Chapter 10: Membrane Transport

Question 1

Nonmediated transport occurs through simple

Answer 1

diffusion

Question 2

occurs through the action of specific carriers

Answer 2

mediated transport

Question 3

The driving force for the nonmediated flow of a substance through a medium is what

Answer 3

chemical potential gradient

Question 4

Consequently, nonpolar molecules such as steroids and O2 readily diffuse through biological membranes by

Answer 4

nonmediated transport

Question 5

types of Mediated transport

Answer 5

Passive-mediated transport
Active transport

Question 6

in which a specific molecule flows
from high concentration to low concentration.

Answer 6

Passive-mediated transport

or

facilitated diffusion

Question 7

in which a specific molecule is transported from low concentration to high concentration, that is, against its concentration gradient. Such an endergonic process must be coupled to a sufficiently exergonic process to make it favorable

Answer 7

Active transport

Question 8

Substances that are too large or too polar to diffuse across lipid bilayers on their own may be conveyed across membranes via proteins or other molecules that are variously
called

Answer 8

carriers, permeases, channels, and transporters.

Question 9

are organic molecules of diverse
types, often of bacterial origin, that increase the permeability of membranes to ions. These molecules often exert an antibiotic
effect.

Answer 9

Ionophores

Question 10

transports up to 104 K+ ions per second across a membrane. It has 10,000-fold greater binding affinity for K+ than for Na+

Answer 10

valinomycin

Question 11

are normally shut and only open transiently to perform some specific task for the cell

Answer 11

Ion channels

Question 12

Types of Ion channels

Answer 12

Mechanosensitive
Ligand-gated
Signal-gated
Voltage-gated

Question 13

channels open in response to local deformations in the lipid
bilayer. Consequently, they respond to direct physical stimuli such as touch, sound, and changes in osmotic pressure.

Answer 13

Mechanosensitive

Question 14

channels open in response to an extracellular chemical stimulus such as a neurotransmitter

Answer 14

Ligand-gated

Question 15

channels open on intracellularly binding a Ca 2+ ion or some other
signaling molecule.

Answer 15

Signal-gated

Question 16

channels open in response to a change in membrane potential.

Answer 16

Voltage-gated

Question 17

cell specialized for electrical signaling

Answer 17

neuron

Question 18

causes Na+ channels to open so that Na+ ions spontaneously flow into the cell.

Answer 18

The stimulation of a neuron

Question 19

induces neighboring voltage-gated Na+ channels to open causing the action potential to travel (10 m/s) in one direction along the length of the nerve cell.

Answer 19

increase in membrane potential

Question 20

transient change in the membrane potential

Answer 20

action
potential

Question 21

induces nearby voltage-gated K+
channels to open. This allows K+ ions to spontaneously flow out of the cell

Answer 21

local depolarization of the membrane

Question 22

allowing the K+ ions to spontaneously flow out of the cell

Answer 22

repolarization

Question 23

what determines what types of substances can pass through.

Answer 23

the size of the central aqueous channel and the residues that form its walls

Question 24

Mediate the Transmembrane Movement of Water

Answer 24

Aquaporins

Question 25

tissues that rapidly transport water

Answer 25

kidneys, salivary glands, and lacrimal glands

Question 26

permit the passage of water molecules at an extremely high rate but do not permit the transport of solutes or ions, including, most surprisingly, protons

Answer 26

Aquaporins

Question 27

free passage would discharge the cell's membrane potential.

Answer 27

protons

Question 28

a nonequilibrium distribution of ions on either side of the plasma membrane

Answer 28

Mammalian cellsmaintain

Question 29

Potassium ions passively diffuse from the cytoplasm to the extracellular space through transmembrane proteins known as

Answer 29

K+ channels

Question 30

Transport Proteins Alternate between Two Conformations

Answer 30

erythrocyte glucose transporter (also known as GLUT1)

Question 31

It is triggered by the motion of a positively charged protein helix

Answer 31

Voltage Gating in K+ Channels

Question 32

Types of mediated transport

Answer 32

uniport symport antiport

Question 33

involves the movement of a single molecule at a time.

Answer 33

uniport

Question 34

what kind of transport is Lactose permease

Answer 34

symporter

Question 35

what kind of transport is GLUT1

Answer 35

uniport

Question 36

what kind of transport is oxalate transporter

Answer 36

antiport

Question 37

simultaneously transports two different molecules in opposite directions

Answer 37

antiport

Question 38

is an endergonic process that, in most cases, is coupled to the hydrolysis of ATP

Answer 38

Active transport

Question 39

Families of A TP-dependent transporters

Answer 39

P-type ATPases F-type ATPases V-type ATPases A-type ATPases ABC transporters

Question 40

undergo phosphorylation as they transport cations such as Na+, K+, and Ca2+ across the membrane

Answer 40

P-type ATPases

Question 41

are proton-transporting complexes located in mitochondria and bacterial membranes. Instead of using the free energy of A TP to pump protons against their gradient, these proteins operate in reverse in order to synthesize ATP

Answer 41

F-type ATPases

Question 42

resemble the F-typeA TPases and occur in plant vacuoles and acidic vesicles such as animal lysosomes

Answer 42

V-type ATPases

Question 43

are named for their A TP-binding cassette and transport a wide variety of substances, including ions, small metabolites, and drug molecules

Answer 43

ABC transporters

Question 44

The most thoroughly studied active transport systems is the

Answer 44

Na+–K+ –ATPase or (Na+–K+) pump

Question 45

what kind of transport is Na+–K+ –ATPase

Answer 45

antiport

Question 46

pumps Na+ out of and K+ into the cell with the concomitant hydrolysis of intracellular ATP .

Answer 46

(Na+–K+) pump

Question 47

is one the most commonly prescribed cardiac drugs which inhibits the (Na+–K+)–ATPase. This causes an increase in intracellular [Na+] which stimulates the cardiac (Na+–Ca2+) antiport system to pump Na+ out of and Ca2+ into the cell

Answer 47

Digitalin

Question 48

triggers muscle contraction and increases the intensity of heart muscle

Answer 48

The release of Ca2+

Question 49

A TP phosphorylates the transporter only in the presence of

Answer 49

Na+

Question 50

resulting phosphorylated aspartic residue hydrolyzes only in the presence of

Answer 50

K+

Question 51

The [Ca2+] in the cytosol (~0.1 μM) is four orders of magnitude less than it is in the

Answer 51

extracellular spaces

Question 52

This large concentration gradient is maintained by the active transport of Ca2+ across the plasma membrane and the endoplasmic reticulum by a

Answer 52

Ca2+–A TPase.

Question 53

actively pumps two Ca2+ ions out of the cytosol at the expense of ATP hydrolysis, while countertransporting 2 or 3 protons

Answer 53

Ca2+ pump

Question 54

trigger numerous cellular responses including muscle contraction, the release of neurotransmitters, and glycogen breakdown.

Answer 54

Transient increases in cytosolic [Ca2+]

Question 55

pump ions, sugars, amino acids, and other polar and nonpolar substances.

Answer 55

ABC transporters

Question 56

a member of the ABC class of transporters, pumps a variety of amphiphilic substances—including many drugs—out of the cell.

Answer 56

P-glycoprotein

Question 57

Active Transport May Be Driven by Ion what?

Answer 57

gradients

Question 58

The immediate energy source for this “uphill” transport process is the what?

Answer 58

Na+ gradient

Question 59

concentrates glucose inside the cell

Answer 59

The Na+–glucose transport system