Carriages of gases Flashcards
Where is oxygen in the body found?
1-In alveolar gas in the lungs
2-In solution in the plasma
3-Bound to Haemoglobin (oxyhaemoglobin)
4-Bound to myoglobin in muscle (Oxymyoglobin)
Describe the oxygen cascade
the physiological steps that brings atmospheroc oxygen into the body where it is delievered and consumed by metabolically active tissue
List the order of partial pressure of O2 in Kpa during the oxygen cascade
highest
-ambient air
-alveolar gas
-areterial blood
-average systemic cappilary blood
-mitochondria
What is the equation of oxygen in solution?
Oxygen in solution = partial pressure oxygen x solubility
what is the total amount of oxygen in arterial blood?
200ml/litre
only 3ml/litre is in solution
What is the oxygen requirement at rest?
- 250ml/min
-can increase up to 4000ml/min on excersise
what is the oxygen requirement in the blood?
-200ml/litre total in bloof
3ml/litre in solution and 197ml/litre bound to Hb
-cardiac output is 5L/min
describe the structure of erythrocytes
-biconcave disk-increases SA for O2 uptake
-no nucleum
-7 micrometer diameter
-flexible
each RBC has approx 280 mil Hb
what is the structure of adult haemoglobin?
-2 alpha globin chains
-2 beta globin chains
each haem group has an iron atom that can bind to an oxygen molecule
What is haemoglobin that releases oxygen known as?
deoxyhaemoglobin (HHb)
what is the equation linking Hb02 and HHb?
HHb = O2 -> Hb02 +H+
deoxyhaemoglobin +oxygen -> oxyhaemoglboin + hydrogen ion
Describe the association/loading of oxygen and haemoglobin
as O2 binds Hb molecules change shape increasing it affinity for O2
What does the oxygen-haemoglobin dissociation curve describe?
the affinity of Hb for O2 at different partial pressures of O2
what shape is the oxygen haemoglobin dissociation curve?
sigmoid shape due to cooperative binding
When the oxygen haemoglobin dissociation curve shifts right what does it show?
a reduced affinity for haemoglobin for oxygen at a give PO2
What are the factors that cause the oxygen haemoglobin dissociation curve to shift right?
-increased temp
-increased PCO2
-Decreased pH (increased acidity)
-increased 2,3- DPG
decreased affinity
If haemoglobin is less saturated what happens to the oxygen?
more oxygen is released to the tissues
what happens to the blood when there is an increase of CO2?
-increased hydrogen ion conc in the blood- reduced PH
Why is there an increased dissociation of oxygen when co2 is increased?
increasing CO2 or reducing the PH weakens the bonds betweeen oxygen and haemoglobin and results in increased dissociation of oxygen to tissue.
Describe the Bohr Effect
increased dissociation of oxygen causing a shift in the oxyhaemoglobin disociation curve to the right.
-oxygen will dissociate from haemoglobin at a lower pO2 than normal.
what are the three forms of CO2 transport in the blood?
10%- dissolved in plasma as dissolved gas, this determines the PCO2 of the blood
15%-bound to plasma proteins and haemoglobin to for carbamino compouds (carbaminohaemoglobin)
75%- transported as carbonic acid and bicarbonate ions
describe the events that occur when CO2 buffers to Bicarbonate ions
-CO2 reactes with H20 to form carbonic acid
-reaction occurs slowly in plasma
-in RBC reaction is catalysed by carbonic anhydrase
-carbonic acid then dissociates to release bocarbonate and hydrogen ions
-Ph is determined by hydrogen ion conc, increased hydrogen ion conc decrases the PH of the blood.
Write the symbol equation for CO2 buffering to Bicarbonate ions.
CO2 +H2O <—> H2CO3 <—>HCO3- + H+
formula for carbonic acid
H2CO3
How are carbamino compounds formed?
-Co2 binds with Amino groups of plasma proteins and haemoglobin
-CO2 combines with haemoglobin to form carboaminohaemoglobin.
What is a buffer?
a solution that resists PH changes
Define the Haldane effect
binding of oxygen to haemoglobin promoting the release of carbon dioxide and hydrogen ions
o2 and cO2 bind to Hb but at different sites
What are the two ways the Haldane effect is achieved?
1-binding of O2 to Hb reduced affinity for CO2 resulting in the dissociation of CO2 in the lungs
2- increased H+ release pushes the reversible equilibrium between bicarbonate and CO2 in the direction of CO2- can be released in the lungs
