Biological membranes

• Cholesterol is an important lipid that helps maintain fluidity and stability of cell membranes.
• What are the functions of a cellular membrane?

  1. providing a partially permeable barrier
  2. compartmentalisation-keeping substances in certain spaces
  3. transport in solutes
  4. cell to cell recognition
  5. receptor sites for hormones
  6. signal transduction for nervous system
• What is the width of a membrane?

  7.5 nm
• What is a glycolipid?

  A type of lipid with a carbohydrate chain attached. It’s works in cell to cell signalling and communication in the extra cellular matrix
• What is a glycoprotein?

  A protein with a carbohydrate chain attached. It works in cell to cell signalling and communication
• What does the ‘mosaic‘ part of the fluid mosaic model describe about the structure of a membrane?

  Describes the pattern/arrangement of the protein molecules in the membrane
• How do glycolipids and glycoproteins work?

  The short carbohydrate chains project into the watery fluids surrounding the membrane to for hydrogen bonds with the water for stability.
• How do phospholipids play a role in the membrane?

  Fluidity and structure. The phospholipids for a bilayer where it acts as a barrier to most water soluble substances (including water) due to its hydrophobic tails
• What is diffusion ?

  The passive net movement of particles from an area of high concentration to an area of low concentration until equilibrium is reached
• What molecules are transported through diffusion of the membrane?

  Small, non-polar molecules

  such as oxygen, CO2
• What are channel proteins?

  Proteins that form water filled channels in cell membranes for the transport of ions or molecules. It is selective (only certain molecules are let through)
• What does cholesterol do?

  Regulates fluidity
• What does compartmentalisation do?

  Separates and isolates different parts or components with different functions. For example mitochondria for cellular reactions