Page 46 - The Miracle of the Blood and Heart

amino acid 1 amino acid 2 amino acid 3 amino acid 4 amino acid 5 amino acid 6

hydrogen bond
hydrogen bond
beta-pleated sheet
alpha helix
PRIMARY STRUCTURE
Determined by the num- SECONDARY STRUCTURE
ber, type and order of Polypeptide can form a
amino acids, and forms a beta-pleated sheet or an
polypeptide. alpha helix. Hydrogen bonds
form between carboxyl and
amino acids.

TERTIARY STRUCTURE
Occurs when the helix (or hemoglobin
Biology, R.A. Wallace, G.P. Sanders, R.J. Ferl, Harpers Collins College Publishers alpha chain beta chain Heme QUATERNARY STRUCTURE
sheet) is folded in specific
ways, and is characteristic of
globular proteins.
subunit

The folded protein chains may
join to form a single protein
consisting of several subunits.
For example, the oxygen-carry-
ing protein hemoglobin pos-
sesses two alpha chains and
beta chain
two beta chains.
alpha chain

The above diagram shows the phases through which hemoglobin forms.
Hemoglobin has a very complex and perfect structure in order to be able to
transport oxygen. Therefore, any change in its amino-acid configuration will
make it lose its ability to transport oxygen.

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