How much oxygen can a gram of haemoglobin carry?

 

3,740,000,000,000,000,000,000

If all haemoglobin could carry oxygen then one gram of haemoglobin could carry 1.39 ml of oxygen:

One molecule of haemoglobin will bind four molecules of oxygen

One 'mole' of haemoglobin will bind four moles of oxygen.

One mole of haemoglobin weighs 64,458.5 grams, and so:

1/64.458.5 mole of haemoglobin (i.e. 1 gram of haemoglobin) will bind 4 x 1/64,458.5 moles of oxygen

One mole of oxygen takes up 22.4 litres

4 x 1/64,485.5 x 22.4 = 1.39 ml of oxygen

 

But, not all haemoglobin is functional - some is damaged (dyshaemoglobin), and some likely to be combined with carbon monoxide, and neither of these can carry oxygen. When the actual oxygen carrying capacity of haemoglobin is measured various values have been found, but 1.34 ml is often taken as the 'true' value, and is known as Hufner's number (or constant).

(BTW 1.39 ml of oxygen = 3,740,000,000,000,000,000,000 molecules of oxygen)

(Sorry, not really a picture! 😅)