Physiology and Biochemistry Basics Flashcards
why does a rbc not have a nucleus
makes it more deformable (needs to be flexible to go through capillaries) and more room for Hb
what cellular organelles do RBCs lack
nucleus
mitochondria
how does the high Hb concentration in RBCs affect them
gives them high oncotic pressure (Hb a protein) - makes them want to swell
creates an oxygen rich environment= oxidative damage risk
how do RBCs make energy
glycolysis (no mitochondrian so cant do krebs cycle)
describe the rbc membrane
has protein spars (e.g. ankyrin) that anchor it an make it flexible
has sodium potassium pumps (Na+ x 3 out, K+ x 2 in), prevents swelling of cell with water
what is the structure of haemoglobin
a tetrameric globular protein
adult= 2 alpha and 2 beta chains
heme group is Fe2+ in a flat porphyrin ring (one haem per sub group)
what form does the haem group have to be in to carry oxygen
Fe2+ (if Fe3+ (e.g. oxidative damage from free radicals) cannot bind to oxygen)
what are the roles of haemoglobin
delivers oxygen to the tissues
acts as a buffer for H+
CO2 transport
what regulates red cell production
hypoxia sensed by kidneys (juxtoglomerular apparatus)
erythopoietin produced
red cell production stimulated
where does red cell destruction occur
in the spleen and liver (old rbc taken up by macrophages)
what is the lifespan of a rbc
~120
what is recycled in rbc destruction
globin chains -> amino acids (used for globin synthesis)
heme group -> iron (goes into iron stores then turned into haem)
what is the haem group broken down into
iron and bilirubin (heme->porphyrin->biliverdin->bilirubin)
bilirubin taken to liver and conjugated then excreted in bile (colours faeces and urine
via what pathway do rbcs make energy
IN EXAM
anaerobic glycolysis or embden meyehof pathway
glucose-> glucose-6-phosphate ->… pyruvate -> lactate
net generation of ATP and NADH
ATP for energy for cell, NADH for prevention of oxidation of Fe2+ to Fe3+
what is the role of glutathione (GSH)
protects rbcs from hydrogen peroxide by reacting with it form water and GSSG
it is replenished by NADPH
what is the rate limiting enzyme in the glutathione/ NADPH/ hexose monophosphate shunt
glucose - 6 - phosphate dehydrogenase (G6PD)
what is the hexose monophosphate shunt
pathway that generates NADPH which maintains GSH (glutathione) levels preventing oxidative damage (limited by G6PD activity)
how does CO2 get from the tissues to the lungs
10% dissolves in plasma
30% bound directly to Hb as carbamino-Hb
60% converts to bicarbonate (generated by RBC) which then floats in blood (equilibrium reaction, high CO2 environment= made into bicarbonate, low CO2 environment (e.g. lungs) converted back to CO2 and released)
how does Hb buffer CO2 for transport
when Hb is deoxygenated it binds with H+ in acidic environments (acidosis, high CO2) to make HHb
how many O2 molecules per Hb
4
what are the subunits in fetal haemoglobin
two alpha, two gamma
what is the shape of the oxygen dissociation curve
michaelis menten kinetics- sigmoidal
what is the allosteric effect
when one oxygen binds to Hb it changes shape making it easier for O2 to bind to the next subunit
(important as Hb needs to bind a lot of O2 where O2 is high in conc e.g. lungs and conversly allows us to tolerate a high level of anaemia or bodily stress as have spare capacity)
how do the dissociation curves differ across the types of Hb molecules
fetal Hb saturates more at the same PO2 as adult (so can effectively get O2 from maternal circulation)
monomeric myoglobin (in muscles) saturates easier than even fetal Hb as takes its O2 from red cells
what molecules shift the oxygen desaturation curve to the right
H+
CO2
2,3 BPG
what does the oxygen desaturation curve shifting to the right mean
more O2 is delivered to tissues by making it harder for O2 to bind to Hb
what is 2,3, BPG
made during glycolysis
can be raised in chronic anaemia
(aka 2,3 DPG)
what is the rapapoport-lubering shunt
generates 2,3 DBG that right shifts the oxygen dissociation curve and allows more oxygen to be released
why might rbc be low
increased destruction (haemolysis) reduced production (e.g. chemotherapy) redistribution (e.g. portal hypertension causing splenomegaly- rbc trapped in spleen)
why might blood cell count be high
increased production due to stimulus (high altitude, COPD, infection) or no stimulus (malignancy)
redistribution (neutrophils raised in those taking steroids as moved from margin to centre of vessel and easier to sample)
what does -cytosis or -philia mean
an excess (neutrophilia, thrombocytosis)
what does thrombophilia mean
excess clotting
what does -penia mean
a shortage of (e.g. lymphopenia)
what does anaemia mean
lack of RBC or Hb
what does bone marrow hyperplasia mean
increase blood cell production
what does bone marrow dysplasia mean
disordered blood cell production
what does bone marrow hypoplasia mean
low blood cell production
what does bone marrow aplasia mean
no blood cell production
what can RBCs be identified as during the first few days after production
reticulocytes
why are folate and B2 important in RBC production
catalyze steps allowing cell division
where in kidneys detects hypoxia
interstitial fibroblasts near to the peritubular capillaries and the proximal convoluted tubule
what does erythropoietin cause
stimulates cell division of red cell precursors and recruits more cells to red cell production in the marrow = erythroid hyperplasia
where are the macrophages that engulf RBC
mostly in spleen
what would low levels of raw material e.g. iron cause
low output of rbcs = low reticulocyte count
Hb will gradually drop = anaemia
no change in breakdown products e.g. bilirubin as rate same
what might be a liminting factor in resolving homeostasis after a big haemorrhage
will need erythoid hyperplasia, this may quickly deplete iron stores
what is a glucose-6-phosphate dehydrogenase deficiency cause
inability to withstand oxidative stress- reduced rbc life span = increased production needed, will have increased breakdown products
increased breakdown of rbc will cause anaemia then hypoxia
how does chronic renal failure affect rbc count
will fall as kidneys no longer able to make erythropoietin
how is rbc count affected by COPD
slowly increased over years due to chronic hypoxia
what is transient erythropenia of childhood
rare condition where red cell production stops for a variable number of weeks because the virus has infected red cell precursors
