module 2 - 5.3 diffusion and passive transport

Question 1

what does a passive process mean?

Answer 1

when something doesn’t require any EXTRA external energy

Question 2

what is diffusion?

Answer 2

net movement of anything from a region of high to low concentration (down concentration gradient)

Question 3

what is diffusion driven by?

Answer 3

a concentration gradient

Question 4

what is a change in concentration over a distance called?

Answer 4

a concentration gradient

Question 5

where does the energy for diffusion come from?

Answer 5

the kinetic energy of the particles
(does not need external energy)

Question 6

what is brownian motion?

Answer 6

relies on the random movement of particles suspended in a liquid or gas

Question 7

what is the entropic force?

Answer 7

no force moving molecules down concentration gradient

Question 8

what is ficks law?

Answer 8

• higher temp, higher diffusion rate
• higher conc. difference, higher diffusion rate
• higher SA of exchange surface, higher diffusion rate
• higher membrane thickness, lower diffusion rate

Question 9

what is equilibrium?

Answer 9

when a concentration gradient has equalised diffusion

Question 10

what happens to the particles at equilibrium?

Answer 10

• they do NOT stop moving
• appears to be no directional movement as particles are all moving in the same direction

Question 11

what is bulk flow?

Answer 11

the movement of a whole substance or all the particles in a direction

Question 12

what happens to the air when the lungs are used as an example of diffusion?

Answer 12

• diffusion of oxygen molecules in air into blood due to concentration gradient
• oxygen particles moving within all other particles in the air

Question 13

what happens to the air when the lungs are used as an example of bulk flow?

Answer 13

• bulk flow of air into alveoli due to a pressure gradient (high outside lungs, low inside) when breathing in
• bulk flow stops when pressure is equalised in alveoli

Question 14

what type of transport and diffusion occurs between the phospholipids?

Answer 14

• passive transport
• diffusion/ simple diffusion

Question 15

what type of transport and diffusion occurs through a transmembrane protein?

Answer 15

• passive transport
• facilitated diffusion

Question 16

what happens to non-polar molecules during simple diffusion across across a membrane?

Answer 16

• small non-polar molecules can freely diffuse through cell membrane (O, CO2, H20 etc)
• bigger non-polar molecule, lower diffusion rate
• water can diffuse through cell membrane more slowly as partial charges being repelled by hydrophobic core of membrane

Question 17

what happens to polar molecules during simple diffusion across across a membrane?

Answer 17

• ## large and polar diffuse through cell slowly or not at all e.g. glucose

Question 18

what happens to fully charged molecules during simple diffusion across across a membrane?

Answer 18

cannot easily diffuse thorough cell membrane as charges are repelled by hydrophobic core

Question 19

what is simple diffusion?

Answer 19

diffusion of substances through tails and phospholipid bilayer

Question 20

which diffusion happens faster and why?

Answer 20

• facilitated diffusion
• happens through a transmembrane protein (direct route)

Question 21

what is the pore in the protein made of in the phospholipid bilayer?

Answer 21

amino acids in a polypeptide chain

Question 22

what happens during facilitated diffusion across a membrane?

Answer 22

• involves intrinsic/ transmembrane proteins
• protein allows diffusion across cell membrane of specific molecule through pore in protein (down conc. gradient)

Question 23

which proteins are involved in facilitated diffusion?

Answer 23

• carrier proteins
• channel proteins

Question 24

what does a channel protein do within facilitated diffusion?

Answer 24

• has a pore that can open or close, pore is specific to a molecule
• high rate of diffusion but is saturable due to limited pores available

Question 25

what does a carrier protein do within facilitated diffusion?

Answer 25

• has a pore that’s never fully open across the membrane
• protein changes shape when specific molecule binds to it (causes conformational (shape) to change)
• low rate of diffusion due to limited pores available

Question 26

why do carrier proteins change shape when a specific molecule binds to it?

Answer 26

allows molecule to cross cell membrane

Question 27

where does the energy for the conformational (shape) to change?

Answer 27

the binding of the molecule
NOT ATP

Question 28

what is dialysis tubing?

Answer 28

artificial semi-permeable membrane tubing

Question 29

what is dialysis tubing used for?

Answer 29

teaching aid to demonstrate principles of diffusion, brownian motion, osmosis, and the movement molecules across restrictive membranes