Lecture 17 Flashcards
What are the two ways that O2 is dissolved in the blood?
- dissolved in the plasma
2. combined with haemoglobin
At 100mmHg, PO2 can only dissolve how much O2 per 10mL of blood? This means that arterial blood with PO2 of 100mmHg contains how much dissolved O2 per litre?
0.3mL
3mL
Is O2 dissolved in O2 an effective way of transporting O2?
no, it only transports 3mL/L x 5L = 15mL/min of O2 but we need it to be about 250mL/O2
How many subunits does haemoglobin have?
4
What are the names of the 4 subunits of Hb?
there are 2 α and two β subunits
Each subunit is known as a what?
a globin
Each subunit is attached to a what?
a heme
Each heme it attached to what atom?
Fe
O2 binds to what?
the Fe in the heme
What is the issue with a lack of iron?
this is a form of anemia and it affects O2 binding/carrying capacity
How many O2 does each Hb carry?
4
O2 forms an ________ ________ combination with Hb to give oxyhaemoglobin
easily
reversible
Why is it important that O2 forms an easily reversible combination wit Hb to give oxyhaemoglobin?
Because this means that it can easily pick up O2 at the alveoli and easily release it at the tissue
The binding of O2 to the haemoglobin depends on the what?
PO2
What colour is blood when O2 is bound to Hb?
red
Deoxygenated blood is what colour?
blue
black (no O2)
What does dark arterial blood indicate?
a problem with PO2
What does haemoglobin saturation do mean?
this is how many O2 can be bound to Hb or how much Hb is saturated with O2
As PO2 increases, the __________ _________ increases
Hb saturation
At the systemic artery PO2 of 100mm/Hg, what is the Hb saturation?
almost 100%
At the systemic venous PO2 of 40mmHg, what is the Hb saturation?
77%
What is the P50?
This is PO2 required for Hb to be 50% saturated (normally 25mmHg)
What shape is the oxygen-haemoglobin dissociation curve?
signmoidal
What are the two parts of the sigmoidal oxygen-haemoglobin dissociation curve?
- upper flat part
2. steep low part
What is good about the upper flat part of the oxygen-haemoglobin dissociation curve?
Normally at 100mmHg, there is 100% saturation. If there is a lung disease, PO2 may drop to 70mmHg and you still have almost 100% saturation. This means that there is some reserve capacity with respect to Hb saturation - even small drops in PO2 doesn’t change saturation so you can still deliver to the tissue assuming Hb is at the normal level
What is good about the lower steep part of the oxygen-haemoglobin dissociation curve?
This helps with the loading and offloading of O2:
in the tissue, there is decreased PO2 so the affinity decreases so Hb readily gives up O2 whereas in the lungs, the PO2 is increased so the affinity increases so Hb quickly binds to O2
Small changes in PO2 result in large changes in the amount of O2 bound to Hb
What effect causes the oxygen-haemoglobin dissociation curve to shift either left or right?
the Bohr effect