Classification according to Function

• Functions: Muscle contraction

  Example: Myosin, actin

  Location: Muscle tissue
• Functions: Regulates blood sugar levels

  Example: Insulin

  Location: Present in blood; secreted from islets of Langerhans (pancreas)
• Functions: Enzymes

  Example: Amylase

  Location: The endosperm of starchy seeds; human duodenum
• Functions: Homeostasis

  Example: Soluble proteins e.g. albumin

  Location: Can act as buffers, stabilising pH
• Functions: Protection

  Example: Antibodies (immunoglobulin), fibrinogen

  Location: Produced by B lymphocytes in the blood; is a part of the blood clotting mechanism
• Functions: Structural support

  Example: Collagen, keratin

  Location: Arteries, connective tissue
• Functions: Transport

  Example: Haemoglobin

  Location: Transport of oxygen in vertebrate blood