Oxygen carriage in the blod Flashcards
How many oxygens can a haem group pick up?
Each haem group can pick up 1 molecule of
O2.
Why is haemoglobin in red blood cells
The protein, being fairly small, could pass
out of the blood during ultrafiltration in the
kidneys so, to ensure that it is not lost, it is
found within red blood cells.
What is Partial Pressure of Oxygen
Essentially it is a measure of the concentration
of oxygen. It is written in shorthand as pO2 and
is measured in kilopascals (kPa).
Inhaled air in the alveoli has a pO2 = 14kPa.
The pO2 of resting tissue = 5.3kPa (lower pO2 =
lower O2 concentration due to respiration) and
the pO2 of active tissues = 2.7kPa.
In either case, blood arriving at the lungs has a
lower pO2 than that in the lungs.
What is the Bohr effect?
The amount of O2 carried and released by Hb
depends not only on the pO2 but also on pH.
An acidic environment causes HbO2 to
dissociate (unload) to release the O2 to the
tissues. Just a small decrease in the pH results
in a large decrease in the percentage saturation
of the blood with O2.
When does the pH decrease because of free H+ in the blood?
During respiration, CO2 is produced.
This diffuses into the blood plasma and into the
red blood cells.
Inside the red blood cells are many molecules of
an enzyme called carbonic anhydrase.
It catalyses the reaction between CO2 and H2O.
The resulting carbonic acid then dissociates into
HCO3- + H+.
How is the majority of CO2 transported?
About 85% of the CO2 produced by respiration
diffuses into the red blood cells and forms
carbonic acid under the control of carbonic
anhydrase.
What happens to some of the CO2 when it diffuses but doesn’t become carbonic acid?
Some CO2 diffuses into the red blood cells but
instead of forming carbonic acid, attaches
directly onto the haemoglobin molecules to form
carbaminohaemoglobin.
How does carbon monoxide bind, and what does it form?
it binds irreversibly with haemoglobin to
form carboxyhaemoglobin.
What happens when carbon monoxide goes into the blood and form carboxylhaemoglobin?
This means that the Hb cannot load and carry O2.
To make matters worse, Hb combines with CO about 250 times more readily than it does with O2 so that, even if the CO concentration is fairly low, it can cause death due to lack of O2 to the tissues.
What makes foetal haemoglobin different?
This has a higher affinity for O2 than adult
Hb (it combines more readily with O2) so
the foetus picks up enough O2.
What is myoglobin?
Skeletal muscle contains a pigment called
myoglobin.
It is very similar to Hb but has a higher affinity for
O2.
It will load with O2 as Hb unloads and will store
the O2 in the muscle until it is required.
It only releases the O2 when the pO2 is very low
- when the Hb cannot supply O2 fast enough
and the demand is great.
The dissociation curve shifts to the left.
Why do Yak’s have a high affinity for oxygen?
Due to the lack of oxygen at high altitudes, Yaks have a high affinity for oxygen so it binds more easily, this does mean that oxygen particles are less eager to unbind when reaching muscles, but they are more immobile animals so this does not effect them?
What happens when CO2 increases (affinity)
The acidity of the acidity of the blood increases, decreasing pH, reducing the affinity for oxygen, more oxygen release to tissues.
Long Explanation of the Bohr Effect?
Explanation of the Bohr Effect
Increased CO₂ leads to increased H⁺ (acidity):
CO₂ reacts with water in the blood to form carbonic acid (H₂CO₃), which dissociates into hydrogen ions (H⁺) and bicarbonate (HCO₃⁻).
More H⁺ lowers blood pH, making it more acidic.
Hemoglobin releases more O₂:
H⁺ binds to hemoglobin (Hb), causing a conformational change.
This reduces hemoglobin’s oxygen affinity, making it easier for O₂ to be released into tissues.
This is crucial during exercise, when muscles produce more CO₂ and need more oxygen.
Rightward shift of the oxygen dissociation curve:
Increased CO₂ causes the oxygen dissociation curve to shift to the right.
This means hemoglobin holds onto O₂ less tightly, allowing more oxygen to be delivered to tissues.
What is tachycardia
a normal heart rate over 100 beats a minute
What is bradycardia
a normal heart rate under 60 beats a minute
