When oxygen diffuses into our blood it combines chemically with hemoglobin • Hemoglobin: (Hb) • a special globular protein with and embedded heme component (iron) • Found in red blood cells • When combined with O2 it forms “oxyhemoglobin” • Each hemoglobin molecule carries 4 O2 molecules
At rest, under normal conditions: • 1 gram of Hb can hold 1.39 ml/g of oxygen • So in 100 ml of blood you can hold 15g/100ml X 1.39 ml/g of oxygen = 20.85 ml of oxygen/100 ml of blood
The greater number of hemoglobin you have, the greater amount of oxygen you carry • The amount of hemoglobin is a fixed amount that varies little between individuals • On average: • Adult males: 14-18 g/100 ml • Adult women: 12-16 g/100 ml
During Exercise Your HB concentration rises • But hold on a second, you just said Hb concentration was a fixed amount • You have to ask yourself, • “ Hey self, how in the world, can we add Hb to our blood during exercise? • I didn’t say we added Hb I said the concentration rose.
To understand this we must know the composition of blood • Blood is made up of solids and liquid • The liquid portion of blood which makes up about 55% of blood, is called PLASMA • The solids in blood make up about 45% of blood
How in the world can the concentration of Hb rise during exercise? • During exercise some of the fluid portion of the blood shifts in the muscle (causing it to swell) • This leaves the same number of RBC’s in a lesser liquid • Therefore a higher CONCENTRATION of Hb in the blood
During exercise the Hb concentration rises as high as 20.1 g/100 ml of blood • So • 20.1 X 1.39 ml/g = 27.94 ml/g (up from 20.85 ml at rest) Not a huge growth but helps carry more oxygen
HB Saturation • All the preceding information is only true if each Hb molecule hold 4 oxygen molecules Or Is completely SATURATED with oxygen To find out if this is true use……….. THE OXYHEMOGLOBIN DISASSOCIATION CURVE
The curve relates Partial pressure of oxygen with the % saturation of hemoglobin with oxygen • At what PO2 is our HB 100% saturated? • At 100mmHg • Why is this an important number? • When is our HB fully saturated?
All The Time The partial pressure in our alveoli is ALWAYS 100mmHg
When is the only time our Hb would not be full (fully saturated)? • When the partial pressure of oxygen is greater or less than 100mm Hg • At Altitude or under water
Our blood (or more specifically) our Hb is always full and cannot take any more • We do not “run out of oxygen” when we exercise • We are full and cannot carry any more
So…. What if we breath pure 100 % Oxygen, can carry more O2? NO According to the Hb disassociation curve at 100mmHg our Hb is 100% saturated (there are other minor benefits but NONE to oxygen carrying capacity) you will read about them in your text page 132 Make notes on the controversy over hyperbaric oxygen therapy and oxygen bars.