Movement across cell membrane

Question 1

two ways for substances to enter / leave a cell

Answer 1

• passive transport
  - diffusion
  - facilitated diffusion
  - osmosis
• active transport

passive transport doesn’t require ATP
molecules, but ATP is needed for active transport as the movement is against the concentration gradient.

Question 2

Diffusion

Answer 2

movement of molecules or particles from a high concentration to a low concentration against the concentration gradient, until equilibrium is reached

Question 3

facilitated diffusion

Answer 3

the movement of polar substances across the membrane with the use of protein molecules

Question 4

facilitated diffusion - carrier protein

Answer 4

Carrier protein :
- has a binding site for a specific chemical
- chemical binding changes the structure of the carrier protein
- change in shape brings the chemical across where it’s released

Question 5

facilitated diffusion - channell

Answer 5

Channel protein :
- has a central pore that’s lined with hydrophilic acid
- allows hydrophilic substances to pass through the channel
- selective for the chemical that can pass through
- open and close depending on the need of the cell

Question 6

Active transport

Answer 6

movement of ions and molecules across a membrane against the concentration gradient.

molecule combines with specific carrier protein outside a membrane ATP transfers a phosphate group to the carrier protein which changes shape to move the molecule inside the cell where its released into the cytoplasm, carrier protein releases phosphate group and returns to normal shape

Question 7

Co-transport

Answer 7

movement of ions and molecules across a membrane against the concentration gradient.

molecule combines with specific carrier protein outside a membrane ATP transfers a phosphate group to the carrier protein which changes shape to move the molecule inside the cell where its released into the cytoplasm, carrier protein releases phosphate group and returns to normal shape

Question 8

Co-transport - sodium-glucose

Answer 8

• glucose and two sodium ions bind to a carrier protein in the cell membrane
• carrier protein changes shape and moves the glucose molecules and sodium ions through the cell
  membrane through facilitated diffusion
• glucose and sodium separately diffuse through the cytoplasm
• glucose - facilitated diffusion
• sodium ions moves out through active transport.
• sodium ion concentration remains low inside the cell so sodium moves in through FD and brings
  glucose with it