For example, eggwhite is protein. The DNA of an organism is essentially a blueprint for making proteins. Other components of an organism, such as lipids and sugars, are made by proteins. Structural proteins form the structure of the cell and the organism. An example would be cartilage, which is made of the protein collagen, and forms the nose.
Functional proteins carry out a job, such as the catalysis of a chemical reaction.
Functional proteins are called enzymes . For example, the metabolic enzymes break down food to provide energy. All enzymes are proteins, but not all proteins are enzymes. Signal proteins communicate information by interacting with other proteins. Hormones such as insulin are signal proteins.