Chapter 9: Lipids and Biological Membranes

Question 1

What are lipids. Difference between lipids and nucleic acids, proteins, and polysaccharides?

Answer 1

-mostly hydrophobic
-The functions of lipids include storing energy, signaling, and acting as structural components of cell membranes.
-Lipids are molecules that contain hydrocarbons and make up the building blocks of the structure and function of living cells

lipids are not polymeric.
Lipids exhibit greater structural variety than the other classes of biological molecules.
However, they do aggregate, and it is in this state that they perform their central function as the structural matrix of biological membranes.

Question 2

What are lipids soluble and insoluble in?

Answer 2

-Not soluble in water
-Soluble in organic solvents such as chloroform and methanol

Question 3

Examples of Lipids

Answer 3

Fats, oils, certain vitamins and hormones, and most nonprotein membrane components are lipids.

Question 4

How are lipids separated and identified?

Answer 4

Hence, they are easily separated from other biological materials by extraction into organic solvents.

They can then be separated chromatographically and identified by mass spectrometry according to their masses and characteristic fragmentation patterns

Question 5

What are the 5 classes of lipids +description?

Answer 5

1.Fatty acids-a common fuel
2.Triacylglycerols-storage form of fatty acids
3.Phospholipids-membrane lipids
4.Glycolipids-membrane lipids composed in part of carbohydrates
5.Steroids-polycylic hydrocarbons with a variety of functions

Question 6

What are fatty acids?

Answer 6

Fatty acids are carboxylic acids with long-chain hydrocarbon side groups
carboxylic acid at one end and a methyl group (CH3) at the other end
fatty acids may be saturated or unsaturated
Make up major components of the various lipids
most basic lipid

Question 7

The Properties of Fatty Acids Depend on What?

Answer 7

Hydrocarbon Chains/Chain Length
also degree of unsaturation

Question 8

Carboxylic acid?

Answer 8

In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group attached to an R-group. The general formula of a carboxylic acid is R−COOH
Found in Fatty acids

Question 9

Fatty acids occur in what form?

Answer 9

-Esterified form

Question 10

Esterified meaning

Answer 10

-a chemical compound produced by a reaction between an acid and an alcohol with the elimination of a molecule of water

Question 11

How many carbons does a fatty acid usually have?
In higher plants and animals, the predominant fatty acid residues are those of?

Answer 11

16-18

Most fatty acids have an even number of carbon atoms because they are biosynthesized by the concatenation of C2 units

C16 and C18 species: palmitic, oleic, linoleic, and stearic acids.

Question 12

Over half of the fatty acid residues of plant and animal lipids are?

Answer 12

unsaturated (contain double bonds) and are often polyunsaturated (contain two or more double bonds).

Question 13

difference between unsaturated and polyunsaturated?Difference between saturated vs unsaturated and polyunsaturated

Answer 13

-unsaturated means it contains one double bond
-polyunsaturated means it contains 2 or more double bonds
both unsaturated and polyunsaturated are rigid due to cis transfiguration
-saturated has no double bonds and is super flexible can assume a wide range of conformations because there is relatively free rotation around each of their C—C bonds.can assume a wide range of conformations because there is relatively free rotation around each of their C—C bonds.

Question 14

methyl group vs methylene group

Answer 14

methyl group=CH3 for fatty acids
methylene group=CH2 to separate the double bonds in polyunsaturated fatty acids

Question 15

Where do the first double bonds occur in an unsaturated fatty acid and where do they occur in polyunsaturated fatty acid

Answer 15

the first double bond of an unsaturated fatty acid commonly occurs between its C9 and C10 atoms counting from the carboxyl C atom. This bond is called a Δ9 - or 9-double bond.

In polyunsaturated fatty acids, the double bonds tend to occur at every third carbon atom
(e.g., —CH-CH-CH2—CHCH—)

Question 16

in polyunsaturated fatty acids the double bonds are separated by?

Answer 16

at least one methylene group (-CH2-)

Question 17

When double bonds are present, they are commonly found in which configuration? How does this effect unsaturated fatty acids?

Answer 17

cis
-puts a rigid 30° bend in the hydrocarbon chain.
-pack together less efficiently than saturated fatty acids.
-The reduced van der Waals interactions of unsaturated fatty acids cause their melting points to decrease with the degree of unsaturation

Question 18

Saturated fatty acids are?

Answer 18

-only single bonds, tightly packed
fully reduced or “saturated” with hydrogen are highly flexible molecules that can assume a wide range of conformations because there is relatively free rotation around each of their C—C bonds.

