Chapter 11: Membrane Structure

Question 1

Three types of lipid motions

Answer 1

Lateral diffusion
Rotation
Flexion
Rare: flip flop

Question 2

How do membrane proteins associate with lipid bilayers

Answer 2

1. Transmembrane
2. Membrane associated
3. Lipid linked
4. Protein attached

1-3 integral, 4 peripheral

Question 3

Process of phospholipid after synthesis from ER

Answer 3

• Membrane asymmetry is established during synthesis in the ER
• scramblases flip phospholipids from one face to the other in ER
• Flippases move specific phospholipids from extracellular face in golgi. Flop ashes move the phospholipids in the opposite direction.
• Membrane assembled at ER is exported by vesicle budding. Cytosolic face at ER remains the cytosolic face.

Question 4

Phospholipid enzymes

Answer 4

Scramblases: flip phospholipids to a different side

Flippases: move phospholipids from outside layer to the inside

Flopases: Move phospholipids from inside layer to outside

Question 5

Membrane associates carbohydrates

Answer 5

Protect the cell from chemical and mechanical damage
Lubrication
Cell-cell recognition

Composed of:
Glycoproteins, proteoglycan, glycolipid

Question 6

Chemical composition of membranes

Answer 6

Composition includes
Lipids (phospholipids and cholesterol)
Proteins
Carbohydrate groups

Question 7

How do cells restrict the movement of membrane proteins

Answer 7

The association with the cytoskeleton. Such as being bound.

Question 8

How does the amino acid composition on the surface of a protein determine whether it is an integral proteins

Answer 8

If the alpha helix contains many nonpolar amino acids, it can span a membrane bilayer

The hydrophobic polypeptide backbone (stabilized by H bonds) is shielded from hydrophobic lipid hydrocarbons.

Question 9

How do detergent molecules “breakup” lipid vesicles

Answer 9

Detergents separate integral proteins from lipid bilayer

• They disrupt hydrophobic associations
• a membrane protein can be combined with a detergent Michelle. The product of this is a water-soluble complexes of transmembrane protein and detergent + water soluble mixed lipid detergent micelles.

Question 10

How can integral membranes be removed from membrane?

Answer 10

Removed by detergents.

Question 11

Properties of detergents

Answer 11

Amphipathic
Single hydrophobic chain
Do not form bilayers
Mono layer micelles

Question 12

FRAP experiments

Answer 12

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Question 13

Why can some proteins freely go through membranes

Answer 13

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