Membrane transport Flashcards
What are the three different forms of membrane transport?
Passive, active, vesicular
Is simple diffusion active or passive transport?
passive
Is diffusion through channels (e.g. aquaporins) active or passive transport?
Passive
Is facilitated diffusion active or passive transport?
Passive
What is the difference between primary and secondary active transport?
Primary = direct usage of ATP
Secondary = ATP used to pump another ion across membrane, then that used to symport/antiport
What are the two forms of vesicular transport?
Endocytosis
Exocytosis
What is uniport?
Carrier transport for only one substance (glucose example)
What is carrier-mediated transport?
Symport vs antiport
What are the molecules that can diffuse through a membrane?
gases, and small, uncharged, polar molecules
Increased lipid solubility increases or decreases simple diffusion?
Increases
As the molecular size increases, the diffusion rate … (?)
Decreases
The rate of diffusion (blanks) as the thickness of
membrane decreases.
increases
How does concentration gradient affect the speed of simple diffusion?
Increases speed as [C] increases
The larger the membrane surface area, the (blank) the rate of net diffusion?
The larger the surface area, the larger the rate of net
diffusion.
How does temperature affect the permeability of cell membranes?
Incresaes permeability as temp rises
Is the composition of the lipid bilayer a factor that affects the speed of diffusion through a cellular membrane?
Yes
What are the three factors that affect the rate of diffusion through channels?
- Permeability (# of open channels)
- Selectivity/affinity
- Concentration gradient
How are aquaporin regulated?
Brought to cell surface just like the GLUT transporters
What is the cause of nephrogenic diabetes insipidus?
A defect in one of the types of aquaporins in the glomerulus of the kidney
What are the two factors that affect the diffusion of ions through ion channels?
Concentration gradient and voltage
What are the three types of gated ion channels?
Voltage gated
Ligand gated
Mechanically gated
What is facilitated diffusion?
Specific transport of a single type of molecule down its concentration gradient
Is the rate of diffusion of ions through an ion transporter higher, lower, or equal to that of facilitated diffusion?
Higher, duh
True or false: there is a linear relationship between the increased in the rate of diffusion of an ion through its transporter, and its concentration?
False–hyperbolic with Vmax.
Is transport direction reversible in ion channels?
Yes
What is Km for a facilitated ion channel?
[C] at which v =0.5(Vmax)
Can facilitated transport transport uncharged substances against their concentration gradient?
No
Can facilitated transport transport ions against their electrochemical gradient?
No
What allows the GLUT transporter to continue to transport glucose at a high rate despite taking in large amounts of glucose?
Phosphorylation of glucose to G6P
Does active transport approach a maximum rate of transport? Can it show competitive or noncompetitive inhibition?
Yes, yes, and yes
The Na/K pump is used for what?
Maintaine normal membrane potential and preventing cell swelling due to influx of Na
What are ABC transporters?
ATP bind cassette–proteins that use ATP for transport (either hydrolyze or just for regulation)
What type of transporter is the CFTR protein?
Active (ABC family)
A mutation in the CFTR protein results in what disease discussed in class?
Cystic fibrosis
What is the gene that causes NDI?
Mutations in the aquaporin-2 gene
How the the Vmax curve shift with increases in [C]? Km? Transporter numner
[C] = get closer to Vmax
Km= shifts curve right
Transporter = increases Vmax, no change in Km
For secondary active transport, what must happen in order for the transport to work [hint, not energy change or ATP binding]?
One of the molecules has to move down its [C] gradient
What are the MDR proteins? What is their clinical significance?
Multi-drug resistant proteins.
These are ABC trasporters that, when overexpressed, cause clinicially important resistance to CA drug therapy
What is an example of antiport?
Movement of Na ions with glucose in the intestines
What is the action of Na/K/Cl transporters?
co-transport of 1 Na:1K:2Cl from extracellular
fluid to cytosol
What are the two examples given in class of ion exchange/counter pumps?
Na/Ca exchanger to pump out Ca
Na/H to pump out H and bring in Na
True or false: vesicular transport requires energy?
true
What type of molecules does vesicular transport?
Large ones
What are the three types of vesiicular transport?
- Phagocytosis
- Pinocytosis
- Fluid-phase endocytosis
True or false: all cells perform pinocytosis?
True
What is fluid phase endocytosis? What are the proteins needed for this to occur (usually)?
uptake of materials that are dissolved in ECF usually via clatharin coated pits and adaptin
What happens when the adaptin/clatharin coated vesicles are endocytosed into the cell?
Adaptin and clatharin recycled, vesicle ready to fuse
True or false: fluid-phase endocytosis is a very efficient way to transport a specific
substance into the cell.
False- very inefficient
What biochemical process is dependent on receptor mediated endocytosis?
LDLs
What is caveolae endocytosis?
Similar to clathrin mediated endocytosis but the process uses caveolae and
caveolin as the coating protein.
Caveolae are well-defined invaginations
in the plasma membrane (diameter ~ 100 nm).
