Cell Transport Mechanism

Question 1

What are the three modes of passive transport?

Answer 1

Simple diffusion
Osmosis
Facilitated diffusion

Question 2

Explain osmosis.

Answer 2

Osmosis is the diffusion of H2O (water) through a membrane. It follows the same principle of diffusion (high to low).

Question 2

What is simple diffusion?

Answer 2

Movement of particles from high to low concentration without protein.

Question 3

What are the three tonicity and explain each one.

Answer 3

Hypotonic - Solute concentration outside is higher than inside the cell. This causes a net flow of water into the cell.

Hypertonic - Solute concentration outside is lower than inside the cell. This causes a net flow of water out of the cell.

Isotonic - Solute concentration outside is the same as inside the cell. This causes no net flow of water into or out of the cell.

Question 4

What happens to animal and plant cells if exposed under a hypotonic solution?

Answer 4

animal cells - burst
plant cells - become turgid (membrane sticks to cell wall)

Question 5

What happens to animal and plant cells if exposed under a hypertonic solution?

Answer 5

animal cells - shrink
plant cells - become plasmolysed (membrane pulls away from cell wall)

Question 5

What are the two proteins that allow facilitated diffusion and how do they differ from each other?

Answer 5

channel proteins - allows water or small ions through the cell membrane.

carrier proteins - allows specific ion, molecule, or group of substances to pass the membrane through changing shape.

Question 6

What is active transportation?

Answer 6

Active transportation let in/out via membrane proteins which actively pump in/out molecules. This requires energy from the cell. It moves molecules in 1 direction against the concentration gradient (low to high).

Question 7

What are the two types of bulk transportation?

Answer 7

Endocytosis and Exocytosis

Question 8

What is endocytosis?

Answer 8

• Large particles enter cells via endocytosis.
• The cell membrane surrounds/engulfs particle or fluid and forms a vesicle.

Question 9

What are the two subdivision of endocytosis and explain each.

Answer 9

Phagocytosis - “cell eating”: involves large particles

Phinocytosis - “cell drinking”: involves liquids

Question 10

What is exocytosis?

Answer 10

• Large particles exit via exocytosis
• Vesicle moves to and merges with membrane.
• Vesicle rupture outwards, releasing its content.