Active Transport

Question 1

What is active transport?

Answer 1

• energy-consuming transport of molecules or ions across a membrane against a concentration gradient, made possible by transferring energy from respiration
• energy is needed because it opposes the natural diffusion of the molecules or ions

Question 2

What are the adaptions of cells that facilitate active transport?

Answer 2

• many mitochondria
• a high respiratory rate
• any factor that will increase the rate of respiration will increase the rate of active transport, e.g. high temperature or oxygen conc

Question 3

What are the role of carrier proteins?

Answer 3

• proteins are specific
• accept the molecule or ion to be transported on one side of the membrane
• induces a change in the structure of the protein and conveys molecule on other side
• coupled with a source of energy in the form of ATP
• only work in one direction

Question 4

Which way does active transport occur?

Answer 4

Against the concentration gradient

Question 5

How does ATP facilitate the role of protein carriers?

Answer 5

• a molecule combines with a protein carrier
• ATP binds to the protein carrier
• ATP is hydrolysed to ADP and Pi (+ ATP hydrolase), releasing energy
• Pi binds to the protein carrier
• a conformational change occurs in the protein causing the molecule to be transported to the other side of the membrane where it is released
• Pi molecule is released from the protein carrier and re-combines with the ADP to form ATP (+ATP synthase) in a condensation reaction
• causes the protein to return to its original shape to repeat the process

Question 6

Active transport definition

Answer 6

• the movement of molecules against a concentration gradient, through a protein carrier, using energy in the form of ATP

Question 7

What are the characteristics of active transport?

Answer 7

• allows substances to move against the concentration gradient
• highly selective process due to specificity of protein carriers
• up to 40% of ATP can be used for active transport

Question 8

Active transport vs simple diffusion

Answer 8

• requires energy while diffusion is a passive process
• moves against the concentration gradient whereas simple diffusion moves down the concentration gradient
• selective process (specific substances only) whereas simple diffusion is non-selective
• requires a protein carrier whereas simple diffusion doesn’t

Question 9

Active transport vs facilitated diffusion

Answer 9

• both facilitated diffusion and active transport use channel and carrier proteins
• facilitated diffusion is a passive process whereas active transport uses energy released from ATP
• facilitated diffusion moves down a concentration gradient, whereas active transport moves against the concentration gradient