plasma membrane

• plasma membrane


  selective permeability, allows some substances in more easily than others

  is made of lipids, proteins, carbohydrates
• fluid mosaic model


  has protein molecules in certain patches of lipids. proteins move laterally slowly and hydrophobic interactions are weak.

  
• temperature decreases

  phospholipids pack together and solidify. membranes can be fluid at a lower temp if they have phospholipids with unsaturated hydrocarbon tails.
• steroid cholesterol


  lowers the temp required for the membrane to solidify. helps resist changes in fluidity
• too solid; too fluid

  solid: enzymatic proteins don't work

  fluid: proteins can't function
• lipid composition


  ability to change lipid composition to respond to temp change. unsaturated phospholipid prevent solidifying in winter
• peripheral proteins


  loosely bound to membrane
• proteins are attached to...

  cytoskeleton and fibers of ECM