5.4 Active Transport

Question 1

How is a concentration gradient maintained?

Answer 1

Particles must be moved up it at a faster rate, than the rate of diffusion.

Question 2

What is active transport?

Answer 2

The movement of molecules or ions into or out of a cell against the concentration gradient

Question 3

What type of energy is required for active transport?

Answer 3

Metabolic energy, supplied by ATP

Question 4

What 2 things does the process of active transport require?

Answer 4

Energy (ATP), and carrier proteins

Question 4

State the steps for the general process of active transport.

Answer 4

1- The molecule or ion to be transported binds to the 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 HYDROLYSED into ADP and phosphate
3- Binding of the phosphate molecule to the carrier protein causes the protein to change shape - OPENING UP to the inside of the cell.
4- The molecule or ion is RELEASED to the inside of the cell
5- The PHOSPHATE molecule is released from the carrier protein, and recombines with ADP to form ATP.
6- The carrier protein RETURNS to its original shape.

Question 5

Is active transport selective or unselective?

Answer 5

Selective, specific substances are transported by specific carrier proteins.

Question 6

What is BULK TRANSPORT?

Answer 6

Another form of active transport. Used when large molecules are too large to move through channel or carrier proteins

Question 7

When is bulk transport used?

Answer 7

When molecules are too large to move through channel or carrier proteins, so they move in and out of cells by bulk transport.

Question 8

What is ENDOCYTOSIS?

Answer 8

The bulk transport of material INTO cells

Question 9

What are the two types of endocytosis?

Answer 9

Phagocytosis and pinocytosis.

Question 10

What is phagocytosis?

Answer 10

Endocytosis for solids

Question 11

What is pinocytosis?

Answer 11

Endocytosis for liquids

Question 12

State the process of endocytosis.

Answer 12

1- Cell-surface membrane INVAGINATES (bends inwards) when it comes into contact with the material to be transported
2- Membrane enfolds the material, until eventually the membrane fuses, forming a vesicle.
3- Vesicle pinches off and moves into the cytoplasm, to transfer the material for further processing within the cell.

Question 13

What is exocytosis?

Answer 13

The reverse of endocytosis, the bulk transport of material out of cells.

Question 14

State the process of exocytosis.

Answer 14

1- Vesicles move towards and fuse with the cell surface membrane
2- Contents of the vesicle are then released outside of the cell.

Question 15

What is energy in the form of ATP required for?

Answer 15

Movement of vesicles along the cytoskeleton, changing the shape of cells to engulf materials, and the fusion of cell membranes as vesicles form or meet the cell-surface membrane.