Question 19

The melting points (mp) of saturated fatty acids, like those of most substances, increase or decrease with their molecular mass?

Answer 19

melting point increases as molecular mass increases

Question 20

In both saturated fatty acids and unsaturated fatty acids, how does the chain length affect the fluidity and melting point? Why?

Answer 20

the longer the side chain, the lower the fluidity and the higher the melting point
-Longer hydrophobic tails allow more hydrophobic interactions

Question 21

In both saturated fatty acids and unsaturated fatty acids, how does the degree of unsaturation affect the fluidity and melting point? Why?

Answer 21

-The presence of cis bonds enhances the fluidity and decreases the melting point of fatty acids.
-The cis double bond gives the hydrophobic tail a “kink” and prevents optimal hydrophobic interactions between the tails

Question 22

what enhances the fluidity of fatty acids

Answer 22

short chain length and present of cis bonds

Question 23

which has lower mp, saturated fatty acids or unsaturated fatty acids

Answer 23

generally, unsaturated fatty acids have lower mp than saturated fatty acids

Question 24

What are triacylglycerols (also called triglycerides).

Answer 24

-Triglyceride molecules consist of 3 fatty acids (blue) linked to a glycerin molecule
-Triacylglycerols function as energy reservoirs in animals and are therefore their most abundant class of lipids even though they are not components of cellular membranes.
-nonpolar, water-insoluble substances are fatty acid triesters of glycerol
The fats and oils that occur in plants and animals consist largely of mixtures of?
energy reserves/store metabolic energy
-This is because triacylglycerols are less oxidized than carbohydrates or proteins and hence yield significantly more energy per unit mass on complete oxidation.
-Are non polar
-energy rich
Their main role in cells is to store excess fatty acids, and they are mostly found within lipid droplets.
-Energy is mostly stored in fat molecules in Triacylglycerols. T

Question 25

Cis polyunsaturated fatty acids are essential components of our diets because?

Answer 25

humans cannot synthesize them
-offer protection from coronary heart disease

Question 26

Triacylglycerols differ according to? Why

Answer 26

the identity and placement of their three fatty acid residues.
because Most triacylglycerols contain two or three different types of fatty acid residues and are named according to their placement on the glycerol moiety,

Question 27

Fats and oils differ how? Their compositions vary with?

Answer 27

differ only in that fats are solid and oils are liquid at room temperature
they are are complex mixtures of triacylglycerols whose fatty acid compositions vary with the organism that produced them. Plant oils are usually richer in unsaturated fatty acid residues than animal fats, as the lower melting points of oils imply.

Question 28

Structure of Triacylglycerols

Answer 28

Three Esterified Fatty Acids
3 fatty acids esterified to one molecule of glycerol
3 fatty acids attached to glycerol

Question 29

Where are Triacylglycerols stored.

Answer 29

• Triacylglycerols are stored in adipose cells which are in adipose tissue.Within these cells Triacylglycerols aggregate in the cytoplasm to form a large fat globule that makes up the majority of the cell.

Question 30

adipocytes do what

Answer 30

synthesis and storage of triacylglycerols and entirely filled with fat globules.

Question 31

where is most energy stored?

Answer 31

-Energy is mostly stored in fat molecules in Triacylglycerols

Question 32

why do Fats provide about six times the metabolic energy of an equal weight of hydrated glycogen.

Answer 32

Because they are hydrophobic and reduced. more compact. triacylglycerols are less oxidized than carbohydrates or proteins and hence yield significantly more energy per unit mass on complete oxidation.
NoNPolar-dont need to be stored with water
triacylglycerols, which are nonpolar, are stored in anhydrous form, whereas glycogen, for example, binds about twice its weight of water under physiological conditions.

Question 33

the three membrane lipids

Answer 33

phospholipids
glycolipids
cholesterol

Question 34

What are Glycerophospholipids? Structure? (or phosphoglycerides)

Answer 34

-membrane lipid
-phospholipid with a glycerol platform
amphiphilic
are the major lipid components of biological membranes. esterified with fatty acids.

Question 35

Glycerophospholipids are amphiphilic meaning ?

Answer 35

Glycerophospholipids are therefore amphiphilic molecules with nonpolar aliphatic (hydrocarbon) “tails” and polar phosphoryl-X “heads.”
contain fatty acids too
A molecule having both hydrophobic (nonpolar) and hydrophilic (polar) regions.

