CGIER 28 - Regulation of Respiration and Gas transport Flashcards
where and how does gas move?
gases in alveoli reach equilibrium in blood by diffusion across the pulmonary epithelium and capillary walls
where does diffusion come from
This diffusion results from the differences in the partial pressure of these gases between the alveoli and the blood.
partial pressure
pressure of an individual in a mixture of gases
Dalton’s law
total pressure of a mixture of gases is equal to sum of individual gases partial pressure
barometric pressure at sea level
typically supports a column of mercury 760mm high.
fick’s law
amount of O2 or CO2 that diffuses across membrane of alveolus depend on difference in partial pressure between membrane and surface area of the membrane
under what conditions do gases diffuse faster
the difference in pressure or the surface area increases
describe solubility of oxygen in transport in arterial blood
poor solubility in blood 20ml per 100 ml blood
how many litres of oxygen is dissovled in 5L of blood
1.25 mL
`where does the remaining 98.5% of oxygen 1.5% of the oxygen is dissolved in blood
transported and bound to hemolgobin within red blood cells
how is oxygen molecule dissolved
2% are dissolved in blood plasma
98% dissolved in red blood cell to combine w/ haemoglobin(Hb) = oxyhaemoglobin
moves to capillary bed
low partial pressure of oxygen in capillary bed = oxygen separates from Hb and is dissolved plasma in cell for respiration
what peptide chains does the haemoglobin contain?
2 alpha and 2 beta
what does each polypeptide chain in haemoglobin contain
each polypeptide chain contains haem at the centre -iron atom bound to centre
can bind to 4 oxygen molecules
function of oxygen haemoglobin dissociation curve
The relationship between the partial pressure of oxygen and the percentage saturation of haemoglobin in the blood
describe relationship w/ oxygen conc and haemoglobin
oxygen concentration increases there is a progressive increase in the binding to haemoglobin - highest in the pulmonary capillaries
describe shape of function of oxygen haemoglobin dissociation curve
The relationship is not linear but sigmoid, due to the cooperative binding of oxygen to haemoglobin
factors that influence binding or release oxygen in hemoglobin
pH, carbon dioxide concentration, 2,3-BPG and temperature.
what does right shift in Oxygen-haemoglobin Dissociation Curve mean?
decreased oxygen affinity of haemoglobin (gives up more Oxygen) caused by; increased CO2 partial pressure H+ ions or pH low increase Temp
what does left shift in Oxygen-haemoglobin Dissociation Curve
increased affinity for oxygen, ie. haemoglobin binds oxygen more easily, but unloads it more reluctantly
low CO2 partial pressure
low H+ ions low temp
How does carbon dioxide produce H+ ions bicarbonate ions and make blood more acidic
CO2 reacts with water in plasma to make carbonic acid broken down byenzyme carbonic anhydrase
dissolution of carbonic acid = bicarbonate H+ ions
bohr effect
when CO2 reacts with water in plasma weak carbonic acid is formed - increases blood pH
higher CO2 conc = increased acidity
oxyhaemoglobin release O2 more readily in acidic cond.
displayed in oxygen-haemoglobin dissociation curve,
end result of H+ ions binding to specific amino acid residue
Binding of H+ ions to specific amino acid residues on the globin chain stabilises haemoglobin in a low affinity state and promotes release of oxygen
what other substance induces a similar reaction to oxygen haemoglobin dissociation curve like CO2
lactic acid released from active muscles also lowers blood pH and has a similar effect on the oxygen-haemoglobin dissociation curve
by how much can exercise increase cardiac output and by how much can it increase oxygen delivery
cardiac output - 5 times
oxygen delivery - 15 times
3 ways to transport CO2
- dissolved in solution
- buffered with water as carbonic acid
- bound to proteins, particularly haemoglobin
how much CO2 is produced a minute
200 ml a minute
what % of oxygen consumed is used at rest and thus what is its respiratory quotient
80%
0.8
2 ways in which CO2 carried in rbc
carboaminohaemoglobin - 20%
as bicarbonate - 75%
explain how CO2 is carried within rbc as carboaminohaemoglobin
CO2 bind to haemoglobin in different location from o2
reversible reaction
Low CO2 conc - CO2 is released from haemoglobin
low CO2 partial pressure = Hb and CO2 separate
high CO2 partial pressure - CO2 combine w/ Hb
explain how CO2 is carried within rbc as bicarbonate
In plasma-carbon dioxide + water = carbonic acid
reaction increased with enzyme carbonic anhydrase
Carbonic acid = unstable intermediate molecule quickly dissociates into hydrogen ions and bicarbonate ions
describe chloride shift
- CO2 converted into bicarbonate - high CO2 uptake - large amount of CO2 is converted to bicarbonate ion
- High amount of H+ made from converting CO2 to bicarbonate can combine w/ carbonic acid - alters blood pH
Haemoglobin combine w/ carbonic acid to limit shift - CO2 and H2O diffuse in RBC but H+ and carbonic acid can’t pass thru membrane
- Bicarbonate w/ transport protein is moved out of RBC in exchanged for Cl-
calculate partial pressure of oxygen at sea level
21% of air is oxygen
760 x 0.21 = 160
rate of diffusion according to Fick’s law
k x A x (P2-P1)/D
k = diffusion constant
A = area for gas exchange
D = distance/thickness of barrier
how come the partial pressure varies across different parts of the body?
Conc. of oxygen varies across the body. = Partial pressure varies across the body
e.g. Partial pressure drops in tissue and in veins as the oxygen as been transported to cells through capillary beds
oxygen carrying capacity
maximum amount of oxygen that haemoglobin can transport - 4
oxygen content
actual amount of oxygen bound to haemoglobin
haemoglobin isn’t always filled with its 4 oxygen molecules
oxygen saturation
ratio of oxygen content to oxygen-carrying capacity
how many ml of oxygen dissolved in the blood will be released in the tissue?
5ml oxygen per 100ml of blood
rest of 15 ml is in venous blood
reverse chloride shift
When blood reaches lungs, bicarbonate moves back into RBC in exchange for Cl-
H+ ions dissociate from Hb and binds to bicarbonate ion
Forms carbonic acid -> CO2 w/ help of carbon anhydrase
CO2 is exhaled thru lungs
