Most of the oxygen in the blood is:Question 21Answera.Dissolved in the blood plasmab.Bound to the haem portion of haemoglobinc.Bound to plasma proteinsd.Bound to the globin portion of haemoglobine.Converted to bicarbonate

The majority of oxygen in the blood is bound to the haem portion of haemoglobin.

Here's a step-by-step explanation:

1. Oxygen enters the bloodstream in the lungs, where it is inhaled into the alveoli (small air sacs).
2. The oxygen then diffuses across the thin walls of the alveoli and into the surrounding capillaries (small blood vessels).
3. Within the capillaries, oxygen binds to a molecule called haemoglobin, which is found inside red blood cells. This binding occurs at the haem portion of the haemoglobin molecule.
4. Each haemoglobin molecule can carry up to four oxygen molecules, and because there are millions of haemoglobin molecules in each red blood cell, and millions of red blood cells in the body, this allows the blood to carry a large amount of oxygen.
5. The oxygen-bound haemoglobin (oxyhaemoglobin) then travels through the bloodstream, delivering oxygen to cells throughout the body.

So, the correct answer to your question is b. Bound to the haem portion of haemoglobin.