RBC- structure + function Flashcards
shape of RBC?
biconcave disc
explain the unique structure of RBC
-Biconcave shape
-Full of Hb
-No nucleus
-No mitochondria
-High surface area/volume
-Flexible
Risk of RBC being full of haemoglobin?
-high oncotic pressure, oxygen rich environment
-This is an oxidation risk
Pros and Cons of RBC having no nucleus
Pros:
-makes it more deformable to squeeze through capillaries
-allows more room for Hb
Cons:
-Cant divide
-cant replace damaged proteins
-this means it has a limited life span (120 days)
Consequences of RBC not having a mitochondria?
-Kreb’s cycle occurs in mitochondria
-due to not having a mitochondria it is limited to glycolysis which doesn’t produce a lot of energy for energy generation
pros and cons of RBC having a high surface area/volume?
Pros:
-allows for gas exchange
Cons:
-need to keep water out that could get in
Pros and cons of RBC being flexible?
Pros:
-Flexible to squeeze through capillaries
Cons:
-Specialised membrane made out of proteins required that can go wrong (proteins should mutate and shorten life span of RBC)
what makes the RBC membrane flexible?
it is not just a lipid bilayer
-it is flexible due to protein ‘spars’ and protein anchors
RBC have a high surface area/ volume to allow gas exchange, a problem with this is they need to keep water out
-what do RBC do to keep water out?
-Red cells use sodium potassium pump to maintain ion balance in the cell and keep water out
(But this needs ATP)
where are RBC produced?
bone marrow
RBC are produced in the _____ as a result of proliferation and differentation of ______
RBC are produced in the bone marrow as a result of proliferation and differentation of Haematopoietic Stem Cells (HSCs)
what regulates red cell production?
Erythropoiten
explain how erythropoiten and the kidneys work to regulate red cell production
Hypoxia sensed by kidneys > erythropoietin produced > erythropoietin stimulates red cell proliferation
average life span RBC?
120 days
where are RBCs destoyed?
normally in the spleen
-(and liver)
explain red cell destruction
Average life span 120 days
Normally occurs in spleen (and liver)
-Aged red cells are taken up by macrophages i.e. taken into circulation
-Red cell contents are recycled
-Globin chains recycled to amino acids
-Heme group broken down to iron and bilirubin
-Bilirubin taken to liver and conjugated
and then excreted in bile (colour faeces and urine)
when a red blood cell is destroyed- what are globin chains recycled into?
Amino acids
when RBC gets destroyed, what does the haem group get broken into?
Iron and bilirubin
-bilirubin is then taken to liver and conjugated and then excreted in bile (colour faeces and urine)
what type of Fe ion can transport O2?
Fe2+ transports O2
(when Fe2+ gets oxidised into Fe3+ it can no longer transport O2)
what does glycolysis give the RBC?
Glycolysis allows the RBC to get ATP
it also stops the Fe2+ from oxidising into Fe3+ as
- NADH acts as an electron donor stopping oxidation of Fe 2+ to Fe 3+ and generating NADH+ in the process
explain how NADH prevents oxidation of Fe2+ into Fe3+
NADH acts as an electron donor stopping oxidation of Fe 2+ to Fe 3+ and generating NADH+ in the process
what is metHb?
Hb with Fe3+ (this doesnt carry O2)
what are reactive oxygen species?
-Are free radicals and have unpaired electrons
-Capable of interacting with other molecules (proteins, DNA) damaging their structures
E.g. superoxide + hydrogen peroxide
role of Glutathione (GSH)?
Protects us from hydrogen peroxide by reacting with it to form water and an oxidised glutathione product (GSSG)
how is GSH (glutathione) replenished?
GSH can be replenished by NADPH which in turn is generated by hexose monophosphate shunt
what is the rate limiting enzyme in the reaction between hydrogen peroxide + GSH to form GSSG + water?
Glucose- 6- phosphate dehydrogenase (G6PD)
CO2 transport:
-what % CO2 is dissolved, bound to Hb and in bicarbonate?
10% dissolved in solution
30% bound directly to Hb as carbamino-Hb
60% gets there as bicarbonate and the red cell has an important role in generating that bicarbonate
shape of the Oxygen dissociation Curve and why?
Dissociation cure for Hb is sigmoidal (does not follow the michaelic menten kinetics)
Due to Allosteric affect- first oxygen binds to a haem in one subunit the Hb changes shape and makes it easier for the rest to bind (Cooperative binding)
Explain how Foetal Hb (alpha2gamma2) has a different dissociation curve to adult Hb (alpha2beta2)
Foetal HB (alpha2gamma2)
-are saturated more at same pO2 as HbA so takes O2 from maternal circulation
Explain hoe Myoglobin (in muscles) has a different dissociation curve to adult Hb
Myoglobin (in muscles)
- takes O2 from red cells and has different kinetics
what would shift the O2 dissociation curve to the right (meaning it would release more O2 into tissue)?
-decrease in pH
-increase in 2,3 DPG (AKA 2,3, BPG)
-increase in temp
what condition may increase 2,3 DPG?
chronic anaemia
explain the shape of Hb
a tetrameric globular protein
most common Hb in adults and structure?
HbA (97% adults)
2x alpha and 2x beta chains
explain structure of HbA2 and how common
HbA2 (2.5%)
2x alpha and 2x delta chains
explain structure of Hbf and who it is seen in
Hbf (fetal)
-usually seen in fetus
-seen in <1% adults)
2x alpha and 2x gamma
structure of the heme group in haemoglobing?
heme group is Fe2+ in a flat porphyrin ring
-one heme per subgroup
-One oxygen molecule binds to one Fe2+ so there are 4 x O2 molecules per Hb as it is tetrameric
function of Hb?
-deliver oxygen to the tissue
-act as a buffer for H+
-CO2 transport
