[2] Class 2:membrane

Question 1

Sheet like structures that form closed boundaries between different compartments:

Answer 1

Biological membranes

Question 2

Biological membranes mainly consist of _____ and _____. ALso, _____ are linked to lipids and proteins.

Answer 2

Lipids,
Proteins,
Carbohydrates.

Question 3

MEbranes have both a _____ and a ______ unit.

Answer 3

hydrophilic and hydrophobic

Question 4

These are embedded in lipid bilayers and mediate distinct functions

Answer 4

Specific proteins.

Question 5

Biological membranes form ________ assemblies.

Answer 5

Non-covalent

Question 6

Biological membranes are symmetric or asymmetric?

Answer 6

Asymmetric

Question 7

3 common features of biological membranes:

Answer 7

Asymmetric

Fluid structure: lipids and proteins can diffuse rapidly in the plane but not across the membrane.

Electrically polarized: (-) inside

Question 8

Membranes are _________ b/c they contain a hydrophilic unit [polar head] and hydrophobic tail [straight or wavy lines]

Answer 8

Amphipathic

Question 9

Why does oil form a monolayer when placed in water?

Answer 9

Polar heads are in contact w/ the water and the nonpolar hydrophobic lipid tails project into air

Question 10

What is a consequence of the amphipathic nature of the membrane lipids?

Answer 10

Membrane formation

Question 11

What are the 2 possible membrane formations of amphipathic membrane lipids?

Answer 11

Micelle

Lipid bilayer

Question 12

THis is a limited structure

Answer 12

Micelle

Question 13

This is favored structure for phospholipids and glycolipids:

10^6 nm =1mm

Answer 13

Lipid bilayer [bimolecular sheet]

Question 14

Formation of lipid bilayers is a _______ process

Answer 14

Self-assembly

Question 15

3 MAjor driving forces for the assembly of lipid bilayer [bimolecular sheet]:

Answer 15

Hydrophobic interactions- major force

Van der waals

Electrostatic and hydrogen-bonding

Question 16

Attractive forces btw hydrocarbon tails

Answer 16

Van der waals

Question 17

Attractions btw polar head groups and water molecules:

Answer 17

Electrostatic and hydrogen-bonding

Question 18

What predominantly holds the lipid bilayer together?

Answer 18

Hydrophobic interactions

Question 19

Hydrophobic interactions have 3 consequences of lipid bilayer formation:

Answer 19

Inherent tendency to be extensive

Tend to close on themselves leaving no edges exposed w/ hydrocarbon chains-forms compartments

Self-sealing- energetically favorable

Question 20

Lipid bilayer low permeability for

Answer 20

Ions and most polar molecules

Question 21

How difficult is it for water to traverse the membrane?

Answer 21

Easy- it is small, high [ ] and lack of a complete charge

Question 22

Are all biological membranes asymmetric?

Answer 22

Yes

Question 23

Is there even distribution of lipid molecules in lipid bilayers?

Answer 23

No, asymmetrically distributed.

Inner and outer leaf =different

Question 24

Membrane ________ have unique orientations.

Answer 24

Proteins

Question 25

Where is cholesterol present?

Answer 25

Large amounts of cholesterol are present in both leaflets- thought to be about equally distributed in both mono layers

Question 26

Hydroxyl group of cholesterol is positioned wherein the membrane?

Answer 26

Near the polar heads of the phospholipid.

Question 27

Rapid diffusion:

Answer 27

Lateral diffusion | -generally not stationary...fluid mosaic

Question 28

Very slow diffusion:

Answer 28

Tranverse or flip-flop diffusion...Req's more energy

Question 29

Do proteins move in the fluid mosaic model? | What diffusion can they perform?

Answer 29

Yes, laterally they do not flip-flop or tranverse diffuse through membrane.

Question 30

How long does it take a phospholipid molecules to flip-flop?

Answer 30

Once in a several hours.

Question 31

During the tranverse and lateral diffusion, can asymmetry be preserved?

Answer 31

Yes

Question 32

Membrane fluidity is controlled by:

Answer 32

FA composition And cholesterol content

Question 33

Fatty acid composition affects membrane fluidity how?

Answer 33

Length of FA chains; Saturation levels; Position of double bonds [cis]-provides more fluidity.

Question 34

How does cholesterol content affect membrane fluidity?

