Topic 5, membrane transport Flashcards
What type of molecules are highly permeable?
Hydrophobic
O2, CO2, N2, steroid hormones
Rank types of molecules in order of permeability
Hydrophobic, small uncharged polar (H2O, urea, glycerol), Large uncharged polar (Glucose, sucrose),
Ions (Impermeable)
What are the four types of transport?
Passive ones: simple diffussion, facilitated diffusion with channel, facillatated with carrier
Active transport.
Example of simple diffusion
High concentration to low, Unassisted. small nonpolar molecules like water and CO2
What if the membrane is impermeable to dissolved solute?
What is OSmosis, Dan
Three states for plants and animals cells
animal: crenation (if in hypertonic solution), normal in isotonic, Lysed in hypotonic.
Plant: plasmolyzed if in hypertomic, flaccid in isotonic, turgid in hypotonic
What three factors determine the ability for something to diffuse?
Size.
Polarity.
Charge.
All key words
Why is facillated diffussion necessary?
So things can diffuse at a reasonable rate.
What do the lines look like for rates of diffussion, facilitated vs linear. why?
FacilITATED= hyperbolic simple= linear
why? bc the transport proteins havea maximum capacity of what they can handle at one time.
Another name for carrier proteins
Permeases
types of carrier proteins (3 specific, two umbrella)
PLUS 3 facts
Uni ports= one guy
Coupled Transport= 2 types of solute.
symports or antiports.
carrier proteins are highly specific.
transport velocity has an upper limit
how do carrier proteins work?
Binding of transported molecules changes the shape of the transporter.
note in glucose transport, molecles is quickly modified to GLUT1 to prevent it from leaving throught the carrier protein.
Are channel proteins selective?
They may display a very high degree.
They may be gated (selectively opened and closed) via ATP but still considered passive diffussion
FOR IONS
Explain cystic fibrosis and the link to
Cftr is the channel protein for Cl- in our airways. Usually Cl- is released, then water and sodium follow it (bc charge and osmosis). This keeps the mucus hydrated.
in cystic fibrosis,
Porins structure
Forms beta barrel hydrophilic channel
and contain transmembrane helices
Types of active transport? (2)
Direct
indirect
What is the difference between direct and indirect active transport?
Drect transport is directly linked to exeronic chemical reactions.
For example, ATP hydrolysis may drive it.
Indirect active transport utilyzes an exhisting concentration gradient to drive the transport of another solute up its gradient with coupled transport.
P-type ATPases
what does P stand for?
How many P-type pumps do humans have?
P=phosphoryl group
transporter temporarily and reversibly phosphorylated during transport
About 70
What are the main types of transport pumps? (ATPases) (4)
P-type
V-type
F-type
ABC-type
What does the V n V pumps stand for?
defining features
V=vacuole
pump protons into organellar compartments, especially lysosomes to maintain acidity.
Pump is not phosphorylated
F-type ATPases
What are the two componants?
defining features
F=factor
This is ATPsynthase in the ETC
Fo=
Mobile: transmembrane pore for protons. 10 c subunits. ONe can bind at a time, and each proton bound rotates the ring 1/10 of a turn.
Static: one a and two b subunits. a is a proton channel that is stuck in the membrane, immobile. b subunit form the peripheral stalk. attach to a subunit and F1.
F1
mobile: gamma and e. the rotating stalk, movement comes from c ring.
Static: alt a and b subunits (3 of each). immobalized by sigma subunit. The part that binds to ATP is here.
Can either pump protons or make ATP
ABC Transporters
How many domains. Config?
how many in human genome?
Role? Name one specific
4 domains in each protein.
2 that span the membrane, and 2 ATP binding cassettes
config, mem, cas, mem, cas. with connective strands inbetween.
at least 70
Multidrug resistance of cancers
CFTR- cystic fibrosis transport (Cl-)
Indirect active transport.
defining features.
Are the symporters or antiports?
link energetically fav with energetically unfav
one solute moves down concentration gradient, while a second goes up.
can be either sym or anti
Na+ and glucose
symporter or anti?
symporter.
2 NA+ bind, then glucose., transported inside cell. Na+ released. pumped out with Na-K pump to maintain gradient.
glucose released inside cell.
