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Biochemistry > Biochem Lipids Lecture 1 > Flashcards

Biochem Lipids Lecture 1 Flashcards

1
Q

Lipids are a chemically diverse group of compounds.

Are they soluble in water?

What about in organic solvents?

A

No

yes

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2
Q

____ have the simplest structure of all lipids. Other types of lipids contain them or are derived from them

A

Fatty acids

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3
Q

What lipids are not derived from fatty acids?

A

Steroids

Lipid Vitamins (A,D,E,K)

Terpenes

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4
Q

What are terpenes derived from?

A

Isoprene

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5
Q

What are the functions of lipids?

A

Storage (fats and oils)

Structural elements of biological membranes (phospholipids)

Signals (hormones), enzyme cofactors, and pigments

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6
Q

Describe the structure of fatty acids

A

Carboxylic acids with long hydrocarbon chains (4 to 36 carbons)

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7
Q

Are all fatty acid chains unbranched and saturated?

A

No, some are unbranched and saturated

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8
Q

Stearic acid has 18 carbons in its chain with no double bonds, so its designated as

Other fatty acids contain one or more double bonds

A

18:0

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9
Q

Oleic acid has 18 carbons in its chain with one double bond between the 9th and 10th carbon. It is described as…

A

18:1(Δ9)

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10
Q

Linoleic acid is a polyunsaturated fatty acid containing 18 carbons and 2 double bonds, between the 9th and 10th and 12th and 13th carbons. it is abbreviated as

A

18:2 (Δ9,12)

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11
Q

The double bonds are in the ___ conformation for nearly all naturally occurring unsaturated fatty acids

A

Cis

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12
Q

____ fatty acids are obtained from dairy products and meat

A

Trans

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13
Q

trans fatty acids are associated with _____ LDL and decreased _____

A

LDL (bad cholesterol)

HDL (good cholesterol)

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14
Q

Do most fatty acids have an even or odd number of carbohydrates? Why?

A

Even because the are synthesized by condensation of two carbon units

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15
Q

The melting points of saturated fatty acids INCREASES/DECREASES as the number of carbon atoms increases

Why?

A

Increases

The increased number of van der Waals interactions increases with each C

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16
Q

The melting point INCREASES/DECREASES as the number of double bonds increases for 18 carbon chain fatty acids

A

Decreases

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17
Q

______ fatty acids can pack tightly while ___ fatty acids have kinks in their hydrocarbon chains due to the cis double bonds. Their interactions with each other are weaker

A

Saturated

Unsaturated

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18
Q

Triglycerols are composed of:

A

Three fatty acids

Each fa is an ester linkage with a single glycerol

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19
Q

Simple triacylglycerols contain the samy fatty acids in all three positions and are named after that fatty acid

For 18:0 (stearic acid) the triacyl glycerol is

A

Stearin

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20
Q

Most naturally occuring triacylglycerols are UNIFORM/MIXED

A

Mixed, they contain a mixture of saturated and unsaturated fatty acids of different chain length

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21
Q

triacylglycerols are CHARGED/UNCHARGED, POLAR/NONPOLAR, HYDROPHILIC/HYDROPHOBIC

A

uncharged, nonpolar, hydrophobic

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22
Q

The polar ____ of glycerol and the ___ of the fatty acids are bound in ester linkages

A

Hydroxyls

Carboxylates

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23
Q

Depending on their melting point, triacylglycerols may be liquids or solids at RT. The melting point depends upon the type of ___ present

Unsaturated —>

Saturated—->

A

Fatty acids

Liquid

Solid

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24
Q

Vegetable oils are mainly triacylglycerols with SATURATED/UNSATURATED

Thus, they are liquid/solid at RT

A

Unsaturated FAs

Liquid

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25
Q

High lipid containing food spol “rancid” when exposed to

Why?

A

Oxygen

Double bonds in unsaturated fatty acids may undergo oxidative
cleavage yielding aldehydes and carboxylic acids of shorter chain
length and higher volatility (odor)

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26
Q

Commercial vegetable oils undergo _______ to improve shelf-life
and high temperature stability

What two things result?

A

hydrogenation

Catalytic hydrogenation reduces some double bonds to single
bonds “saturated”

Catalytic hydrogenation converts others to trans double bonds
(french fries, donuts and cookies have historically contained trans fatty
acids).

