Transport Mechanisms
Sodium-potassium pump simultaneously moves
3 sodium ions, 2 potassium ions
Secondary active transport & Na+/glucose
ATP doesn't directly power this process. Uses the downhill gradient of 1 ion/molecule (i.e. if Na+ is moving into the cell) to drive the uphill movement of another ion/molecule (glucose uses that to push itself out of the cell)
Primary active transport & the Na/K pump
ATP used directly to power this process (ATP hydrolysis), Na+ leaves of the cell, K+ enters
Sodium-potassium pump is classified as what kind of pump?
Antiporter, since it moves sodium and potassium (2 solutes) in opposite directions, with sodium leaving the cell and potassium entering.
Solute Pump
Carrier proteins (i.e. the sodium-potassium pump) that moves substances across membranes in an enzyme-substrate interaction. These pumps move substances against their concentration gradients.
What type of transport does the sodium potassium pump participate in?
Coupled Transport (form of active transport)
Vesicles fuse with the plasma membrane and release their contents to the extracellular fluid (outside of the cell). This describes:
Exocytosis
Osmosis is a form of passive transport and an example of what kind of diffusion?
Facilitated diffusion (via aquaporins)
Coupled Transport
Form of active transport, this type of transport happens when more than 1 substance/solute is transported across a membrane (i.e. sodium and potassium)
Na+/glucose
Glucose's ability to leave the cell (uphill movement) is powered by the downhill movement of sodium that is entering the cell. One is going in (sodium) and one is going out (glucose). Not directly powered by ATP
K+ and active transport
K+ is actively transported inside of the cell (2 ions) via the sodium-potassium pump
Simple diffusion come in what kind of molecules?
Lipids
K+ tendencies
More K+ inside of the cell than outside at rest, so K+ tends to stay outside the cell unless it is actively transported in
Na+ tendencies
More Na+ outside of the cell than inside at rest, so Na+ tends to stay inside the cell unless it is actively transported out
Na+ and active transport
Na+ is actively transported outside of the cell (3 ions) via the sodium-potassium pump
Secondary vs. Primary Active Transport
Primary directly powered by ATP. Secondary is powered by uphill/downhill gradients of molecules entering and leaving a cell.
The movement of sodium and potassium maintained by the Na+/K+ pump
Requires energy (ATP) and is against a concentration gradient
2 types of carrier proteins that move multiple solutes (coupled transport)
Symporters (if solutes move in the same direction) and Antiporters (if solutes move in opposite directions - i.e. sodium and potassium)
Solutes that require active transport for movement might be
Too large to pass through pores of the membranes, lipid insoluble, or need to move against their concentration gradient (as opposed to moving down it)
Carrier protein that transports a single solute
Uniporter
Some transport proteins use transport processes in the plasma membrane but do NOT require ATP. These transport proteins participate in:
facilitated diffusion
The majority of water molecules moving across the plasma membrane via osmosis do so via a process that is most similar to:
facilitated diffusion
A primary AT process is one
in which molecules move through transport proteins that have been activated by ATP
2 big differences between passive and active transport
passive: no ATP required from cell, moving down a concentration gradient (high --> low); active: requires ATP from cell, moving against a concentration gradient (low --> high)
Na/K pump uses ATP to move Na/K ions across the plasma membrane. This best describes the process of:
primary active transport
Active Transport includes
primary active transport & secondary active transport
Passive Transport includes
simple diffusion & facilitated diffusion
