Transport Across Membranes Flashcards
1
Q
Describe how surfaces can cross a cell surface membrane.
A
- small molecules pass via phospholipid bilayer
- by diffusion from a high to low concentrate
- water moves by osmosis from high to low concentrate
- active transport is movement from low to high
- active transport involves carrier proteins
- active transport requires ATP
2
Q
What is the fluid-mosaic model?
A
- phospholipid molecules form a bilayer
- constantly moving
- protein molecules unevenly distributed
- selective permeability
3
Q
Components of fluid-mosaic model.
A
- phospholipids = hydrophobic fatty acid tails and hydrophilic heads
- cholesterol = decreases permeability and increases stability
- channel proteins = pores that allow specific charged ions to move in by facilitated diffusion
- carrier proteins = aid larger molecules by facilitated diffusion and active transport
- receptor proteins = act as specific receptors for complimentary molecules
- enzymes = allows formation of enzyme-substrate complexes
- glycoproteins = cell recognition, act as antigens
- aquaporins = channel proteins specific to water, allows osmosis to be carried out easier
4
Q
Describe simple diffusion.
A
- passive process
- stops when equal number on each side
- only involves non-polar, small, lipid-soluble molecules
5
Q
Factors affecting rate of diffusion include…
A
- temperature = increased kinetic energy so faster
- surface area= larger so provides more molecules to pass through
- concentration gradient = as it increases, so does rate of diffusion
- diffusion distance = shorter means molecules travel from one area to another faster
6
Q
Ficks Law =
A
Surface area x Concentration gradient / diffusion distance
7
Q
Describe facilitated diffusion.
A
- specific proteins help specific molecules pass through
- by carrier/channel proteins
- have specific shape
8
Q
Describe osmosis.
A
- net movement of water for a high to a low concentration, through a selectively permeable membrane
9
Q
Describe active transport.
A
- molecules transported against concentration gradient
- low to high concentration
- only uses carrier proteins
- requires source of ATP
