Membrane Transport Flashcards
The membrane transport proteins
- Transporters
- Channels
- transfer solutes across cell membranes
- transfer specific molecular species or a class of molecules
Membrane transport proteins
single-gene mutations
Cystinuria
(carriers or permeases)
– bind, conformational changes
Transporters
form continuous pores
Channels
“downhill” transfer
Passive transport
uncharged molecule
Concentration gradient
charged molecule
membrane potential
“uphill”, against their electrochemical gradients
Active transport
negative insided
Electrical potential
What resembles an enzyme-substrate reactions
Transport of solute in the lipid bilayer
inaccessible-occluded
Intermediate state
Main ways of active transport
- Coupled transport
- ATP-Driven pumps
- Light-or redox- driven pumps
energy stored in concentration gradients
Coupled transport
hydrolysis of ATP
ATP-driven pumps
energy from light
light- or redox-driven pumps
passive transport
Uniporters
transfer of one solute depends on the transport of a second
Coupled transporters
transfer in the same direction
Symporters
transfer in opposite direction
Antiporters
pseudosymmetric
inverted repeats
Three classes of ATP-driven pumps
- P-type pumps
- ABC transporters
- V-type pumps
phosphorylate themselves during pumping cycle
P-type pumps
pump small molecules
ABC transporters
Full name of ABC transporters
ATP-binding Cassette transporters
turbine-like; made from multiple different subunits
- pumps transfers H+ into organelles
V-type pumps
use the H+ gradient across the membrane
F-type (ATP synthase)
Example of P-type pumps
Ca2+ ATPase and Na+/K
pumps Ca2+ out of the cell
Ca2+ ATPase
intracellular storage of Ca2+ in muscle cells
Sarcoplasmic reticulum
effects of the release of Ca2+ into the cytosol
Muscle contraction
create an electric potential
Electrogenic
contains highly conserved ATPase domains.
First found in bacteria
ABC transporters
causes malaria, pumps out chloroquine
Plasmodium falciparum
form pores across membrane
Channels
connects the cytoplasm of two cells
Gap junctions
inorganic ion transport
Ion channels
- water channels
- allow water to move more rapidly
- narrow pore that allows water molecules to traverse the membrane in single file
Aquaporins
inorganic ions; selectivity filters
Ion selectivity
open briefly and then close again
Gated
Types of ion channels
- Voltage-gated ion channels
- Mechanical-gated ion channels
- Ligand-gated ion channels
Examples of ligand-gated ion channel
- Transmitter-gated channels
- Ion-gated channels
- Nucleotide-gated channels
form a central pore through the membrane
Four identical transmembrane subunits
receive, conduct, and transmit signals
changes in the electrical potential across the neuron’s plasma membrane
Neurons
- photosensitive ion channels
- covalently bound retinal group
Channelrhodopsins
what did channelrhodopsins revolutionized?
the study of neural circuits
increase the rate at which the axon can conduct an action potential
Myelination
formed by specialized non-neuronal supporting cells called glial cells.
Myelin
formed by glial cell
Oligodendrocytes and Schwann cells
where neuronal signals are transmitted
Synapses
Types of neurotransmitter receptors
- Ionotropic receptors
- Metabotropic receptors
ion channels and feature at fast chemical synapses
Ionotropic receptors
G-protein coupled receptors that bind to all other neurotransmitter
Metabotropic receptors
Chemical synapses can be
- Exicitatory or inhibitory
open cation channels, influx of Na+ or Ca2+; firing an action potentia
Excitatory neurotransmitters
open Cl- or K+ channels, suppresses firing
Inihibitory neurotranmistters
Example of excitatory neurotransmitters
- acetylcholine
- glutamate
- serotonin
Example of inihibitory neurotransmitters
- γ-aminobutyric acid (GABA)
- glycine
