Diffusion, Active Transport, Osmosis 2.1.5 (d,e)

Question 1

what are the two types of exchange of substances between cells?

Answer 1

passive
active

Question 2

what is active exchange?

Answer 2

exchange which requires metabolic energy

Question 3

what is diffusion?

Answer 3

the net movement of particles from a region of high concentration to low concnetration

Question 4

what is simple diffusion?

Answer 4

diffusion in the absence of a barrier/membrane

Question 5

which molecules can freely pass through the phospholipid bilayer?

Answer 5

non-polar molecules (like oxygen)
small molecules

Question 6

which molecules cannot pass freely through the phospholipid bilayer?

Answer 6

charged molecules (ions)
polar molecules (water)
large molecules

Question 7

why can’t charged molecules pass through the phospholipid bilayer?

Answer 7

they are charged and thus repelled by the hydrophobic fatty acid core

Question 8

can water diffuse through the phospholipid bilayer?

Answer 8

yes but very slowly
as it is polar it is only partially charged

Question 9

why are membranes partially permeable?

Answer 9

they allow certain molecules in and not others

Question 10

what affects the rate of diffusion?

Answer 10

temperature
concentration gradient
surface area
thickness of membrane

Question 11

how does an increased temperature affect the rate of diffusion?

Answer 11

a higher temperature means the particles have more kinetic energy to so move at higher speeds

Question 12

how does an increased concentration gradient affect the rate of diffusion?

Answer 12

a steeper concentration gradient between two regions will increase the rate of diffusion

Question 13

how does the thickness of the membrane affect the rate of diffusion?

Answer 13

the thinner the membrane the shorter the diffusion distance so the rate of diffusion increases

Question 14

how does surface area affect the rate of diffusion?

Answer 14

a larger surface area the faster the rate of diffusion

Question 15

what is facilitated diffusion?

Answer 15

diffusion across a membrane through the use of a channel and carrier proteins

Question 16

what two proteins are used in facilitated diffusion?

Answer 16

carrier proteins
channel proteins

Question 17

how are carrier proteins used in facilitated diffusion?

Answer 17

used to move large molecules (polar molecules and ion) down the concentration gradient

Question 18

how does a carrier protein work passively?

Answer 18

large molecule binds to the carrier protein
protein changes shape
the molecule is released on the opposite side

Question 19

how are channel proteins used in facilitated diffusion?

Answer 19

they have hydrophilic interiors which allow large polar molecules to pass through

Question 20

what factors affect facilitated diffusion?

Answer 20

temperature
concentration gradient
surface area
membrane thickness
number of channel proteins present

Question 21

how does the number of channel proteins present affect the rate of diffusion?

Answer 21

the more channel proteins the higher the rate of diffusion

Question 22

what is active transport?

Answer 22

the movement of molecules/ions into a cell from a region of low concentration to high concnetration

Question 23

is active transport active or passive?

Answer 23

active
require ATP

Question 24

outline active transport

Answer 24

the molecule binds to receptors in the carrier protein

ATP binds to the carrier protein and is hydrolysed to from ADP + P

the P group binds to the carrier protein to cause it to change it’s shape

this new shape opens up on the other side of the cell, with the molecule being released to enter the cell

ADP + P recombine to form ATP and the carrier protein returns to it’s original shape

Question 25

what is bulk transport?

Answer 25

the movement of large molecules too large to be transported by facilitated diffusion

Question 26

what are examples of molecules too large to be transported by facilitated diffusion?

Answer 26

enzymes hormones bacteria

Question 27

what are the two types of bulk transport?

Answer 27

endocytosis exocytosis

Question 28

what is endocytosis?

Answer 28

the bulk movement of material INTO cells

Question 29

what are the two types of endocytosis?

Answer 29

phagocytosis pinocytosis

Question 30

what is phagocytosis?

Answer 30

bulk transport of solids INTO a cell

Question 31

what is pinocytosis?

Answer 31

bulk transport of liquids INTO a cell

Question 32

what is exocytosis?

Answer 32

the bulk movement of material OUT of cells

Question 33

is bulk transport active or passive?

Answer 33

active requires ATP for the movement of vesicles along the cytoskeleton

Question 34

what is osmosis?

Answer 34

the movement of water from a region of high water potential to low water potential across a partially permeable membrane

Question 35

what is water potential?

Answer 35

the pressure exerted by water molecules on a container/membrane

Question 36

what is the water potential of pure water?

Answer 36

0 kPa

Question 37

the more concentrated the solution

Answer 37

the more negative the water potential

Question 38

what is an isotonic solution?

Answer 38

when the water potential outside the cell and inside the cell are equal

Question 39

what is the net movement in an isotonic solution?

Answer 39

no net movement water moves in both directions

Question 40

what is a hypertonic solution?

Answer 40

when the water potential inside the cell is greater than outside the cell

Question 41

what is the net movement in a hypertonic solution?

Answer 41

water moves out of the cell

Question 42

what happens to an animal cell in a hypertonic solution?

Answer 42

the cell shrink and shrivel

Question 43

what happens to a plant cell in a hypertonic solution?

Answer 43

the cell becomes plasmolysed as the plasma membrane and cytoplasm ew pulled away from the cell wall

Question 44

what solution fills the gap between the cell membrane and cell wall in a plasmolysed cell?

Answer 44

the contents of the outside solution

Question 45

what is a hypotonic solution?

Answer 45

when the water potential outside the cell is greater than inside

Question 46

what is the net movement in a hypotonic solution?

Answer 46

water moves into the cell

Question 47

what happens to an animal cell in a hypotonic solution?

Answer 47

the cell swells and will eventually burst (cytolysis)

Question 48

what happens to a plant cell in a hypotonic solution?

Answer 48

the cell swells and becomes turgid it does not burst

Question 49

why does a plant cell not burst when in a hypotonic solution?

Answer 49

it has a cell wall which can withstand the turgor pressure generated by the influx of water