Membrane Transport topic 1.4

Question 1

Cell membranes have two key properties

Answer 1

• Semi-permeable (only certain things can cross)
• Selective (membranes can regulate material passage)

Question 2

Membrane transport can either be:

Answer 2

• Passive (along concentration gradient, no ATP expenditure)
• Active (against concentration gradient, ATP is required)

Question 3

Simple Diffusion

Answer 3

The net movement of particles from a region of higher
concentration to a region of lower concentration (i.e. along
the gradient) until equilibrium is reached

Question 4

Facilitated Diffusion

Answer 4

The passive movement of molecules across a cell membrane
via the aid of a membrane protein (carrier / channel protein)

Question 5

Osmosis

Answer 5

The net movement of water molecules across a semi-permeable
membrane from a region of low solute concentration to a region
of higher solute concentration (diffusion of free water molecules)

Question 6

Osmolarity

Answer 6

Osmolarity is a measure of solute concentration

Question 7

Solutions can be measured as:

Answer 7

• Hypertonic: High solute concentration (gains water)
• Hypotonic: Low solute concentration (loses water)
• Isotonic: Same solute concentration (no net flow)

Question 8

Active Transport

Answer 8

Active transport uses energy (ATP) to move molecules
against a concentration gradient (i.e. from low to high)

Question 9

Molecule co-transport

Answer 9

• Symport: Both molecules move the same direction
• Antiport: Molecules move in opposite directions

Question 10

Vesicular Transport

Answer 10

The fluidity of the plasma membrane allows it to break and
reform around certain materials (this process requires ATP)

Question 11

Exocytosis

Answer 11

Materials released from a cell via vesicles

Question 12

Endocytosis

Answer 12

Materials internalised within a vesicle

Question 13

Intracellular vesicles can

Answer 13

move materials between cell organelles
* E.g. rough ER → Golgi complex → plasma membrane