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Biomolecules of life > Week 4 - lipids and cell membranes part 1 > Flashcards

Week 4 - lipids and cell membranes part 1 Flashcards

1
Q

Name some common features of biological membranes

A
  • sheet like, to molecules thick, between 60-100 A thick
  • mainly comprise lipids and proteins
  • membrane lipids are small amphipathic molecules
  • specific proteins mediate distinctive functions
  • membrane are non-covalent
  • asymmetric - two faces always differ
  • fluid structures - lipids diffuse rapidly in the plane
  • polarised, inside cell typically -60mV
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2
Q

Name 6 membrane functions

A
  • selective barrier
  • transport and excretion
  • defence
  • energy storage/ accumulation
  • assimilation/ synthesis
  • information
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3
Q

Describe the nature of membrane lipids

A
  • amphipathic molecules containing hydrophilic an hydrophobic moiety
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4
Q

name the three functional groups of a fatty acid

A
  • hydrogen
  • alkyl
  • carboxyl
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5
Q

what are fatty acids?

A

long chain hydrocarbons

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6
Q

How many saturated carbons does octadecanoic have?

A

18:0

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7
Q

How many saturated carbons does octadecenoic have?

A

18:1

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8
Q

How many saturated carbons does octadecadienoic have?

A

18:2

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9
Q

How many saturated carbons does octadecatrienoic have?

A

18:3

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10
Q

What does palmitate consist of?

A

16 carbon saturated fatty acids

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11
Q

What does oleate consist of?

A

18-carbon with a single cis double bond

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12
Q

Atom numeration

A
  • double bond nomenclature:
    1. triangle and nr of C from C1
    2. or omega and nr of C form CH3
    eg. cis-delta^9-octadecenoate or omega-9
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13
Q

What do you know about the chain length and saturation in common fatty acids?

A
  • usually contain an even number of carbon atoms (14-24)
  • 16- and 18- are common
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14
Q

Why is there a dominance of even numbered carbon atoms?

A

according eight eh way fatty acids are biosynthesised

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15
Q

How does an increasing number of double bonds affect fluidity?

A
  • increases fluidity
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16
Q

How does an increasing number of carbons affect fluidity?

A

decreases fluidity

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17
Q

name three common types of membrane lipids

A
  1. phospholipids
  2. glycolipids
  3. cholesterol
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18
Q

What does a phospholipid consist of?

A
  • constructed from four components:
    1. one or more fatty acids
    2. platform to which they are attached (alcohol eg. glycerol or sphingosine)
    3. phosphate
    4. alcohol attached to phosphate
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19
Q

Describe the chemical structure of the simplest phospholipid

A
  • acyl groups with fatty acid hydrocarbon chains
  • phosphatidate (diacylglycerol 3-phosphate)
  • a phosphate
  • an alcohol attached to phosphate
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20
Q

What is phosphatidate?

A
  • simplest phoshoglyceride consists of glycerol platform esterified to the carboxyl groups of the two fatty acid chains C-1 and C-2, C-3 is esterified to phosphoric acid
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21
Q

how are the main phospholipids created?

A
  • derived from phosphatidate
  • by formation fo ester bond between phosphate group of phosphatidate and hydroxyl group of one of several alcohols
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22
Q

What are the most common alcohols?

A
  • serine
  • ethanolamine
  • choline
  • glycerol
  • inositol
23
Q

What does PS stand for?

A

phospatidylserine

24
Q

What does PC stand for ?

A

phosphatidylcholine

25
Q

What does PE stand for?

A

Phosphatidylthanolamine

26
Q

What does PI stand for?

A

Phosphatidylinositol

27
Q

What does DPG stand for?

A

Diphosphatidylglycerol (cardioplipin)

28
Q

is sphingomyelin derived form glycerol?

A

no

29
Q

Where is sphingomyelin derived from?

A

sphingosine, an amino alcohol with long saturated hydrocarbon chain - sphingosine backbone linked to fatty acid by amide bond
- primary alcohol esterified to phosphorylcholine

30
Q

What are glycolipids?

A

sugar containing lipids derived form sphingosine
- aino gourp is acylated by fatty acid
- primary alcohol esterified to one or more sugars
- glycolipids asymmetric - sugar always on the extracellular side of membrane

31
Q

What else do more complex glycolipids eg. gangliosides contain?

A

a branched chain of as many as seven sugars

32
Q

What is cholesterol?

A

a lipid based on a steroid nucleus
- in membrane oriented parallel to fatty acid chains of the phospholipids, hydroxyl group interacts with the nearby head groups
- absent in prokaryotes
- distribution varies in mammals high in nerve cells, Low in some intracellular membranes

33
Q

What are Racheal membranes built form?

A

ether lipids and branched chains

34
Q

How do the membranes of archaea differ from those of eukaryotes?

A
  • non-polar chains are attached by ether rather than ester bonds
  • alkyl chains are branched
35
Q

what might the ability of archaean lipids to resist hydrolysis and oxidation help organisms to survive?

A

in extreme conditions such as high T, low pH and high salt, under which some of these archaea grow

36
Q

What do phospholipids and glyocolipids readily form?

A

sheets in aqueous media

37
Q

What are the favoured structures for most phospholipids and glycolipids in aqueous media?

A

bimolecular sheet rather than micelle (bulkiness of fatty acids)

38
Q

How do lipid players form?

A

spontaneously by a self-assembly process to minimise the exposure to water of the hydrophobic tails

39
Q

What can be formed from phospholipids?

A

lipid vesicles, liposomes

40
Q

What are lipid vesicles or liposomes?

A

aqueous compartments enclosed by a. lipid bilayer used to study memebrane permeability or to deliver chemicals to cells

41
Q

what will happen after glycine and H20 are filled into a beaker with phospholipid layer on the bottom ?

A

sanitation -> lipids will form into circles, form a bilayer
gel filtration -> glycine trapped in lipid vesicles

42
Q

What are liposomes?

A
  • outer aqueous compartment, inner aqueous compartment separated by a bilayer membrane
43
Q

How can larger vesicles than 500 A be prepared?

A

by slowly evaporating the organic solvent form a suspension of phospholipid in a mixed solvent system

44
Q

Explain experiments to develop clinical uses of liposomes

A
  • liposomes containing drugs or DNA for gene therapy can be injected into patients
  • these liposomes fuse with plasma membrane of many kinds of cells, introducing into the cell the molecules they contain
  • drug delivery using such lysosomes can lessen drug toxicity particularly if selective fusion of lipid vesicles with specific cell types become possible
45
Q

What are lipid bilayers highly impermeable to?

A

ions and most polar molecules

46
Q

What is an exception to the permeability of membranes?

A

because of its small size, high conc and lack of full charges, water can pass the membrane even tho its polar

47
Q

Why carries out most membrane function?

A
  • proteins
48
Q

Do membranes differ in their protein content? give examples

A

yes - myelin, a membrane that insulates nerve fibres has a low protein content - 18 %

49
Q

Relatively pure lipids such as myelin are what?

A

good insulators

50
Q

What does a plasma membrane of most cells that are metabolically active contain?

A

pumps, channels, receptors, enzymes

51
Q

What is the typical protein content of some plasma membrane?

A

50%

52
Q

Which membranes have the highest protein content? And what % is it?

A
  • energy-transduction membranes
  • eg. internal membranes of mitochondria and chloroplasts have highest content of protein
  • around 75 %
53
Q

what technique can be used to show the listing protein composition?

A

SDS page

54
Q

What are the types of proteins association with the lipid bilayer?

A

integral and peripheral

Biomolecules of life (10 decks)

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