Answer 34

Bidirectional...stabilizes at high Temp. And more flexibility at low temps.

Question 35

Provides an environment where signal transduction and molecule transportation take place:

Answer 35

Cholesterol content

Question 36

How do you classify difference in membrane proteins?

Answer 36

Based on the difference in dissociability

Question 37

Interact extensively w/ hydrocarbon chains of membrane lipids. Can be released ONLY by agents that compete for these nonpolar interaction-organic solvents and detergents. Spans the entire lipid bilayer:

Answer 37

Integral membrane proteins

Question 38

What aspect of the bimolecular sheet [lipid bilayer-membrane] is responsible for most of the dynamic processes?

Answer 38

Membrane proteins

Question 39

How do different membranes differ?

Answer 39

Protein content

Question 40

HOw can one view proteins in a membrane?

Answer 40

Sodiumdodecylsulfate polydactyl amine gel electrophoresis (SDS/PAGE)

Question 41

A light-driven proton pump converts the energy of light into trans membrane proton gradient that is used to synthesize ATP:

Answer 41

Bacteriorhodopsin (BR)

Question 42

Bacteriorhodopsin is built almost entirely of ______ b/c most amino acids are nonpolar and arranged ________ to the bilayer plane.

Answer 42

Alpha helices Perpendicularly

Question 43

The most common structure motif in membrane proteins:

Answer 43

Membrane-spanning alpha helices

Question 44

Ex of integral protein that binds to luminal leaflet of the ER. It is a homodimer consisting of primarily Alpha helices. It is NOT a membrane-spanning protein

Answer 44

Cyclooxygenase [COX] 1 ALso called Prostaglandin H2 synthase [PGHS] 2

Question 45

These are bound to membranes primarily by electrostatic and hydrogen-bond interactions:

Answer 45

Peripheral membrane proteins

Question 46

Peripheral membrane proteins dissociate from membrane by adding:

Answer 46

Salt or pH changes

Question 47

Peripheral membrane proteins are bound to surfaces of:

Answer 47

Integral proteins bound on either: Cytosolic or extracellular side of membrane OR Anchored to lipid bilayer by COVALENTLY attached hydrophobic chain; i.e. FA

Question 48

How are lipids asso. W/ proteins?

Answer 48

Covalently

Question 49

Lipids anchor their attached proteins to membrane and mediate protein-protein interactions. 3 kinds of modification:

Answer 49

Palmitoylation Farnesylation Glycosylphosphosphatidylinositol

Question 50

Modification Of cysteine residues by a thioester bond.

Answer 50

Palmitoylation

Question 51

Modification of cysteine residues at the C-terminus

Answer 51

Farnesylation

Question 52

modification link to the carboxyl terminus

Answer 52

Glycosylphosphatidylinositol

Question 53

Covalent attachment of a farnesyl (c15) unit to C-terminal tetrapeptide CAAX in which cys is followed by 2 aliphatic residues. After farnesyl group is appended to protein in thioETHER linkage w/ cys residue, the AAX trip eptide is hydrolytic ally cleaved away.

Answer 53

Farnesylation at the C-terminus

Question 54

Functions of farnesylation at the C-terminus :

Answer 54

Anchoring the protein to the membrane and facilitating the protein-protein interaction.

Question 55

Thioester bond

Answer 55

Palmitoylation

Question 56

Thioether bond

Answer 56

Farnesylation

Question 57

Looks like O-glycosidic linkage:

Answer 57

GPI anchor

Question 58

GPI anchor:

Answer 58

Links proteins to OUTER leaflet Many Cell-surface hydrolytic enzymes and adhesions are tethered by GPI unit

Question 59

Mitochondria 2 membrane systems:

Answer 59

Outer membrane and inner membrane

Question 60

Internal ridges and cristae

Answer 60

Inner membrane mito.

Question 61

2 compartments in mito.

Answer 61

Intermembrane space Matrix

Question 62

Oxidative phosphorylation takes place in the:

Answer 62

Inner-mitochondrial membrane

Question 63

The site of most of the TCA cycle and FA oxidation:

Answer 63

Matrix

Question 64

This membrane is permeable to most small molecules and ions

Answer 64

Outer membrane

Question 65

Impermeable to nearly all ions and polar molecules:

Answer 65

Inner membrane

Question 66

VDAC

Answer 66

Mitochondrial porin