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Miscellaneous > MCB Lecture 9 Lipids and Bilayers > Flashcards

MCB Lecture 9 Lipids and Bilayers Flashcards

0
Q

What are the three features of lipid Bilayers?

A
  1. Amphipathic
  2. Asymmetrical
  3. Variable fluidity
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1
Q

Describe lipid Bilayers’ role in compartmentalisation

A

Lipid bilayer provides a physical barrier -> compartments

These compartments can have different properties and conditions

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2
Q

Describe how the lipid bilayer is amphipathic

A

The head is hydrophilic

The fatty acid tails are hydrophobic

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3
Q

Describe the structure of a phospholipid

A

Phosphate head
Glycerol

Two fatty acid chains (hydrocarbons)

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4
Q

Draw the structure of cholesterol

A

.

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5
Q

Describe how lipid Bilayers have variable fluidity

A
  1. Cholesterol
  2. Shorter chain fatty acids
  3. Double bonds in fatty acids
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6
Q

Shorter chain fatty acids in the lipid bilayer lead to … of ordered packing

A

Decrease

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7
Q

Cholesterol lead to … of ordered packing

A

Decrease

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8
Q

Presence of double bonds in the fatty acid chains leads to … of ordered packing

A

Decrease

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9
Q

Reduction of ordered packing leads to …

A

Membrane sets at a lower sptemp

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10
Q

Describe how the lipid bilayer is asymmetric

A

There is differential distribution of membrane proteins and another associated molecules/complexes

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11
Q

Glycolipids are almost always found … ?

A

On the outside of the cell

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12
Q

Where is Phosphotidyl-Serine almost always found?

What is its charge?

A

Inside

Negatively charged

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13
Q

What is important about phosphotidyl-inositols in the membrane?

A

These are important parts of signal transduction pathways

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14
Q

What is the structure of lipid rafts?

A

These are made up of sphingolipids which have long saturated fatty acid chains

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15
Q

What is the function of lipid rafts?

A

These provide regions for membrane proteins to reside and be localised

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16
Q

Lipid rafts are resistant to what?

A

Detergent

17
Q

Are lipid rafts dynamic or static?

A

Dynamic

18
Q

Describe the structure of sterols in terms of polarity

A

Sterols have a tiny polar group (-OH)

Rigid steroid ring structure

Non polar aliphatic chain

19
Q

What is a glycolipid?

A

Sugar associated with fatty acid chains

20
Q

What is a sphingolipid? Where is it usually found?

A

Sphingolipids are usually found in lipid rafts

They are long, saturated, fatty acids

21
Q

What type of molecule is a galactocerebroside?

A

Glycolipid

22
Q

What type of molecule is a ganglioside?

A

Glycolipid

23
Q

From what are all animal glycolipids a derived?

A

Serine

24
Q

What are the two types of membrane proteins?

A

Integral and peripheral

25
Q

What are the requirements for integral membrane proteins?

A

They must have some part attached or within the membrane

Need detergent to remove it

26
Q

What are the two ways that helices can be embedded in a membrane?

A

Amphipathic: Hydrophobic stripe embedded (long ways)

Transmembrane, hydrophobic residues

27
Q

What are peripheral proteins. For example…?

A

Peripheral protein are connected to the membrane only through interactions with other molecules

28
Q

Where are the termini in transmembrane proteins (in general)?
What is the exception?

A

The N and C termini are usually on the cytosolic side.

The exception is

29
Q

What are the two types of structure that can form transmembrane proteins?

A

Beta barrels - porins

Helices

30
Q

What are the features of transmembrane helices?
How many residues span the bilayer?
How does the helix interact with lipids?

A

20-30 residues

Hydrophobic side chains within the membrane

31
Q

What are the features of transmembrane b-proteins?

How does the structure interact with the hydrophobic lipids?

A

These are beta sheets that are bent around to form channels through a membrane: porins

Hydrophobic residues protrude out into the lipids
Hydrophilic residues protrude into the channel

32
Q

What are porins?

Describe their presence in prokaryotes and eukaryotes.

A

Porins are channels in the membrane

They are mostly found in prokaryotes.
In eukaryotes, they are seen in the inner mitochondrial membrane (bacterial origin)

33
Q

What is special about the Translocase on the Outermitochondrial membrane?
What is its structure?

A

Translocase on outer mitochondrial membrane; a porin (beta barrel)
Many subunits

34
Q

Why is there differential distribution of amino acids in transmembrane proteins?

A

Different amino acid residues have different properties, as does the membrane

Lipophilic, hydrophobic residues (ala, val, leu, ile, phenylalanine) are found within the membrane
Hydrophilic, polar residues are on the outside
Tryptophan and tyrosine are found at the interface between the two regions

35
Q

Where are charged residues localised in the bilayer?

A

Outside

36
Q

Where are non polar residues localised in the bilayer?

A

In the fatty acid chains

37
Q

Which residues are often found at the polar/nonpolar interface?

A

Tryptophan

Tyrosine

38
Q

Washing will remove what sort of proteins?

How do we remove the other ones?

A

Washing removes peripheral proteins

Detergents are required to remove integral proteins

39
Q

Serine is the derivative of all what?

A

Glycolipids

40
Q

High cholesterol content makes the membrane more …

A

Fluid

41
Q

Membranes become more rigid as they are …

A

Cooled

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