Haemoglobin and gas transport Flashcards
what is blood’s oxygen carrying capacity without haemoglobin?
3ml/L
what is blood’s oxygen carrying capacity with haemoglobin?
200ml/L
what is partial pressure?
the pressure of a substance in solution, this pressure is equal to the pressure in the gaseous phase that results in the concentration in the liquid phase
what oxygen saturation is deoxygenated venous blood?
75%
does oxygen bind loosely or tightly to haem groups?
loosely
what are the 4 types of haemoglobin
-HbA most abundant
-HbA2
-HbF
glycosylated Hb
what is the major determinant for the degree of haemoglobin saturation?
partial pressure of oxygen in arterial blood (this is determined by alveolar partial pressure so this indirectly determines saturation)
how is the partial pressure gradient maintained at the alveoli?
the oxygen moves into the arterial blood then binds to haemoglobin, removing it from solution and maintaining a low PP in solution
what shape is the oxygen-haemoglobin dissociation curve?
sigmoidal
what does the sigmoidal oxygen-haemoglobin dissociation curve tell us about the Hg saturation at PP of oxygen of 100 to 60 mmHg?
when the PP is high a small decrease in PP doesn’t cause a large decrease in saturation, as there is a plateau it stays relatively constant
why does feotal haemoglobin have a higher affinity than HgA ?
it means that a feotus is able to strip oxygen from the mother’s haemoglobin in utero
why does myomoglobin have a higher affinity than HgA ?
so that it can strip oxygen from HgA in the blood when the skeletal muscle it is contained in is working hard.
what is anaemia?
any condition where the oxygen carrying capacity of the blood is compromised
what are some examples of anaemia causing conditions?
iron deficiency, haemorrhage, vit B12 deficiency
what would the partial pressure of oxygen be in arterial blood in someone with anaemia?
normal (40mmHg).
so anaemics have normal PP of oxygen but lowered total blood oxygen content
what would the sturation of haemoglobin be in an anaemic?
normal (100%)
what does acidosis do to haemoglobin’s affinity for oxygen/
it decreases it, dissociation curve shifts to right
what does alkalosis do to haemoglobin’s haemoglobin’s affinity for oxygen?
increases it, dissociation curve shifts to left
what does an increase in partial pressure of carbon dioxide do to haemoglobin’s affinity for oxygen?
It causes it to decrease
what does a decrease in partial pressure of carbon dioxide do to haemoglobin’s affinity for oxygen?
it increases it
what does an increase in temperature do to haemoglobin’s affinity for oxygen
causes it to decrease
what does a decrease in temperature do to haemoglobin’s affinity for oxygen
causes it to increase
what is 2, 3-DPG?
2, 3-diphosphoglycerate, it is produced by RBCs when the metabolise in hypoxic condions
what does an increase in 2, 3-DPG do to Hg’s affinity for oxygen?
it causes it to decrease
what does a decrease in 2, 3-DPG do to Hg’s affinity for oxygen?
it causes it to increase
why is carbon monoxide a poison?
it has a much higher affinity for Hg than oxygen so it binds and doesn’t unbind this means oxygen cant be transported round the body
what are the symptoms of carbon dioxide poisoning?
Hypoxia and anaemia, nausea and headaches, cherry red skin and mucous membranes. Respiration rate unaffected due to normal arterial PCO2. Potential brain damage and death.
what are the 5 main types of hypoxia?
- Hypoxaemic Hypoxia
- Anaemic Hypoxia
- Stagnant Hypoxia
- Histotoxic Hypoxia
- Metabolic Hypoxia
what is hypoxaemic hypoxia?
Reduction in O2 diffusion at lungs either due to decreased PO2atmos or tissue pathology. (most common type of hypoxia)
what is anaemic hypoxia?
Reduction in O2 carrying capacity of blood due to anaemia (red blood cell loss/iron deficiency).
what is stagnant hypoxia?
Heart disease results in inefficient pumping of blood to lungs/around the body
what is histotoxic hypoxia?
poisoning prevents cells utilising oxygen delivered to them e.g. carbon monoxide/cyanide
what is metabolic hypoxia?
oxygen delivery to the tissues does not meet increased oxygen demand by cells.
what is the treatment for CO poisoning?
give 100% oxygen to increase PP of oxygen in arteries
how is carbon dioxide absorbed into the blood?
7% remains dissolved in plasma and erythrocytes,
23% combines in the erythrocytes with deoxyhemoglobin to form carbamino compounds
70% combines in the erythrocytes with water to form carbonic acid, which then dissociates to yield bicarbonate and H+ ions
what is the main way in which carbon dioxide is transported?
it combines in the erythrocytes with water to form carbonic acid, which then dissociates to yield bicarbonate and H+ ions. Most of the bicarbonate then moves out of the erythrocytes into the plasma in exchange for Cl- ions (chloride shift) & the excess H+ ions bind to deoxyhemoglobin
what causes respiratory acidosis?
hypoventilation
what causes respiratory alkalosis?
hyperventilation