Chapter 11

Question 1

Having both hydrophobic and hydrophilic regions, as in a phospholipid or a detergent molecule.

Answer 1

amphipathic

Question 2

Pigmented protein found in abundance in the plasma membrane of the salt-loving archaeon Halobacterium halobium; pumps protons out of the cell in response to light.

Answer 2

bacteriorhodopsin

Question 3

Short, rigid lipid molecule present in large amounts in the plasma membranes of animal cells, where it makes the lipid bilayer less flexible.

Answer 3

cholesterol

Question 4

Soapy substance used to solubilize membrane proteins.

Answer 4

detergent

Question 5

Protective layer of carbohydrates on the outside surface of the plasma membrane formed by the sugar residues of membrane glycoproteins, proteoglycans, and glycolipids.

Answer 5

glycocalyx

Question 6

Functionally and structurally specialized region in the membrane of a cell or organelle; typically characterized by the presence of specific proteins.

Answer 6

membrane domain

Question 7

A protein associated with the lipid bilayer of a cell membrane.

Answer 7

membrane protein

Question 8

Common phospholipid present in abundance in most cell membranes; uses choline attached to a phosphate as its head group.

Answer 8

phosphatidylcholine

Question 9

A major type of lipid molecule in many cell membranes. Generally composed of two fatty acid tails linked to one of a variety of phosphate-containing polar groups.

Answer 9

phospholipid

Question 10

Describes an organic molecule that contains a full complement of hydrogen; in other words, no double or triple carbon–carbon bonds.

Answer 10

saturated

Question 11

Describes an organic molecule that contains one or more double or triple bonds between its carbon atoms.

Answer 11

unsaturated

Question 12

Protective layer of sugar residues, including the polysaccharide portions of proteoglycans and oligosaccharides attached to protein or lipid molecules, on the outer surface of a cell. Also called the glycocalyx.

Answer 12

carbohydrate layer

Question 13

The space inside a hollow or tubular structure; can refer to the cavity in a tissue or within an organelle.

Answer 13

lumen

Question 14

Water molecules readily form hydrogen bonds with other polar molecules, and when they encounter nonpolar molecules they must form hydrogen-bonding networks with neighboring water molecules. Which of the following molecules will cause a “cage” of water to form?

Answer 14

2-methylpropane

Question 15

The endothelial cells found closest to the site of an infection express proteins called lectins. Each lectin binds to a particular ____________ that is presented on the surface of a target cell.

Answer 15

oligosaccharide

Question 16

Water molecules readily form hydrogen bonds with other polar molecules, and when they encounter nonpolar molecules they must form hydrogen-bonding networks with neighboring water molecules. Which of the following molecules will cause a “cage” of water to form?

Answer 16

2-methylpropane

Question 17

Cholesterol serves several essential functions in mammalian cells. Which of the following is not influenced by cholesterol?

Answer 17

membrane thickness

Question 18

There are two properties of phospholipids that affect how tightly they pack together: the length of the hydrocarbon chain and the number of double bonds. The degree of packing, in turn, influences the relative mobility of these molecules in the membrane. Which of the following would yield the most highly mobile phospholipid (listed as number of carbons and number of double bonds, respectively)?

Answer 18

15 carbons with 2 double bonds

Question 19

A group of membrane proteins can be extracted from membranes only by using detergents. All the proteins in this group have a similar amino acid sequence at their C-terminus: -KKKKKXXC (where K stands for lysine, X stands for any amino acid, and C stands for cysteine). This sequence is essential for their attachment to the membrane. What is the most likely way in which the C-terminal sequence attaches these proteins to the membrane?

Answer 19

The cysteine residue is covalently attached to a membrane lipid.

Question 20

The amino acid sequences below represent the sequences of transmembrane helices. The characteristics (hydrophobic, amphipathic etc.)of α helices that form a channel that contains a pore are different from those that form a single transmembrane domain. Select the helix that forms a single transmembrane domain.

Answer 20

IMIVLVMLLNIGLAILFVHF

Question 21

Diversity among the oligosaccharide chains found in the carbohydrate coating of the cell surface can be achieved in which of the following ways?

Answer 21

varying the types of sugar monomers used, varying the types of linkages between sugars, varying the number of branches in the chain