4. Membrane Transport Flashcards by huh? yunjin.

transferring specific water-soluble molecules and ions across their membranes

membrane transport proteins

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allowing passive transmembrane movement, primarily of water and small inorganic ions. interact with the solute to be transported much weaklier

Channels

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Passive transport

downhill

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2 active transport

Secondary active transport
Primary transport

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undergo sequential conformational changes to transport specific small molecules across membranes

transporters

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Active transport

Uphill and uses ATP

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2 passive transport

Passive diffusion
Facilitated diffusion

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cannot transport certain amino acids (including cystine, the disulfide-linked dimer of cysteine) from either the urine or the intestine to the blood

cystinuria

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their polypeptide chains traverse the lipid bilayer multiple times

multi pass transmembrane proteins

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impermeable to ions

Lipid bilayers

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“uphill”, against their electrochemical gradients

Active transport

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uncharged molecule

concentration gradient

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charged molecule

membrane potential

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intermediate state, inaccessible

occluded

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negative insided

electrical potential

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three principal classes of ATP-driven pumps

P-type pumps
ABC transporters
V-type pumps

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energy stored in concentration gradients

coupled transport

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energy from light

light- or redox-driven pumps

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hydrolysis of ATP

ATP-driven pumps

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passive transport,

Uniporters

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structurally and functionally related multipass trans membrane proteins. they phosphorylate themselves during the pumping cycle

P-type pumps

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transfer of one solute depends on the transport of a second

coupled transporters

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e the free energy of ATP hydrolysis is used to directly drive the transport of a solute against its concentration gradient.

primary active transport

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transfer in the same direction

Symporters (co-transporters)

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transfer in opposite direction

Antiporters (exchangers)

co-transported ion

Na+

The Na+ that enters the cell during coupled transport is sub sequently pumped out by an _____

ATP-driven Na+-K+ pump

ion-driven coupled transporters as just described are said to mediate

secondary active transport

pseudosymmetric

inverted repeats

T he first eukaryotic ABC transporters identified were discovered because of their ability to pump ___out of the cytosol.

hydrophobic drugs

differ structurally from P-type ATPases and primarily pump small molecules across cell membranes.

ABC transporters (ATP-Binding Cassette

turbine-like protein machines, constructed from multiple different subunits.

V-type pumps

intracellular storage of Ca2+ in muscle cells specialized type of endoplasmic reticulum that forms a network of tubular sacs

sarcoplasmic reticulum

present at elevated levels in many human cancer cells and makes the cells simul taneously resistant

multidrug resistance (MDR) protein or P-glycoprotein

use the H+ gradient across the membrane

F-type (ATP synthase)

pumps Ca2+ out of the cell

Ca2+ ATPase in sarcoplasmic reticulum

10 transmembrane α helices connected to three cytosolic domains

the nucleotide-binding domain (N) the phosphorylation domain (P) the activator domain (A)]

release of Ca2+ into the cytosol (Ca+-release channels)

muscle contraction

contains highly conserved ATPase domains

ABC transporters

established Na+ and K+ gradient across the plasma membrane

Na+-K+ pump

create an electric potential

Electrogenic

connects the cytoplasm of two cells

gap junctions

constitute the largest family of membrane transport proteins

ABC transporters

cystic fibrosis transmembrane conductance regulator protein (CFTR)

Cl- transport protein

displayed at the cell surface for scrutiny by cytotoxic T lymphocytes

TAP transporter

receive, conduct, and transmit signals

Neurons

causes malaria, pumps out chloroquine

Plasmodium falciparum

open briefly and then close again

Gated

tilting the inner helices

close K+ channels

actively pumps a wide variety of peptides from the cytosol into the ER lumen

transporter associated with antigen processing, or TAP transporter

membrane potential K+ leak channels active electrogenic pumping and from passive ion diffusion

Voltage-gated channel

3 types of gated channels

Voltage-gated channel Mechanically gated channels Ligand-gated channel

inorganic ion transport

ion channels

structural and functional diversity alternative splicing of RNA transcripts

voltage-gated Ca2+ channels

water channels which allow water to move more rapidly

Aquaporins

diffuse down electrochemical gradients

Channels

changes in the electrical potential across the neuron’s plasma membrane

action potential or nerve impulse

Ion channels that pass inorganic ions; selectivity filters

Ion selectivity

polypeptide chain that connects the two transmembrane helices forms a short α helix a crucial loop that protrudes into the wide section of the cone to form the selectivity filter

pore helix

An important subset of K+ channels opens even in an unstimulated or “resting” cell

K+ leak channels

K+ ion must lose almost all of its bound water molecules

selectivity filter

voltage-gated Na+ channels in skeletal muscle cells

Myotonia

Numerous proteins are known to be capable of responding to such mechanical forces, and a large subset of those proteins has been identified as possible

mechanosensitive channels

Na+ or K+ channels in the brain

Epilepsy

the glial cells that myelinate axons in peripheral nerves

Schwann cells

Myelin is formed by specialized non-neuronal supporting cells called

glial cells

The myelin sheath is interrupted at regularly spaced where almost all the Na+ channels in the axon are concentrated

nodes of Ranvier

photosensitive ion channels that open in response to light. covalently bound retinal group * light-driven cation channel * revolutionized the study of neural circuits

Channelrhodopsins

mechanical stretching of the lipid bilayer

Hypotonic

allowing a small amount of Na+ to enter the cell down its electrochemical gradient.

Voltage-gated Na+ channels

arrangement allows an action potential to prop agate along a myelinated axon by jumping from node to node

saltatory conduction

glial cells that myelinate axons in central nerves

Oligodendrocytes

Increases the Speed and Efficiency of Action Potential Propagation in Nerve Cells

Myelination

neuronal signals are transmitted at?

Synapses

open Cl- or K+ channels, suppresses firing

inhibitory neurotransmitters

Process of synapsis

presynaptic cell – synaptic cleft postsynaptic cell

open cation channels, influx of Na+ or Ca2+; firing an action potential

excitatory neurotransmitters

Release of neurotransmitter from the

presynaptic cell

bind to and open _____in the postsynaptic cell

transmitter-gated ion channel

G-protein coupled receptors that bind to all other neurotransmitter

metabotropic receptors

Excitatory neurotransmitters

acetylcholine, glutamate, serotonin

Inhibitory neurotransmitters

γ-aminobutyric acid (GABA) and glycine

ion channels and feature at fast chemical synapses

ionotropic receptors