key concepts ++ transporting substances

Question 1

how’re substances transported ?

Answer 1

substances are transported by diffusion, osmosis and active transport

Question 2

describe how substances are transported by active transport (including the need for energy)

Answer 2

Active transport is the movement of dissolved molecules into or out of a cell through the cell membrane, from a region of lower concentration to a region of higher concentration. The particles move against the concentration gradient , using energy released during respiration

Question 3

explain how substances are transported by diffusion

Answer 3

particles move from an area of high concentration to low concentration

Question 4

explain how substances are transported by osmosis

Answer 4

water molecules move from a high concentration to a lower concentration across a partially permeable membrane

Question 5

explain the effects of osmosis on cells and tissues

Answer 5

animal cells also take in and lose water by osmosis. They do not have a cell wall, so will change size and shape when put into solutions that are at a different concentration to the cell contents. Red blood cells lose water and shrink in a concentrated solution. They swell and burst in a solution that is too dilute

Question 6

describe how you would investigate osmosis in potatoes

Answer 6

1. cut equal-sized pieces of potato
2. blot with tissue paper and weigh
3. put pieces into different concentrations of sucrose solution for a few hours
   remove,
4. blot with tissue paper and reweigh

The percentage change in mass can be calculated for each piece of potato.

Question 7

how do you calculate percentage change in mass ?

Answer 7

percentage change in mass =

end mass - start mass/start mass ×100