channels and transporters lecture 2

Question 1

what are examples of active transporters

Answer 1

ions, small hydrophilic molecules, lipids, ATP powered pumps.

Question 2

what are the 4 basic ATP powered pumps

Answer 2

1) P-class pumps
2) V-class proton pumps
3) F-class proton pumps
4) ABC superfamily

Question 3

which class doesnt use ATP hydrolysis to transport substrate uphill

Answer 3

F-class

Question 4

what do F-class use to synthesis ATP

Answer 4

use a proton-motive force in the inner membrane of mitochondria, thylakoid membrane, plasma membrane of bacteria/

Question 5

how do V-class ATPases work

Answer 5

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.

Question 6

how do V ATPases work in transcellular transport

Answer 6

1) the osteoplast transports HCl the H+ transport is done by V ATPase.

Question 7

there are chloride channels in V ATPases but in E.coli how do they function differently

Answer 7

they are Cl-/H+ exchanger

Question 8

P class pumps are found in eukaryotes name where they are found

Answer 8

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

Question 9

what domains are there in P class

Answer 9

transmembrane pump, phosphorylation site, ATPase domain, actuator domain.

Question 10

how does transcellular transport work in p class ATPases

Answer 10

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.

Question 11

give some examples of ABC transporters

Answer 11

maltose transporter, vitamin B12 transporter both are bacterial impoters. multidrug resistance protein 1 which is a mammalian exporter.

Question 12

which 2 domains in ABC transporter bind ATP

Answer 12

the cytoplasmic domains known as the nucleotide binding domains

Question 13

where does the actual transport occur in ABC transporter

Answer 13

membrane domains known as transmembrane domains

Question 14

there are 3 types of abc transporters where are they found

Answer 14

1-3 found in prokaryotes function as substrate import.
1-2 work in conjunction with substrate biding protein

Question 15

give examples of type 1,2,3

Answer 15

1-maltose transport
2-vitamin B12
3- folate ECF transporter

Question 16

what does type 3 abc not contain

Answer 16

substrate binding domain

Question 17

in type1-3 the transporters are not phosphorylated in the cycle what does ATP binding do

Answer 17

conformation change. the substrate affintiy will differ in the 2 states

Question 18

what do abc type 4-6 do

Answer 18

function as exporters

Question 19

give example of type 4 abc

Answer 19

multidrug resistance associated protein and CFTR

Question 20

what are type 5 abc

Answer 20

they are extractors so export substrates from inner to outer membrane

Question 21

give examples of type 6

Answer 21

tripartite pump they export substrates toxins from the cytoplasm to periplasm to outside gram negative bacteria.

Question 22

do both nucleotide binding sites actively hydrolyse ATP during cycle in type 4-6

Answer 22

only one

Question 23

is CFTR a pump

Answer 23

no its a chloride channel it also has a regulatory domain which needs to be phosphorylated before ATP opens the channel

Question 24

where is R domain found in CFTR

Answer 24

in between the NBD