active transport 5.4 Flashcards
what is 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
what is needed to carry out active transport
The process requires energy and carrier proteins.
energy is needed as the particles are being moved up a concentration gradient
carrier proteins span the membranes and act as pumps
Describe the general process of active transport
1)The molecule or ion to be transported binds to receptors in the channel of the carrier protein on the outside of the cell
2)On the inside of the cell ATP binds to the carrier protein and is hydrolyses into ADP and phosphate
3)Binding of the phosphate molecule to the carrier protein causes the protein to change shape - opening up the inside of the cell
4)The molecule of ion is released to the inside of the cell
5)The phosphate molecule is released from the carrier protein and recombines with ADP to from ATP
6)The carrier protein returns to its original shape
The process is selective (specific substances are transported by specific proteins)
what is bulk transport and why do it
Bulk transport is another form of active transport. Large molecules such as enzymes, hormones and whole cells like bacteria are too large to move through channel or carrier proteins, so they are moved into and out of cell by bulk transport
what is endocytosis
Endocytosis is the bulk transport of material into cells.
what are the 2 types of endocytosis and what are there differences and similarites
phagocytosis for solids and pinocytosis for liquids - the process is the same for both
describe the process of endocytosis
The cell-surface membrane first invaginates (bends inwards) when it comes into contact with the material to be transported.
The membrane enfolds the material until eventually the membrane fuses, forming a vesicle.
The vesicle pinches off and moves into the cytoplasm to transfer the material for further processing within the cell
For example, vesicles containing bacteria are moved towards lysosomes, where bacteria are digested by enzymes
what are the 2 types of bulk transport
endocytosis and exocytosis
what is exocytosis
Exocytosis is the bulk transport of material out of the cell
explain the process of exocytosis
Vesicles, usually formed by the Golgi apparatus, move towards and fuse with the cell-surface membrane. The contents of the vesicle are then released outside of the cell
what is the difference between facilitated and active transport
- Both use carrier proteins
- facilitated diffusion occurs down concentration gradient (does not require energy)
- active transport requires energy
