MCB Lecture 9 Lipids and Bilayers

Question 0

What are the three features of lipid Bilayers?

Answer 0

1. Amphipathic
2. Asymmetrical
3. Variable fluidity

Question 1

Describe lipid Bilayers’ role in compartmentalisation

Answer 1

Lipid bilayer provides a physical barrier -> compartments

These compartments can have different properties and conditions

Question 2

Describe how the lipid bilayer is amphipathic

Answer 2

The head is hydrophilic

The fatty acid tails are hydrophobic

Question 3

Describe the structure of a phospholipid

Answer 3

Phosphate head
Glycerol

Two fatty acid chains (hydrocarbons)

Question 4

Draw the structure of cholesterol

Answer 4

.

Question 5

Describe how lipid Bilayers have variable fluidity

Answer 5

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

Question 6

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

Answer 6

Decrease

Question 7

Cholesterol lead to … of ordered packing

Answer 7

Decrease

Question 8

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

Answer 8

Decrease

Question 9

Reduction of ordered packing leads to …

Answer 9

Membrane sets at a lower sptemp

Question 10

Describe how the lipid bilayer is asymmetric

Answer 10

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

Question 11

Glycolipids are almost always found … ?

Answer 11

On the outside of the cell

Question 12

Where is Phosphotidyl-Serine almost always found?

What is its charge?

Answer 12

Inside

Negatively charged

Question 13

What is important about phosphotidyl-inositols in the membrane?

Answer 13

These are important parts of signal transduction pathways

Question 14

What is the structure of lipid rafts?

Answer 14

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

Question 15

What is the function of lipid rafts?

Answer 15

These provide regions for membrane proteins to reside and be localised

Question 16

Lipid rafts are resistant to what?

Answer 16

Detergent

Question 17

Are lipid rafts dynamic or static?

Answer 17

Dynamic

Question 18

Describe the structure of sterols in terms of polarity

Answer 18

Sterols have a tiny polar group (-OH)

Rigid steroid ring structure

Non polar aliphatic chain

Question 19

What is a glycolipid?

Answer 19

Sugar associated with fatty acid chains

Question 20

What is a sphingolipid? Where is it usually found?

Answer 20

Sphingolipids are usually found in lipid rafts

They are long, saturated, fatty acids

Question 21

What type of molecule is a galactocerebroside?

Answer 21

Glycolipid

Question 22

What type of molecule is a ganglioside?

Answer 22

Glycolipid

Question 23

From what are all animal glycolipids a derived?

Answer 23

Serine

Question 24

What are the two types of membrane proteins?

Answer 24

Integral and peripheral

Question 25

What are the requirements for integral membrane proteins?

Answer 25

They must have some part attached or within the membrane Need detergent to remove it

Question 26

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

Answer 26

Amphipathic: Hydrophobic stripe embedded (long ways) Transmembrane, hydrophobic residues

Question 27

What are peripheral proteins. For example...?

Answer 27

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

Question 28

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

Answer 28

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

Question 29

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

Answer 29

Beta barrels - porins Helices

Question 30

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

Answer 30

20-30 residues | Hydrophobic side chains within the membrane

Question 31

What are the features of transmembrane b-proteins? | How does the structure interact with the hydrophobic lipids?

Answer 31

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

Question 32

What are porins? | Describe their presence in prokaryotes and eukaryotes.

Answer 32

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

Question 33

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

Answer 33

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

Question 34

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

Answer 34

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

Question 35

Where are charged residues localised in the bilayer?

Answer 35

Outside

Question 36

Where are non polar residues localised in the bilayer?

Answer 36

In the fatty acid chains

Question 37

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

Answer 37

Tryptophan | Tyrosine

Question 38

Washing will remove what sort of proteins? How do we remove the other ones?

Answer 38

Washing removes peripheral proteins Detergents are required to remove integral proteins

Question 39

Serine is the derivative of all what?

Answer 39

Glycolipids

Question 40

High cholesterol content makes the membrane more ...

Answer 40

Fluid

Question 41

Membranes become more rigid as they are ...

Answer 41

Cooled