Flashcards in Carriage of Oxygen Deck (28)
What is oxidation?
Loss of electrons --> releases energy
What is reduction?
Gain of electrons --> requires energy
How is haemoglobin chemically adapted to carry oxygen?
Combines rapidly and reversibly without becoming oxidised
Why is oxygen a difficult molecule to transport?
Powerful oxidising agent
What are reticulocytes?
Immature red blood cells (just left bone marrow) - have mesh-like rRNA network
Why do erythrocytes require ATP?
To maintain Na+ pumps in membrane, so they make ATP via glycolysis (glucose --> pyruvate)
What is methaemoglobin?
Oxidised form of haemoglobin after much oxygen exposure (prior to breakdown) which cannot carry oxygen
How many unpaired electrons does oxygen have?
How many unpaired electrons does Fe2+ have?
Describe the chemical structure of haemoglobin
Ferrous iron (Fe2+) is core molecule:
4 bonds go to nitrogen groups (covalent) with haem attached
1 bond goes to histidine amino acid below
1 bond is free to bind to oxygen
What is steric hindrance?
3D folding of haemoglobin prevents oxygen molecule getting close enough to the ferrous iron to remove the spare electron (prevents oxidation --> reversible bond)
Describe the molecular structure of haemoglobin
4 subunits (2 alpha, 2 beta) bound together by salt bridges, hydrogen bonds and hydrophobic interactions with prosthetic haem attached
What happens to methaemoglobin?
May be converted back to functioning oxygen-carrying capacity by NADH-dependent methaemoglobin reductase (if newly formed) or broken down in liver/spleen
Describe the structure of foetal haemoglobin
2 gamma subunits with higher affinity for oxygen than adult haemoglobin
What may affect the ability of haemoglobin to bind to oxygen?
pH, partial pressure of CO2 etc
Describe sickle cell disease
Defective form of haemoglobin formed (haemoglobin S) which has mutant beta subunits, causes RBCs to change shape to sickle-shaped which may stack and block blood vessels
Inherited autosomal recessive blood disease which results in less/no globin chains which make up haemoglobin --> abnormal RBCs --> reduction of oxygen transport --> anaemia
Describe the oxygen dissociation curve
How does temperature affect the oxygen dissociation curve?
High temp (metabolising tissue) - curve moves right to unload more oxygen at any given partial pressure
Low temp (slow metabolism) - curve may more left, so less oxygen is given up --> hypoxia and fatigue
How does pH affect the oxygen dissociation curve?
Bohr shift - curve moves to the right with lower pH (more acidic from CO2 production) --> greater oxygen unload
How does carbon monoxide affect the oxygen dissociation curve?
Greater affinity for haemoglobin than oxygen, forming carboxyhaemoglobin --> death by hypoxia may result
What is myoglobin?
Form of haemoglobin found in muscle, it's single subunit and has greater oxygen affinity than haemoglobin (so O2 is transferred in capillaries)
What is rhabdomyolysis?
When myoglobin is released from damaged muscle tissue
How may rhabdomyolysis cause acute renal failure?
Released myoglobin from muscle damage is filtered by kidney but is toxic to renal tube epithelia so can cause kidney failure
What is haematocrit?
Percentage of blood that is red blood cells
What controls red blood cell production?
Erythropoietin (EPO) produced by kidneys and liver.
If kidney is hypoxic --> EPO increased
In what ways is carbon dioxide removed from respiring cells?
Diffuses into water/plasma, converted to bicarbonate (carbonic anhydrase) and carried in plasma, carboxyhaemoglobin (direct binding to haemoglobin)