4.4 - 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

Give four ways in which is differs from passive forms of transport

Answer 2

1. Metabolic energy in the form of ATP is needed
2. Substances are moved against a concentration gradient, that is from low to high
3. Carrier proteins that act as pumps are involved
4. The process is very selective, with specific substances being transported

Question 3

Describe the direct active transport of a single molecule or ion

Answer 3

• the molecule or ions into binds to receptor sites on the carrier protein
• on the inside of the cell, ATP binds to the protein, casing it to split into ADP and a phosphate molecule. As a result, the protein molecule changes shape and opens to the opposite side of the membrane
• the molecule or ions into binds is then released to the other side of the membrane
• the phosphate molecule is released from the protein which causes the protein to revert to its original shape, ready for the process to be repeated. The phosphate molecule then recombines with the ADP to form ATP during respiration

Question 4

Give one similarity and difference between facilitated diffusion and active transport

Answer 4

Similarity - both use carrier proteins
Differences - active transports goes agains the concentration gradient, facilitated diffusion goes down the concentration gradient

Question 5

Give an example of when the molecule or ions is moved into a cell at the same time as a different one is being removed from it

Answer 5

Sodium potassium pump

Question 6

What happens in the sodium potassium pump?

Answer 6

Sodium ions are actively removed from the cell while potassium ions are actively taken in from the surroundings