Transport methods

• Permeability- can't pass because:

  -Not soluble in lipids so no bilayer

  -Too large for protein channels

  -Same charge as protein channels so repel

  -Polar molecule so can't pass through non-polar fatty acid tails
• Molecules that pass through anyways

  Small molecules pass between phospholipids

  Oxygen- non polar and lipid soluble and very small

  CO2- polar but very small

  Water- polar but also very small
• Functions of plasma membranes INSIDE cells

  -compartmentalise certain organelles eg lysosomes containing hydrolytic enzymes

  -control entry and exit of materials in discrete agents e.g chloroplasts and mitochondria

  -Provide internal transport system e.g RER

  -Isolate enzymes inside lysosomes

  -Provide surfaces for chemical reactions
• Functions of plasma membrane on OUTSIDE of cell

  -separating cell contents from outside environment

  -regulating transport of substances

  -cell recognition, signaling and adhesion

  -stable binding site for enzymes

  -Receptor site for hormones
• Facilitated diffusion

  From high to low concentration using a carrier protein or protein channel
• Active transport

  from low too high concentration using ATP and a carrier protien -selective process- carrier is specific to a protein
• Transport of Glucose/AA in Ileum

  1- Na+ ions move from epithelial cells to blood by active transport using a protein pump

  2-creating a Na+ concentration gradient in the cell with low conc in the cell

  3Na+ and glucose/AA move from the lumen into the epithelial cell by facilitated diffusion/co-transport using a co transport protein

  4- Glucose/AA move from epithelial cell to blood by facilitated diffusion using a carrier protein