Structure and function of RBC's Flashcards
do rbcs contain a nucleus
no making them more deformable and more room for hb molecules
do rbcs contain mitochondira
no
surface area to volume ratio
high to allow for gas exchange
consequences of rbcs strtucture
Full of haemoglobin
High oncotic pressure, oxygen rich environment (oxidation risk)
No nucleus Can’t divide, can’t replace damaged proteins - limited cell lifespan
No mitochondria Limited to glycolysis for energy generation (no Krebs’ cycle)
High Surface area/volume ratio Need to keep water out
Flexible Specialised membrane required that can go wrong
red cell membrane structure
complex
not just a lipid bilater
flexible
maintains fluidity and deformability allowing rbcs to squeeze through capillaries
protein spars
why do rbcs require energy
to maintain specific ion concentration gradients and keep water out
what pump is used
sodium potassium pump
keeps water out
needs atp
keeps ion concs right
keeps system working in the cell
structure of haemoglobin
tetrameruc globular protein
adult has two alpha and 2 beta chains
what is a heme group
prosthetic group responsible for biding and transporting oxygent
structure of heme group
iron containing porphyrin ring structure
ferrous iron fe2+ at centre of ring
does oxygen bind to fe3+
no
how many o2 moleculels bind to one fe2+ molecule
one
function of haemoglboin
deliver o2 to tissues
act as buffer for h+
co2 transport
what is red cell production regulated by
erythropoietin- growth factore which stimulates bone marrow to make rbcs
red cell destruction
Normally occurs in spleen (and liver) -
Aged red cells taken up by macrophages
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
Then excreted in bile (colours faeces and urine)
energy source of rbcs
only glycolysis as no mitochondira no krebs cycle
low energy yielding procwss
red cell challenges
Lots of oxygen about - oxygen free radicals are easily generated
Free radicals are dangerous
Can oxidise Fe2+ to Fe3+ which doesn’t transport oxygen
Free radicals damage proteins ~(remember we can’t repair/replace proteins as no machinery to do so -so once they’re damaged that’s it)
what does a red cell need
A way of generating energy i.e. ATP
A way to keep Fe2+ from becoming Fe3+ (ie stop it oxidising)
A way to prevent oxidative damage to cellular enzymes and Hb from free radicals
A way of buffering CO2 for transport
A way of holding onto oxygen in transport and dumping it in hypoxic environments
A way of improving tissue oxygen delivery when it needs it most (when anaemic or when high demand for oxygen - metabolic acidosis, high CO2 concentrations, anaemia)
what prevents oxidation of fe2 to fe3
nadh acting as an electron donor
reactive oxyxgen species assoc
such as superoxide and hydrogen peroxide are free radicals so can interact with other molecules damaging their structure
role of glutathione
protects us from hydrogen peroxide by reacting with it to form watter and an oxidised glutathione product
how does co2 get from tissues to lungs
dissolved in plasma so transported in dissolved form
bound to haemoglobin to form carbaminohaemoglobin
as bicarb ions through a reaction facilitated by the enzyme carbonic anhydrase
how many o2 molecules per hb
4
dissociation curve for haemoglobin
sigmoidal
cooperative binding haemoglobin
first oxygen binds to a haem in one subunit the hb shape changes altering how easy it is for the next o2 to bind and so on
foetal haemoglobin
2 alpha 2 gamma
what is increased in chronic anaemia
2.3 BPG
CO2 AND BOHR EFFECT
co2 indirectly lowers haemoglobins affinity for 02
what is cooperative bindings modulated by
several allosteric effectors that influence its affinity for oxygen
allosteric effectors and their role
2,3 biphosphoglycerate , protons, c02
stabilisize the t tense state reducing oxygen affinity and promoting oxygen release
mechanism of 2,3 bpg
binds to deoxygenated form haemoglobin stabilizing it and reducing its affinity for oxygen
when does haemoglobin shift to the r state - relaxed
in the lugs where co2 and h+ levels are lower increasing oxygen affinity for efficient oxygen uptake
r state
High oxygen affinity.
More stable when oxygen is bound.
Occurs when oxygen is bound to hemoglobin, leading to a conformational change
found in oxygen rich environment s- lungs
t state
Low oxygen affinity.
More stable when oxygen is not bound.
Predominates in deoxygenated hemoglobin.
The heme group is slightly distorted, and the interactions between subunits are stronger.
Found in tissues where oxygen needs to be released.
found in oxygen poor environments- muscles
