2.5.4 active transport

Question 1

what’s active transport?

Answer 1

the movement of molecules/ions into or out of a cell from a region of lower concentration to a region of higher concentration
this process requires metabolic energy in the form of ATP in order to move particles against the concentration gradient

Question 2

how does active transport work?

Answer 2

1. the molecule/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 where it’s hydrolysed into ADP and phosphate; binding of the phosphate molecules to the carrier protein causes the protein to change shape and allow passage to the inside of the cell
3. the molecule/ion is released to the inside of the cell and the phosphate molecule is released from the carrier protein and recombines with ADP to form ATP again
4. the carrier protein returns to its original shape

Question 3

what’s bulk transport?

Answer 3

a form of active transport to move large molecules (like enzymes or hormones) or whole cells (like bacteria) that are to large to move through channel/carrier proteins

Question 4

what’s endocytosis?

Answer 4

bulk transport into cells
phagocytosis=solids
pinocytosis=liquids

Question 5

how does endocytosis work?

Answer 5

the cell surface membrane invaginates when in contact with material and enfolds until the membrane fuses and forms a vesicle; it then buds off to transfer the material for further processing

Question 6

what’s exocytosis?

Answer 6

bulk transport out of cells

Question 7

how does exocytosis work?

Answer 7

vesicles formed by the golgi move/fuse to cell surface membrane where contents are released outside the cell