1.3

• cell membrane functions

  -boundary that separates the living cell from its non living surroundings

  -controls which substances leave and enter the cell

  -responsible for secreting substances such as enzymes and glycoproteins

  -cell recognition
• diffusion is the net movement is the movement of molecules or ions from a high concentration to a low concentration across a concentration gradient
• factors affecting diffusion

  • the difference in a concentration gradient
  • the length of the diffusion pathway
  • the surface area
  • the size of the diffusing particle
  • the nature of the diffusing molecule
  • temperature
• what different molecules make up the cell membrane

  • extrinsic protein
  • intrinsic protein
  • glycolipid
  • glycoprotein
  • phospholipid
  • cholesterol
  • channel protein
  • carrier protein

  
• Active Transport is a process that moves molecules against their

  concentration gradient and therefore requires ATP energy, it uses and instinct protein as a pump, this energy is used to change the shape of the protein pump and it transports the ion/molecule against the concentration gradient, across the membrane, into the cell

  
• Cytosis is a form of active

  transport involving the

  formation of membrane-bound

  vesicles, because it is a form of active transport it requires ATP, regions of the cell membrane

  become infolded (invagination)

  or outfolded (evaginated) to

  transport substances across the

  membrane. The 2 forms cytosis are

  endocytosis and exocytotosis
• Large particles enter cells by endocytosis. A section of the cell membrane folds inwards (invagination) engulfing solid particles or liquids. The membrane then fuses forming a vesicle which then enters the cytoplasm.
• Exocytosis occurs by fusion of a vesicle membrane

  with the cell membrane. The vesicle contents are

  then released to the outside of the cell.
• Vesicle


  A small, membrane-bound sac that stores and transports materials within a cell.
• Cell membrane


  The outer boundary of a cell that separates it from its environment, also known as the plasma membrane.
• Fusion


  The process by which two membranes come together and merge, forming a single continuous membrane.
• Exocytosis


  The process by which a vesicle releases its contents to the outside of the cell through fusion of the vesicle membrane with the cell membrane.
• Endocytosis


  The process by which a cell takes in materials from its surroundings by engulfing them with its cell membrane, forming a vesicle.