Diffusion, osmosis, active transport

Question 1

diffusion definition

Answer 1

the net movement of particles from a region of higher concentration to a region of lower concentration

Question 2

is diffusion an active or passive process

Answer 2

passive

Question 3

what two factors affect the rate of diffusion and how?

Answer 3

temperature - increases rate of diffusion as higher temperatures have more kinetic energy and move at higher speeds

concentration difference - greater diff in conc increases rate of diffusion as overall movement from higher to lower concentration will be larger

Question 4

what does diffusion across membranes involve

Answer 4

particles passing through the phospholipid bilayer- however this can only happen if the membrane is permeable to the particles

Question 5

what kind of molecules tend to move across a membrane via diffusion

Answer 5

small molecules
lipid soluble molecules
non-polar molecules

Question 6

what 4 factors affect rate of diffusion across a membrane

Answer 6

temperature
concentration gradient
surface area - larger the area of an exchange surface the higher the rate of diffusion
thickness of membrane - thinner the exchange surface the higher the rate of diffusion

Question 7

what type of membranes are selectively permeable and why

Answer 7

membranes containing protein channels because most channel proteins are specific to one molecule or ion therefore only these molecules/ions are able to move across the membrane

Question 8

facilitated diffusion definition

Answer 8

the diffusion across a membrane through protein channels

Question 9

are polar molecules able to pass through membranes in facilitated diffusion

Answer 9

yes

Question 10

membranes with protein channels are __________ _________

Answer 10

selectively permeable as most protein channels are specific to one molecule or ion

Question 11

is facilitated diffusion an active or passive process

Answer 11

passive as it doesn’t require energy from respiration

Question 12

what 5 factors affect the rate of facilitated diffusion

Answer 12

temperature
concentration gradient
membrane surface area
membrane thickness
number of channel proteins present - the more channel proteins present the higher the rates of diffusion overall

Question 13

what can facilitated diffusion also involve

Answer 13

carrier proteins which change shape when a specific molecule binds

Question 14

active transport definition

Answer 14

the movement of particles from a region of low concentration to a region of high concentration across a cell membrane using ATP and carrier proteins

Question 15

what does active transport require

Answer 15

energy because the particles are being moved against the concentration gradient

Question 16

process of active transport

Answer 16

1. molecule/ion binds to receptors in channel of carrier protein on the outside of the cell
2. on inside of cell, ATP binds to the carrier protein and is hydrolyses into ADP and phosphate
3. binding of phosphate molecule to carrier protein causes protein to change shape opening up to the inside of the cell
4. molecule/ion is released into the cell
   5.phophate molecule is released from carrier protein and recombines with ADP to form ATP
5. the carrier protein return to its original shape

Question 17

why is active transport a selective process

Answer 17

specific substances are transported by specific carrier proteins

Question 18

what is bulk transport

Answer 18

another form of active transport. large molecules (enzymes, hormones, whole cells) are too big to move through channel or carrier proteins so are moved in and out of the cell by bulk transport

Question 19

endocytosis

Answer 19

bulk transport of material into cells. there are two types of endocytosis : phagocytosis for solids and pinocytosis for liquids

Question 20

process of endocytosis

Answer 20

cell surface membrane invaginates when comes into contact with material to be transported.
membrane enfolds material until membrane fuses, forming a vesicle.
vesicle pinches off and moves into the cytoplasm to transfer material for further processing within the cell

Question 21

invaginates definition

Answer 21

bends inwards

Question 22

exocytosis

Answer 22

bulk transport of material out of cells

Question 23

exocytosis process

Answer 23

vesicles move towards and fuse with cell surface membrane. contents of vesicles then released outside of the cell

Question 24

osmosis definition

Answer 24

the movement of water from an area of higher water potential to an area of lower water potential across a partially permeable membrane

Question 25

is osmosis an active or passive process

Answer 25

passive

Question 26

what is water potential

Answer 26

the pressure exerted by water molecules as they collide with the membrane or contained.
measured in Pa or kPa.
symbol of water potential is Ψ
the more concentrated the solution, the more negative the water potential

Question 27

effect of osmosis on animal cell - higher Ψ than cytoplasm

Answer 27

net movement of water into the cell.
cause cell to swell and burst
in a red blood cell, cell contents lost and haemoglobin released

Question 28

effect of osmosis on animal cell - equal Ψ of cytoplasm

Answer 28

water constantly and enters and leaves cell but at equal rates so state of cell won’t change

Question 29

effect of osmosis on animal cell - lower Ψ than cytoplasm

Answer 29

net movement of water out of the cell. cause cell to shrink resulting in a crenation.
in a red blood cell - haemoglobin is more concentrated giving cell darker appearance, cell shrunken and shrivelled

Question 30

effect of osmosis on plant cell - higher Ψ than cytoplasm

Answer 30

net movement of water into the cell.
cause protoplast to swell and become turgid. protoplast will be pushed up against cell wall

Question 31

effect of osmosis on plant cell - equal Ψ to cytoplasm

Answer 31

water constantly enters and leaves cell so the state of the cell won’t change

Question 32

effect of osmosis on plant cell - lower Ψ than cytoplasm

Answer 32

net movement of water out of the cell.
will cause plasmolysis and the contents will shrink
protoplast will be completely pulled away from cell wall, the space will be filled with external solution of lower water potential

Question 33

concentration definition

Answer 33

the amount of solute in a certain volume of aqueous solution