Membrane Structure

Question 1

What are peripheral proteins?

Answer 1

not embedded in the lipid bilayer (don’t penetrate bilayer)
temporarily attached by non-covalent interactions

Question 2

What are integral proteins?

Answer 2

penetrate the hydrophobic core
often completely spanning the membrane (a transmembrane protein)

Question 3

Integral protein examples?

Answer 3

a-helix, helical bundle, b-barrel

Question 4

What are peripheral protein examples?

Answer 4

Enzymes, Anchorage, transporters (carriers)

Question 5

What is the purpose of steroid cholesterol in the phospholipid bilayer?

Answer 5

acts as a “temperature buffer” to maintain membrane fluidity over a range of temperatures

warm = restrains phospholipids and reduces fluidity.
cool = maintains fluidity by preventing tight packing.

Question 6

What was the Davson-Danielli Model?

Answer 6

the lipid layer was sandwiched between two protein layers

Question 7

What were some problems with the davson-Danielli model?

Answer 7

It assumed all membranes were of a uniform thickness and would have a constant lipid-protein ratio
It assumed all membranes would have symmetrical internal and external surfaces (i.e. not bifacial)
It did not account for the permeability of certain substances (did not recognise the need for hydrophilic pores)
The temperatures at which membranes solidified did not correlate with those expected under the proposed model