Cell Membrane

• The cell membrane separates the cell contents from the external environment and controls the movement of substances in and out of the cell
• The structure of a cell membrane is a fluid mosaic model
• The membrane is fluid because the molecules that make up the membrane are not stationary
• The membrane is mosaic because it is composed of many different types of molecules
• The cell membrane is composed of phospholipid molecules which are lipid molecules containing a phosphate group
• The phospholipids are arranged into two layers known as a bilayer
• Phospholipid molecules contain a hydrophilic (water loving) tail and a hydrophobic head (water hating)

  
• Cholesterol and protein molecules are also embedded into the phospholipid bilayer
• Many protein molecules are involved in the movement of substances in and out of the cell such as channel proteins
• Channel proteins form a channel through the membrane and allow ions, water, and other small molecules to pass through
• Cell (plasma) membrane

  
• Cell requirements:

  • All cells need oxygen and glucose for cellular respiration
  • Respiration produces carbon dioxide and water which need to be removed by the cell
  • Cells also produce hormones and enzymes, which need to be removed from the cell