Blood gas transport Flashcards
Describe the adaptations to increase volume of oxygen transported within circulatory fluids
Haemoglobin with higher oxygen binding affinity
Within the haemoglobin -> Cooperative binding: Oxygen affinity increases as oxygen molecules bind due to changes in shape of the protein
What factors may affect haemoglobin structure and therefore oxygen affinity
PCO2, pH, temperature and 2,3-DPG
What is 2,3-diphosphoglycerate
Intermediate of glycolysis, produced within red blood cells during anaerobic metabolism
Describe the difference of oxygen-haemoglobin binding affintiy at resting tissue, respiring tissue and the lungs
Resting tissue -> Decrease in partial pressure of oxygen, decreased oxygen saturation, O2 moves from Hb to tissue
Respiring tissue -> Large decrease in PO2, and increase in 2,3-DPG, decrease in pH (lactic acid), CO2, so more O2 moves from Hb to tissue
Lungs -> Increased PO2, decreased PCO2, increased pH, so increase in oxygen saturation in haemoglobin
What is hypoxia
Deficient supply of oxygen to tissues. Can occur despite adequate ventilation and perfusion, if not enough oxygen is available
Describe anaemia
Decrease in num of RBC per unit of blood volume, related to either decreased production of RBCs or rapid and excessive loss of RBCs.
Decreased haemoglobin as a result, and therefore decreased oxyhaemoglobin and deoxyhaemoglobin
Describe carbon monoxide poisoning
Exposure to large amounts of CO, decreases total oxygen carrying capacity due to decrease Hb binding sites.
CO displaces O2 at Hb binding sites. Less oxygen in the body. CO also inhibits 2,3-DPG
Describe cyanosis
Blue-purplish discoloration of the skin and tissues that occur when the concentration of deoxyhaemoglobin (Blue) present becomes excessive
Central cyanosis - Discoloration of core, mucous membranes and extremities reflects inadequate oxygenation within lungs
Peripheral cyanosis - Discoloration confined to the extremities - Reflects inadequate oxygen supply to only these tissue e.g. hands
What is erythropoietin
Hormone secreted by kidney in response to hypoxia, induces production of red blood cells within the bone marrow.
What is the cardiac response to hypoxia
Cardiac output increased via increased heart rate, increases overall oxygen transport (faster Hb molecule cycling)
Describe the EPO secretion response to chronic hypoxic respiratory disease (or high altitude)
Increased EPO secretion, increase in number of RBCs per unit of plasma. This is termed polycythaemia. Normoxia -> EPO secretion decreases
How is CO2 transport in the blood different to O2 transport in the blood
CO2 binds at a different site, and forms carbaminohaemoglobin. Less CO2 binds to haemoglobin per molecule than oxygen. More CO2 is carried in plasma as CO2 is more soluble. Most CO2 is transported as carbonic acid and bicarbonate
How is CO2 converted to HCO3-
CO2 reacts with water to form carbonic acid (H2CO3), catalysed by carbonic anhydrase (when high conc of RBC), carbonic acid ionises to form H+ and HCO3-
What happens when CO2 and H+ bind to the Hb molecule
Conformational change in Hb molecule, alters O2-Hb binding affinity as the structure of the O2 binding site changes.
This is the Bohr effect. (factors affecting O2-Hb dissociation curve)
Describe the effect of Hb-H+ binding (Haldane effect of oxygen on CO2 transport)
O2 binds Hb, so Hb has less affinity for H+
Acts as a buffer, removes H+ from the environment. Removal of H+ shifts equilibrium to the right. More dissolved CO2 pulled out f plasma to form bicarbonate. Fresh CO2 replaces the lost CO2, so the overall amount of CO2 carried within the blood increases.
Equilibrium
CO2 + H2O = H2CO3 = H+ + HCO3-
