All proteins are made up from Amino Acids. Amino Acids
( like polysaccharides) are polymers. All Amino Acids are combinations of an
amino lever ( as shown in Chapter 8) and a chemical "tag".
The "tag" components of Amino Acids themselves are
made up of simpler molecular combinations. 20 different Amino Acids make up the
proteins of all living things.
The 20 Amino Acids from which all body proteins are
constructed are:
alanine - ala - A
arginine - arg - R
asparagine - asn - N
aspartic acid - asp - D
cysteine - cys - C
glutamine - gln - Q
glutamic acid - glu - E
glycine - gly - G
histidine - his - H
isoleucine - ile - I
leucine - leu - L
lysine - lys - K
methionine - met - M
phenylalanine- phe
proline - pro - P
serine - ser - S
threonine - thr - T
tryptophan - trp - W
tyrosine - tyr - Y
valine - val - V
Of the 20 amino acids, 12 can be synthesized in the
human body from other food materials. The remaining 8 cannot be formed in the
human body and must be provided in the diet. For this reason they're known as
the essential amino acids.
Of the structural proteins of the body, the most
important is collagen. This is a family of fibrous proteins that form into
bundles with high tensile strength. That is, they are capable of withstanding
high stresses without breaking. Collagen is the most abundant protein in
mammals and makes up about 25% of body weight.
Each of the large number of different proteins is
formed by stringing these amino acids together in a particular, specific order.
A choice of two amino acids from 20 gives 400 permutations. A string of 10 from
20 can be arranged in 100,000,000,000,000 different ways.