Cell Transport Flashcards
Permeability (2)
Determines what moves in and out of a cell
Plasma membranes are selectively permeable
Plasma Membrane: Selective Permeability
Restricts materials based on: (4)
size
electrical charge
molecular shape
lipid solubility
Passive and Active Transport Methods
Passive (2)
Active or Passive (1)
Active (1)
Passive:
Diffusion and Osmosis
Active or Passive:
Carrier-mediated (active or facilitated diffusion)
Active:
Vesicular
Diffusion and Concentration Gradient Definitions
Diffusion:
Net movement of substance from area of high to area of low concentration.
Concentration Gradient:
Difference between high and low concentrations of a substance.
Factors that influence diffusion (5)
distance particle needs to move
size of ion and molecule: smaller is faster
temperature: hotter is faster
concentration gradient: steeper is faster
electrical forces: opposites attract, like repel
Passive Diffusion across plasma membranes:
Concentration Gradient Direction
Simple diffusion substances
Channel-mediated diffusion substances
Carrier mediated (facilitated) diffusion substances
Passive Diffusion moves substances with the gradient (from high to low) and requires no energy
Simple:
lipid soluble compounds (eg. steroids, fatty acid)
dissolved gases (oxygen, CO2)
Water molecules- through aquaporins
Channel Mediated:
water soluble compounds and ions
Carrier Mediated:
Molecules too large to fit through channel proteins (eg. glucose, amino acids) use carrier proteins
Active Carrier Mediated Transport:
How carrier proteins work
Concentration Gradient Direction
Specificity
Saturation Limits
Regulation
Carrier Proteins:
transport ions or substances across plasma membranes by binding and changing shape
Concentration Gradient Direction:
move substances against the concentration gradient (from low to high) and requires energy
Specificity:
Protein Carrier/Receptor is specific to a substance
Saturation Limits:
Availability of transport proteins determines rate of transport
Regulation:
Cofactors (eg. hormones) affect carrier activity
Carrier Mediated Transport:
Symport and Antiport
Pumps
Secondary Active Transport
Symport/co-transport:
substances move through carrier: same direction
Antiport/counter-transport:
substances move through carrier: opposite directions
Pumps:
Ion Pumps move ions
Exchange Pumps- move ions in opposite directions (eg. sodium-potassium pump)
Secondary Active Transport:
ATP used to create a concentration gradient of one substance (eg. sodium) and passively co-transports another (eg. sodium-glucose)
Vesicular (bulk) Transport
Endocytosis- how are vesicles formed?
Pinocytosis
Phagocytosis
Exocytosis
Materials move in or out of cells in vesicles.
Endocytosis: substances move into the cell
Receptors bind target molecules (ligands)
Receptors and ligands form pockets in plasma membrane surface
Pockets pinch off into endosomes/vesicles
Pinocytosis: liquids
Phagocytosis: solids
Exocytosis: substances move out of the cell
Granules or droplets are released from the cell as a vesicle fuses to the plasma membrane
Osmosis
Water and Solute Movement
Osmotic Pressure
Hydrostatic Pressure
Aquaporins
Osmolarity
Osmosis:
movement of water across a selectively permeable membrane.
Water moves towards a solution with more solute.
Osmotic Pressure:
the force with which water moves into a solution (caused by solute concentration)
Hydrostatic Pressure:
needed to block osmosis
Aquaporins:
channels water passes through
outnumber solute channels so osmosis occurs more rapidly than solute diffusion
Osmolarity:
Osmotic Concentration- the total solute concentration in a solution
Tonicity
Solutions:
Isotonic
Hypotonic
Hypertonic
Tonicity describes how a solution will affect a cell based on concentration of solutes.
Isotonic:
same in cell and solution
no net water movement
cell unchanged
Hypotonic:
lower concentration in solution than cell
water moves into cell
cell swells and ruptures
Hypertonic:
higher concentration in solution than cell
water moves out of cell
cell shrinks and crenates
