Active Transport

What is active transport?

The movement of molecules or ions from a region of lower concentration to a region of higher concentration using energy and carrier proteins.

Why does active transport require energy?

Because particles are moved against their concentration gradient

What supplies energy for active transport?

ATP (adenosine triphosphate).

What type of membrane protein is used in active transport?

Carrier proteins that act as pumps.

What binds to the carrier protein on the outside of the cell?

The molecule or ion to be transported.

What happens on the inside of the cell during active transport?

ATP binds to the carrier protein and is hydrolysed into ADP and phosphate.

What effect does phosphate binding have on the carrier protein?

It changes the protein’s shape, opening it to the inside of the cell.

What happens after the molecule enters the cell?

The phosphate group detaches and recombines with ADP to form ATP; the carrier protein returns to its original shape.

Why is active transport selective?

Each carrier protein is specific to a particular substance.

What is bulk transport?

The movement of large molecules or whole cells into or out of a cell using vesicles, requiring ATP.

What types of substances are moved by bulk transport?

Large molecules such as enzymes, hormones, or whole cells like bacteria.

What are the two types of bulk transport?

Endocytosis and exocytosis.

What is endocytosis?

The process by which the cell membrane engulfs material to bring it into the cell.

What is exocytosis?

The process by which vesicles fuse with the cell membrane to release materials out of the cell.

Why do endocytosis and exocytosis require ATP?

ATP provides energy for moving vesicles and changing membrane shape.