5.4- Active Transport Flashcards
1
Q
What is active transport?
A
The movement of molecules/ions into or out of a cell from a region of lower conc to a region of higher conc.
- requires energy + carrier proteins.
- particles moved up a concentration gradient.
- metabolic energy supplied by ATP.
2
Q
Explain the 6 stages of active transport.
A
- Molecule/ion binds to receptors in the channel of the carrier protein on the outside of the cell.
- Inside the cell, ATP binds to the carrier protein and is hydrolysed into ADP and phosphate.
- The phosphate molecule binds to the carrier protein so it changes shape and opens up towards the inside of the cell.
- Molecule/ion is released to the inside of the cell.
- Phosphate molecule is released and recombines with ADP = ATP.
- Carrier protein returns to its original shape.
3
Q
What is bulk transport?
A
A form of active transport where large molecules (such as enzymes ) or whole bacteria cells are moved into and out of the cell by bulk transport.
They are too large to move through channel and carrier proteins.
4
Q
Explain endocytosis.
A
Bulk transport of materials into cells.
- phagocytosis= solids.
- pinocytosis= liquids.
- Cell surface membrane invaginates (bends inwards) when it comes in contact with the material.
- Membrane enfolds the material, until the membrane eventually fuses, forming a vesicle.
- Vesicle pinches off and moves to the cytoplasm so material can be processed further.
(Vesicles with bacteria= pushed to lysosomes= bacteria digested by enzymes)
5
Q
Explain exocytosis.
A
Reverse of endocytosis.
- Vesicles (made from golgi) move towards the cell membrane.
- Vesicles fuse with the cell surface membrane.
- Content of vesicles released outside the cell.
6
Q
Why is ATP needed in endo/exocytosis?
A
Energy (ATP) is needed for:
- movement of vesicles along the cytoskeleton.
- changing shape of cells to engulf materials.
- fusion of cell membranes as vesicles form/meet it.
