Transporters

Outline by Shelby Pickett and Avalon Marker

Transporters

• Active Transport: Primary/secondary
  • Active Transport: The two types of active transports are Primary and Secondary. Primary active transport is defined by the direct use of ATP hydrolysis to supply needed energy to transport ions against their concentration gradient. Secondary active transport uses ATP indirectly by utilizing the energy created (high electrochemical concentration) resultant of primary active transport activity to move one class of ion against its gradient.
• Antiporter/Exchangers: Transports ions in opposing physical direction
  • Examples of Antiporters:
    • Sodium-Calcium Exchanger (NCX): Found in neurons, this antiporter exchanges three sodium ions for one calcium ion, playing a crucial role in maintaining calcium homeostasis.
    • Sodium-Hydrogen Exchanger (NHE): Neuronal NHEs exchange sodium ions for protons, contributing to intracellular pH regulation and cell volume control.
    • Sodium-Potassium Pump (Na+/K+ Pump) or Sodium-Potassium ATPase: actively transports three sodium ions out of the cell and two potassium ions into the cell, maintaining the resting membrane potential. Functions akin to a proton pump (atp as energy – Proton ATPase) in plant cells.

• Symport/Cotransporters: Cotransports ions in the same physical direction.
  • Examples of Cotransporters:
    • Sodium-Glucose Co-transporter (SGLT): SGLTs facilitate transport of sodium and glucose across the cell membrane.  In some neurons, SGLTs facilitate the co-transport of sodium ions (driver) and glucose across the cell membrane.Glucose is high in concentration inside, thus glucose outside the cell moves inward against its gradient in coordination with driver (Na+)
    • Excitatory Amino Acid Transporters (EAATs): EAAT1-5 are responsible for the uptake of glutamate
    • Sodium-Chloride Symporter (NCC): NCC co-transports sodium and chloride ions across the cell membrane, contributing to ion homeostasis.
    • GABA Transporters (GATs): Neuronal GATs (GAT-1 to GAT-4) reuptake of gamma-aminobutyric acid (GABA) from the synaptic cleft.
    • Dopamine Transporter (DAT): reuptake of dopamine from the synaptic cleft.
    • Norepinephrine Transporter (NET): reuptake of norepinephrine from the synaptic cleft.
    • Serotonin Transporter (SERT): reuptake of serotonin from the synaptic cleft.