Lecture 1: membrane transport processes Flashcards
what are the mechanisms of membrane transport?
- pores
- ion channels
- solute carriers
- ATP dependent transporter pumps
- vesicular transport
how is facilitated diffusion different from regular diffusion?
facilitated diffusion can saturated as the number of transporter proteins is finite
what factors does cell membrane permeability depend on?
- lipid composition
- aquaporins
- ion channels
- solute carriers
what are aquaporins?
transmembrane proteins consisting of 4 subunits with 6 a-helical regions
allow fast diffusion
what types of gated ion channels are there?
membrane voltage gated
gated by extracellular messengers
gated by intracellular messengers
gated by mechanical stress
what is the difference between primary and secondary active transport?
primary active transport is driven by the direct usage of ATP whereas secondary active transport is dependent on an electrochemical gradient
what are the features of the Na/K ATPase?
-complex transmembrane protein
4 domains: nucleotide binding domain, phosphorylation domain, actuator domain and transmembrane domain
a comformational change causes movement of 3Na out of the cell and 2K inside the cell
what are the key features of ABC transporters?
- they all have an ATP binding cassette
- usually homodimers
- each subunit has a transmembrane domain and nucleotide binding domain
what is the mode of action for ABC transporters?
open dimer has high ligand affinity -> ligand binding increases ATP affinity -> conformational change -> reduced ligand affinity -> ligand released -> ATP hydrolysed and released
what is co-transport?
when 2 or more solutes are carried in one transport cycle
what is a symporter?
a co-transporter where both solutes are transported in the same direction
what is an antiporter?
a co-transporter in which the solutes are transported in different directions
name 3 examples of a P-type ATPase transporter
Na/K ATPase
H+/K+ ATPase
H+/Ca2+ ATPase
what effect do P-type ATPase transporters cause?
ATP hydrolysis leading to phosphorylation causing a conformational change
name an example of a V-type ATPase transporter, what is it used for?
H+ ATPase
sets up a pH gradient
