Transport in Cells

Question 1

what is diffusion?

Answer 1

The random movement of particles from an area of high concentration to an area of low concentration (down a concentration gradient) until there is no net movement and equilibrium is reached.

Question 2

what state can diffusion occur in?

Answer 2

• solid
• gas

Question 3

what is a concentration gradient?

Answer 3

difference in concentration

Question 4

the bigger the concentration gradient…

Answer 4

the faster the rate of diffusion

Question 5

why does temperature affect diffusion?

Answer 5

• higher temp
• particles carry more energy and move around faster
• faster rate of diffusion

Question 6

how does surface area affect diffusion?

Answer 6

• larger surface area of membrane
• more contact
• more particles can pass through
• faster rate of diffusion

Question 7

how does diffusion distance affect diffusion?

Answer 7

• shorter diffusion distance
• particles can go through more quickly
• faster rate of diffusion

Question 8

list 4 factors which affect diffusion

Answer 8

• concentration gradient
• temp
• surface area
• diffusion distance

Question 9

small organisms have a higher SA:V ratio than larger organisms

Answer 9

• diffusion can happen through a large area of small organism
• makes diffusion useful for transporting molecules

Question 10

large multicellular organisms have a small SA:V ratio

Answer 10

• need transport system with specialised surface to exchange molecules
• cells are too far from the environment

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Question 11

how are alveoli adapted to transfer gases in the lungs?

Answer 11

large surface area

Question 12

if an animal has a large SA:V ratio…

Answer 12

it can lose heat quickly

Question 13

what type of molecules can diffuse through a cell membrane?

Answer 13

• small molecules e.g oxygen, glucose, amino acids and water
• big molecules can’t fit through membrane e.g proteins and starch

Question 14

what does concentration mean?

Answer 14

mass of a solute per unit volume

Question 15

does diffusion require energy?

Answer 15

• no
• particles still move randomly
• but concentration of different areas stay the same

Question 16

explain why we dissolve cocoa powder into warm milk instead of cold

Answer 16

• higher temp provides particles more energy
• diffusion will be quicker

Question 17

what is osmosis?

Answer 17

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

Question 18

how is diffusion and osmosis different?

Answer 18

diffusion: gases and solids
osmosis: water particles

Question 19

what is partially permeable membrane?

Answer 19

one with very small holes in it

Question 20

what state can osmosis occur in?

Answer 20

water

Question 21

what type of molecules is allowed in osmosis?

Answer 21

• tiny molecules e.g water
• bigger molecules can’t e.g sucrose

Question 22

describe how the water would move in this scenario

Answer 22

1) right-hand side more dilute, higher concentration of water
2) allows water to go through semi-permeable membrane into the left-hand side, lower concentration of water
3) after an hour: fresh water level drops, brine water level rises

Question 23

what specialised plant cell uses osmosis to absorb water?

Answer 23

root hair cell

Question 24

water doesn’t diffuse…

Answer 24

it moves by osmosis

Question 25

in an osmosis experiment, give an example of the independant variable

Answer 25

concentration of sugar solution

Question 26

in an osmosis experiment, give an example of the dependant variable

Answer 26

change in the mass of the object being used

Question 27

what is an isotonic solution in regard to a cell?

Answer 27

same water concentration inside and outside the cell

Question 28

what is a hyp**o**tonic solutionin regard to cell?

Answer 28

- outside is more diluted than inside - water will go into the cell (osmosis)

Question 29

what is a hypertonic solution in regard to a cell?

Answer 29

- inside the cell is more diluted than outside - water will move into the more concentrated (osmosis)

Question 30

normal blood glucose concentration is 8 grams per litre. suggest the possible glucose solutions that are isotonic, hyp**o**tonic and hypertonic

Answer 30

isonotic: 8 hyp**o**tonic: any number below 8 hypertonic: any number above 8

Question 31

what is active transport?

Answer 31

movement of particles from an area of low concentration to an area of high concentration across a cell membrane

Question 32

give examples of active transport in humans and plants

Answer 32

- mineral absorption in plants: necessary for healthy growth - sugar absorption in human gut: needed for cell respiration

Question 33

does active transport require energy?

Answer 33

- yes - required to absorb subtances against a concentration gradient - cells need lost of mitochondria to release energy - proteins from cell membrane

Question 34

how do root hair cells take in minerals using active transport?

Answer 34

allows plant to absorb mineral ions from a dilute solution against a concentration gradient

Question 35

what is passive transport?

Answer 35

- diffusion - osmosis

Question 36

why do root hair cells have lots of mitochondria?

Answer 36

- need lots of energy - for active transport of minerals

Question 37

explain the transport of glucose into the blood in the small intestine

Answer 37

- higher concentration of glucose will diffuse naturally into the blood - level of concentration even out in the blood and gut - active transport occurs to gain more glucose into bloodstream - then transfered to cells, used for respiration

Question 38

how do humans exchange substances such as urea?

Answer 38

- urea diffuses from cells into the blood plasma - for removal from the body by the kidneys

Question 39

what is the job of the lungs?

Answer 39

- transfer oxygen to blood - remove waste CO₂ from it - lungs contain alveoli where gas exchange takes place

Question 40

how are alveoli adapted to have max diffusion of oxygen and CO₂?

Answer 40

- large surface area - moist lining for dissolving gases - very thin walls - extensive blood supply

Question 41

how does villi provide a big surface area?

Answer 41

- inside of small intestine covered in villi - increases SA so digested food is absorbed more quickly into blood - has single layer of surface cells - extensive blood supply to assist quick absorption

Question 42

how does stomata help to diffuse CO₂ into air spaces of leaf and then into the cell?

Answer 42

1. underneath of leaf (exchange surface) covered in stomata which CO₂ diffuses in through 2. oxygen and water vapour diffuses out through stomata 3. guard cells close stomata cells if plant is losing water faster than it is being replaced by the roots

Question 43

how does the shape of leaf make diffusion more effective?

Answer 43

- thin - increases area of exchange surface

Question 44

how does the walls of the cells in a leaf make diffusion more effective?

Answer 44

- air spaces inside leaf increases area of exchange surface - more chance for CO₂ to enter cells