The fluid mosaic model

Fluid mosaic = membrane structure model; main features are:

  1. phospholipid bilayer
  2. various protein molecules, some free, some bound to other components
  3. some proteins partially embedded in bilayer [extrinsic; inside/outside]; some proteins spanning the bilayer [intrinsic]

External image

Membrane components and roles:

Stability and fluidity:

  • Cholesterol - fits inbetween fatty acid tails; causes water molecules and ions pass through less easily


  • Channel proteins - molecules too large to pass directly through bilayer [sugar, glucose, also too-hydrophilic molecules…]
  • Carrier proteins - actively transports molecules against concentration gradient [ions in plant roots…]

Recognition and communication:

  • Receptor sites - a cell responds to a hormone only if it has a receptor for the hormone on its cell surface membrane
  • Glycoproteins [protein molecule with carbohydrate attached] and glycolipids [phospholipid molecule with carbohydrate attached] - involved in cells signalling that they are “self”

Metabolic processes:

  • Enzymes and coenzymes - may be bound to membranes [the more membrane there is, the more enzymes/coenzymes there are]

Membranes and temperature

Increase of temperature = more kinetic energy; membranes become leaky, allowing more substances to enter/leave

28.01.15 @7:54pm

Going through Chapter 2 of my Biology textbook! It’s centred around membranes and organelles, which is quite honestly my favourite part of Bio. I’m slowly getting all the memories back from learning this last year, and I’m excited to further my knowledge of the cell :D I’ve also tried a new method of annotating a textbook and I’m thoroughly enjoying it. My only hope is that I figure out what a fluid mosaic model is!

IB Biology Notes. Standard Level. (or is it HL? It just feels like SL somehow.)

Fluid mosaic model –> Membrane structure and proteins

Phospholipids <– partly hydrophobic and partly hydrophillic. 

-Duo layer formed by Phospholipids are kept stable due to this property. Attraction between hydrophobic tails in the centre + Hydrophillic heads and water

This will keep me revising.