Page 128 - The Miracle of Protein

126 THE MIRACLE OF PROTEIN

Active tissues have high
levels of Co . When hemo-
2
globin reaches these tis-
sues, it will tend to give O Hemoglobin
2
to them. This allows the he-
moglobin to quickly release
its oxygen to tissues that
need it and receive the car-
bon dioxide in exchange.

Erythrocyte

Blood vessel

Hemoglobin emerges from a combination of four different
proteins, containing special structures known as heme groups
that carry iron atoms. These iron atoms are the ‘tongs’ by which

the hemoglobin holds oxygen molecules. Each heme group can
53
hold one oxygen molecule. Special folds and angles inside the
molecule allow the heme groups to capture oxygen without

coming into contact with it, to hold it to, and later deposit it in
the tissues. The binding angle changes at specific rates during