P1 - 2d movement of substances in and out of cells

Question 1

what is diffusion?

Answer 1

it is the movement of particles from a region where their concentration is higher to a region where their concentration is lower.

Question 2

why is the diffusion of gases and solutes important?

Answer 2

all living things use diffusion, substances move in and out of cells by diffusion

• respiration and gas exchange in plants
• obtains many of their requirements
• rid of waste products

Question 3

how do substances move into and out of cells?

Answer 3

they move through the membrane, it is permeable to many substances

Question 4

where does the energy for diffusion come from?

Answer 4

energy for diffusion comes from kinetic energy (from the random movement of molecules and ions)

Question 5

what is a concentration gradient?

Answer 5

a model showing a high place of concentration and a low place (it gets lower as the concentration decreases)

Question 6

how does surface area influence diffusion?

Answer 6

the greater the surface area to volume ratio the shorter time is will take to diffuse

Question 7

how does temperature influence diffusion?

Answer 7

diffusion in hot water occurs more rapidly than in cold water.

Question 8

how does concentration gradient influence diffusion?

Answer 8

the higher the concentration gradient the quicker the diffusion

Question 9

how does distance influence diffusion?

Answer 9

the rate of diffusion does change so its quicker for diffusion to happen in a shorter distance

Question 10

what is osmosis?

Answer 10

net movement of water molecules from a region of higher water potential to a region of lower potential, through a partially permeable membrane

Question 11

what is water potential?

Answer 11

• how freely the water molecules can move

the concentration of water or H2O molecules in a solution

Question 12

what happens if a plant can’t get enough water to the vacuole?

Answer 12

it becomes less rigid and the plant wilts

- cell wall doesn’t allow for the plant cell to break

Question 13

how do you investigate the effect of osmosis?

Answer 13

• peel potatoes
• cut cylinders using a cork borer
• trim so same length
• measure the mass of cylinders
• place each cylinder into a separate test tube, add 10cm^3 of 0.5 molar sugar solution
• 0.25 molar sugar solution to the second
• and distilled water to the third
• leave overnight
• take out and dry
• measure mass
• calculate % change
  change in value / original value x 100

Question 14

in the practical, why did the mass of the potato in test tube 2 not change?

Answer 14

because there were equal amounts of water in the potato and in the sugar solution no osmosis occurred

Question 15

when do the potatoes gain mass?

Answer 15

when put in water

Question 16

when do potatoes lose mass?

Answer 16

when put into a concentrated solution (of sugar)

Question 17

turgid plant cell

Answer 17

when it gains lots of water

Question 18

flaccid plant cell

Answer 18

when it loses water

Question 19

what is plasmolysis?

Answer 19

its when the plant loses so much water that the cytoplasm and vacuole pull away from the cell wall

Question 20

how does water enter root hair cells?

Answer 20

osmosis

Question 21

what is active transport?

Answer 21

it moves substances from a more dilute concentration to a more concentrated solution (against the concentration gradient)

Question 22

where does active transport get its energy?

Answer 22

from respiration

Question 23

how do protein molecules move particles across a membrane in active transport?

Answer 23

transport proteins can bind to specific molecules and transport them into the cell
(they can change their shape to make it happen)
- this process also uses energy supplied by respiration

Question 24

describe the practical to test the factors that influence diffusion

Answer 24

• investigate temp by beetroot
  1. cut two equally sized beetroot pieces using cork borer
  2. rinse beetroot
  3. put water into two test tubes
  4. keep one at room temp and put another in a water bath set to temp investigating
  5. leave test tubes for a few mins
  6. add beet pieces, then after ten mins observe colour in both test tubes

Question 25

what is osmoregulation?

Answer 25

the homeostatic control of water potential across membranes within the body

Question 26

how is the human body adapted to maintain optimum osmotic balance?

Answer 26

sweating

increasing and decreasing urine concentration