transport across membranes 2.15, 2.16, 2.17

Question 1

what’s the definition of diffusion?

Answer 1

diffusion is the net movement of particles from an area of high concentration to low concentration, moving down the concentration gradient

Question 2

what are four factors that could affect the speed/rate of diffusion?

Answer 2

• temperature, higher the temp the higher the kinetic energy and speed of particles
• concentration gradient, the greater the concentration gradient the greater the rate of diffusion
• distance, the shorter the distance the quicker diffusion
• surface area, large surface area increases the rate of diffusion

Question 3

what’s the definition of osmosis?

Answer 3

osmosis is the net movement of water from an area of high water concentration to an area of low water concentration, across a partially permeable membrane

Question 4

what is a partially permeable membrane?

Answer 4

a membrane that only lets certain particles through

Question 5

what is water potential?

Answer 5

the measure of concentration of water molecules in a solution

Question 6

what is the name of a solution that has the same water potential as inside a cell?

Answer 6

isotonic solution

Question 7

what is the name of a solution with a higher water potential than a cell?

Answer 7

hypotonic solution

Question 8

what’s the name of a solution with a lower water potential than a cell?

Answer 8

hypertonic solution

Question 9

whats the name of an animal and plant cell that is in a hypotonic solution?

Answer 9

animal cell - lysed
plant cell - turgid (normal for a plant cell)

Question 10

whats the name of an animal and plant cell that is in a hypertonic solution?

Answer 10

animal cell - shrivelled
plant cell - plasmolyzed, cell membrane shrinks from cell wall, cell wall fully permeable and cell membrane partially permeable and plants will wilt

Question 11

whats the name of an animal and plant cell that is in an isotonic solution?

Answer 11

animal cell - normal
plant cell - flaccid

Question 12

whats the definition of active transport?

Answer 12

active transport is the movement of particles from an area of low concentration to an area of high concentration using atp, against the concentration gradient

Question 13

does active transport need energy to transport substances?

Answer 13

yes, uses ATP to provide energy

Question 14

whats two examples of active transport?

Answer 14

absorb glucose in the small intestine
plants use it in their hair root cells to absorb mineral ions

Question 15

practical
demonstrating the relationship between surface area : volume ratio and the rate of diffusion

Answer 15

agar cubes
cubes contain alkali and an indicator that’s pink
place in acid and it diffuses into the cube and reacts with the alkali - this causes it to become neutralised and colourless
the smallest cube becomes colourless quickest

Question 16

practical
investigating the water potential of a potato

Answer 16

potato chips placed in sucrose or salt solutions of different concentrations
osmosis will occur until the water potential of the tissue and solution are the same causing a mass change
this method can determine the water potential of a potato by the change in mass

Question 17

practical
investigating osmosis in a non-living system

Answer 17

visking tubing
the tubing is partially permeable so only allows small soluble molecules to pass through, therefore osmosis can occur
place sucrose solution in the tubing and then water around it, the liquid level in the tubing will increase
you could increase sucrose solution or the temperature of the water to investigate the effect on osmosis