Module 2A - Membrane Structure

Question 1

Enclose the cell, defines its boundaries, and maintains the essential difference between the cytoplasm and the extracellular matrix.

Answer 1

Plasma membrane

Question 2

Maintains the characteristic differences between the contents of each organelle and the cytosol.

Answer 2

Plasma membrane

Question 3

Components of the plasma membrane:

Answer 3

1. Ion gradients
2. Protein receptors or sensors
3. Lipid bilayer
4. Membrane proteins

Question 4

The main structural component of all cell membrane.

Answer 4

Lipid bilayer

Question 5

Lipid make about ___% of the total mass of most animal cells.

Answer 5

50%

Question 6

Lipid molecules are __________, which means they have a hydrophobic and a hydrophilic sides.

Answer 6

Amphiphilic

Question 7

The most abundant type of membrane lipids.

Answer 7

Phospholipids

Question 8

Parts of a phospholipid:

Answer 8

1. Phosphate head (Hydrophilic)
2. Two hydrocarbon tails (hydrophobic)

Question 9

Bonds that creates the slight deformation on a phospholipid tail.

Answer 9

cis-double bonds

Question 10

Different types of lipids in the cell membrane:

Answer 10

1. Phosphoglycerides
2. Sphingolipids
3. Glycolipids

Question 11

What is the main type of phospholipid?

Answer 11

Phosphoglycerides

Question 12

Characteristics of Phosphoglycerides:

Answer 12

1. Three-carbon glycerol backbones
2. Two long chains of fatty acids
3. 3rd carbon attached to a phosphate group

Question 13

Type of lipid from sphingosine (long acyl chain with an amino group and two hydroxyl groups)

Answer 13

Sphingolipids

Question 14

Most common type of Sphingolipids:

Answer 14

Sphingomyelin

Question 15

Sub-types of phosphoglycerides:

Answer 15

1. Phosphatidylethanolamine
2. Phosphatidylserine
3. Phosphatidylcholine

Question 16

Type of lipid that resembles sphingolipids with a carbohydrate attached through a glycosidic bond.

Answer 16

Glycolipids

Question 17

A sterol that contains a rigid ring structure, where a single polar hydroxyl group and a short non-polar hydrocarbon chains are attached.

Answer 17

Cholesterol

Question 18

The shape and amphiphilic characteristic of the phospholipid molecules causes them to form:

Answer 18

bilayers spontaneously in an aqueous environment.

Question 19

Aggregation of phospholipids that cause them to bury their hydrophobic tails inward, forming a sphere.

Answer 19

Spherical micelles

Question 20

Aggregation of phospholipids that cause them to bury their hydrophobic tails inward, sandwiching them in between.

Answer 20

Bilayer/Lipid bilayer

Question 21

The phospholipid layer forms into a sphere, closing the gaps to seal the hydrophobic tails exposed to water because it is:

Answer 21

Energetically favorable

Question 22

What molecules are able to diffuse directly through the plasma membrane?

Answer 22

Lipid molecules

Question 23

The characteristic of molecules to rapidly exchange places with their neighbors within a monolayer.

Answer 23

Rapid lateral diffusion

Question 24

The rare migration of phospholipid molecules from one side of the monolayer into the other side.

Answer 24

Flip-flop

Question 25

Catalyzes the rapid flip-flop of phospholipids from one monolayer to the other.

Answer 25

Phospholipid translocator (flippases)

Question 26

Lipid component that allows the molecules of the plasma membrane to freely move laterally.

Answer 26

Two-dimensional fluid

Question 27

The change of the two-dimensional fluid from a liquid state, into a rigid crystalline state at characteristic temperatures.

Answer 27

Phase transition

Question 28

How does cholesterol regulates the properties of the lipid bilayer?

Answer 28

1. Enhances the permeability-barrier properties 2. Makes the lipid bilayer less deformable; decreases the permeability of the bilayer from small water molecules 3. Prevents the hydrocarbon chains from coming together and cystalizing

Question 29

Plasma membranes of most _______ are more varied than prokaryotes and archaea

Answer 29

Eukaryotic cells

Question 30

How many different species of lipids are there?

Answer 30

Around 500-200 species

Question 31

Membrane microdomains that serves as organizing centers for assembly of signaling molecules, influence membrane fluidity, trafficking of membrane proteins, regulate cellular processes, and receptor trafficking.

Answer 31

Lipid rafts

Question 32

Specific lipids come together in separate domains.

Answer 32

Phase segregation

Question 33

Where lipids are stored (e.g. fat cells or adipocytes). Forms rapidly when cells are exposed to high concentration of fatty acids.

Answer 33

Lipid droplets

Question 34

Specialized cells for lipid storage

Answer 34

Adipocytes (fat cells)

Question 35

Types of neutral lipids:

Answer 35

Triacylglycerols and cholesterol esters

Question 36

A condition where two monolayers have different compositions. Important in converting extracellular signals into intracellular ones.

