1.4 Membrane Transport

Question 1

Osmosis (definition)

Answer 1

The passive movement of water molecules, across a partially permeable membrane, form an area of low solute concentration to an area of high solute concentration

Question 2

There are two general ways to transport stuff across the membrane. Passive and Active transport.

Answer 2

Passive transport - simple diffusion, osmosis, facilitated diffusion
Active transport - membrane pump, endocytosis, exocytosis

Question 3

Simple diffusion.
The movement of particles form an area of higher concentration to an area of lower concentration down a concentration gradient. NO ATP

Answer 3

• Molecules that can easily cross the cell membrane are small, nonpolar and uncharged.
• They pass between the phospholipids in the membrane. Only if it’s permeable to the particle.

Question 4

Facilitated Diffusion.
Protein channels help particles pass through the membrane from an area of higher to lower concentration down a concentration gradient.

Answer 4

• Molecules that are too big, polar or charged

- ATP

Question 5

Active transport (membrane pump)
Particles are moved against their concentration gradient form low to high

Answer 5

• Carried out by globular proteins in membranes (pump proteins)
• ATP required

Question 6

Vesicle

Membrane bound compartment used to shuttle substances around within a cell.

Answer 6

Involved in endocytosis and exocytosis. Both require ATP

Question 7

Endocytosis

Answer 7

The folding of the cell membrane to bring large molecules into the cell. ATP required. E.g. phagocytosis

Question 8

Exocytosis

Answer 8

The fusing of a vesicle with the cell membrane to send a large particle out of a cell. ATP required.