erythrocytes Flashcards
what gas is poorly soluble in plasma?
oxygen
what is the equation for respiration in muscle?
C6H1206 + 6O2 —> 6CO2 + 6H2O + ~36 ATP
what is the equation for anaerobic glycolysis?
C6H12O6 —> 2 lactate + 2 ATP
what makes up 95% of the dry weight of red blood cells?
haemoglobin
what is haemoglobin’s allosteric property?
cooperatively
how many haem groups does each haemoglobin & myoglobin subunit have?
one
what structure is a haem group?
a porphyrin ring
why is the haem group coloured?
due to the sharing of electrons
what state is the iron in a haem group?
ferrous (Fe2+)
how many molecules of oxygen can one haemoglobin subunit carry?
one
what subunits does adult haemoglobin (HbA) consist of?
2 alpha & 2 beta (tetramer as 4 subunits)
what subunits does foetal haemoglobin (HbF) consist of?
2 alpha & 2 gamma
what type of haemoglobin has a stronger affinity for oxygen?
foetal haemoglobin (HbF)
what is the bohr effect?
the shift in oxygen dissociation curve caused by changes in the concentration of carbon dioxide or the pH of the surrounding environment
what happens when there is a decrease in blood pH?
there is a decreased affinity of haemoglobin for oxygen
what percentage of carbon dioxide is dissolved?
10%
what percentage of carbon dioxide is a carbamino?
22%
what percentage of carbon dioxide is HCO3-?
68%
what shape is the myoglobin curve?
hyperbolic
what shape is the haemoglobin curve?
sigmoidal
what does the rightward shift (R) mean?
lowered affinity for oxygen
what does muscle activity do to haemoglobin?
encourages it to release oxygen
what is 2,3-DPG?
2,3-diphosphoglycerate (or 2,3-bisphosphoglycerate/2,3-BPG)
what does 2,3-DPG do?
binds to haemoglobin and lowers it’s affinity for oxygen
what does increasing the concentration of 2,3-DPG do?
decreases the affinity for oxygen causing a right shift in affinity
why is blood slightly acidic?
due to carbon dioxide and lactic acid
how does the oxygen leave the haemoglobin?
cooperatively
what must happen before respiratory drive increases?
plasma oxygen must drop precipitously
what is the main driver to increase respiratory rate?
H+ in cerebral spinal fluid (CSF)
why is the response to carbon dioxide greater than the response to H+?
due to the blood h+ is only based on signal from carotid arch
describe some features of a red blood cell
- biconcave
- anucleate, lack organelles
- 7 micrometre diameter & 2 micrometre height
- contain haemoglobin
- red when oxygenated
- very flexible: fold and stack in blood vessels
what are the functions of erythrocytes?
- ‘bag’ of haemoglobin
- transport oxygen and carbon dioxide
how many days do erythrocytes survive for?
120 days
what is erythropoiesis?
development/production of red blood cells
where are red blood cells produced after birth?
bone marrow only
where are red blood cells produced after age 20?
membranous bones only (eg - vertabrae)
where are red blood cells produced during embryogenesis?
- liver
- spleen
- lymph nodes
- yolk sac
what is haematopoiesis?
development of all blood cells
what are the 4 steps of development of erythrocytes from stem cells?
multipotent stem cells —> multipotent progenitor cells
—> lineage-committed progenitor cells —> mature cells
what is erythropoietin (EPO)?
- a cytokine/hormone that drives erythropoiesis
- performance-enhancing drug
where is erythropoietin made?
made in the kidney in response to hypoxia in the kidney
what is a reticulocyte?
a red blood cell precursor
how many days does a reticulocyte last for and then what happens?
it lasts 2 days then it becomes a definitive red blood cell
what can the reticulocyte count be used for, why and what are the results?
- used as a diagnostic tool in anaemia
- it indicates the bone marrow activity
- high in haemolytic anaemias & low when erythropoiesis is low
what is methaemoglobinaemia?
- when haemoglobin cannot transport oxygen
- the iron in haemoglobin is oxidised to Fe3+
what is methaemoglobinaemia due to?
- congenital globin mutations (HbM)
- hereditary decrease of NADH
- toxic substances
what happens during carbon monoxide poisoning?
blood turns bright red
what is affected first during carbon monoxide poisoning?
brain = disorientation
what is the treatment for carbon monoxide poisoning?
95% oxygen/5% carbon dioxide
what is polycythaemias?
- increased number of red blood cells
- increases viscosity of blood: clogs blood vessels
what is physiologic polycythaemia due to?
living at high altitudes
what percentage of all iron is in red blood cell haemoglobin?
65%
how is iron stored?
intracellularly as ferritin and haemosiderin (30%)
where is iron stored?
in the reticuloendothelial system
liver, spleen, erythrocytes, bone marrow, macrophages/monocytes
how much iron is lost a day & what factors may alter this?
1mg/day and it is altered by pregnancy, menstruation and peptic ulcers
what is vitamin B12 & folic acid needed for?
- important for rapidly dividing tissue
- essential for forming DNA (thymidine)
what is the condition called where you are deficient in vitamin B12 & folic acid?
megaloblastic anaemia (macrocytic)
cells keep filling up but can’t divide quick enough
what is the treatment for megaloblastic anaemia?
oral folic acid, intramuscular hydroxocobalamin
what condition is caused by iron deficiency?
hypochromic microcytic anaemia
cells keep dividing but cannot fill up with haemoglobin
