Haemoglobin

Question 1

what kind of structure does haemoglobin have?

Answer 1

quarternary

Question 2

describe the structure of haemoglobin?

Answer 2

primary - 4 polypeptide chains of amino acids linked by peptide bonds
secondary - each chain is coiled into an alpha helix held by H+ bonds
tertiary - each chain is folded into a specific shape held by hydrogen, ionic and disulphide bonds
quartenary - four polypeptide chains link, each one is associated with a haem group, which can associate with O2

Question 3

how many O2 molecules can haemoglobin carry?

Answer 3

each haem molecule can carry 4 O2 molecules since there are 4 haem groups

Question 4

what is it called when haemoglobin picks up and releases oxygen?

Answer 4

picks up = association
delivers = dissociation

Question 5

how does haemoglobin pick up oxygen at the lungs then release at the tissues?

Answer 5

haemoglobin responds to the partial pressure of O2 in the lungs and tissues, when there is high ppO2 the haemoglobin will load up, when there is low ppO2 the haemoglobin will release

Question 6

why does haemoglobin change shape when in the presence of a high level of CO2? (e.g in active muscle)

Answer 6

the CO2 dissolves to form carbonic acid which breaks ionic bonds in the tertiary structure

Question 7

describe the O2, CO2 and affinity of haemoglobin for oxygen in the lungs

Answer 7

O2 conc. (pp02) = high
CO2 conc. = low
affinity = high
result = loads to oxygen

Question 8

describe the O2, CO2 and affinity of haemoglobin for oxygen in active muscle tissue

Answer 8

O2 conc. (ppo2) = low
CO2 conc. = high
affinity = low
result = releases O2 to tissue/cell

Question 9

what is the name of the curve on an oxygen dissociation curve?

Answer 9

sigmoidal

Question 10

describe haemoglobin loading with oxygen

Answer 10

• haemoglobin combines with oxygen in the lungs (oxyhaemoglobin)
• the haemoglobin becomes fully loaded with oxygen (98%) so is fully saturated

Question 11

describe what fully saturated haemoglobin does when passing cells with a low ppo2?

Answer 11

• as the haemoglobin passes cells with a low ppo2, the haemoglobin releases oxygen.
• the amount unloaded depends on the ppo2 in the tissue cells (the lower = more oxygen released)

Question 12

MODEL ANSWER: why does haemoglobin load with oxygen in the lungs?

Answer 12

Haemoglobin loads with O2 in the lungs because there is a high ppo2, therefore the haemoglobins affinity for oxygen is higher.
Haemoglobin releases O2 at respiring tissues because there is low ppo2, so haemoglobin has a low affinity for O2

Question 13

what does it mean if the curve on a oxygen disassociation curve shifts to the left or right?

Answer 13

left = LOADS more, Haemoglobin had a higher affinity for O2, Haemoglobin loads/fully saturated at lower ppo2
right = RELEASES more, Haemoglobin has lower affinity for o2, Haemoglobin dissociates at higher ppo2

Question 14

why do different organisms have slightly different haemoglobin molecules?

Answer 14

• different haemoglobins have different shapes due to different tertiary structures (due to different DNA base sequences)
• different haemoglobins have different affinities for o2
• so each organism has different DNA/genes to code for its correct haemoglobin structure and affinity for O2

Question 15

why does foetal haemoglobin have a higher affinity for oxygen?

Answer 15

the fetus receives its oxygen from its mothers blood, therefore the haemoglobin must have a higher affinity to be able to fully load from the lower ppo2

Question 16

what is a bohr shift?

Answer 16

when CO2 lowers affinity of haemoglobin for oxygen, this means the curve shifts to the right.
when there is more CO2 in a group of cells the O2 will unload more readily

Question 17

what myoglobin?

Answer 17

myoglobin acts as a oxygen store in the muscles and only releases O2 when the ppo2 becomes very low.
myoglobin is a protein that can bind to oxygen and has a very high affinity for oxygen.