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BISC 312 > Lecture 13 > Flashcards

Lecture 13 Flashcards

1
Q

T or F, lipids are structurally and functionally diverse group of molecules

A

True

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2
Q

Describe the amphipathic properties of membrane lipids.

A
    • Apolar tail (hydrophobic)
    • Polar head (hydrophilic)
    • polar head associates with water and nonpolar tail hides from water

– don’t form large covalent polymers instead they ten to associate w/ each other through noncovalent interactions

– stabilized through the hydrophobic effect

– also stabilized through van Der Waals interactions between hydrocarbon regions of molecules

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3
Q

What are primary components of membranes?

A

lipids

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4
Q

What are key components of lipids?

A

– fatty acids –> long hydrocarbon chains (14-24 C) with carboxyl group

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5
Q

What is an oleate ion?

A

– an unsaturated fatty acid with one cis double bond

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6
Q

What is a stearate ion?

A

Stearate (the anionic deprotonated form of stearic acid) it is a saturated fatty acid

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7
Q

In most naturally occurring unsaturated fatty acids what is the orientation?

A
    • Orientation is about double bonds is cis rather than trans
    • this has an important effect on molecular structure bc each cis double bond inserts a bend into the hydrocarbon chain
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8
Q

What is the difference between saturated and unsaturated fatty acids

A
    • unsaturated –> liquid at room temp
    • Saturated –> solid

– usually an even number of carbons

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9
Q

Why is unsaturation important?

A
    • because it keeps membranes fluid instead of solid

- - helps with movement and conformation changes of transmembrane proteins

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10
Q

What is the importance of straight fatty acid tails?

A

– they can pack together and interact

– increasing number of van der Waals contacts to form regular semi crystalline structures

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11
Q

What is the nomenclature of a double vs saturated fatty acid

A

double is enonated whereas saturated is anoate

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12
Q

What makes up a triaglycerol?

A

Fatty acids + glycerol

– a glycerol molecule, which is a 3 carbon with OH at each carbon and a three carboxylic acids esterified to the

– water-insoluble, so must have a specific mechanism of transport in the body

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13
Q

What are the effects of the amphipathic nature of membrane lipids?

A

They will preferentially arrange into micelles or bilayers to bury phobic tails away from the aqueous environment

– self assembly process driven by hydrophobic interactions between fatty acid cahins

– close packing is directed by van der Waals interactions between hydrocarbon chains

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14
Q

What is the most abundant lipid in membranes?

A

– Glycerophospholipids

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15
Q

What is the general structure of glycerophospholipids?

A

carbon one and to have an acyl group and carbon three has an orthophosphate group attached with a philic group attached

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16
Q

What is the general structure of a sphingolipid? What is this basic structure called?

A

it is a C15 on the C1, an amine on C2, and C3 containing a hydroxyl group. Called a sphingosine unit

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17
Q

What is the structure of glycosphingolipids? What category do these lipids fall under?

A

contains a C15 on C1, an amide on C2, and a sugar on C3. Categorized as glycolipids

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18
Q

What is the non-sugar portion of glycosphingolipids generally referred to as?

A

Ceramide

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19
Q

True or false. glycolipids can have many carb residues and are oriented asymmetrically in the plasma and are always facing the extracellular side.

A

True

20
Q

True or false.

glycolipids can be components of RBC membranes

A

True

21
Q

What is the general function of cholesterols in the membrane?

A

act as a fluidity buffer

22
Q

What does cholesterol due at each extreme in temperature?

A

it cold temps it prevents close packing and increases fluidity whereas at high temps it prevents excessive movement and decreases movement.

23
Q

What is the general structure and characteristic of cholesterol

A

tetracyclic molecule that has a weak ampihatic nature, polar groups, rigid ring system, and a flexible tail.

24
Q

True or false. Brain cells commonly have cerebrosides and ganliosides

A

True

25
Q

True or false

axons are rich in glycosphingolipids

A

True

26
Q

What maintains glycolipids in the rigid aqueous face configuration?

A

the inability of these lipids to move from these positions maintained by the limited flip flip ability of proteins

27
Q

What are the typical ratios of lipid:protein?

A

1:4 or 4:1

28
Q

What type of proteins exist in RBC membrane, retinal rod cells, vs SAR muscle cells in terms of size?

A

larger exist in RBC + SAR and smaller size exist in Retinal rod cells

29
Q

What differentiated anchored proteins from peripheral and integral proteins?

A

anchored protein are covalently linked to fatty acids chains or glycolipids at surface whereas the other types are associated by non-covalent interactions

30
Q

True or false

Diffusion is mainly lateral and rapid and rarely transverse.

A

True

31
Q

What factors of membranes increase fluidity?

A

short fatty acid tails, unsaturated fatty acids, and cholesterol

32
Q

True or false.

Saturated fatty acids decrease the Tm of the membrane

A

false they increase by increasing number of hydrogen bonds

33
Q

true or false

outer and inner membrane differ in lipid composition and in types of associated proteins

A

true

34
Q

What enzyme is responsbile for flipping lipids between inner and outer membranes?

A

flippase

35
Q

True or false

orientation of transmembrane proteins does not change over time

A

true

36
Q

true or false.

outer plasma membrane is rich in cholesterol

A

false. it is rich in glycosylated protein and lipids

37
Q

true or false

fats tend to be saturated in animals and unsaturated in plants

A

true

38
Q

Integral proteins are held by noncovalent forces. True or false?

A

true

39
Q

What are the characteristics of the glycophorin integral protein?

A

ampihphatic with extracelluar portion that is rich in phillic AA Ser Thr Asp and a phobic alpha helix in the membrane that has phobic amino acid.
It is also a glycoprotein meaning it has sugars attached to its structure

40
Q

What are common characteristics of protein/membrane interactions in integral protein?

A

typically 7 alpha helices that span the membrane with 20aa/helix with extensive H bonding
there are the typical 3.6aa/turn and 1 turn=0.54nm
bilayer core is about 3nm

41
Q

What characteristic does bacteriorhodopsin have?

A

has a light absorbing pigment at its center that captures light energy and pumps protons from cell to outside

– acts as a proton pump

42
Q

If a phobic index is positive, does it mean it is phobic or phillic?

A

phobic. negative values are phillic.

43
Q

What information can you get from a phobic index?

A

it can help you see which sections of the protein is in the membrane/ specific AA involved at teach section. The groups let you see how many helices the protein has in the membrane

44
Q

What is the structure of a transmembrane porin?

A

it is made of an amphiphatic b barrel structure. Hydrophillic residues on the inside of the channel and phobic residues on the outside facing the lipid bilayer.

45
Q

What is the general function of membranes?

A 
transport of substance in and out of cell
ion transport and nerve cell conductance
cell signaling
maintaining shape
cell-cell interaction

BISC 312 (31 decks)

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