CH 5: MEMBRANE TRANSPORT Flashcards
(25 cards)
Selective permeability of plasma membrane
very permeable: non-polar molecules
somewhat permeable: small, uncharged polar molecules
not permeable: ions and large uncharged polar molecules
Diffusion
Random mixing of substances across plasma membrane due to their kinetic energy
what kinds of molecules move through membrane via simple diffusion?
nonpolar hydrophobic molecules (e.g., oxgen, carbon dioxide)
Difference between simple vs facilitated diffusion
Simple diffusion happens without any help, facilitated diffusion happens with either carrier or channel
Both are PASSIVE processes
Transport Maximum (Tm)
maximum rate at which solute is transported via facilitated diffusion. Carrier protein is saturated
What method is normally used for glucose transport across membrane?
carrier-mediated facilitated transport (GLUT - glucose transporter)
Osmosis
movement of water from area of lower solute concentration to higher solute concentration
Two ways that water diffuses via osmosis
simple diffusion, or via aquaporins (channel protein)
hydrostatic pressure
pressure exerted just by weight of a liquid
what does it mean if a solution has a higher osmolarity?
higher concentration of solute particles compared to other solution.
In hypoosmotic solution, how does water concentration and solute concentration differ?
water concentration is GREATER than solute concentration (less osmotic pressure required to oppose movement of water, since not a lot of solute)
Osmolarity vs Tonicity
Osmolarity refers to TOTAL amount of dissolved particles in a solution
Tonicity refers only to NON PENETRATING solutes (think of effect on blood cell)
What happens to a blood cell in a hypotonic vs hypertonic solution
Hypotonic solution –> hemolysis (burst)
hypertonic solution –> crenation (shrink)
Types of active transport
Primary active transport, secondary active transport
Difference between two types of active transport
Primary active transport: Gets energy directly by hydrolysing ATP
Secondary active transport: Uses energy stored in electrochemical gradient that was created during primary transport (indirectly uses ATP)
What type of transport is the sodium-potassium pump?
PRIMARY active transport
what is functional significance of Na+/K+ ATPase?
Create large Na electrochemical gradient that can be used for Na to leak back into cell for secondary active transport
How does secondary active transport work?
carrier protein uses energy from Na electrochemical gradient (generated in primary active transport) to move Na and another solute across membrane (in same or different directions)
Two types of transporters that can be used in secondary active transport
Symporters (two solutes in same direction)
Antiporters (two solutes in opposite directions)
Example of a symporter
symporters in small intestine that carry glucose and amino acids
sodium potassium pumps maintain low Na+ concentration in the ______
cytosol
Example of an antiporter
Na/Ca antiporters keep Ca2+ moving OUT of cytosol
Endocytosis vs Exocytosis
Endocytosis: Movement of particles INTO cell through vesicle created by plasma membrane
Exocytosis: Movement of particles OUT of cell by merging vesicle to plasma membrane and eject
Three types of endocytosis
Receptor-mediated endocytosis, phagocytosis, bulk-phase endocytosis (“pinocytosis”)
