Protect organisms against disease
Defense proteins
Increase rates of chemical reactions
metabolic enzymes
Enable cells to communicate with each other and with the environment
Cell signaling proteins
Support and strengthens structures
structural proteins
Promote movement of solutes across plasma membrane
Transporters
Leads to hydrophobic interactions
nonpolar
Leads to hydrogen-bonding interactions
polar
Leads to ionic and hydrogen bonding interactions
acidic & basic
Initiate movement
motor proteins