Active Transport & Co-transport

Question 1

Active transport is the

Answer 1

movement of molecules and ions through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration

Question 2

Active transport requires

Answer 2

carrier proteins (each carrier protein being specific for a particular type of molecule or ion)

Question 3

Although facilitated diffusion also uses carrier protein, active transport is different as

Answer 3

it requires energy

Question 4

The energy is required to make the carrier protein ………….

which allows

Answer 4

change shape,

allowing it to transfer the molecules or ions across the cell membrane

Question 5

The energy required is provided by

Answer 5

ATP (adenosine triphosphate) produced during respiration.

The ATP is hydrolysed to release energy

Question 6

Active transport is important in:

Answer 6

Absorption of some products of digestion from the digestive tract

Loading sugar from the photosynthesising cells of leaves into the phloem tissue for transport around the plant

Loading inorganic ions from the soil into root hairs

Question 7

Co-transport is the

and a example

Answer 7

coupled movement of substances across a cell membrane via a carrier protein

It involves a combination of facilitated diffusion and active transport

A well-known example of a co-transporter protein can be found on the cell surface membrane of the epithelial cells lining the mammalian ileum

Question 8

This specific co-transport protein is involved in the absorption of glucose how does this happen

Answer 8

Sodium ions and glucose molecules are transported into the epithelial cells via facilitated diffusion

The facilitated diffusion can only continue if a concentration gradient is maintained

The active transport of sodium ions out of the cell into the blood helps to maintain this gradient

The glucose molecules exit the epithelial cell and enter the blood via facilitated diffusion

Question 9

Be careful not to get carrier proteins and channel proteins confused when answering questions on active transport. Active transport requires carrier proteins (transmembrane transport proteins that undergo conformational change) not channel proteins.