membrane transport Flashcards
what is the permeability of molecules through the membrane?
hydrophobic molecules > small uncharged polar molecules > large uncharged molecules > ions
what are the types of transport
simple diffusion
facilitated diffusion via carrier
facilitated diffidino via channel
active transport
what is simple diffusion?
unassisted movement of solute molecules from an area of high concentration to low concentration
what is osmosis?
when the membrane is permeable to solvent but not solutes, solvent moves from an area of low concentration of solute to high concentration of solute
what are the results of a cell being placed in a hypertonic solution
animal –> shrivels
plant –> plasmolyzed
water floods out of cell to balance out high concentration outside of cell
what are the results of cell being placed in a hypoton solution?
animal –> lyse
plant –> turgid
water floods in to balance out high concentration inside of cell
what molecules are able to use simple diffusion?
hydrophobic molecules
- small, non polar
ex gases (CO2)
what is facilitated diffusion
moving down a concentration gradient but requires a transport protein
ex. aquaporin
why is the rate of simple diffusion linear but facilitated diffusion is not?
because simple diffusion does not require the assistance of proteins, and proteins restrict the rate at which molecules can diffuse across
what are the 3 types of carrier proteins
- uniporter –> carries one substance at a time
- symporter –> transports 2 substances going the same direction
- antiporter –> transports 2 substances going opposite ways
what type of carrier protein is GLUT1 and what does it transport
an uniporter –> glucose
what type of carrier protein is anion exchange protein? and what does it transport
an antiporter –> chloride- bicarbonate exchanger
what is a channel protein?
forms a hydrophilic channel that can display a high degree of selectivity
can be selectively opened and closed
diffusion is passive
what is CFTR and what does it do?
allows Cl ions to enter the mucus as well as water to dilute, Na ions flood in to balance out the charge
what happens to CFTR in cystic fibrosis patients
the channels are not functioning properly and Cl ions cannot penetrate the mucus, therefor more prone to infections
what are aquaporins?
a type of channel protein that forms a B-barrel hydrophilic channel with transmembrane helices
what is active transport?
movement of molecules up a concentration gradient, requires an input of energy
what are the 2 types of active transport?
direct –> linked to exergonic chemical reaction (ATP hydrolysis)
indirect –> utilizes existing gradients to drive transport
direct active transport: P-type ATPases
P–> phosphoryl group
transporter is temporarily phosphorylated during transport
ex. Na/K
direct active transport: V- type ATPases
v–> vacuole
pump protons into organellular compartments
pump NOT phosphorylated
direct active transport: F-type ATPases
F–> factor
two components:
F0 (transmembrane pore for protons)
F1 (ATP binding sites)
ABC transporters
4 domains: 2 ABC 2 membrane spanning
important role in multidrug resistance of cancers
ex. CFTR
general characteristics of indirect transport
link energetically favourable transport with energetically unfavourable
one solute moves down concentration gradient while other moves up
utilizes symporters and antiporters
what type of transporter is the Na/glucose
supporter
bacteriorhodopsin general characteristics
proton pump
retinal embedded in protein
retinal changes from trans to form one cis bond
light driven proton pump, not dependant on ETC