Proteins

• There are two main ways proteins are embedded into the plasma membrane- explain one.


  Some proteins (peripheral) occur in the surface of the bilayer and never extend completely across it.
• What are the function of peripheral proteins?


  They act either to give mechanical support to the membrane or, in conjunction with glycolipids, as cell receptors for molecules such as hormones.
• What are the other kind of protein embedded into plasma membrane?


  Ones that span the phospholipid bilayer completely- transport protiens.
• What are the two types of channel proteins?


  Protein channels and carrier proteins.
• What is a protein channel?


  Protein channels form water-filled tubes to allow water soluble ions to diffuse across the membrane.
• What is a carrier protein?


  A protein that bind to ions or molecules like glucose and amino acids, then change shape in order to move these molecules across the membrane.
• What are the function of the proteins in a membrane? (6)


  Provide structural support.

  Act as channels transporting water soluble substances across.

  Allow active transport across the membrane through carrier proteins.

  Form cell-surface receptors for identifying cells.

  Helps cell adhere together.

  Acts as receptors for example hormones.