Membrane Transport Flashcards
What type of process is Non-mediated diffusion?
Linear and non saturable
Differential Permeability
Ability of a membrane to let some molecules through but not others
Chemical potential
relative concentrations of solutes on each side of the membrane
Electrical potential
relative concentrations of ions on each side of the membrane
Uniport
Movement of a single molecule at a time
Symport
simultaneous transport of two molecules in the same direction
Antiport
simultaneous transport of two molecules in opposite directions
Electroneutral transport
transport of molecules does not change charge separation across the membrane
Electrogenic transport
transport of molecules that results in charge separation across the membrane
What are the properties of facilitated transport?
requires carrier proteins, exhibits substance specificity, can be inhibited like an enzyme, kinetics are non-linear and saturable
What are the two classes of Transport Proteins?
Carrier protein and channel protein
Channel proteins
Passive mediated diffusion, consist of water-filled pores which cross the membrane
Ionophores
disrupt vital concentration gradients through mediated transport of ions or compounds
What are the two types of ionophores?
Carriers and Channel Formers
Carrier proteins
undergo conformational changes as they transfer substance across the membrane, transport may be active or passive
PMF
proton motive force
Cotransport
two different substances move across the membrane in a coupled manner
“P” class pumps
have several components, proteins change shape in response to auto-phosphorylation of the pump, transport ions such as H+,Na+,K+ and Ca2+
Na+/K+ pump
3 Na+ for 2 K+
“F” class pumps
multiple transmembrane and cytosolic subunits, synthesize ATP by moving H+ across an electrochemical gradient
Where are F-class proton pumps found?
Bacterial Plasma Membrane, Inner mitochondrial membrane, thylakoid membrane of chloroplast
“V” class pumps
multiple transmembrane and cytosolic subunits, Move H+ across a membrane in order to acidify a cell compartment (lysosomes)
Where are V-class proton pumps found?
Vacuolar membranes in plants, yeast, other fungi, endosomal an lysosmal membranes in animal cells, plasma membrane of osteoclasts and some kidney tubule cells
“ABC” superfamily of Pumps
two transmembrane domains form a pathway, Use ATP binding and hydrolysis to move the solute, transport small molecules (sugars, phospholipids, peptides)
Where are “ABC” pumps found?
Mammalian plasma membranes, bacterial plasma membranes
What are the 3 types of coupled transport?
- Use concentration gradient to couple uphill transport of 1 molecule with downhill transport of another
- ATP-driven pumps couple uphill transport to hydrolysis of ATP
- Light- or redox-driven pumps in bacteria couple uphill tranpsort to energy from light
Competitive inhibitors
compete for the same binding site
Noncompetitive inhibitors
bind elsewhere and alter the structure of the transporter
What is G-protein Switching?
When a “G” protein is bound to GTP the switch is “on” (or “off”)
The G protein has intrinsic GTPase activity.
Use a GTPase Activating Protein (GAP) to activate the GTPase activity of the protein
This forms a “G” protein that is bound to GDP and triggers a conformational change in the shape of the protein that switches the protein to an “off” stat (or “on”)
Use a GTP Exchange Protein (GEF) to cause exchange of the GDP for a GTP to reactivate the protein. A conformational change in the shape of the protein will switch the protein to the “on” (or “off”) position or structure
