Cells

• The movement of substances across cell membranes is affected by membrane structure. Describe how:


  The cell surface membrane consists of a phospholipid bilayer, cholesterol and protein molecules which can be intrinsic or extrinsic.
• How are substances secreted out of the cell?

  Through secretory vesicles which transport substances to the plasma membrane and release them out of the cell by fusing with the membrane
• What is the first step of cell fractionation and ultracentrifugation?


  First the tissue is homogenised to break open cells using an ice cold isotonic buffer solution