3.4 Active Transport Flashcards
When a molecule has gone into a cell by active transport, how is it stopped from leaking back?
By the barrier of the cell-surface membranes bilayer.
Active transport requires…
Energy from metabolism
Define active transport
Active transport is the movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration using energy and carrier molecules.
How does active transport differ from passive transport?
Metabolic energy in the form of ATP is needed
Materials are moved against a concentration gradient
Carrier protein molecules which act as ‘pumps’ are involved
The process is very selective with specific substances being transported.
How does active transport use ATP?
By using ATP directly to move molecules
By using a concentration gradient that has already been set up by direct active transport. This is also known as co-transport.
What are the two differences between active transport using carrier proteins and facilitated diffusion using carrier proteins?
Active transport requires energy from respiration/metabolism but facilitated diffusion does not.
Active transport is up a concentration gradient but facilitated diffusion is down a concentration gradient.
Describe how active transport of a single molecule or ion occurs…
Carrier proteins span the cell-surface membrane and accept the molecules or ions to be transported on one side of it.
The molecules or ions bind to receptors on the channel of the carrier protein.
On the inside of the cell ATP binds to the protein causing the protein to split into ADP and a phosphate molecule, as a result the protein molecule changes shape and opens to the opposite side of the membrane.
The molecules/ions are released to the other side.
The phosphate molecule is released from the protein and recombines with ADP to form ATP DURING RESPIRATION
This causes the protein to revert to its original shape ready for the process to be repeated. (See page 62 for help)
What happens in the sodium potassium pump?
In the sodium-potassium pump, sodium ions are actively removed from the cell while potassium ions are actively taken in from the surroundings.
Why is the process caused by the sodium potassium pump essential to the organism?
It is essential for creating a nerve impulse
