Lesson 2 - Diffusion and Facilitated Diffusion Flashcards
(13 cards)
meaning diffusion
the net movement of particles of a liquid or gas from an area of high concentration to an area of low concentration, down the concentration gradient, until there is a uniform distribution. This is a passive process, so does not require ATP
how does diffusion occur
due to the random motion of molecules, resulted by the thermal energy they have, dependent on temperature
meaning facilitated diffusion
when specific large, polar molecules and ions move passively across the cell membrane with the help of membrane proteins
name 2 types of mechanisms of facilitated diffusion
channel protein, carrier protein
compare channel proteins to carrier proteins
- both involved in facilitated diffusion
- both are highly specific
- a carrier protein changes its shape to move molecules across, whilst channel proteins provide a hydrophilic pore
- channel proteins have a higher rate of transport than carrier proteins
- carrier proteins cannot be gated, whilst channel proteins can
what are the conditions needed for passive transport of molecules to occur
molecules need to be moved from an area of high concentration to a low concentration down the concentration gradient. No energy is needed
why can’t water and ions pass through the protein pores like oxygen and carbon dioxide
Water can’t pass across the hydrophobic region in the middle of the membrane, and ions are not lipid-soluble and are charged
what are 5 factors affecting diffusion
- concentration gradient
- surface area
- diffusion distance
- size of molecule
- temperature
meaning simple diffusion
when small, non-polar, lipid-soluble molecules diffuse directlu through the phospholipid bilayer
name 3 molecules that diffuse through simple diffusion
oxygen, carbon dioxide, glycerol
how do channel proteins help diffuse large molecules across the membrane
integral proteins that form pores through the membrane, which are selectively, as they allow only one particular type of ion or molecule through based on its shape and charge
how do carrier proteins help diffuse large molecules across the membrane
once the carrier protein has picked up a molecule, it changes its shape and moves the molecule through the membrane within the carrier, and then releases the molecule on the other side. Carrier proteins only bind to specific molecules, depending on its shape.
name 4 molecules that diffuse by facilitated diffusion
glucose, amino acids, nucleic acids, mineral ions
