Membranes protein structure

Question 1

what are the essential functions of membranes

Answer 1

they act as barriers and also support localization of the cell so it can do lots of different things in different places

Question 2

what mediates signaling across membranes

Answer 2

proteins and lipids

Question 3

what allows for the cell membrane to regulate cell-cell communication

Answer 3

glycoproteins and glycolipids

Question 4

what is responsible for membrane formation

Answer 4

a decrease in ionic interactions with water. this is basically the hydrophobic effect

Question 5

are membranes asymmetrical or symmetrical

Answer 5

they are asymmetrical composed of lipids and proteins

Question 6

what mediates the process of proteins carrying molecules and signals being transmitted across the membrane

Answer 6

conformation changes

Question 7

____ and ____ play an important role in membrane fluidity

Answer 7

lipids and cholesterol

Question 8

What recent modifications have been made to the fluid mosaic model

Answer 8

the movement of lipids is restricted based on if they are in pure lipids or biological membranes

Question 9

What technique is useful in measuring membrane movement

Answer 9

FRAP (fluorescence recovery after photobleaching)

Question 10

lipid raft

Answer 10

area in the membrane where lipids tend to hang out for a longer period of time

Question 11

What does the addition of sugars and proteins to the membrane post-translationally impact?

Answer 11

cell recognition and membrane insertion

Question 12

Flip-Flop diffusion

Answer 12

movement of lipids from one leaflet to the other

Question 13

is flip flop diffusion energetically favourable or unfavourable?

Answer 13

unfavourable

Question 14

How do enzymes mediate membrane asymmetry

Answer 14

by creating active sites and spaces on the membrane

Question 15

Flippase

Answer 15

ATP dependent translocase that moves lipids to the inner leaflet

Question 16

Floppase

Answer 16

contains an active site and it moves things to the outer leaflet

Question 17

Scramblase

Answer 17

ATP independent enzyme that is less specific and will be used to even out the lipids across the membrane. Moves all lipids down their concentration gradient
ensures that there is not too much flipping or flopping and the lipids are unbalanced

Question 18

Lipids

Answer 18

molecules involved in providing structural support for cells and organelles

Question 19

what defines classes of lipids

Answer 19

their physical properties, ie. whether they are hydrophobic or amphipathic

Question 20

What type of lipids are involved in metabolism

Answer 20

triacylglycerides (carbon storage)

Question 21

what lipids are important for the structure of membranes

Answer 21

phospholipids
sphingolipids
glycolipids
sterols

Question 22

at physiological pH will fatty acids be deprotonated or protonated

Answer 22

deprotonated because its pka<pH

Question 23

what is a saturated fatty acid

Answer 23

this is a fatty acid with single bonds

Question 24

what is an unsaturated fatty acid

Answer 24

contains double bonds

Question 25

what is the usual numbering of double bonds in fatty acids

Answer 25

they are numbered relative to the carboxylic acid but it can also be named relative to the methyl group for omega fatty acids

Question 26

Fatty acid nomenclature

Answer 26

C's : # of double bonds

Question 27

what makes a fatty acid an omega fatty acid ?

Answer 27

the location of the double bond. a fatty acid is considered an omega fatty acid when the double bond is situated three or six carbons away from the methyl group

Question 28

what does delta refer to?

Answer 28

this is when we label carbons relative to the carboxylic group

Question 29

What are considered the good fats

Answer 29

unsaturated and omega fats

Question 30

what type of fats decrease membrane fluidity

Answer 30

saturated fats because they form lots of non-covalent bonds that act like glue

Question 31

What about unsaturated fats increase membrane fluidity

Answer 31

they have kinks that participate in cis double bonds, increasing fluidity by causing there to be more room in the membrane

Question 32

what does a higher melting temperature of lipids mean?

Answer 32

a higher Tm means that there are more covalent bonds that need to be broken

Question 33

if a membrane has a higher Tm does it mean it is more or less fluid?

Answer 33

it would be less fluid because a higher temperature means it is more rigid and contain more non-covalent interactions that need to be broken down

Question 34

Tri-acyl-glycerols (TAGs)

Answer 34

3 fatty acids attached to a glycerol

Question 35

what attaches the fatty acids to the glycerol

Answer 35

ester linkage

Question 36

what are tags good for

Answer 36

they are good for storing carbon that can be used for energy

Question 37

how are amphipathic molecules made?

Answer 37

By attaching fatty acyl chains to polar (OH, sugar, or phosphate) head groups

Question 38

what is the most common steroid found in membranes?

Answer 38

hydrophobic cholesterol

Question 39

Glycerophospholipids

Answer 39

they contain 2 fatty acid tails with a glycerol head and a phosphate group

Question 40

examples of glycerophospholipids

Answer 40

phosphatidylethanolamine (PE) and PS. these bind to flippase

Question 41

sphingolipids

Answer 41

lipids that contain 1 fatty acid bounded to N on sphingosine

Question 42

examples of sphingolipids

Answer 42

sphingomyelin and gangliosides

Question 43

cholesterol

Answer 43

can be metabolized to other hormones needed for dietary lipid absorption can form lipid rafts

Question 44

three types of membrane lipids

Answer 44

glycerophospholipids, sphingolipids, and cholesterol

Question 45

peripheral membrane proteins

Answer 45

located on the outside of the membrane that either interacts with outer or inner leaflets by non-covalent interactions

Question 46

Integral membrane proteins

Answer 46

span membrane

Question 47

what is the difference between peripheral and integral proteins

Answer 47

removal

Question 48

how can peripheral membrane proteins be removed

Answer 48

by milder conditions like increasing salt in pH

Question 49

how are integral membrane proteins removed

Answer 49

through more harsh conditions like detergents that break apart the membrane

Question 50

how are lipid anchored proteins removed? why?

Answer 50

they also require harsher detergents because their tails are covalently attached to the amino side chains and functional groups

Question 51

for membrane proteins what extra steps are taken during protein purification

Answer 51

adding detergents

Question 52

Critical micelle concentration (CMC)

Answer 52

concentration at which the detergent spontaneously forms stable micelle structures

Question 53

what does it mean for a concentration above CMC

Answer 53

sufficient enough for you to extract protein from membrane

Question 54

how can you predict membrane spanning segments

Answer 54

by scanning primary sequences for long stretches of hydrophobic amino acids that represent TM segments

Question 55

hydropathy scale

Answer 55

takes into consideration factors about amino acids that could indicate transmembrane segments

Question 56

why does a negative hydropath index indicate

Answer 56

more polar segments

Question 57

what does a positive hydropathy index indicate

Answer 57

more non-polar/hydrophobic segments

Question 58

how can you read a topology chart to indicate a transmembrane protein

Answer 58

high peaks that are 20 amino acids wide