Haemoglobin

Question 1

what is haemoglobin?

Answer 1

• groups of chemically similar molecules found in many different organisms
• large globular protein with a quaternary structure
• 4 polypeptide chains, so 4 oxygen molecules can bind
• each polypeptide chain has a haem group which contains an iron ion, this is charged allowing oxygen to bind
• iron ion also gives the red colour
• haemoglobin is tetrameric = 2 alpha chains and 2 beta chains

Question 2

what is loading//associating?

Answer 2

• haemoglobin binds to oxygen
• takes place at gas exchange surfaces, e.g. lungs
• haemoglobin has a higher affinity for oxygen, so associates with oxygen
• takes place at areas with a high partial pressure for oxygen

Question 3

what is unloading//dissociating?

Answer 3

• haemoglobin releases oxygen
• takes place at tissues
• haemoglobin has a lower affinity for oxygen, so dissociates from oxygen at respiring tissues
• takes place at areas with a low partial pressure for oxygen

Question 4

what is the role of haemoglobin?

Answer 4

transports oxygen over large distances to get oxygen to and from exchanging surfaces

Question 5

how does oxygen for red blood cells become available in active tissues?

Answer 5

-due to carbon dioxide then Is a low pH and more H+ ions
- this changes the tertiary structure of haemoglobin
- increases the dissociation of oxygen from haemoglobin
- oxygen diffuses from RBCs to tissues

Question 6

what is the explanation for the curve in oxygen dissociation?

Answer 6

• its hard for the first oxygen to bind to haemoglobin
• once the first oxygen binds, tertiary structure changes which uncovers another binding site for oxygens
• the 2nd and 3rd bind to haemoglobin more easier = cooperative binding
• haemoglobin is saturates so it is hard for the 4th oxygen to bind

Question 7

what does it mean when the oxygen dissociation curve shifts left?

Answer 7

• greater affinity for oxygen
• loads oxygen more readily
• unloads oxygen less readily
• good for organisms living in low oxygen concentration

Question 8

what does it mean when the oxygen dissociation curve shifts right?

Answer 8

• lower affinity for oxygen
• oxygen loads less readily
• oxygen unloads more readily
• good for organisms living in high oxygen concetrations

Question 9

what is the Bohr effect?

Answer 9

• due to a low pH
• when cells respire, they produce carbon dioxide, so the partial pressure of carbon dioxide increases
• greater concentration of carbon dioxide = more readily haemoglobin unloads oxygen = oxygen dissociation curve shifts right
• saturation of blood with oxygen is lower than the given partial pressure of oxygen, more oxygen is unloaded

Question 10

what does a low partial pressure of carbon dioxide mean?

Answer 10

• high affinity
• oxygen loads more readily
• oxygen unloads less readily

Question 11

what does a high partial pressure of carbon dioxide mean?

Answer 11

• low affinity
• oxygen loads less readily
• oxygen unloads more readily