Answer 36

Lipid asymmetry

Question 37

Lipid that moves from the inner monolayer of the bilayer to the outer monolayer when the cell undergoes apoptosis (cell death).

Answer 37

Phosphatidylserine

Question 38

Cleaves an inositol phospholipid within the cytosolic monolayer to create fragments that activates protein kinase C, and stimulates the release of Ca2+ from the endoplasmic reticulum.

Answer 38

Phospholipase C

Question 39

Sugar-containing lipid molecule with the most extreme asymmetry in their membrane distribution. Occurs in all eukaryotic plasma

Answer 39

Glycolipids

Question 40

The function of glycolipids vary from their:

Answer 40

Location/Localization

Question 41

Exposed apical surface; may help to protect the membrane against the harsh conditions.

Answer 41

Epithelial cells

Question 42

Charged glycolipids; important because of their electric effects

Answer 42

Gangliosides

Question 43

Performs most of the membrane’s specific tasks and therefore give each type of cell membrane its characteristic functional properties.

Answer 43

Membrane proteins

Question 44

Type of membrane protein that extends throughout the lipid bilayer, located entirely on the cytosol, and are attached to the cytosolic monolayer.

Answer 44

Transmembrane proteins

Question 45

Membrane protein that is not found in the hydrophobic interior, but is bound to either sides of the membrane by non-covalent interactions.

Answer 45

Peripheral proteins

Question 46

Controls the membrane localization of some signaling proteins.

Answer 46

Lipid anchors

Question 47

The membrane-spanning segment of the polypeptide chain that contacts the hydrophobic area of the lipid bilayer are formed into:

Answer 47

α-helix

Question 48

A polypeptide chain that spans the lipid bilayer only once.

Answer 48

Single-pass transmembrane proteins

Question 49

Used to localize potential α-helical membrane spanning segments in a polypeptide chain.

Answer 49

Hydropathy plots

Question 50

It is estimated that about ___% of an organisms proteins are transmembrane proteins

Answer 50

30%

Question 51

Multi-pass transmembrane strands of a polypeptide chain are arranged to be a:

Answer 51

β sheet that is rolled up into a cylinder

Question 52

Many membrane proteins are:

Answer 52

Glycosylated

Question 53

They extensively coat the surface of all eukaryotic cells:

Answer 53

Carbohydrates

Question 54

__________ chains are always present on the non-cytosolic side of the plasma membrane.

Answer 54

Oligosaccharide

Question 55

Stabilizes either the folded structure of a polypeptide chain, or its association with other polypeptides. Forms on the non-cytosolic side of the membrane.

Answer 55

Disulfide bonds

Question 56

Small amphiphilic molecules that disrupts hydrophobic associations and destroy the lipid bilayer, solubilizing the membrane proteins.

Answer 56

Detergents

Question 57

Polar side of detergents can be either:

Answer 57

Ionic or non-ionic

Question 58

Surfactant concentration at which micelle formation is first seen in the solution.

Answer 58

Critical micelle concentration

Question 59

How does detergents work on solubilizing membranes?

Answer 59

Hydrophobic ends of detergent binds with the hydrophobic regions of the membrane, where they displace the lipid molecules.

Question 60

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 60

Nanodiscs

Question 61

Membrane proteins can often function as a part of large:

Answer 61

Multicomponent complexes

Question 62

How does membrane proteins able to move laterally across the lipid bilayer?

Answer 62

Lateral diffusion

Question 63

Procedure that measures the rate of lateral diffusion by the membrane proteins.

Answer 63

Fluorescence recovery after Photobleaching (FRAP)

Question 64

Procedure that labels individual membrane molecules and tracks their movement by video microscopy.

Answer 64

Single-particle tracking

Question 65

FACT: Cells are capable of confining/distributing membrane proteins across specific regions in the cells.

Answer 65

This asymmetric distribution of membrane proteins is often essential for the function of the epithelium.

Question 66

Asymmetric distribution of ___________ is often essential for the function of the epithelium.

Answer 66

Membrane proteins

Question 67

This interactions within the membrane creates nanoscale raft domains that functions in cell signaling and membrane trafficking.

Answer 67

Protein-protein interactions

Question 68

Gives the plasma membrane mechanical strength and restricts the diffusion of membrane proteins.

Answer 68

Cortical cytoskeleton

Question 69

A long, thin, and flexible rod protein that maintains the structural integrity and shape of the plasma membrane

Answer 69

Spectrin

Question 70

Specific type of cytoskeleton that enables the red blood cells to withstand the stress acted upon its membrane when passing through narrow capillaries.

Answer 70

Spectrin-based cytoskeleton

Question 71

Proteins that deforms the lipid bilayer through the dynamic pushing and pulling forces exerted by the cytoskeleton or extracellular structures.

Answer 71

Membrane-bending proteins

Question 72

During vesicle budding, cell movement, and cell division; The shape of the cell is controlled-

Answer 72

Dynamically