Active Transport

Question 1

What is the definition of 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.
• Individually move molecules using a concentration gradient which has already been set up by active transport, known as co-transport.

Question 3

How does active transport differ from passive forms of transport?

Answer 3

• Metabolic energy in the form of ATP is needed.
• Substances are moved against a concentration grad.
• Carrier proteins acting as ‘pumps’ are involved.
• Process is selective, only specific substances transported.

Question 4

What happens in Stage 1 of direct active transport of a single molecule or ion?

Answer 4

Carrier proteins bind to molecule or ion to be transported on one side of it.

Question 5

What happens in Stage 2 of direct active transport of a single molecule or ion?

Answer 5

The molecule or ion binds to receptor sites on the carrier protein.

Question 6

What happens in Stage 3 of direct active transport of a single molecule or ion?

Answer 6

On the inside of the cell/organelle, ATP binds to the protein causing it to split into ADP and a phosphate molecule. As a result, protein molecule changes shape, opening to opposite side of the membrane.

Question 7

What happens in Stage 4 of direct active transport of a single molecule or ion?

Answer 7

The molecule or ion Is released to the opposite side of the membrane.

Question 8

What happens in the final stage of direct active transport of a single molecule or ion?

Answer 8

The phosphate molecule is released from the protein, causing it to revert back to its original shape, ready for the process to be repeated. The phosphate molecule then recombines with ADP to form ATP during respiration.

Question 9

When is the sodium-potassium pump needed?

Answer 9

• More than one molecule or ion needs to move in the same direction at the same time by active transport.
• One molecule or ion is moved into the cell/organelle/ at the same time as a different one is being removed.

Question 10

What does the sodium-potassium pump do?

Answer 10

Sodium ions are actively removed from the cell/organelle, while potassium ions are actively taken in from the surroundings.

Question 11

Why is the sodium-potassium pump important?

Answer 11

The process it carries out is important to the creation of a nerve impulse.