Fundamentals of Anatomy and Physiology

24

organs as a surrounding layer such as the layer around our

kidneys to protect them from severe jolts.

Proteins

Proteins are composed of carbon, hydrogen, oxygen, and

nitrogen covalently bonded. Most proteins also contain

some sulfur. The basic building blocks of proteins are

Chapter 2

20 amino acids. They vary in both the length of their car-

bon chain backbones and the atoms connected to that

backbone. However, each amino acid has a carboxyl group

(^2 COOH), an amine group (^2 NH 2 ), a hydrogen atom, and

the R group. The R group refers to the different types of at-

oms and length of the chain (Figure 2-8). Covalent bonds

form between different amino acids to form proteins. These

are referred to as peptide bonds (Figure 2-9).

General structure Special structure property (^)
CH (^3)
(^) R S (^)
H 2 N (^) C C OH CH 2 CH 2 CH 2 SH (^)
(^) H O (^) CH 2 CH C OH CH 2 CH (^2)
(^) N (^) O H 2 N C C OH H 2 N C C OH (^)
H^ H^ O^ H O^
Amine Carboxyl Proline Methionine Cysteine (^)
group group (pro) (met) (cys) (^)
Nonaromatic Aromatic (^)
Nonpolar CH 3 CH 3 CH (^3)
(^) CH 3 CH 3 CH CH (^2)
CH 3 CH CH 2 H C CH (^3) NH
H 2 N C C OH H 2 N C C OH H 2 N C C OH H 2 N C C OH
(^) C CH (^)
(^) H O H O H O H O (^) CH 2 CH 2
Alanine^ Valine^ Leucine^ Isoleucine^
(^) (ala) (val) (leu) (ile) H 2 N C (^) C OH H 2 N (^) C C OH (^)
Polar uncharged O NH 2 H O H O (^)
O NH 3 C Phenylalanine Tryptophan (^)
CH 3
C
(phe) (trp) (^)
(^) OH CH (^2)
H CH 2 H C OH CH 2 CH 2
OH (^)
(^)
H 2 N C C OH H 2 N C C OH H 2 N C C OH H 2 N C C OH H 2 N C C OH (^)
H O H O H O H O H O (^) CH 2
Glycine Serine Threonine Asparagine Glutamine (^)
(gly) (ser) (thr) (asn) (gln) H 2 N^ C C OH
Ionizable NH^2 H O (^)
(^) C NH Tyrosine (^)
(tyr)
CH 2 NH 2
(^)
O OH HC N NH^
CH 2
(^)
C O OH CH CH (^2)
CH 2 C C N CH 2 CH (^2)
CH 2 CH 2 CH 2 H CH 2 CH (^2)
H 2 N C C OH H 2 N C C OH H 2 N C C OH H 2 N C C OH H 2 N C C OH
®^
Learning^

H O H O H O H O H O

Cengage^

Glutamic acid(glu) Aspartic acid(sap) Histidine(his) Lysine(lys) Arginine(arg)

©^

Figure 2- 8 The general structure of an amino acid and the list of the 20 amino acids found in the human body.