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27
Q

Two advantages to using triacylglycerols as energy stores rather than polysaccharides

A
  1. Carbon atoms of fatty acids are more reduced
    then those of sugars. Oxidation of triacylglycerols
    yield twice as much energy as carbohydrates.
  2. Triacylglycerols are hydrophobic and
    unhydrated. No extra water needs to be stored in contrast to polysaccharides
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28
Q

These are esters of long chain (C14 to C36) saturated and unsaturated fatty acids with long chain (C16 to C30) alcohols

Their melting points are HIGHER/LOWER than triacylglycerols

A

Waxes

Higher

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29
Q

Are waxes water repellant?

Are they firm?

A

Yes

Yes

Lanolin, beeswax, carnauba wax and wax
extracted from spermaceti oil (whales) are used to make lotions, ointments and polishes.

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30
Q

What are the two major components of biological membranes

A

Glycerophospholipids and Sphingolipids

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31
Q

These are membrane lipids with two fatty acids esterified to the first and second carbons of glycerol, and a highly polar or charged group attached through a phosphodiester bond to the third carbon.

A

Glycerophospholipid

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32
Q

Glycerophospholipids are named as derivatives of their parent compound _____, according to the nonpolar/polar alcohol in the heat group

One example is

A

Phosphatidic acid

Polar

Phosphatidylserine

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33
Q

T/F: the polar alcohol in glycerophospholipids may be negatively charged, positively charged, or neutral

A

True

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34
Q

What three glycerophospholipids are the most common?

Do the fatty acids on them vary?

A

Choline, ethanolamine, and serine

Yes widely

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35
Q

Sphingolipids are composed of

A

sphingosine (a long chain amino alcohol)

a long chain fatty acid

a polar head group joined by either a glycosidic or
phosphodiester linkage

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36
Q

Draw the structure of a glycerophospolipid

How many total bonds are on phosphate?

A

!

5

37
Q

C1, C2, and C3 of sphingosine are structurally analagous to the three carbons of

A

Glycerol

38
Q

When a fatty acid of sphingolipids is attached in amide linkage to NH2 on C2, the resulting compound is a

A

Ceramide

39
Q

What are the three classes of sphingolipids?

All are derivatives of ____ but have different head groups

A

sphingomyelins, glycosphingolipids and gangliosides

Ceramides

40
Q

This subclass of sphingolipids there is a phosphodiester linkage to the OH of C1 of sphingosine

A

Sphingomyelin

41
Q

This subclass of sphingolipids one or more sugar molecules are
connected in a glycosidic bond to the OH of C1 of
sphingosine.

A

Glycosphingolipids

42
Q

This subclass of sphingolipids have oligosaccharides as their polar head
groups and one or more residues of N-acetylneuraminic
acid

A

Gangliosides

43
Q

Know phosphatidylchoine, phosphatidylethanolamine and phosphatidylserine structures.

A

!

44
Q

This is the major sterol in animal tissues

A

Cholesterol

45
Q

How many fused rings does cholesterol have?

What else are they composed of?

A

4 (the steroid nucleus)

Alkyl Side chain

Polar head group (OH and C3)

46
Q

The steroid nucleus of cholesterol is nearly ___ and ____, with no rotation about C-C bonds

A

Planar and rigid

47
Q

What type of phospholipids are predominate in biological membrane?

A

Double chain phospholipids

48
Q

Synthetic membranes, made from pure phospholipids, possess many of the same basic characteristics of natural membranes

A

!

49
Q

Glycerophospholipids and sphingolipids are “polar lipids” which can be represented as follows:…

A

?

50
Q

Glycerophospholipids and sphingolipids are “polar lipids” that form ___ in aqueous dispersions

A

Bilayers

51
Q

The hydrocarbon chains of the lipids are ____. They aggregate together and minimize their contact with water (hydrophobic effect)

A

nonpolar

52
Q

The hydrophilic, polar head groups aggregate together towards the surface where they maximize their contain with water through ___ and ___

A

H bonding

Dipole-dipole interactions

53
Q

The planar bilayers of glycerophospholipids and sphingolipids form a vesicle aka..

The __ regions at the edges of the bilayer are in contact with water

The bilayer folds back on itself to form a hollow ____

A

Liposome

Hydrophobic

Sphere (vesicle)

54
Q

Maximum stability of liposomes is present when there is a ______ inside the spherical bilayer

A

Water cavity

55
Q

Precursors to the first living cells may have resembled ____

A

Vesicles

56
Q

Biological membranes are composed of polar lipids and

A

Proteins

57
Q

The ____ for membrane structure was developed to more fully describe the fundamental properties of membranes

A

Fluid Mosaic Model

58
Q

In the fluid mosaic model, the ____ form a bilayer

____ are embedded in the bilayer sheet

A

Phospholipids

Integral protein molecules

59
Q

The integral proteins in the phospholipid bilayer are held by ______ interactions between membrane lipids and the hydrophobic domain of the protein

A

Hydrophobic

60
Q

Some integral proteins protrude only from one side of the bilayer while
others span the entire membrane thickness

A

!

