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A transport protein (variously referred to as a transmembrane pump, transporter, escort protein, acid transport protein, cation transport protein, or anion transport protein) is a protein that serves the function of moving other materials within an organism. Transport proteins are vital to the growth and life of all living things.
In terms of membrane transport the gradient is of interest as it contributes to decreased system entropy in the co-transport of substances against their gradient. One of the most important pumps in animal cells is the sodium potassium pump , that operates through the following mechanism: [ 9 ]
An example of an antiporter mediated transport protein is the sodium-calcium antiporter, a transport protein involved in keeping the cytoplasmic concentration of calcium ions in the cells, low. This transport protein is an antiporter system because it transports three sodium ions across the plasma membrane in exchange for a calcium ion, which ...
Transcellular transport often involves energy expenditure whereas paracellular transport is unmediated and passive down a concentration gradient, [4] or by osmosis (for water) and solvent drag for solutes. [5] Paracellular transport also has the benefit that absorption rate is matched to load because it has no transporters that can be saturated.
Secondary active transport is when one solute moves down the electrochemical gradient to produce enough energy to force the transport of another solute from low concentration to high concentration. [ citation needed ] An example of where this occurs is in the movement of glucose within the proximal convoluted tubule (PCT).
They are responsible for the active transport of calcium out of the cell for the maintenance of the steep Ca 2+ electrochemical gradient across the cell membrane. Calcium pumps play a crucial role in proper cell signalling by keeping the intracellular calcium concentration roughly 10,000 times lower than the extracellular concentration. [ 1 ]
Intracellular transport is the movement of vesicles and substances within a cell. Intracellular transport is required for maintaining homeostasis within the cell by responding to physiological signals. [1] Proteins synthesized in the cytosol are distributed to their respective organelles, according to their specific amino acid’s sorting ...
Gas exchange is the physical process by which gases move passively by diffusion across a surface. For example, this surface might be the air/water interface of a water body, the surface of a gas bubble in a liquid, a gas-permeable membrane, or a biological membrane that forms the boundary between an organism and its extracellular environment.