Lecture 6

Question 1

Fluid Mosaic Model

Answer 1

A fluid lipid bilayer with the main classes of membrane lipids beings phospholipids, glycolipids and sterols; plus a mosaic of proteins attached to or embedded in the bilayer.
Permits random and rapid movement of lipids and proteins.

Question 2

FRAP

Answer 2

Fluorescence Recovery After Photobleaching, technique used to illustrate lateral diffusion.

Question 3

Membrane Asymmetry

Answer 3

Difference in between the two monolayers of the membrane, established during the synthesis of the membrane.

Question 4

Phospholipids

Answer 4

The most abundant lipids in membrane, includes the glycerol-based phosphoglycerides and sphingosine-base sphingophospholipids

Question 5

Glycolipids

Answer 5

Formed by the addition of carbohydrates to lipids, found on the outer surface of eukaryotic cell membranes, used in cell adhesion and cellular identity

Question 6

Transition Temperature

Answer 6

The temperature at which a lipid bilayer becomes a fluid, depends mainly on the fatty acids present (both their length and degree of saturation)

Question 7

Desaturase

Answer 7

Enzyme which introduces double donds into fatty acids, used to increase membrane fluidity in cold temperatures

Question 8

TLC

Answer 8

Thin Layer Chromatography, used to separate different kinds of lipids based on their relative polarities

Question 9

Integral Membrane Proteins

Answer 9

Proteins that possess one or more hydrophobic region that is inserted into the lipid bilayer, difficult to remove, contain a large amount of alpha helix structure

Question 10

Peripheral Membrane Proteins

Answer 10

Membrane associated proteins that do not have a domain that spans the lipid bilayer, bound to the membrane surface through weak electrostatic forces and hydrogen bonds, easy to remove by changing pH or ionic strength

Question 11

Lipid-Anchored Membrane Proteins

Answer 11

Proteins that are covalently bound to lipid molecules that can be embedded in the lipid bilayer

Question 12

Fatty Acid Anchored Membrane Proteins

Answer 12

Proteins attached to a saturated fatty (either myristic acid or palmitique acid), strongly associated with the plasma membrane

Question 13

Isoprenylated Membrane Proteins

Answer 13

Proteins that are synthesized in the cytosol and then modified by the addition of multiple isoprenyl groups (farnesyl or geranygeranyl), reversibly associated with the membrane

Question 14

Glycoproteins

Answer 14

Proteins with carbohydrate chains covalently linked to amino acid side chains, can be soluble or membrane anchored, used for cell-cell recognition (carbohydrate groups protrude on the outer surface of the cell membrane)

Question 15

Glycosylation

Answer 15

The addition of a carbohydrate side chain to a protein, occurs in the ER and Golgi compartments

Question 16

Lipid Rafts

Answer 16

Localized regions of membrane lipids in association with specific proteins, often have elevated levels of cholesterol and are less fluid than the rest of the membrane