Chapter 15

Question 1

outer leaflet mainly (2 things)

Answer 1

phosphatidylcholine + sphingomyelin.

Question 2

Inner leaflet mainly (2 things)

Answer 2

phosphatidylethanolamine + phosphatidylserine

Question 3

glycolipids are only in the _____ leaflet

Answer 3

outer

Question 4

present in about the same molar amounts as phospholipids.

Answer 4

cholesterol

Question 5

These 2 things are free to diffuse laterally within the membrane.

Answer 5

lipids, proteins

Question 6

transient structures in which specific proteins can be concentrated to facilitate interactions.

Answer 6

lipid rafts.

Question 7

two classes of membrane proteins

Answer 7

peripheral, integral

Question 8

associated with membranes through protein-protein interactions; often ionic bonds.
The bonds can be disrupted by polar reagents

Answer 8

Peripheral membrane proteins

Question 9

inserted into the lipid bilayer; they can be dissociated only by reagents that disrupt hydrophobic interactions.

Answer 9

Integral membrane proteins

Question 10

amphipathic molecules with hydrophobic and hydrophilic groups that can solubilize these proteins.

Answer 10

detergents

Question 11

integral proteins that span the lipid bilayer with portions exposed on both sides.

Answer 11

transmembrane proteins

Question 12

2 transmembrane protein exmaples

Answer 12

Glycophorin and band 3

Question 13

These are added to the C terminus of some proteins in the ER.

Answer 13

GPI anchors

Question 14

carbohydrate coat

Answer 14

Glycocalyx

Question 15

covered by microvilli that increase surface area for absorption.

Answer 15

apical surface

Question 16

mediate transfer of absorbed nutrients to the blood.

Answer 16

basolateral surface

Question 17

separate the apical and basolateral domains.

Answer 17

tight junctions

Question 18

small lipid rafts that start as invaginations of the plasma membrane, organized by caveolin.

Answer 18

Caveolae

Question 19

bind molecules on one side of the membrane, then undergo conformational changes that allow the molecule to pass through and be released on the other side.

Answer 19

carrier proteins

Question 20

form open pores through the membrane, allowing free diffusion of any molecule of the appropriate size and charge.

Answer 20

channel proteins

Question 21

transporters function by alternating between two

Answer 21

conformational states.

Question 22

Allow water molecules to cross the membrane more rapidly than they can diffuse through the phospholipid bilayers.

Answer 22

aquaporins

Question 23

open in response to binding of neurotransmitters or other signaling molecules.

Answer 23

ligand-gated channels

Question 24

open in response to changes in electric potential across the plasma membrane.

Answer 24

voltage-gated channels

Question 25

use energy from ATP hydrolysis to actively transport ions across the plasma membrane to maintain concentration gradients.

Answer 25

ion pumps

Question 26

inside of the cell is ______ with respect to the outside.

Answer 26

negative

Question 27

As nerve impulses (action potentials) travel along axons, the membrane _______

Answer 27

depolarizes

Question 28

the Na+ channel pore is too ______ for K+ or larger ions.

Answer 28

narrow

Question 29

In active transport, molecules are transported against their

Answer 29

concentration gradients.

Question 30

Ion pumps in bacteria, yeasts, and plant cells actively transport ____ out of the cell.

Answer 30

H+

Question 31

In both prokaryotic and eukaryotic cells they transport toxic substances out of the cell.

Answer 31

ABC transporters

Question 32

Uptake of glucose and Na+ is an example of transport of:

Answer 32

two molecules in the same direction.

Question 33

Phagosomes fuse with lysosomes to form

Answer 33

phagolysosomes

Question 34

uptake of extracellular fluids in large vesicles.

Answer 34

Macropinocytosis

Question 35

a mechanism for selective uptake of specific macromolecules.

Answer 35

Clathrin-mediated endocytosis

Question 36

Cholesterol is transported through the bloodstream mostly in the form of

Answer 36

low-density lipoprotein (LDL)

Question 37

After internalization, clathrin-coated vesicles shed their coats and fuse with

Answer 37

early endosomes.

Question 38

. Early endosomes have membrane H+ pumps which maintain ______ internal pH

Answer 38

acidic