Objec&ve 2.12: Proteins
• Iden&fy the monomers and polymers.
• Compare and contrast general molecular structure.
• Provide speciﬁc examples.
• Iden&fy dietary sources.
• Discuss physiological and structural roles in the human body.
• Proteins give structure to the body, regulate
processes, provide protec&on, help muscles to
contract, transport substances, and serve as
• Contain carbon, hydrogen, oxygen, and
• Constructed from combina&ons of 20 amino
– dipep&des formed from 2 amino acids
joined by a covalent bond called a pep&de
– polypep&des chains formed from 10 to 2000
• Pep&de = 10 – 100 amino acids (aa)
• Protein = 100+ amino acids
4 Components of an Amino Acid
• Central carbon atom
• Amino group (NH2)
• Carboxyl group (COOH)
• Side chains (R groups) vary
between amino acids
• 4 classes of side chains:
Forma&on of a Dipep&de Bond
• Dipep&des formed from 2 amino acids joined by a covalent
bond called a pep&de bond
– dehydra&on synthesis
• Polypep&des chains contain 10 to 2000 amino acids.
A Few Roles of Proteins
• Enzymes: catalyze chemical reac&ons
• An&bodies: immune response
• Transporters: move material into and out of a
cell, through the body
• Channels: move material into and out of a cell
• Cytoskeleton: support the cell
• Hormones & Receptors: signaling and
regula&on, maintain homeostasis