Question 36

what do the heads represent in glycerophospholipids

Answer 36

In the glycerophospholipids that commonly occur in biological membranes, the head groups are derived from polar alcohols

Question 37

four components that makeup phospholipids

Answer 37

fatty acids (2 or more), platform (glycerol or sphingosine), a phosphate, and alcohol(known as head group)

Question 38

The chemical structures including fatty acyl chains and head groupsof glycerophospholipids can be determined from the products of?

Answer 38

Phospholipases Hydrolyzing Glycerophospholipids.
-the products of the hydrolytic reactions catalyzed by enzymes known as phospholipases.

can break down to form lysophospholipid

Question 39

difference between lysophospholipid and Glycerophospholipids

Answer 39

lysophospholipid- 1 fatty acid
Glycerophospholipids- 2 fatty acids

Question 40

hydrolyze meaning

Answer 40

break down (a compound) by chemical reaction with water.

Question 41

what are plasmalogens

Answer 41

Plasmalogens Contain an Ether Linkage. -vinyl ether replaces c1 ester

-are glycerophospholipids in which the C1 substituent of the glycerol moiety is linked via an α, β -unsaturated ether linkage in the cis configuration rather than through an ester linkage. Ethanolamine, choline, and serine (Table 9-2) form the most common plasmalogen head groups.

Question 42

what are Sphingolipids? most common? which configration on double bonds

Answer 42

phospholipids built on the amino alcohol Sphingosine platform with trans configuration
-Sphingomyelin found in myelin sheath of nerve cells

Question 43

The N-acyl fatty acid derivatives of sphingosine are known as ?

Answer 43

ceramides which are the parent compounds of the more abundant sphingolipids

Question 44

the most abundant Sphingolipids? which is most common

Answer 44

Sphingomyelins, Cerebrosides, Gangliosides
Sphingomyelins

Question 45

difference between Sphingomyelins vs Cerebrosides, and Gangliosides

Answer 45

Cerebrosides and Gangliosides are carbohydrate containing lipids.(Glycolipids)

cerebrosides contain a single glucose,Cerebrosides, in contrast to phospholipids, lack phosphate groups and hence are nonionic.

ganglioside is a much more complex lThey are ceramides with attached oligosaccharides that include at least one sialic acid residue.

Has sugar

Question 46

where do the carbohydrate components of glycolipds have their cell to cell interactions

Answer 46

on the extracellular surface of the cell membrane

Question 47

What are steroids? structure of steroids?

Answer 47

Lipids

steroids have four fused rings: three cyclohexane rings and a cyclopentane ring fused together

Question 48

most common steroid, classification and function

Answer 48

cholesterol, precursor to steroid is a sterol, maintains membrane fluidity

. Cholesterol is a major component of animal plasma membranes, typically constituting 30 to 40 mol % of plasma membrane lipids. IIts polar OH group gives it a weak amphiphilic character, whereas its fused ring system provides it with greater rigidity than other membrane lipids.

Question 49

why is cholesterol a sterol

Answer 49

because of its C3-OH group

Question 50

what plays the role of cholesterol in plants and prokaryotes

Answer 50

hopanoids and various sterols pla

Question 51

In mammals, cholesterol is the metabolic precursor of

Answer 51

steroid hormones, substances that control a great variety of physiological functions through their regulation of gene expression
such as cortisol, testosterone , estrogen

Question 52

Vitamin D which Regulates ? The various forms of vitamin D, which are really hormones, are

Answer 52

Ca 2+ Metabolism.
sterol derivatives

Question 53

Some representative steroid hormones.

Answer 53

The glucocorticoids, such as cortisol (a C 21compound), affect carbohydrate, protein, and lipid metabolism and influence a wide variety of other vital functions, including inflammatory reactions and the capacity to cope with stress.

2. Aldosterone and other mineralocorticoids regulate the excretion of salt and water by the kidneys.
3. The androgens and estrogens affect sexual development and function. Testosterone, a C 19 compound, is the prototypic androgen (male sex hormone), whereas 𝛃 -estradiol, a C 18 compound, is an estrogen (female sex hormone).

