Topic 4: Membrane Proteins

Question 1

Describe the types of membrane proteins based on their association with the lipid bilayer:
a. Integral transmembrane proteins (embedded)

Answer 1

a) proteins that go through to at least a hydrophobic part of the membrane
–> transmembrane: completely passes a membrane
–> not-transmembrane: only has a specific region that goes until the hydrophobic region the rest remains on the side of the polar heads

Question 2

1. Describe the types of membrane proteins based on their association with the lipid bilayer:
   b. Peripheral membrane proteins (non-covalently-associated)

Answer 2

b) proteins found on the hydrophilic ends or can attach to another protein which can go through the hydrophobic region (weak covalent bonds)

Question 3

1. Describe the types of membrane proteins based on their association with the lipid bilayer:
   c. lipid-anchored proteins

Answer 3

Proteins are only attached to a lipid (hydrocarbon). (strong covalent bond) and that lipid is what comes into contact with the membrane

protein is (GPI anchored protein and is made up of phosphatidylinositol and sugars

Question 4

What are hydropathy plots

Answer 4

Since transmembrane proteins go through hydrophobic and hydrophilic regions, the plot shows if the protein is in the hydrophobic or hydrophilic area, by showing a negative number for polar and positive number for non-polar part of the protein

Question 5

2. Describe the following aspects of integral membrane proteins:
   a. single pass vs multipass

Answer 5

a) single pass can only go through the bilayer once whereas multipass can go to the bilayer more than once

Question 6

2. Describe the following aspects of integral membrane proteins:
   c. hydrophobicity

Answer 6

Needs amphipathic ( a hydrophobic hydrophilic parts) detergent to extract it

Question 7

2. Describe the following aspects of integral membrane proteins:
   d. lateral movement

Answer 7

d) proteins need to move laterally in order to ensure they move when they’re needed

Question 8

What is FRAP

Answer 8

Fluorescence recovery after photobleaching: fluorescence molecule is attached to proteins and when a random region is bleached eventually the proteins move to cover up the region that was bleached

Question 9

Single Particle tracking

Answer 9

A protein gets a fluorescent molecule and live footage of it moving as shown. we can see the proteins on top and bottom of Polar cells junctions try to restrict proteins coming in and out

Question 10

What do Detergents do

Answer 10

Integral proteins are deep in the membrane I need detergent to make the protein more soluble, once it’s water soluble it can become a vesicle, for sodium and potassium to move through