Chapter 12. Lipids and Cell Membranes

Question 1

a sterol that is an important constituent of eukaryotic membranes as well as lipoproteins; also a precursor of steroid hormones.

Answer 1

Cholesterol

Question 2

a ceramide, common in membranes of the nervous system, in which an oligosaccharide is linked to the ceramide by a glucose residue.

Answer 2

Ganglioside

Question 3

a sphingolipid in which glucose or galactose is linked to the terminal hydroxyl of a ceramide.

Answer 3

Cerebroside

Question 4

sugar-containing lipids that are derived from sphingosine. The sugar moiety is attached at the alcohol on sphingosine.

Answer 4

Glycolipid

Question 5

Phospholipids constructed on a glycerol backbone.

Answer 5

Phosphoglyceride

Question 6

carboxylic acids containing long hydrocarbon chains that are an important fuel source as well as a key component of membrane lipids.

Answer 6

Fatty acid

Question 7

a molecule, such as a membrane lipid, that contains both a hydrophobic and hydrophilic moiety.

Answer 7

Amphipathic (amphiphilic) molecule

Question 8

a bimolecular sheet formed by amphipathic molecules in which the hydrophobic moieties are on the inside of the sheet and the hydrophilic ones are on the aqueous outside.

Answer 8

Lipid bilayer

Question 9

lipid vesicles in which an aqueous region is enclosed by a lipid bilayer

Answer 9

Liposome

Question 10

important constituents of membranes, composed of three components: a backbone (usually glycerol or sphingosine), two fatty acid chains, and a phosphorylated alcohol.

Answer 10

Phospholipid

Question 11

the description of membranes as two-dimensional solutions of oriented lipids and globular proteins.

Answer 11

Fluid mosaic model

Question 12

A protein that coats the cytosolic side of coated pits and can form a lattice around the pit, excising it from the membrane to form a coated vesicle.

Answer 12

Clathrin

Question 13

An intracellular membrane vesicle that is a component of receptor-mediated endocytotic pathways. The endosome is formed when the plasma membrane in the vicinity of the cargo-receptor complex invaginates . The endosome is acidified, which causes the receptor to release its cargo. The receptor is then returned to the cell membrane.

Answer 13

Endosome

Question 14

proteins found in membranes that interact extensively with the hydrocarbon chains of the membrane lipids and usually span the membrane.

Answer 14

Integral membrane protein

Question 15

a sphingolipid common in brain tissue in which the terminal hydroxyl group of ceramide has a phosphorylcholine substituent.

Answer 15

Sphingomyelin

Question 16

a means of determining transmembrane sequences in proteins by measuring the change in free energy required to move a 20-amino acid segment of the protein from a hydrophobic environment to water. The free-energy change is plotted against the position of the 20-amino acid sequence in the protein.

Answer 16

Hydropathy plot

Question 17

proteins that are associated with the surface of membranes by electrostatic and hydrogen bond interactions.

Answer 17

Peripheral membrane protein

Question 18

Membrane structures that result when cholesterol forms specific complexes with sphingolipids, certain glycolipids, and specific GPI-anchored proteins. These complexes concentrate within small (10-200 nm) and highly dynamic regions within membranes.

Answer 18

Lipid raft

Question 19

the ability of lipid and protein molecules to move laterally in the membrane rapidly and spontaneously.

Answer 19

Lateral diffusion

Question 20

a means of importing specific proteins into a cell by their binding to plasma membrane receptors and their subsequent endocytosis and inclusion into vesicles.

Answer 20

Receptor-mediated endocytosis

Question 21

an amino alcohol containing a long, unsaturated hydrocarbon chain that is a component of the phospholipid sphingomyelin as well as glycolipids; serves a role analogous to glycerol in phosphoglycerides.

Answer 21

Sphingosine

Question 22

A transport protein that carries iron in the blood serum.

Answer 22

Transferrin

Question 23

(soluble N-ethylmaleimide-sensitive-factor attachment protein receptor proteins) Membrane proteins that help draw appropriate membranes together to initiate the membrane fusion process.

Answer 23

SNARE (soluble N-ethylmaleimide-sensitive-factor attachment protein receptor) proteins

Question 24

A membrane protein that binds iron-loaded transferrin and initiates its entry into cells.

Answer 24

Transferrin receptor