5.4 active transport (d) Flashcards
1
Q
What is active transport?
A
The movement of molecules or ions into or out of a cell from a region of concentration to a region of high concentration, against a concentration gradient.
2
Q
What is needed for the process?
A
Energy (from ATP) and carrier proteins are needed.
3
Q
Is the process specific?
A
The process is selective as specific substances are transported by specific carrier proteins.
4
Q
Describe the process
A
- Molecule of ion to be transported binds to receptors in the channel of the carrier protein on the outside of the cell
- On the inside, ATP binds to the carrier protein and is hydrolysed into ADP and phosphate
- Binding of the phosphate molecule to the carrier protein causes the protein to change shape - opening to the inside
- The molecule or ion is released to the inside of the cell
- The phosphate molecule is released from the carrier protein + recombines with ADP to form ATP
- The carrier protein returns to its original shape
5
Q
What is bulk transport?
A
A form of active transport where large molecules or whole bacterial cells are moved in or out of a cell by endocytosis or exocytosis.
6
Q
What is endocytosis?
A
- bulk transport of materials into cells - phagocytosis (solids) + pinocytosis (liquids)
- membrane invaginates enfolding the material until eventually the membrane fuses, forming a vesicle. the vesicle pinches off + moves into the cytoplasm to transfer the material for further processing within the cell
7
Q
What is exocytosis?
A
- bulk transport of material out of cells
- vesicles move towards + fuse with the cell-surface membrane. contents released outside of the cells.
8
Q
Why is energy needed for bulk transport?
A
- required for movement of vesicles along the cytoskeleton
- changing the shape of cells to engulf materials
- the fusion of cell membranes as vesicles form or as they meet the cell-surface membrane
