Cell Membranes

Question 1

membrane functions

Answer 1

1) separate cells from the external medium to create an intracellular environment of unique and defined composition
2) allow selective transport of substrates in and out of the cell
3) provide a location for specialized pathways and processes
4) rapid changes in electric potential across the membrane of neurons as a basis of the nervous system
5) localization of rectors to facilitate response to physiological signals
6) mediate cell-cell recognition and interaction

Question 2

what is the basic structual element of a membrane

Answer 2

the lipid bilayer

Question 3

vesicles are made of

Answer 3

lipid bilayers

Question 4

exposure of hydrophobic tails is…

Answer 4

energetically unfavourable

Question 5

membranes are _____ to charged and polar molecules

Answer 5

impermeable

Question 6

True or false membranes are asymmertrical

Answer 6

true

Question 7

are membranes fluid

Answer 7

yes and dynamic

Question 8

what are membranes mostly made out of

Answer 8

lipids and proteins, active have a higher ratio of proteins

Question 9

plasma lipids are ______ distributed

Answer 9

asymmetrically

Question 10

three classes of membrane proteins

Answer 10

1) peripheral
2) integral
3) lipid-anchored

Question 11

peripheral membrane proteins associate with membrane though

Answer 11

charge-charge, h-bonding

Question 12

change in pH or ionic strength often releases these proteins from the membranes

Answer 12

peripheral membrane proteins

Question 13

what do peripheral membrane proteins do

Answer 13

regulators or tethers for interglacial membrane proteins

Question 14

membrane proteins span___

Answer 14

the lipid bilayer

Question 15

types of membrane proteins

Answer 15

alpha-helical bundles, and beta-barrels

Question 16

carbonyl and amide groups of the proteins backbones inside the bilayer are

Answer 16

hydrogen bonded

Question 17

stretches of 20 hydrophobic resides in a row are likely

Answer 17

membrane spanning

Question 18

________ and ____ are often positioned at the interface between the polar face and the non-polar inter-membrane region

Answer 18

tyrosine, tryptophan

Question 19

lipids which are covalently attached to the protein can serve as ___ to link the protein to the membrane

Answer 19

anchors

Question 20

GPI anchored proteins ___________, fatty acyl or prenylated proteins always to inner face

Answer 20

always at outer face

Question 21

Fluid Mosaic Model

Answer 21

membranes are dynamic due to the nature of the non-covalent interactions, lateral movement of proteins and lipids within the membrane is very rapid

Question 22

below the phase transition temp the membrane is an

Answer 22

ordered paracrystalline gel state

Question 23

well above the phase transisiton temp the membrane is in a

Answer 23

liquid disordered state

Question 24

near the phase transition temp thte membrane is in a

Answer 24

liquid ordered state

Question 25

transbilayer movement requires

Answer 25

polar head group to pass through hydrophobic environment

Question 26

patches function as

Answer 26

aggregates on the membrane surface in which the movement of proteins is restricted

Question 27

fenced higher order structes within

Answer 27

the membrane

Question 28

acetylcholoine recptors

Answer 28

on neuron plasma membranes at synapses

Question 29

glycosphingolipids form clustors that exclude

Answer 29

glycerophospholipids

Question 30

non-covalent nature of membranes allows

Answer 30

fusing of membranes

Question 31

what does membrane fusion involve

Answer 31

1) appropriate recognition 2) close association of membrane surfaces with exclusion of water molecules 3) localization distription of the membrane to allow fusion of oouter leaflets 4) fusion of bilayers to form single bilayer 5) regulation

Question 32

four types of movement across the membrane

Answer 32

1) simple diffusion 2) facilated difussion - channels and carriers 3) active transport - primary and secondary

Question 33

does simple diffusion use a carrier, saturable, gradient, energy

Answer 33

no, no, down, no

Question 34

faciilated diffusion with channels carrier, saturable, gradient, energy

Answer 34

yes, no, down, no

Question 35

facialted diffusion carriers- carrier, saturaable, gradient, energy

Answer 35

yes, yes, down, no

Question 36

primary active transport carrier, saturable, gradient, energy

Answer 36

yes, yes, up, yes

Question 37

secondary active trnssport carrier, saturable, gradient, energy

Answer 37

yes, yes, up, yes

Question 38

channels

Answer 38

membrane pores that can only transport molecules and ions down the electrochemical gradient

Question 39

do channels show saturation behaviour

Answer 39

no

Question 40

electroneural exchange of ____ prevents changing the electric potential across the membrane

Answer 40

ions

Question 41

reversible ATP-driven proton pumps

Answer 41

use energy of ATP to move protons against a concentration gradient

Question 42

F--type ATPase

Answer 42

in reverse a proton gradient can be used to generate ATP

Question 43

V-type ATPasse

Answer 43

acidification of intracellular compartments

Question 44

ABC transporters

Answer 44

ATP=Binding Cassette Transporters

Question 45

rapid changes in the activity of ion channels cause

Answer 45

the changes in membrane potential in neurons

Question 46

ion channels differ from ion transporters in three ways

Answer 46

1) much faster 2) no saturation limits 3) gated