module 9: Membranes

Question 1

what does the membrane structure formation depend on?

Answer 1

ratio of cross-sectional areas of the polar head group and hydrophobic tail

Question 2

what do fatty acids favour?

Answer 2

formation of micelles

Question 3

what 2 lipids tend to form bilayers?

Answer 3

glyceophospholipids & sphingolipids

Question 4

what are membranes primary made of?

Answer 4

lipids and proteins

Question 5

do more active membranes have a higher or lower ratio of protein to lipid?

Answer 5

higher

Question 6

why are membranes dynamic?

Answer 6

because of non-covalent interactions

Question 7

what is flip flop diffusion?

Answer 7

slow uncatalyzed rate of lipid molecule crossing from 1 sheet to another

Question 8

what are the enzymes called that translocation of lipids across membranes

Answer 8

flippases

Question 9

what is the function of flippases?

Answer 9

provide environment so lipids can go through

Question 10

what happens below the phase transition temp?

Answer 10

membrane is too solid

Question 11

what happens above the phase transition temp?

Answer 11

membrane is too fluid

Question 12

what happens at the phase transition temp?

Answer 12

hydrocarbon chains are partially ordered but lateral

Question 13

why are lipid rafts formed?

Answer 13

to optimize interactions between hydrocarbon tails of membrane lipids

Question 14

what proteins perform active roles in membranes?

Answer 14

receptors & transporters

Question 15

how do peripheral membrane proteins associate with the membrane?

Answer 15

through electrostatic or hydrogen-bonding interactions

Question 16

where are peripheral membranes found?

Answer 16

in cytosol or extracellular space

Question 17

are peripheral membrane proteins strong or weak?

Answer 17

weak

Question 18

where are GPI anchored proteins found on the membrane?

Answer 18

outer face

Question 19

where are integral membrane proteins found?

Answer 19

immersed & span the membrane

Question 20

where are charged amino acids found in the membrane?

Answer 20

intracellular & extracellular portions of the proteins

Question 21

where are amino acids with non-polar side chains found in the membrane?

Answer 21

inside the hydrophobic slab of bilayer

Question 22

where do tryptophan & tyrosine cluster on the membrane?

Answer 22

interface between the hydrocarbon chain & polar head region

Question 23

how can membrane spanning regions be predicted?

Answer 23

amino acid sequence

Question 24

how many hydrophobic membranes in a row are membrane spanning?

Answer 24

20-24

Question 25

what does the hydropathy index look at?

Answer 25

the hydrophobic characteristics of a protein to predict transmembrane regions

Question 26

side chains within the transmembrane region tend to be...

Answer 26

non-polar, but carbonyl & amide groups are polar

Question 27

what groups are energetically unfavourable in the bilayer core?

Answer 27

polar, unpaired carbonyl & amide groups

Question 28

what is simple diffusion?

Answer 28

non-polar gases (O2 & CO2) and hydrophobic molecules can directly cross the membrane

Question 29

what is facilitated diffusion?

Answer 29

membrane transporters lower the activation energy barrier to cross the bilayer

Question 30

what is facilitated diffusion through channels?

Answer 30

membrane pores that allow transport of molecules down the concentration gradient

Question 31

are channels or carriers faster?

Answer 31

channels

Question 32

do channels or carriers saturate?

Answer 32

carriers

Question 33

what is facilitated diffusion through carriers?

Answer 33

membrane proteins undergo substrate induced confirmation change to release substrate to other side of membrane

Question 34

uptake of glucose into red blood cells is an example of which type of diffusion?

Answer 34

facilitated diffusion through a carrier

Question 35

what is uniport?

Answer 35

transport of a single molecule

Question 36

what are antiporters?

Answer 36

move molecules in different directions

Question 37

what are symporters?

Answer 37

move molecules in the same direction

Question 38

what does co-transport through antiport or symport depend on?

Answer 38

the charge of the molecule

Question 39

what happens in secondary active co-transport?

Answer 39

system couples a molecule moving down its gradient to another one moving down its gradient

Question 40

what is active transport?

Answer 40

input of energy that allows movement of molecules against concentration gradients

Question 41

what is primary active transport?

Answer 41

driven by direct source of ATP & establishes a gradient for secondary active transport to use

Question 42

what is secondary active transport?

Answer 42

couples the movement of one molecule down its gradient within the movement of another molecule down its gradient

Question 43

what does P-Type ATPase use for active transport?

Answer 43

antiport

Question 44

cells maintain high gradients of ( ) outside the cell and ( ) inside the cell

Answer 44

Na+ outside, K+ inside

Question 45

Why is it called a P-type transporter?

Answer 45

bc it undergoes a phosphorylated intermediate

Question 46

what is pumped in/out of the cell during P-type ATPase primary active transport?

Answer 46

pumps 3 Na out & 2 K + in

Question 47

what is V-type ATPases active transport?

Answer 47

uses energy of ATP to move protons against a concentration gradient

Question 48

what are ABC transporters?

Answer 48

contain ATP binding domains (ATP-Binding-Cassette)

Question 49

what do ABC transporters do?

Answer 49

transport a variety of biomolecules out of the cell against a concentration gradient

Question 50

glucose uptake into intestinal epithelial cells is an example of which type of transport?

Answer 50

secondary active transport

Question 51

glucose uptake into intestinal epithelial cells is uniport, antiport or symport?

Answer 51

symport

Question 52

what is the function of ion channels?

Answer 52

enable rapid movement of ions across membranes

Question 53

action of ion channels can cause...

Answer 53

action potentials

Question 54

function of the K+ ion channel

Answer 54

allows rapid movement of K+ ions out of the cell