channels and transporters lecture 2 Flashcards
what are examples of active transporters
ions, small hydrophilic molecules, lipids, ATP powered pumps.
what are the 4 basic ATP powered pumps
1) P-class pumps
2) V-class proton pumps
3) F-class proton pumps
4) ABC superfamily
which class doesnt use ATP hydrolysis to transport substrate uphill
F-class
what do F-class use to synthesis ATP
use a proton-motive force in the inner membrane of mitochondria, thylakoid membrane, plasma membrane of bacteria/
how do V-class ATPases work
1)hydrolyse ATP
2) proton transport due to rotary movement.
3) they lower PH in intracellular organelles also present in some animal plasma membrane.
4) they also contain chloride channels this prevents electrochemical potential building up.
how do V ATPases work in transcellular transport
1) the osteoplast transports HCl the H+ transport is done by V ATPase.
there are chloride channels in V ATPases but in E.coli how do they function differently
they are Cl-/H+ exchanger
P class pumps are found in eukaryotes name where they are found
1) plasma membrane plants and fungi-proton pump
2)plasma membrane higher eukaryotes-Na+/K+ pump
3) apical membrane higher eukaryote-H+/K+ pump
4)plasma membrane eukaryotic cells-Ca2+ pump
5) sarcoplasmic reticulum membrane in muscle cells -Ca2+ pump
6) plasma membrane and golgi higher eukrayote-metalv pump
7) plasma embrane eukaryotes-flippases
what domains are there in P class
transmembrane pump, phosphorylation site, ATPase domain, actuator domain.
how does transcellular transport work in p class ATPases
in stomach lumen PH lowered by K+/H+ ATPase. Ph in cell maintained by CI-/HCO3- antiporter with passive diffusion of CO2 across the membrane. CI- AND K+ homeostasis maintained by non gated ion channels.
give some examples of ABC transporters
maltose transporter, vitamin B12 transporter both are bacterial impoters. multidrug resistance protein 1 which is a mammalian exporter.
which 2 domains in ABC transporter bind ATP
the cytoplasmic domains known as the nucleotide binding domains
where does the actual transport occur in ABC transporter
membrane domains known as transmembrane domains
there are 3 types of abc transporters where are they found
1-3 found in prokaryotes function as substrate import.
1-2 work in conjunction with substrate biding protein
give examples of type 1,2,3
1-maltose transport
2-vitamin B12
3- folate ECF transporter
what does type 3 abc not contain
substrate binding domain
in type1-3 the transporters are not phosphorylated in the cycle what does ATP binding do
conformation change. the substrate affintiy will differ in the 2 states
what do abc type 4-6 do
function as exporters
give example of type 4 abc
multidrug resistance associated protein and CFTR
what are type 5 abc
they are extractors so export substrates from inner to outer membrane
give examples of type 6
tripartite pump they export substrates toxins from the cytoplasm to periplasm to outside gram negative bacteria.
do both nucleotide binding sites actively hydrolyse ATP during cycle in type 4-6
only one
is CFTR a pump
no its a chloride channel it also has a regulatory domain which needs to be phosphorylated before ATP opens the channel
where is R domain found in CFTR
in between the NBD
