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Chapter 4.4 - Active transport (direct transport of a single molecule/ion,…
Chapter 4.4 - Active transport
difference and similarity between active transport and facilitated diffusion?
similarity - both use carrier proteins in the plasma membrane
difference - active transport requires energy(ATP) - occurs against the concentration gradient
ATP is used for...
directly move molecules
individually move molecules using a concentration gradient which has already been set up by active transport
this is known as co-transport
the movement of molecules/ions into or out of a cell from a region of low concentration to a region of higher concentration using ATP and carrier proteins
it differs from passive forms of transport e.g.
substances are moved against the concentration gradient - low to high
carrier protein molecules act as pumps
ATP is needed (metabolic energy)
process is selective - only specific substances get transported
direct transport of a single molecule/ion
carrier proteins span the membrane and bind to the molecule/ion
the molecule/ion binds to receptor sites on the carrier protein
as a result protein molecule changes shape and opens to the opposite side of the membrane
on the inside of the cell, ATP binds to protein, causing it to split into ADP and a phosphate molecule
molecule/ion is then released to the other side of the membrane
phosphate molecule is released from protein which causes the protein to go back to original shape
process can then be repeated
phosphate molecule then recombines with the ADP to form ATP during respiration
sodium - potassium pump
sodium ions are actively removed from the cell while potassium ions are actively taken in from the from the surroundings