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Biochemistry > Chapter 10: Membrane Transport > Flashcards

Chapter 10: Membrane Transport Flashcards

1
Q

Nonmediated transport occurs through simple

A

diffusion

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2
Q

occurs through the action of specific carriers

A

mediated transport

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3
Q

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

A

chemical potential gradient

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4
Q

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

A

nonmediated transport

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5
Q

types of Mediated transport

A

Passive-mediated transport
Active transport

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6
Q

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

A

Passive-mediated transport

or

facilitated diffusion

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7
Q

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

A

Active transport

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8
Q

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

A

carriers, permeases, channels, and transporters.

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9
Q

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.

A

Ionophores

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10
Q

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

A

valinomycin

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11
Q

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

A

Ion channels

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12
Q

Types of Ion channels

A

Mechanosensitive
Ligand-gated
Signal-gated
Voltage-gated

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13
Q

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.

A

Mechanosensitive

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14
Q

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

A

Ligand-gated

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15
Q

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

A

Signal-gated

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16
Q

channels open in response to a change in membrane potential.

A

Voltage-gated

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17
Q

cell specialized for electrical signaling

A

neuron

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18
Q

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

A

The stimulation of a neuron

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19
Q

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.

A

increase in membrane potential

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20
Q

transient change in the membrane potential

A

action
potential

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21
Q

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

A

local depolarization of the membrane

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22
Q

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

A

repolarization

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23
Q

what determines what types of substances can pass through.

A

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

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24
Q

Mediate the Transmembrane Movement of Water

A

Aquaporins

25
Q

tissues that rapidly transport
water

A

kidneys, salivary glands, and lacrimal
glands

26
Q

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

A

Aquaporins

27
Q

free passage would discharge the cell’s membrane potential.

A

protons

28
Q

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

A

Mammalian cellsmaintain

29
Q

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

A

K+ channels

30
Q

Transport Proteins Alternate between Two Conformations

A

erythrocyte glucose transporter

(also known as GLUT1)

31
Q

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

A

Voltage Gating in K+ Channels

32
Q

Types of mediated transport

A

uniport
symport
antiport

33
Q

involves the movement of a single molecule at a time.

A

uniport

34
Q

what kind of transport is Lactose permease

A

symporter

35
Q

what kind of transport is GLUT1

A

uniport

36
Q

what kind of transport is oxalate transporter

A

antiport

37
Q

simultaneously transports two different molecules in opposite directions

A

antiport

38
Q

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

A

Active transport

39
Q

Families of A TP-dependent transporters

A

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

40
Q

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

A

P-type ATPases

41
Q

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

A

F-type ATPases

42
Q

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

A

V-type ATPases

43
Q

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

A

ABC transporters

44
Q

The most thoroughly studied active transport systems is the

A

Na+–K+ –ATPase

or

(Na+–K+) pump

45
Q

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

A

antiport

46
Q

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

A

(Na+–K+) pump

47
Q

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

A

Digitalin

48
Q

triggers muscle contraction and increases the intensity of heart muscle

A

The release of Ca2+

49
Q

A TP phosphorylates the transporter only in the presence of

A

Na+

50
Q

resulting phosphorylated
aspartic residue hydrolyzes only in the presence of

A

K+

51
Q

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

A

extracellular spaces

52
Q

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

A

Ca2+–A TPase.

53
Q

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

A

Ca2+ pump

54
Q

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

A

Transient increases in cytosolic [Ca2+]

55
Q

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

A

ABC transporters

56
Q

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

A

P-glycoprotein

57
Q

Active Transport May Be Driven by Ion what?

A

gradients

58
Q

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

A

Na+ gradient

59
Q

concentrates glucose inside the cell

A

The Na+–glucose transport system

Biochemistry (17 decks)

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