Diffusion and Osmosis

Question 1

Explain the permeability of particles with high diffusion coefficients

Answer 1

Particles with higher diffusion coefficients have higher permeability

Question 2

Describe ways of increasing rate of diffusion according to Fick’s Law

Answer 2

• increase of concentration/pressure
• increased area
• diffusion constant
• thickness of wall

Question 3

What is passive diffusion

Answer 3

• process by which molecules diffuse from a region of higher concentration to a region of lower concentration
• refers to lipophilic molecules

Question 4

What is facilitated diffusion

Answer 4

• molecule passes through membrane via carrier/channel

Question 5

Ways in which small molecules can cross cell membranes

Answer 5

• passive diffusion
• aqueous diffusion
• facilitated diffusion
• active transport
• endocytosis (pinocytosis)

Question 6

What is aqueous diffusion

Answer 6

• diffusion via a channel that transverses the plasma membrane
• does not require energy
• requires concentration gradient

Question 7

What is active transport

Answer 7

• diffusion via specialised carrier proteins
• requires energy
• can move molecules against concentration gradient

Question 8

What is endocytosis

Answer 8

• invagination of a part of the membrane
• molecule is encased in small vesicle and released inside cell

Question 9

Impact of saturation on rate of diffusion

Answer 9

high saturation = slower diffusion rate

Question 10

Define simple diffusion

Answer 10

random movement of solute molecules in solvent tending towards an evenly-distributed state

Question 11

Rate of diffusion equation

Answer 11

Rate of diffusion (J) is proportional to concentration gradient over distance (dc/dx)

Question 12

What is rate of diffusion related to

Answer 12

• physical properties of solute and solvent molecules (e.g. size, electric charge)
• temperature
• electric field

Question 13

Diffusion of solute across membrane is dependant on…

Answer 13

• membrane (selective barrier properties)
• concentration gradient across membrane barrier
• permeability of solute (diffusion + partitioning)

Question 14

Diffusion is vital for …

Answer 14

• gas exchange
• lipophilic drug actions

Question 15

Fick’s Law states that…

Answer 15

Rate of diffusion (J) of a solute (S) across a medium is proportional to the thickness of the medium, the cross-sectional area, and the concentration gradeint across the medium

Question 16

Decrease in membrane thickness

Answer 16

increase in diffusion -> less membrane to overcome

Question 17

What is a concentration gradient

Answer 17

measure of the relative difference in concentration across the membrane