W1 LECT 2: The red cell Flashcards
outline the characteristics of the red cell
-Anucleate – in mammals
* No protein synthesis - no ribosomes/ mRNA
* No mitochondria
* Energy is obtained from anaerobic
glycolysis despite (or because of?) the high
concentration of oxygen in the cell
describe the haemoglobin?
95% of the cell content.
Basic structure:
* 4 globin chains each with a haem molecule
* Two α and two non-α chains, e.g., β or γ
* Two αβ dimers combine to form a tetramer
- plantar
-polar
what is the function of the globin chains?
the function of the globin chains is to modify this
haem-oxygen bond:
* reducing its strength
*maintaining the ferrous state
*allowing dissociation of the oxygen
The globins also prevent other potential ligands from
binding.
what are the two types of haemoglobin?
The Tense form – the unoxygenated state
The Relaxed form – the fully oxygenated state
What causes the transition from the tense (T) state to the relaxed (R) state?
- Binding O2 to the first haem leads to strain in the
molecule because of the flattening of the haem. - After the second O2 has bound, this strain leads to
movement of one αβ dimer relative to the other. - This is achieved by breaking H bonds and
releasing H+
what does the O2 affinity of haemoglobin increase by a factor of?
500
what are the physiological factors affecting the O2 affinity of haemoglobin?
- Ph
- Temperature
- CO2
- 2,3 DPG
What is gives rbc its biconcave shape
haem pocket
what steps occurs in the synthesis of haem?
- cytoplasmic
- mitochondrial steps
rate limiting step in haem formation?
formation of ALA
when does methaemoglobin occur?
when the iron atom is oxidised from Fe2+ to Fe3+
what prevents toxification in the red cell cytosol?
glutathione
what generates the NADPH?
HMP shunt hexose monophosphate shunt
rate limiting step of HMP shunt?
G6PD
*CAN CAUSE HEMOLYSIS
What are the layers of the the red cell membrane?
outer lipid bilayer
- inner protein cytoskeleton: spectrin, actin, ankyrin
