Lecture 2.3

Question 1

Lipid rafts: what are they, how do we know they need cholesterol, what is the umbrella hypothesis, and what lipid is favoured to be used alongside cholesterol?

Answer 1

Lipid microdomains - regulate interactions with other membrane components (protein interactions, signalling interactions, etc)

Drugs that eliminate cholesterol cause break up of rafts

Neighbouring lipids ‘protect’ cholesterol as its small head group is not sufficient to shield from water

Sphingolipids - large headgroups, saturated tails (tighter packing)

Less fluid lipid microdomains that are typically more packed

Question 2

FRAP

Answer 2

Uses fluorescent tags to monitor lipid movement

Question 3

Cell membrane proteins: what do they do?

Answer 3

Involved in every membrane function excluding the basic barrier function of lipids

• Transporters/channels
• Anchors
• Receptors
• Enzymes
• Transmembrane proteins
• Surface-bound proteins
• Peripheral membrane proteins

Question 4

Transmembrane proteins

Answer 4

Span the bilayer

Connect two aqueous compartments

Can function as transporters, receptors, adhesion molecules, and enzymes

Question 5

Surface-bound proteins

Answer 5

Don’t span the entire membrane

Monotopoic - membrane-embedded, anchors proteins with nearest monolayer

Lipid-anchored - outside of hydrophobic core but have a lipid anchor to hold them

Question 6

Peripheral membrane protiens

Answer 6

Associate to the membrane using lipid head groups and/or ionic attraction etc