Membranes

Question 1

What are the most abundant types of lipids in membranes?

Answer 1

Palmitate (16C) - Glycerophospholipid
Oleate (18C) - Glycerophospholipid
Cholesterol - Sterol

Question 2

Importance of cholesterol in membranes

Answer 2

Without it cell membranes would be too fluid, not firm enough, and too permeable to molecules
Provides RIDGIDITY

Question 3

Cell membrane selective permeability

Answer 3

Hydrophobic Molecules - Highly Permeable (O2, CO2, N2)
SM uncharged polar - Slightly permeable (H2O, glycerol, indole)
LG uncharged polar - Impermeable (glucose, sucrose)
Ions - Impermeable (Cl-, K+, Na+) why? CHARGE

Question 4

Types of Membrane Proteins

Answer 4

Transmembrane
Integral
Peripheral
Associate Membrane 
Anchored

Question 5

Transmembrane Proteins

Answer 5

Touch both intracellular and extracellular surface of membrane (all the way through and out both sides)
Can move freely throughout bilayer
Removed with detergent only

Question 6

Integral Proteins

Answer 6

Embedded within the membrane but don’t transverse entire bilayer.
Removed with detergents

Question 7

Peripheral Proteins

Answer 7

Attached to exterior surface of bilayer, not the membrane itself. Can’t move laterally in membrane
Easily removed without membrane damage via SHAKING or PH CHANGE
Includes Associate Membrane and anchored

Question 8

Associate Membrane Proteins

Answer 8

Doesn’t touch the membrane at all, usually attached to peripheral/other proteins in the bilayer.

Question 9

Anchored Proteins

Answer 9

Have a “tail” that holds onto one side of the bilayer. Anchors them to the membrane

Question 10

Type I Integral Proteins

Answer 10

Crosses membrane once

C-terminus inside, N-terminus outside

Question 11

Type II Integral Protein

Answer 11

Crosses membrane once

C-terminus outside, N-terminus inside

Question 12

Type III Integral Protein

Answer 12

A single peptide crosses the membrane many times

Question 13

Type IV Integral Protein

Answer 13

Anchored to the lipid bilayer through covalently linked lipids

Question 14

Type V Integral Protein

Answer 14

Several different polypeptides assembled together in a channel through the membrane

Question 15

Type VI (6) Integral Protein

Answer 15

Single peptide has both a transmembrane domain AND a lipid anchor

Question 16

Composition of a Cell Membrane

Answer 16

Composition will change based on function of the organ/cell/organelle etc
Example:
Most plasma proteins are synthesized in the liver so they have more proteins than phospholipids.
Example: Mitochondria have hardly any cholesterol but lots of cardiolipin, plasma membrane has lots of cholesterol but no cardiolipin!

Question 17

Carbohydrates on membranes

Answer 17

Act as “antennae” for cell signaling