membrane receptors

• proteins in the cell membrane act as receptors for messenger molecules
• what are the receptor proteins called

  membrane-bound receptors
• receptor proteins have specific shapes - only messenger molecules with a complementary shape can bind to them
• different cells have different types of receptors, they respond to different messenger molecules
• a cell that responds to a particular messenger molecule is called a target cell
• many messenger molecules are hormones, they work by binding to receptors in the cell membranes and triggering a response in the cell

  • e.g. glucagon - released when there isn't enough glucose in the blood. Binds to receptors on liver cells causing them to break down glycogen into glucose
  • e.g. FSH - Released by the pituitary glands during menstrual cycle and it binds to receptors in the ovaries causing an egg to mature for ovulation