61
Q

The surfaces of integral membranes exposed to water are hydrophobic/hydrophilic

The surfaces of integral proteins embedded in the
bilayer are hydrophobic/hydrophilic

A

Hydrophilic

Hydrophobic

62
Q

The bilayer membrane also contains ______ which interact with polar head groups of lipids and proteins on both sides of the bilayer

A

Peripheral Proteins

63
Q

The membrane bilayer is fluid because most of the interactions among its components are _____

A

Weak (non-covalent)

64
Q

T/F: Lipid and protein molecules are NOT free to diffuse laterally into the bilayer

A

False, they are free to move laterally in the bilayer

65
Q

Lipids and proteins can diffuse ____ in the bilayer

A

Laterally

66
Q

Lateral diffusion is very slow/fast

A

Very fast

67
Q

Experimentally, lateral diffusion can be shown by using a method called

A

fluorescence recovery after photobleaching (FRAP)

68
Q

In FRAP, fluorescent probes are attached to the ______ groups of lipids, and fluorecence microscopy is used to monitor the probes over time

A

Head groups

69
Q

In FRAP, an intense laser light pulse is focused on a small area of a cell
surface containing fluorescence-tagged lipids, and the fluorescence
groups are bleached (i.e. they no longer fluoresce when viewed in
the dimmer light of the fluorescence microscope.

A

!

70
Q

Within milliseconds of bleaching in FRAP, the fluorescence in the bleached area returns
indicating that the bleached molecules moved out of the region
while unbleached molecules diffused into the region.

The rate of fluorescence recovery after photobleaching (FRAP) is a
measure of the rate of lateral diffusion of the lipids

A

!

71
Q

Membrane proteins also diffuse laterally in the plane of the bilayer

A

!

Slide 24

72
Q

Two sides of a membrane are different with respect to the lipids and proteins present in the inner and out layers, these layers are also called

A

Leaflets

73
Q

Different integral proteins are embedded in each side of the membrane during synthesis, assymetric arrangement of membrane proteins results in

A

functional asymmetry

74
Q

`What must be overcome to move the hydrophilic portion of a protein across the lipid bilayer?

A

A large energy barrier

75
Q

A protein must give up its interactions with water and then diffuse through a solvent (lipid) in which it is poorly soluble

This prevents proteins from distributing themselves equally on both sides of the membrane

A

!

76
Q

For membrane lipids, even with a single leaflet, the lipid distribution is not

Cholesterol and sphingolipids form ____ in the outer monolayer of the plasma membrane

They can often be thought of as rafts within a sea of more liquid disordered phospholipids, certain integral membrane proteins are more associated with these rafts

A

Random

Microdomains

77
Q

This type of diffusion of lipid molecules across the bilayer is caled “flip flop”

A

Transverse Diffusion

78
Q

Is flip flop a fast process?

A

No, its half life is in days

79
Q

Membranes are also impermeable to these two things

Specific proteins are needed to help diffusion across the nonpolar lipid bilayer, called

A

Ions and polar most substances

Transporters

80
Q

Membranes are, however, permeable to ___ molecules

A

Water Molecules

81
Q

_____ transporters can move substrates across the membrane against a concentration gradient

A

Active Transporters

82
Q

A family of integral proteins, called ___, provide channels for the rapid movement of water molecules across plasma membranes

A

Aquaporins

83
Q

How many aquaporins with specialized roles are there in humans?

What speed do water molecules flow through them?

A

10

10^9 (s^-1)

84
Q

Do aquaporins allow the transport of protons?

A

No.

85
Q

Selectivity of AQP-1 is based upon its

A

Structure

86
Q

How many monomers, each forming a transmembrane pore large enough for water to move through, does AQP-1 have?

A

4

87
Q

Each of the 4 monomers of AQP-1 has how many transmembrane helical segments and __ shorter helices with the sequence N P A

A

6 transmembrane helical segments, 2 shorter helices

88
Q

Where do the 6 transmembrane proteins of AQP-1 form a pore?

A

Through the monomer

89
Q

The NPA-containing helices extend to the middle of the bilayer from opposite sides. The NPA regions overlap in the middle to form a structure that only allows water to pass

A

!

Biochemistry (27 decks)

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