Movement of Substances into and out of cells Pg8-11

Question 1

Define Diffusion

Answer 1

Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration

Question 2

What type of process is diffusion and osmosis

Answer 2

passive - it doesn’t require energy

Question 3

Where does diffusion happen

Answer 3

In liquids and gases because particles are free to move about randomly

Question 4

Where does diffusion occur in a cell

Answer 4

cell membrane

Question 5

Define Osmosis

Answer 5

Osmosis is the net movement of water molecules across a partially permeable membrane from an area of high water potential to area of low water potential

Question 6

What is a partially permeable membrane

Answer 6

A partially permeable membrane is just a membrane with very small holes in it which allows tiny molecules such as water to pass through and bigger molecules such as sucrose to not pass through. A cell membrane is a partially permeable membrane

Question 7

Describe and experiment for diffusion in a non-living system

Answer 7

• Phenolphthalein is a pH indicator it is pink in alkaline solution and colourless in acidic solutions
• First make up some agar jelly with phenolphthalein and dilute sodium hydroxide
• Put some dilute hydrochloric acid in a beaker. Cut out a few cubes from the jelly and put them in a beaker of acid.
• If you leave the cubes for a while they will eventually turn colourless as the acid diffuses into the agar jelly and neutralises the sodium hydroxide

Question 8

name the two living and non-living ways you can test for osmosis

Answer 8

Living system - Potato cylinders
Non-living system - Visking tube

Question 9

Describe the investigation for Potato cylinders to show osmosis

Answer 9

• Cut up a potato into identical cylinders and get some beakers with different sugar solution in them
• One should be pure water, another should be very concentrated sugar solution and some others with different concentrations in between.
• measure the length of cylinders, then leave a few cylinders in each beaker for half an hour or so
• take them out and measure their lengths again
• If the cylinder has drawn water in by osmosis the length should have increased. If water has been drawn out, they would have shrunk a bit.

Question 10

Describe the investigation for Visking tube to show osmosis

Answer 10

• fix some fisking tube over the end of thistle funnel. Then pour some sugar solution down the glass tube into the thistle funnel.
• Put the thistle funnel into the beaker of pure water - measure where the sugar solution comes up to on the glass tube
• leave the apparatus overnight, then measure where the solution is in the glass tube. Water should be drawn out through the visking tube by osmosis and this will force the solution up the glass tube

(a visking tube is a partially permeable membrane)

Question 11

Define active transport

Answer 11

Active transport is the movement of particles against a concentration gradient (lower to higher concentration) using energy released during respiration.

Question 12

What are the 4 factors that affect the movement of substances e.g. diffusion, osmosis and active transport

Answer 12

1. Surface area to volume ratio
2. Distance
3. Temperature
4. Concentration gradient

Question 13

How does surface area affect diffusion

Answer 13

The bigger the surface area to volume ratio, the faster the rate of diffusion as substances can move into and out of substances faster

Question 14

How does distance affect diffusion

Answer 14

The smaller the distance the substance has to move, the quicker they can move into and out of cells

Question 15

How does temperature affect diffusion

Answer 15

The higher the temperature, the more energy the particles will have so they will move faster and be able to move into and out of cells faster

Question 16

How does concentration gradient affect diffusion

Answer 16

substances move into and out of cells quicker if there is a big concentration gradient between the inside and outside of the cell. This only happens in diffusion and osmosis as concentration gradient don’t affect the rate of active transport