Question 54

Other Lipids Perform a Variety of Metabolic Roles such as

Answer 54

-Isoprenoids which are not structural components if the membrane but soluble in the lipid bilayerThe plant kingdom is rich in isoprenoid compounds, which serve as pigments, molecular signals (hormones and pheromones), and defensive agents.
-Vitamin A, or retinol,which functions as the eye’s photoreceptor at low light intensities
-Vitamin K, participates in blood clotting
-Vitamin E, prevents oxidative damage
-Eicosanoids, many functions The eicosanoids act at very low concentrations and are involved in the production of pain and fever, and in the regulation of blood pressure, blood coagulation, and reproduction.

Question 55

What three structures can lipids form into?

Answer 55

Micelles, Lipid Bilayer, and liposome

When added to water, single chain amphiphiles form both monolayers on the surface of the water and micelles, while some monomers remain in solution. Double chain amphiphiles form bilayers instead of micelles.
Spherical bilayers that enclose an aqueous compartment are called vesicles or liposomes. help with drug delivery, heads interact with water, tails interact with each other

Question 56

In living systems, lipids are seldom found as free molecules but instead associate with other molecules, usually other lipids. Why is this important?

Answer 56

lipids aggregate to form micelles (globular aggregates whose hydrocarbon groups are out of contact with water) and bilayers (consisting of two layers of lipids). We are concerned with the physical properties of lipid bilayers because these aggregates form the structural basis for biological membranes.

Question 57

What influences bilayer formation, how does this help

Answer 57

The hydrophobic effect causes hydrophobic groups in the presence of water or other polar solvents to aggregate.

eliminates unfavorable contacts between water and the hydrophobic tails of the amphiphiles and yet permits the solvation of the polar head groups.

Question 58

single tails amphiphiles vs double tailed glycerophospholipids and sphingolipids

Answer 58

Single-tailed amphiphiles, such as soap anions, form spheroidal or ellipsoidal micelles because of their tapered shapes (their hydrated head groups are wider than their tails). The number of molecules in such a micelle depends on the amphiphile, but for many substances it is on the order of several hundred. Too few lipid molecules would expose the hydrophobic core of the micelle to water, whereas too many would give the micelle an energetically unfavorable hollow center (Fig. 9-13c). Of course, a large micelle could flatten out to eliminate this hollow center, but the resulting decrease of curvature at the flattened surfaces would also generate empty spaces (Fig. 9-13d).

The two hydrocarbon tails of glycerophospholipids and sphingolipids give these amphiphiles a somewhat rectangular cross section (Fig. 9-14a). The steric requirements of packing such molecules together yield large disklike micelles (Fig. 9-14b) that are really extended bimolecular leaflets. These lipid bilayers are ∼60 Å thick, as measured by electron microscopy and X-ray diffraction techniques, the value expected for more or less fully extended hydrocarbon tails.

Question 59

all membrane lipids are what kind of molecules? what parts of them contribute which

Answer 59

amphipathic contenting hydrophobic and hydrophilic properties, this nature allows them to form membranes

-fatty acid components provide hydrophobic properties whereas the alcohol and phosphate components called the polar head group provide the hydrophilic properties

Question 60

characteristics of membranes

Answer 60

na

Question 61

Phospholipids and glycolipids form what in aqueous solutions

Answer 61

lipid bilayers

Question 62

difference in membrane lipids and proteins concerning their functions

Answer 62

membrane lipids establish a permeability barrier that separates the contents of the cell from the outside environment. membrane proteins allow transport of molecules and information across the membrane.
Membranes vary in protein content from as little to 18% to as much as 75%

Question 63

Lipid Bilayers are highly impermeable to? The ability of small molecules to cross a membrane is a function of?

Answer 63

Ions and most polar molecules
hydrophobicity

Question 64

Why can’t ions cross membranes?

Answer 64

because of their energy cost of shedding their associated water molecules

Question 65

permeability meaning

Answer 65

he state or quality of a material or membrane that causes it to allow liquids or gases to pass through it.

Question 66

membrane processes depend on membrane fluidity and membrane fluidity is controlled by? does it increase or decrease it

Answer 66

Fatty acid composition and cholesterol content Cholesterol, which by itself does not form a bilayer, decreases membrane fluidity

Question 67

membrane protein function

Answer 67

Membrane proteins catalyze chemical reactions, mediate the flow of nutrients and wastes across the membrane, and participate in relaying information about the extracellular environment to various intracellular components.

Question 68

The transfer of a lipid molecule across a bilayer, a process termed ?

