Structure and Functions in Living Organisms - Movement of Substances

Question 1

what is diffusion?

Answer 1

Passive net movement of particles down the concentration gradient (from region of high concentration to region of low concentration) until equilibrium

Question 2

what is osmosis?

Answer 2

Passive net movement of water molecules down the water potential gradient (from region of higher water potential to region of lower water potential) across a partially permeable membrane

Question 3

what is active transport?

Answer 3

Movement of substances against the concentration gradient (from region of low concentration to region of high concentration) using energy (usually ATP)

Question 4

what factors affect the rate of movement of substances?

Answer 4

surface area to volume ratio, distance, temperature and concentration gradient

Question 5

how does the surface area to volume ratio affect the rate of movement of substances?

Answer 5

• As the surface area to volume ratio increases, the rate will increase
• This is because there is a larger surface area in which substances can move through.

Question 6

how does the distance affect the rate of movement of substances?

Answer 6

• as distance increases, the rate will decrease
• this is because substances have a higher distance to travel

Question 7

how does the temperature affect the rate of movement of substances?

Answer 7

• As temperature increases, the rate will increase
• This is because particles gain more kinetic energy and so will move faster

Question 8

how does the concentration gradient affect the rate of movement of substances?

Answer 8

• As the concentration gradient increases, the rate will increase
• This is because a stronger concentration gradient is present

Question 9

how would you investigate diffusion in a non-living system?

Answer 9

• when a dye of Potassium Permanganate is added to Water, molecules of Potassium Permanganate will diffuse into the water.
• overtime, the colour of the solvent will be weaker compared to the initial dye as molecules will be less concentrated and have diffused through the water.

Question 10

how do you investigate osmosis in a living system?

Answer 10

put identical cylinders in two beakers with a concentrated sugar solution and pure water. leave the potatoes for half an hour, take them out and measure their lengths.

Question 11

how do you investigate osmosis in a non-living system?

Answer 11

put some visking tubing at the end of a thistle funnel. pour some sugar down the funnel and put it into a beaker of pure water and measure where the sugar solution comes up to. leave overnight and the solution should be forced up the tube as water is drawn in.