Haemoglobin and myoglobin

Question 1

what results from the structural change of HB when oxygen binds?

Answer 1

oxygen binding promotes stabilisation of the r state

Question 2

describe Hb cooperative binding of oxygen

Answer 2

the binding of one oxygen molecule promotes the binding of subsequent oxygen molecules.

when low pp of oxygen most Hb will be in low affinity T state
as oxygen binds as pp increases the affinity of Hb increases as it changes into its higher affinity r state.

Question 3

give an allosteric inhibitor of Hb

Answer 3

2,3 BPG
lowers the affinity of Hb for oxygen
haemoglobin oxygen dissociation curve shifts to the RIGHT.
with more bpg the same partial pressure of oxygen there is a lower saturation than with little bpg

Question 4

what affect does CO and H+ have on Hb?

Answer 4

lowers affiniyt of Hb for oxygen - BOHR effect

Lower ph, increases h+ ions. This will cause hb to take up less oxygen, graph moves to right
localised effect at metabolically active tissues - oxygen will be released from Hb

Question 5

Describe the binding of CO to HB

Answer 5

co binds much more readily to Hb than O2

fatal when CO binds to more than 50% of Hb

will also increase the affinity of Hb for oxygen - shifts curve to left. - will take up o2 in lungs but does not release o2 in the tissues

Question 6

Describe sickle cell anaemia

Answer 6

one base pair mutation
glutamate changed to valine
changed to hydrophobic aa on surface of Hb
causes two beta subunits to stick togehter formin a stick patch and a long chain
aggrigations cannot transport oxygen
cell membrane of rbc becomes rigid an no longer passes through small vessels causing microvascularture or they lyse.

Question 7

descrbe thalassaemia

Answer 7

imbalance betwee alpha and beta subunits
one is being produced more or being broken down more
beta thal - absence of beta globin gnee - two alleles = excess fo aplpha subunits

hb barts - ghb only made of gamma subunits

alpha thal - four copies of alpha globin genes = excess beta subtunits - high affinity for oxygen

Question 8

How can you have different forms of Hb at different times in life?

Answer 8

globin genes are on two different locations on two different chromosomes

expressed at differtn time s
in foetus the gamma subunit gene is expressed.