Answer 68

transverse diffusion or a flip-flop, is an extremely rare event. This is because a flip-flop requires the hydrated, polar head group of the lipid to pass through the anhydrous hydrocarbon core of the bilayer. The flip-flop rates of phospholipids have half-times of several days or more. In contrast to their low flip-flop rates, lipids are highly mobile in the plane of the bilayer (lateral diffusion)

Question 69

The Fluidity of a Lipid Bilayer depends on?what are the rules? how does cholesterol effect fluidity

Answer 69

temperature
The transition temperature of a bilayer increases with the chain length and the degree of unsaturation of its component fatty acid residues for the same reasons that the melting points of fatty acids increase with these quantities.
As temperature increases, so does phospholipid bilayer fluidity.
Cholesterol, which by itself does not form a bilayer, decreases membrane fluidity because its rigid steroid ring system interferes with the motions of the fatty acid side chains in other membrane lipids.
presence of proteins affect fluidity

Question 70

Which Membrane Proteins Interact with Hydrophobic Lipids

Answer 70

Integral or intrinsic proteins

Question 71

Integral protein function

Answer 71

Integral proteins associate tightly with membranes through hydrophobic interactions and can be separated from membranes only by treatment with agents that disrupt membranes

Question 72

examples of how Integral proteins are separated from hydrophobic lipids

Answer 72

only by treatment with agents that disrupt membranes. For example, detergents such as sodium dodecyl sulfate (Section 5-2D) solubilize membrane proteins by replacing the membrane lipids that normally surround the protein. The hydrophobic portions of the detergent molecules coat the hydrophobic regions of the protein, and the polar head groups render the detergent–protein complex soluble in water. Chaotropic agents such as guanidinium ion and urea (Section 6-4B) disrupt water structure, thereby reducing the hydrophobic effect, the primary force stabilizing the association of the protein with the membrane. Some integral proteins bind lipids so tenaciously that they can be freed from them only under denaturing conditions.

Question 73

explain how Integral Proteins Are Asymmetrically Oriented Amphiphiles.

Answer 73

Integral proteins are amphiphiles; the protein segments immersed in a membrane’s nonpolar interior have predominantly hydrophobic surface residues, whereas those portions that extend into the aqueous environment are by and large sheathed with polar residues. this was demonstrated by surface labeling, a technique employing agents that react with proteins but cannot penetrate membranes

Question 74

difference between integral and peripheral proteins

Answer 74

integral proteins are embedded in the whole bilayer whereas peripheral proteins are located on the inner or outer surface of the phospholipid bilayer.

Question 75

difference between integral and peripheral proteins

Answer 75

-integral proteins is a transmembrane protein meaning it spans the whole membrane. permeenately attached to the plasma membrane. interact a lot with hydrophobic tails of phospholipids
have to use detergents to remove integral proteins
London dispersion forces
-whereas peripheral proteins are located on the inner or outer surface of the phospholipid bilayer.temporarily attached to the plasma membrane. hardly interact
have to change ph or add salt to remove peripheral proteins
attach to the polar heads of the phospholipid or polar region
hydrogen bonds/ionic bonds
-can easily dissociate

Question 76

transmembrane proteins contain which 2 types of secondary strucutres? why

Answer 76

𝛂 Helices and β Barrels
Transmembrane Proteins May Contain 𝛂 Helices. For a polypeptide chain to penetrate or span the lipid bilayer, it must have hydrophobic side chains that contact the lipid tails and it must shield its polar backbone groups. This second requirement is met by the formation of secondary structure that satisfies the hydrogen-bonding capabilities of the polypeptide backbone.
Transmembrane Proteins May Contain B barrels A protein segment immersed in the nonpolar interior of a membrane must fold so that it satisfies the hydrogenbonding potential of its polypeptide backbone. A

Question 77

What are Lipid-linked proteins and the three types?

Answer 77

Some membrane-associated proteins contain covalently attached lipids that anchor the protein to the membrane. The lipid group, like any modifying group, may also mediate protein–protein interactions or modify the structure and activity of the protein to which it is attached.

Lipid-linked proteins come in three varieties: prenylated proteins, fatty acylated proteins, and glycosylphosphatidylinositol-linked proteins.

Question 78

describe the structure of the membrane

Answer 78

not rigid, horizontal latteral motion/diffusion

Question 79

what is the fluid mosaic model

Answer 79

describes the structure of the plasma membrane and the lateral diffusion of membrane proteins and lipids

describes the cell membrane as a 2D liquid that restricts the lateral diffusion of membrane components

Question 80

The rates of diffusion of proteins in membranes can be determined from measurements of?/what measures rates of lateral diffusion in membranes

Answer 80

fluorescence recovery after photobleaching (FRAP).FRAP measurements demonstrate that membrane proteins vary in their lateral diffusion rates. Some 30 to 90% of these proteins are freely mobile; they diffuse at rates

Question 81

lateral diffusion?Transverse diffusion? The prohibition of transverse diffusion accounts for what?

