Active transport

what does active transport require?

ATP and carrier proteins

is active transport against the conc gradient?

yes

which is against the conc gradient

how does active transport use carrier proteins?

• Shape of carrier protein is complementary to molecule to be transported. 

• ATP binds to carrier protein and is hydrolysed to ADP and P(i). 

• This causes the carrier protein to change shape, releasing the molecule or ion inside the cell.  

• As the carrier protein changes shape, molecules can therefore not move back through the membrane. 

• (The P(i) is then released and recombines with ADP to form ATP and the carrier protein returns to its original shape). 

what are 2 examples of active transport?

exocytosis and endocytosis (they are bulk transport)

what is bulk transport?

• Bulk transport also requires ATP and is therefore another form of active transport.  

• It is for large molecules and whole cells (e.g. bacteria). 

what is exocytosis?

-vesicles containing a molecule move to and fuse will cell surface membrane - remember protein production step by step from cell chapter. 

-molecules (e.g. proteins – hormones) are released outside cell.  

what is endocytosis?

- cell surface membrane surrounds and forms a vesicle around the molecule or cell e.g. phagocytosis 

- vesicle pinches off from membrane and is transported inside cell to organelle (e.g. phagolysosome)