Module 2 : Internal Organization of the Cell Membrane Structure

Question 1

encloses the cell, defines its boundaries, and maintains the essential differences between the cytosol and the extracellular environment

Answer 1

Plasma membrane

Question 2

provides the basic structure for all cell membranes

Answer 2

The Lipid Bilayer

Question 3

50% of the mass of the most animal cell membranes

Answer 3

Lipids

Question 4

most abundant membrane lipids

Answer 4

Phospholipids

Question 5

Parts of Lipids

Answer 5

Head : Phosphate group, hydrophilic
Tail : 2 hydrocarbon tail, hydrophobic

Question 6

The bonds that create links in the tail

Answer 6

cis-double bonds (unsaturated)

Question 7

Major Classes of Lipids in Cell membranes

Answer 7

• Phosphoglycerides
• Glycolipids
• Cholesterol

Question 8

main phospholipids

Answer 8

Phosphoglycerides

Question 9

Two subclasses of phospholipids

Answer 9

• gylcerophospholipids
• sphingolipids

Question 10

from sphingosine (long acyl chain with an amino group (NH2) & two hydroxyl groups (OH)

Answer 10

Sphingolipids

Question 11

most common sphingolipid

Answer 11

spingomyelin

Question 12

a fatty acid tail is attached to the amino group, and a phosphocholine group is attached to the terminal hydroxyl group

Answer 12

Sphingomyelin

Question 13

resemble sphingolipids;
sugars

Answer 13

Glycolipids

Question 14

sterol; contains a rigid ring structure, to which attached a single polar hydroxyl group and a short nonpolar hydrocarbon chain

Answer 14

Cholesterol

Question 15

Major Phospholipids in Mammalian cells

Answer 15

phosphatidylethanolamine, phosphatidylserine, and phosphatidylcholine

Question 16

tails inward

Answer 16

Spherical micelles

Question 17

hydrophobic tails sandwiched

Answer 17

Bilayers

Question 18

What does unpaired electron spin create?

Answer 18

Paramagnetic signal

Question 19

can be detected by electron spin resonance (ESR) spectrum

Answer 19

Paramagnetic signal

Question 20

phospholipid molecules in synthetic bilayers very rarely migrate from the monolayer on one side to that on the other

Answer 20

Flip-flop

Question 21

lipid molecules rapidly exchange places with their neighbors within a monolayer

Answer 21

Rapid lateral diffusion

Question 22

the lipid component of a biological membrane is a ___ ____

Answer 22

two-dimensional liquid

Question 23

catalyzes the rapid flip
flop of phospholipids from one
monolayer to the other

Answer 23

Phospholipid translocators (flippases)

Question 24

a change from a liquid state to a two dimensional rigid crystalline state at a characteristic temperature

Answer 24

Phase transition

Question 25

How does cholesterol modulates the properties of lipid bilayers

Answer 25

- Enhances the permeability-barrier properties - Decretase motility of the few CH2 groups - Prevents the hydrocarbon chains from coming together and crystallizing

Question 26

Has 20–25-carbon long prenyl chains

Answer 26

Archea

Question 27

specialized membrane microdomains that serve as to organizing centers for assembly of signaling molecules

Answer 27

Lipid rafts

Question 28

in which specific lipids come together in separate domains

Answer 28

Phase segregation

Question 29

storage of lipids

Answer 29

Lipid droplets

Question 30

- specialized for lipid storage - contain a giant liquid droplet

Answer 30

Fat cells or adipocytes

Question 31

neutral lipids; exclusively hydrophobic molecules, and therefore aggregate into 3 dimensional droplets

Answer 31

triacylglycerols and cholesterol esters

Question 32

contains a large variety of proteins

Answer 32

Single monolayer of phospholipids

Question 33

by definition, the two monolayers have different composition

Answer 33

Lipid asymmetry

Question 34

Mainly found in the outer layer of RBC

Answer 34

phosphotidylcholine and sphingomyelin

Question 35

translocate from the inner monolayer to the outer monolayer when cells undergo apoptosis

Answer 35

Phosphotidylserine

Question 35

Mainly found in the outer layer of RBC

Question 36

are used in yet another way to convert extracellular signals into intracellular ones

Answer 36

Phospholipids in the plasma membrane

Question 37

cleaves an inositol phospholipid in the cytosolic monolayer of the plasma membrane to generate to fragments

Answer 37

Phospholipase C

Question 38

- sugar-containing molecules - most extreme asymmetry in their membrane distribution

Answer 38

Glycolipids

Question 39

results from the addition of sugar groups to the lipid molecules in the lumen of the Golgi apparatus

Answer 39

Asymmetric distribution of glycolipids in the bilayer

Question 40

- exposed apical surface; - may help to protect the membrane against the harsh conditions

Answer 40

Epithelial cells

Question 41

charged glycolipids; important because of their electric effects

Answer 41

Gangliosides

Question 42

Functions of glycolipids

Answer 42

- Come from their localization - Provide entry points for certain bacterial toxins and viruses - Cell-to-cell recognition

Question 43

Types of integral proteins

Answer 43

- polytopic - bitopic - monotopic

Question 44

extends through the lipid bilayer

Answer 44

Transmembrane proteins

Question 45

do not extend into the hydrophobic interior of the lipid bilayer; bound to either face of the membrane by noncovalent interactions

Answer 45

Peripheral proteins

Question 46

control the Membrane Localization of Some Signaling Proteins

Answer 46

Lipid anchors

Question 47

– small amphiphilic molecules; more soluble in water than lipids

Answer 47

Detergents

Question 48

Three commonly used detergents to disrupt lipid bilayer

Answer 48

- Sodium dodecyl sulfate - Triton X-100 - β-octylglucoside

Question 49

Detergent that is anionic

Answer 49

SDS (Sodium dodecyl sulfate)

Question 50

Two nonionic detergents

Answer 50

- Triton X-100 and β-octylglucoside

Question 51

– surfactant concentration at which micelle formation is first seen in the solution

Answer 51

critical micelle concentration

Question 52

small, uniformly sized patches of membrane that are surrounded by a belt of protein, which covers the exposed edge of the bilayer to keep the patch in solution

Answer 52

Nanodiscs

Question 53

Movements of membrane proteins

Answer 53

- Flip-flop - Lateral diffusion - Rotation

Question 54

measures lateral diffusion rates of membrane proteins

Answer 54

FRAP (Flourescence recovery after photobleaching)

Question 55

labeling individual membrane molecules and track their movement by video microscopy

Answer 55

Single-particle tracking

Question 56

Gives Membranes Mechanical Strength and Restricts Membrane Protein Diffusion

Answer 56

Cortical cytoskeleton

Question 57

long, thin, flexible rod; it maintains the structural integrity and shape of the plasma membrane

Answer 57

Spectrin