What is the definition of active transport?
The movement of ions or molecules across a cell membrane from an area of low concentration to an area of high concentration. Active transport a carrier protein, using energy supplied by ATP.
Order these steps of active transport…
- The molecule or ion is released to the inside of the cell.
- The carrier proteins returns to its original shape.
- The phosphate molecule is released from the carrier protein and recombines with ADP to form ATP.
- The molecule or ion to be transported binds to receptors in the channel of the carrier protein on the outside of the cell.
- On the inside of the cell 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 of the cell.
4 5 6 1 3 2
Large molecules such as enzymes, hormones and whole cells such as bacteria are too large to move into the cell via carrier or channel proteins. What method do they use instead?
What is endocytosis?
The bulk transport of material into cells
What are the two forms of endocytosis?
Phagocytosis and pinocytosis
What is phagocytosis?
The movement of solids into a cell
What is pinocytosis?
The movement of liquids into cells
Describe the stages of endocytosis?
The cell surface membrane invaginates when it comes into contact with the material to be transported. The membrane enfolds the material until the membrane infuses forming a vesicle. The vesicle pinches of and moves into the cytoplasm.
What is exocytosis?
The bulk transport of material out of cells
How is ATP required during bulk transport?
It is used for the movement of vesicles along the cytoskeleton, changing the shape of cells to engulf the material, and for the fusion of the cell membrane after the vesicles form.