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BIOL2171 > Biological Membranes > Flashcards

Biological Membranes Flashcards

1
Q

Definition of a complex lipid

A

A lipid with multiple parts

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2
Q

Purpose of a head group

A

To allow amphipathic capacity

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3
Q

Definition of amphipathic

A

A molecule having both hydrophobic and hydrophillic parts

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4
Q

Basic structure of sphingolipids

A

A sphingosine (long chain alcohol), a fatty acid (attaching via acyl group), and a polar head group

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5
Q

X group of ceramide

A

None

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6
Q

X group of sphingomyelin

A

phospho-choline

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7
Q

X group of lactosyl-ceramide

A

> 1 saccharide

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8
Q

X group of neutral glycolipid

A

Glucose

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9
Q

X group of ganglioside

A

Complex saccharide, including various types of branching

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10
Q

Cholesterol size, typology, building blocks, place of biosynthesis

A

27 carbons, planar typology (can be stacked), built from carbon units of acetyl-CoA, synthesized by all cells (mainly the liver) in the cytosol

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11
Q

How are micelles formed

A

By fats and detergents; the head group is larger, so the chemicals wrap around to form balls easily. Only a single fatty acid tail.

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12
Q

How are liposomes formed

A

By phospholipids; the two fatty acid tails cause no difference between the head group and the tail group, so the curvature is slight and a bilayer is formed.

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13
Q

Issues with early view of biomembranes

A

1) Didn’t consider heterogenity of components, as each layer may be made up of different components
2) Didn’t consider heterogenity of protein insertion, as each layer may have different proteins
3) Leaflet asymmetry (leaflets being glycolipids, oligosaccharides, etc.)
4) Motional restrictions inherent in the layer (not just fluid)
5) Interaction with the cytoskeleton

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14
Q

Most abundant biological lipid

A

Cholesterol, ~20%

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15
Q

Relative concentration of sphingomyelin and phosphatidylcholine

A

50/50

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16
Q

Phosphatidylserine composition and role

A

Nearly 10%, relatively high, used for signalling

17
Q

Are lipids glycosylated

A

Yes, extensively

18
Q

Why membranes are asymmetric (why are the two membranes comprising the bilayer different?)

A

Facilitates association / integration of membrane proteins, provides membrane curvature, and provides correct localization of signalling molecules

19
Q

Name three kinds of enzymes that mediate membrane asymmetry

A

Flippases, floppases and scramblases

20
Q

Main phospholipids on outside surface of membrane in erythrocytes

A

Phosphatidylcholine and sphingomyelin

21
Q

Main phospholipids on inside of membrane in erythrocytes

A

Phosphatidylethanolamine and phosphatidylserine

22
Q

Term for ‘ lipid rafts’ on membrane

A

Mini-domains

23
Q

Main composition of mini-domains

A

Cholesterol and sphingolipids with long acyl lengths

24
Q

Phase of lipids in mini-domains

A

Ordered; becomes more rigid.

25
Q

Size and timespan of mini-domains

A

10-300nm, short-lived

26
Q

Protein composition of mini-domains

A

Caveolae proteins, theoretically for a structural role, GPI-anchored proteins

27
Q

Advantage rafts have with proteins

A

Localizing proteins for related processes can help accomplish that process, such as for signalling

28
Q

Name four ways to aggregate proteins for lipid rafts

A

(1) Protein-protein coupling
(2) Protein-lipid coupling
(3) Extracellular matrix
(4) Cytoskeleton

29
Q

What aggregation does to proteins

A

Affects motion and localization of the proteins

30
Q

Types of lateral movement in proteins

A

(1) Transient confinement by obstacle clusters
(2) Transient confined by the cytoskeleton, which acts like a fence
(3) Directed motion by attachment to the cytoskeleton
(4) Free and random diffusion in the membrane plane

31
Q

Which phospholipid, out of sphingosine, sphingomyelin, neutral glycolipids, lactosyl-ceramide, ceramide and ganglioside has a fatty acid (amide) residue?

A

All except sphingosine.

32
Q

Which phospholipid, out of sphingosine, sphingomyelin, neutral glycolipids, lactosyl-ceramide, ceramide and ganglioside, has a polar X group?

A

All except sphingosine and ceramide.

BIOL2171 (14 decks)

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