Cell membranes and transport

Question 1

Diffusion definition

Answer 1

net movement as a result of random motion of its molecules of a substance from a region of higher to lower concentration

Question 2

How does steepness of concentration gradient affect rate of diffusion

Answer 2

about how large the difference is in concentration between two sides of the molecule

if one side is of much greatewr concentration of molecules, more molecules will have random motion so more going from high to low

diffusion rate increases

Question 3

how does temperature affect the rate of diffusion

Answer 3

increased kinetic energy of molecules

faster movement so increased rate of diffusion

Question 4

how does surface area affect rate of diffusion

Answer 4

greater number of molecules can diffuse at any given time

so Rate increases

can be caused by folding of cell membrabe

as SA:V ratio increases with size of cell, rate of diffusion slows as the distance becomes too large to diffuse through cell

Question 5

size of molecule or ion affect on rate of diffusion

Answer 5

decreases rate as more energy is required for molecules to move

Question 6

facilitated diffusion
transports what molecules

Answer 6

large
polar
charged

Question 7

two types of proteins that enable facilitated diffusion:

Answer 7

channel and carrier

Question 8

what are channel proteins

Answer 8

water-filled pores
allow charged substances to diffuse through the cell membrane
pores can open and close (gated) - this means that they control the exchange of ions

Question 9

what are carrier proteins

Answer 9

carrier proteins switch between two shapes
only one binding site of the protein is open at a time
direction that molecules will diffuse through carrier proteins depends on the concentration of ions

Question 10

osmosis definition

Answer 10

net diffusion of water molecules from high to low water potential
through a partially permeable membrane

Question 11

water potential definition

Answer 11

tendency of water to move out of a solution.

Question 12

water potential of a dilute solution

Answer 12

high

Question 13

water potential of a concentrated solution

Answer 13

low

Question 14

water potential of pure water

Answer 14

0Kpa

Question 15

cell membrane of plants and animal cells with relation to osmosis

Answer 15

partially permeable with phospholipid bilayer - water is free to move by osmosis

Question 16

cell wall of plants (relating to osmosis)

Answer 16

composed of cellulose

fully permeable

Question 17

what happens when a plant cell is placed into a solution with low water potential

Answer 17

water leaves the cell through cell membrane
volume of cell decreases
protoplast pulls away from the cell wall
cell is plasmolysed

Question 18

what happens when an animal cell is placed into a solution with low water potential

Answer 18

water leaves cell through membrane

volume of cell decreases

cell shrivels

Question 19

what happens when a plant cell is placed into a solution with high water potential

Answer 19

water enters cell
protoplast expands against the cell wall
cell is turgid as cell wall withstands pressure
no more water can enter

Question 20

what happens when an animal cell is placed into a solution with high water potential

Answer 20

water enters cell through cell membrane by osmosis

volume of cell increases

no cell wall to withstand turgor pressure

cell membrane bursts

Question 21

Experiment for investigating the water potential using calibration curves

Answer 21

Immersing plant tissues in different solutions of different water potentials
Use results to estimate the water potential of plant tissue itself

Question 22

Potato cycling’s water potential calibration curve test method

Answer 22

Cut all potatoes to same length and shape
Blot dry
Record initial mass
Place potatoes into solution for 30min at 30degrees
Remove and dry excess liquid
Final mass of each potato cylinder is recorded
Plot a graph of change of mass and concentration of sucrose

Question 23

Results achieved from calibration curve osmosis experiment

Answer 23

For both 0 percent sucrose and 0.2 , the potato cylinders gained weight. This is as water moves from the higher water potential solution into the lower water potential potato.

All other sucrose concentrations, the potato loses mass. This is as there is a lower water potential outside than inside the plant tissue. This means that water moves out of the cell.

Question 24

How to calculate percentage change

Answer 24

(Final mass -initial mass) / initial mass. X 100

Question 25

Active transport definition

Answer 25

Movement of molecules and ions through a cell membrane from a region of lower to higher concentration using ATP

Question 26

What type of protein in the cell membrane does active transport use

Answer 26

Carrier proteins Specific for a particular type of molecule of ion

Question 27

How does AT use carrier proteins

Answer 27

ATP makes the carrier proteins change shape allowing it to transfer the molecules or ions across the cell membrane

Question 28

factors which rate of diffusion depends on

Answer 28

temperature thickness of exchange surface surface area of exchange surface concentration gradient

Question 29

affect of surface area on rate of diffusion (simple)

Answer 29

the larger the SA, the higher the rate as more molecules can diffuse at a given time

Question 30

affect of concentration gradient on rate (simple)

Answer 30

rater increases with increasing concentration gradient as higher conc on one side. as diffusion occurs, conc gradient slowly decreases thus decreasing rate

Question 31

affect of TOES on rate (simple)

Answer 31

thicker = longer diffusion distance which decreases rate

Question 32

affect of concentration gradient on rate (facilitated)

Answer 32

higher rate with more conc on one side dependant on the number of carrier and channel proteins available

Question 33

number of channel or carrier proteins affect on rate of diffusion facilitated

Answer 33

these proteins are required. Once all the carrier and channel proteins are used up , rate cannot increase any further. more channel and carrier proteins = more rate

Question 34

root hair cells adaptations to diffusion

Answer 34

adapted for the absorbtion of water and mineral ions from soil shape increases the surface area - rate of water uptake by osmosis is greater thinner walls means less diffusion distance permanant cell vacuole containing cell sap which is more concentrated that high water potential gradient is maintained

Question 35

experiment for factors affecting membrane fluidity method

Answer 35

cut 5 equal size cubes of beetroot rinse the beetroot peices add pieces to 5 test tubes containing same vol of water put each tube in different temp water baths leave 30min remove beetroot pieces leaving just liquid use a colorimeter to test how permeable the membrane is

Question 36

experiment for factors affecting membrane fluidity results

Answer 36

as temperature increases, membrane permeability increases as phospholipids gain more energy so move more and are less tightly packed temperature also affects the 3D shape of proteins as at high temperatures the inter molecular forces between amino acids are broken.

Question 37

how does PH affect membrane fluidity

Answer 37

Excess OH and H ions disrupts the amino acids in the proteins which disrupts function.

Question 38

fluid mosaic model explains

Answer 38

movement of molecules cell to cell interactions cell signalling

Question 39

phospholipid structure

Answer 39

phosphate head (polar and hydrophilic) and 2 fatty acid tails (non polar and hydrophobic) forms a bilayer phospholipids can move (FLUID mosaic)

Question 40

cholesterol function

Answer 40

regulate the fluidity of the cell membrane

Question 41

glycolipid function

Answer 41

lipids with carbohydrate chains added. project out whatever fluid is surrounding the cell

Question 42

glycoprotein function

Answer 42

proteins with carbohydrate chains added also project out whater fluid is covering the cell