Active Transport

Question 1

Define active transport.

Answer 1

The movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration using ATP and carrier proteins.

Question 2

What is ATP used for in active transport?

Answer 2

• Directly move molecules. - Co-transport

Question 3

How does active transport differ from passive transport?

Answer 3

• Metabolic energy in the form of ATP is needed. - Substances move against concentration gradient (this is why ATP is needed). - The process is very selective (only specific substances are transported). - carrier protein molecules which act as a ‘pump’ are involved.

Question 4

Describe the 1st step of active transport.

Answer 4

1) Molecule/ion binds to receptor sites on the carrier protein.

Question 5

Describe the 2nd step of active transport.

Answer 5

2) On the inside of the cell/organelle, ATP binds to the protein causing it to split into ADP and 1 phosphate molecule. Therefore, the protein molecule changes shape and opens to the opposite side of the membrane.

Question 6

Describe the 3rd step of active transport.

Answer 6

The molecule/ion is then released to the other side of the membrane.

Question 7

Describe the 4th step of active transport

Answer 7

The phosphate molecule is released from the protein which allows the protein to revert to its original shape, ready for the process to repeat. The phosphate molecule then recombines with the ADP to from ATP during respiration.

Question 8

Describe the structure of ATP.

Answer 8

Adenine, Ribose and 3 phosphate sugars.

Question 9

Why is it important for the bond between the 2nd and 3rd phosphate sugar to be unstable?

Answer 9

So that it can easily be hydrolysed into ADP.

Question 10

What is the Sodium-Potassium Pump?

Answer 10

The pump moves sodium and potassium ions in opposite directions, each against its concentration gradient. In a single cycle of the pump, three sodium ions are extruded from and two potassium ions are imported into the cell.

Question 11

What is the Sodium-Potassium Pump powered by?

Answer 11

ATP.

Question 12

In the Sodium-Potassium Pump, what is actively removed from the cell/organelle?

Answer 12

3 sodium ions / 3 Na+

Question 13

In the Sodium-Potassium Pump, what is actively taken in from the surroundings?

Answer 13

2 potassium ions / 2 K+

Question 14

What is the Sodium-Potassium Pump essential for?

Answer 14

A number of important processes in organisms, including the creation of nerve impulses.