Answer 81

Lateral diffusion refers to the lateral movement of lipids and proteins found in the membrane. Membrane lipids and proteins are generally free to move laterally if they are not restricted by certain interactions. Lateral diffusion is a fairly quick and spontaneous process.The capability to show movement in the membrane is measured as its fluidity.

accounts for the stability of the membrane assymetryu

Question 82

What Helps Define Cell Shape

Answer 82

The Membrane Skeleton

Question 83

main protein found in The Membrane Skeleton

Answer 83

spectrin: consists of a and b chains which are made up from helical repeats of 106 amino acid length
others include actin, tropomyosin, and ankyrin which connects the spectrum b chain to a variety of integral membrane proteins

Question 84

Membrane Lipids Are Distributed Asymmetrically t or f

Answer 84

true

Question 85

How do phospholipids synthesized on one side of the membrane reach its other side so quickly?

Answer 85

Phospholipid flip-flops in bacteria as well as eukaryotes appear to be facilitated in two ways:

1. Membrane proteins known as flippases catalyze the flip-flops of specific phospholipids. These proteins tend to equilibrate the distribution of their corresponding phospholipids across a bilayer; that is, the net transport of a phospholipid is from the side of the bilayer with the higher concentration of the phospholipid to the opposite side. Such a process, as we will see in Section 10-1, is a form of facilitated diffusion.
2. Membrane proteins known as phospholipid translocases transport specific phospholipids across a bilayer in a process that is driven by ATP hydrolysis. These proteins can transport certain phospholipids from the side of a bilayer that has the lower concentration of the phospholipid to the opposite side, thereby establishing a nonequilibrium distribution of the phospholipid. Such a process, as we will see in Section 10-3, is a form of active transport

Question 86

what are lipid rafts and function

Answer 86

lipid raft, appears to consist of closely packed glycosphingolipids (which occur only in the outer leaflet of the plasma membrane) and cholesterol. By themselves, glycosphingolipids cannot form bilayers because their large head groups prevent the requisite close packing of their predominantly saturated hydrophobic tails. Conversely, cholesterol by itself does not form a bilayer due to its small head group. It is therefore likely that the glycosphingolipids in lipid rafts associate laterally via weak interactions between their carbohydrate head groups, and the voids between their tails are filled in by cholesterol.

function as platforms for the assembly of complex intercellular signaling systems. cholesterol
0:30
act like dynamic glue which hold this
0:33
domain together

Question 87

What Generates Secreted and Transmembrane Proteins, why’s it named that

Answer 87

The Secretory Pathway, It’s named ‘secretory’ for being the pathway by which the cell secretes proteins into the extracellular environment.

Question 88

In living systems, lipids are seldom found as free molecules but instead associate with other molecules, usually other lipids. Why is this important?

Answer 88

lipids aggregate to form micelles (globular aggregates whose hydrocarbon groups are out of contact with water) and bilayers (consisting of two layers of lipids). We are concerned with the physical properties of lipid bilayers because these aggregates form the structural basis for biological membranes.

Question 89

What three structures can lipids form into?

Answer 89

Micelles, Lipid Bilayer, and liposome

When added to water, single chain amphiphiles form both monolayers on the surface of the water and micelles, while some monomers remain in solution. Double chain amphiphiles form bilayers instead of micelles.
Spherical bilayers that enclose an aqueous compartment are called vesicles or liposomes.

Question 90

Lipid Bilayers are highly impermeable to? The ability of small molecules to cross a membrane is a function of?

Answer 90

Ions and most polar molecules
hydrophobicity

Question 91

vehicles that transport proteins ? exocytosis vs endocytosis?

Answer 91

coated vesicles
Coated vesicles transport membrane-embedded and luminal proteins from the ER to the Golgi apparatus for further processing, and from there to other membranes.
exo- contents of a vesicle are released into exterior
endo-contents are taken up by cell

Question 92

lipid raft?

Answer 92

Membrane proteins and lipids are distributed asymmetrically in the two leaflets of the bilayer and may form domain

Question 93

membrane processes depend on membrane fluidity and membrane fluidity is controlled by?

Answer 93

Fatty acid composition and cholesterol content