2O –> H2CO3

Question 11

disassociation of carbonic acid

Answer 11

H2CO3 –> H+ + HCO3-

reversible reaction

Question 12

reaction for protons binding with haemoglobin

Answer 12

HbO2 + H+ –> H+Hb + O2

reversible reaction

Question 13

reaction for CO2 binding w Hb

Answer 13

CO2 + HbO2 –> Hb-COO- + O2 + H+

Question 14

what happens to hydrogencarbonate after carbonic acid disassociates?

Answer 14

it moves out of the RBC and into the blood plasma

Question 15

name of molecule formed after Hb and CO2 bind

Answer 15

carbaminohaemoglobin

Question 16

reasons for O2 uploading (2)

Answer 16

1. low pCO2

2. O2 competes with CO2 & H+ for Hb

Question 17

what happens to protons when RBCs are in the alveoli (ie. high pO2)?

Answer 17

combine with HCO3- to form carbonic acid, which turns back to water & CO2

Question 18

CO2 TRANSPORTATION

list the different ways it is transported in the blood

Answer 18

as hydrogencarbonate ions (85%)
as carbaminohaemoglobin (10%)
dissolved in blood plasma (5%)

Question 19

what is the bohr shift?

Answer 19

change in Hb saturation levels that occurs when CO2 conc. increases (curve shifts to right)

Question 20

what is the chloride shift and why does it happen?

Answer 20

Cl- ions shift into RBCs as HCO3- ions move out. this is to balance the charge in the RBCs caused by protons and prevent it from getting too positive.