Week 7 - Transport Across Membranes Flashcards
Describe membrane structure
Thin film of lipids and proteins held by non covalent interactions held in a bilayer.
Impermeable to water soluble molecules
Explain how a bilayer forms
Phospholipids are amphipathic and they arrange with the polar heads on the outside and non polar tails on the inside
What is the fluid mosaic model
The bilayer can move and is fluid and act as an asymmetrical 2D fluid
What are regulators of membrane fluidity
Double carbon bonds make it more fluid whereas more single bonds make it less fluid
How are fats held together
Sphingolipids have long fatty acid chains and attractive forces hold molecules together in lipid rafts
What is the glycocalyx
A carbohydrate coating acting as a protective layer
Transport of non polar molecules across membranes
Dissolve freely an the bilayer and diffuse across
Small uncharged polar molecules across the bilayer
Slow process but can move across membrane
Large uncharged or Ions moving
Will need a transport medium as well as energy
What are the two types of transport proteins
Carrier proteins and Channel proteins
How do carrier proteins work
Solute binds and protein undergoes a change to transfer across membrane
How do channel proteins work
They form an aqueous pore that solutes can pass through freely
What determines direction of flow in passive transport
Concentration
What determines direction of flow of ions
Concentration and charge
What is active transport
Moving solutes across membrane against concentration gradient and mediated by carriers only
