Transportation of materials across the plasma membrane Flashcards
Osmosis
The net diffusion of water across a membrane toward a higher solute concentration
Hydration shells
H2O molecules that surround charged solute molecules
A higher concentration = fewer free H2O molecules
Aquaporins
Facilitate osmosis
channels in the cell membrane that allows water to be regulated and maintain osmotic concentration
Passive transport
Simple diffusion of O2, CO2, non-polar molecules
No energy is required
Includes facilitated diffusion - Ionic (charges) polar molecules - H2O, glucose, larger molecules
Active Transport
requires energy
Low conc outside cell to high conc inside cell
charged ions e.g Na, K, metabolites, glucose
uses cell channels/ carrier proteins
Same concentration in and out of cell
Isotonic
High concentration
Hypertonic
low concentration
hypotonic
osmotic pressure
force needed to stop osmotic flow
maintain osmotic flow
Extrusion- Expelling H2O through contractile vacuoles
Isomotic regulation - keeping cells isotonic with their environment
Turgor- Plant cells
Carrier Proteins
Uniporters- moves 1 molecule at a time
Symporters- two molecules in the same direction
Antiporters- two in opposite directions
Na/K pump
1) 3 Na ions bind to the cytoplasmic side of the pump and its conformation changes.
2) ATP phosphorylates the channel
3) Phosphorylation causes conformational change and the proteins affinity for NA decreases and increases for K so Na diffuses out.
4) 2x K bind to the extracellular sites
5) this causes dephosphorylation
6) changes back to its original conformation so K diffuses into the cell
Bulk Transport
Used if cells need large molecules to cross the hydrophobic lipid bilayer for growth
Endocytosis
allows substances to come into the cell
Phagocytosis
WBC engulf bacteria
