Lecture 6- Oxygen in blood and tissues Flashcards
is oxygen soluble in water
Oxygen is not very soluble in water
Solubility factor O2= 0.01 mmol/:/kPa
Less soluble than CO2
[O2] dissolved =
partial pressure of Oxygen in alveoli x solubility coeffiecient of oxygen
= 13.3 x 0.01
[O2] dissolved at a PaO2 of 13.3 kPa
(Solubility factor O2= 0.01 mmol/kPa) x (13.3 kPa)= so only 0.13 mmol/L O2 is dissolved in blood
at rest how much oxygen do we need per minute
12 mmol
oxygen binding to Hb features
Haemoglobin features
binds 4 o2 reversibly
- haem molecule- iron at its centre
States of hb
tense state of Hb
The T state has a less of an affinity for oxygen than the R state. The T-state is the deoxy form of hemoglobin (meaning that it lacks an oxygen species) and is also known as “deoxyhemoglobin”.
relaxed state
High affinity for oxygen in R state (relaxed)- easier for oxygen to bind
What determines whether Hb is in T or R stat
PP of oxygen is the most important
feature of hb which means the right amount of O2 is being carried by Hb
cooperativity
Cooperativity of haemoglobin
describe the oxygen haemoglobin dissociation curve
kPa when Hb becomes saturated
9-10kPa
viturally unsaturated below
1kPa
half saturared at
Saturation changes greatly over a
Wide range of safe partial pressure oxygen- esp at rest- however…..
Though once past the safe region (zone A), rapid fall in the danger zone (zone B)
Hb in arterial blood leaving the lungs
Alveolar pO2 ≈ 13.3 kPa (Hb saturated at around 9-10kPa) therefore Hb leaving the lungs well saturated
how to calculate oxygen content of arterial blood
what about oxygen content in an anaemic pt
if patient is anaemic though pO2 will be normal, and Hb saturation with oxygen 100% – O2CONTENTwillbelower
Fewer Hb, but all Hb will have 4 oxygen binded
Summary: Oxygen in Blood and Tissues (part One)
- Oxygen poorly soluble in blood
- Therefore a carrier is required to which oxygen binds through a
chemical rxn – binding must be reversible
- Carrier is haemoglobin
- Saturation depends on partial pressure oxygen in blood
- Exhibits + cooperativity that facilitates picking up and carrying oxygen in oxygen rich environment – lungs! And then releasing oxygen in low oxygen environment – tissues!
- Haemoglobin is almost 100% saturated over a fairly wide range of oxygen partial pressure so we have a wide safety margin for oxygen levels
- Once past safety margin though saturation drops dramatically and delivery of oxygen to tissues compromised – tissue hypoxia
Tissue pO2 depends on
Haemoglobin saturation in venous blood
a shift to the right on the oxygen dissociation curve represents
decreased affinity of the haemoglobin for oxygen and hence an increased tendency to give up oxygen to the tissues.
what factors will push the oxygen dissociation curve to the right?
- increased temp
- decreased pH
- increased CO2
- increased 2,3 DPG
what factors will push the oxygen dissociation curve to the right?
- decreased temp
- increased pH
- decreased CO2
- decreased 2,3 DPG
