Page 94 - Demo 1

PROTEINS

Proteins are a major group of biological molecules in living systems and
have the most diverse range of funcons of all macromolecules. Some of their
many funcons are:

1. Support - Some proteins provide structural support, like the protein
in spider webs. Keran promotes the healthy growth of hair and
fingernails, while collagen offers support to skin, ligaments, and
tendons.
2. Metabolism - Many proteins are enzymes; they bring reactants
together and help speed up chemical reacons in cells.
3. Transport - Channel and carrier proteins in the cell membrane
regulate the passage of substances in and out of the cell. Other
proteins, like hemoglobin, are complex molecules that carry oxygen
in red blood cells.
4. Defense - Anbodies are proteins that help fight off disease-causing
agents.
5. Regulaon - Hormones are regulatory proteins that act as chemical
messengers. Insulin controls the concentraon of glucose in the
blood, while the human growth hormone (hGH) aids in determining
the height of an individual.
6. Moon - Muscle contracon and cell movement are made possible by
the proteins acn and myosin. These contracle proteins enable
animals to move from place to place and for substances to move
throughout the body.

Each cell in a living system may contain thousands of different proteins,
each with a unique funcon. Despite their diverse funcons, all proteins have the
same basic structure: a long polymer chain made of monomers called amino
acids. Amino acids are small molecules with a simple basic structure: a central
carbon atom to which an amino group (–NH2), a carboxyl group (–COOH), a
hydrogen atom (H), and a funconal group, designated as “R”. There are 20
common kinds of amino acids that differ from one another by the identy of
their funconal R group. The R groups range from simple to complex, based on
the chemical properes of the R group. For example, some R groups are
charged, some are hydrophobic, and some are polar.

86