Chapter 12 Flashcards by Mia Sassano

Lipid bilayers are impermeable to

Solutes and ions

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Membrane transport proteins fall into two classes:

transporters and channels

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Solutes cross membrane by either

Passive or active transport

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What concentrations are high outside the cell

Na, Cl, Mg, Ca

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What concentration is high inside the cell

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The rate at which a molecule crosses a lipid bilayer depends on its

Size and solubility

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Membranes are permeable to

Small, hydrophobic and uncharged molecules

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Membranes less permeable to

Large, polar molecules and ions

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change shape to move solutes

Transporters

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Can be passive or active

Transporters

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Function as pores

Ion channel

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Ion channels are always

Passive

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What gradient drives transport

Electrochemical

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Movement of charged molecules depends on

Both the concentration and electrical gradient

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Transitions between conformations are

Random, reversible, and don’t depend on solute binding

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move solutes across the membrane
along their electrochemical gradients (no ATP required)

Passive transporters

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actively transport solutes against their
electrochemical gradients (requires an input of energy, like ATP)

Pumps

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use a gradient of one solute across a
membrane to drive the active transport of a second molecule

Coupled pumps

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Glucose transporter mediates

Passive transport

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Because __ is uncharged, the electrical component of its electrochemical gradient is zero.

glucose

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transport moves solutes against their electrochemical
gradients (e.g., moving Na + out of the cell)

Active

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Animal cells use __ to pump Na + out and K+ in

ATP Hydrolysis

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The __ is driven by a cycle of phosphorylation and dephosphorylation

Na+-K+ pump

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helps maintain the osmotic balance of animal cells

Na+-K+ pump

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Intracellular Ca2+ concentrations are kept

Low by Ca pumps (driven by atp hydrolysis)

The Glucose-Na+ symport is a

Coupled pump

uses energy from transporting Na+ along its electrochemical gradient to transport glucose against its gradient

Glucose Na symport

drive membrane transport in plants, fungi, and bacteria

Proton (H+) pumps

Na K pump, pumps what in and out

3 Na out and 2 K ions against gradients

__ drives conformational changes

Phosphorylation

Ca2+ ATPase/pump reduces

cytosolic calcium

Ca2+ ATPase/pump located in the

ER membrane and membrane

Cytosolic levels must be kept

Low

Calcium concentration important for

Cell signaling

A gradient of any solute across a membrane can be used to drive the active transport of a second molecule

Coupled pumps

use ion gradients to drive the active transport of two solutes in the same or opposite direction

Symport & antiport

passive transport of one solute

Uniport

Coupled transporters use __ to take up nutrients actively

ion gradients

Glucose-Na+ symport in apical membrane

Active

Glucose uniport in basal membrane

Passive

Na+-K+ pump maintains ion gradients by hydrolyzing ATP

Active

What determines the direction of passive transport across the membrane?

The electrochemical gradient of the solute

Pumps actively transport solutes __ their electrochemical gradients

against

couples the transport of one solute against its electrochemical gradient with the transport of another solute along its electrochemical gradient

Gradient driven/coupled

Three types of active transport

Gradient driven, atp driven, or light driven

uses energy from ATP hydrolysis

ATP driven

2 types of gradient-driven pumps, based on the direction of coupled transport:

Symport and aniport

Glucose transporter is __ and an example of a __

Passive, uniport

Active transporters atp driven

Na/K, Ca ATPase and H pump

Ca2+ ATPase moves what

2 ions out of cell or into the ER

Active transporters gradient driven

Glucose Na symport

The movement of an ion down its electrochemical gradient is a form of active transport. T or F

False, passive

Coupled transporters use electrochemical gradients to drive active transport of other solutes. T or F

True

The transport of glucose across the membrane can be active or passive, depending on the nature of the transporter. T or F

True, active is glucose sodium symport and passive is glucose transporter

Ion channels are

selective and gated

Ion channels randomly...

snap between open and closed

VG ion channels respond to the

membrane potential

Small pores that filter ions by size and charged

ion channel

The frequency of opening and closing of an ion channel depends on the

presence of a specific stimulus

what channel responds to neurotransmitters binding

ligand gated

what channel responds to mechanical stimulus

mechanically or stress gated channel

What accounts for RMP

K leak channels

if a membrane is permeable to an ion, then the membrane potential is

determined by the Nernst equation

The nerst equation is dependant on the

ratio of ion concentration outside vs. inside

In a resting cell, the Nernst equation is determined by

In the ear, sound vibrations on auditory hair cells opens what channel

stress gated ion channels, leading to AP

Tilting the stereocilia in the ear in response to sound vibrations has what effect

pulls on linking filament, opening ion channel

Action potentials are usually mediated by

voltage-gated Na+ channels

Voltage-gated Ca2+ channels convert

electrical signals into chemical signals at nerve terminals

Ligand-gated channels in target cells convert

chemical signals back into electrical signals

Neurons receive what kind of inputs

excitatory and inhibitory

major targets for psychoactive drugs

Ligand-gated ion channels (transmitter)

Action potentials are converted into __ signals via the release of neurotransmitters at the nerve terminal

electrical converted into chemical

When a neuron is stimulated, the membrane potential of the plasma membrane shifts to a

less negative value

After opening, Na+ channels rapidly become

inactivated

The Na+ channels remain in the inactivated state until the

membrane potential has returned to its resting, negative value

Action potential only moves in

1 direction

prevents the action potential from moving backwards

Na+ channel inactivation

channels at nerve terminals of pre-synaptic cell

Voltage-gated Ca2+

Convert electrical signal (ions from the action potential) to a chemical signal (neurotransmitter)

voltage gated calcium channels

The acetylcholine (Ach) receptor is a

transmitter-gated ion channel

After Ach binds to a channel what happens

influx of sodium, causing AP

Influx of __ tends to keep the membrane polarized, decreasing firing of an action potential

Cl, inhibitory synapse

Excitatory synapse has what ion

sodium

Acetylcholine and glutamate are __ neurotransmitters, bind __ channels

excitatory, ligand-gated cation

GABA and glycine are __, bind __ channels

inhibitory, ligand-gated Cl-

Chapter 12 Flashcards

(86 cards)