DIFFUSION, OSMOSIS, ACTIVE TRANSPORT

1. Clicking here will move you to the next page DIFFUSION, OSMOSIS, ACTIVE TRANSPORT BUTTONS Click here; Clicking here will allow you to hear some information on the topic. Clicking here again will stop the sound. Clicking here will move you back a page. Clicking here will reveal some information Clicking here will reveal an answer Jump to… Clicking here will bring you back to this page. TOPICS Jump to… …Diffusion (two pages). Jump to… …Osmosis (five pages). Jump to… …Active transport – higher tier (one page). Jump to… …practice questions (four pages). …exam questions (five pages).

2. DIFFUSION After a solid has dissolved in a liquid, the solid particles spread throughout the liquid. This is called diffusion. This is a passive process, and therefore does not need energy. Diffusion definition: the movement of particles from a High concentration tolow concentration Click on the button below to see this process in action. DIFFUSION Low concentration High concentration CONCENTRATION GRADIENT DIFFUSION The greater the concentration gradient, the greater the number of molecules diffusing. CONCENTRATION GRADIENT outside cell inside cell CONCENTRATION GRADIENT inside cell outside cell

3. DIFFUSION IN HUMAN BEINGS CARBON DIOXIDE /CO2 BREATHED OUT OXYGEN/O2 BREATHED IN O2 Click on the buttons to see examples of diffusion between the alveolus and the blood between blood and the body cells. O2 O2 alveolus LUNGS BODY CELLS ALVEOLUS Oxygenated blood to the body Deoxygenated blood from the body O2 O2 O2 O2 CO2 O2 blood capillary CO2 CO2 CO2 CO2 CO2 BODY CELLS 1. Oxygen is breathed in and diffuses from a high concentration in the alveolus to a low concentration in the blood stream down the concentration gradient. o2 co2 2. Carbon dioxide diffuses from a high concentration in the blood stream to a low concentration in the alveolus before being breathed out. body cells

4. OSMOSIS DEFINITION: The diffusion of water from a high concentration of water to a low concentration of water, through a selectively permeable membrane Click on the button below learn more. A membrane with microscopic pores which only allows certain particles through. Selectively permeable membrane VOLUME INCREASING Selectively permeable membrane Osmosis animation VOLUME DECREASING OSMOSIS Here, only the blue particles are small enough to fit through the pores in the membrane

5. OSMOSIS in animals and plants Animal cells which gain water swell up and burst. When they lose water they shrink. However, plant cells which gain water swell up and become turgid. When they lose water they become flaccid (limp). This would cause the plant to wilt. Click on the PICTURES below to learn more. Plant cell in weak (hypotonic) salt solution, (high water concentration) Red blood cells in weak (hypotonic) salt solution, (high water concentration) ANIMAL PLANT Red blood cells in isotonic solution (equal water concentration in and out) Plant cell in isotonic solution (equal water concentration in and out) Plant cell in strong (hypertonic) salt solution, (low water concentration) Red blood cells in strong (hypertonic) salt solution, (low water concentration)

6. OSMOSIS IN ISOTONIC SOLUTIONS Click on the button to start the animation. DIFFUSION OF WATER start DIFFUSION OF WATER ssy The cell volume and mass will remain constant

7. OSMOSIS EXPERIMENTS 1 A visking tube can be used as a selectively permeable membrane. It has microscopic pores which allow small molecules such as water through, but not large molecules such as glucose (sugar). Before you click on the button, try to predict the outcome of this experiment. The sugar solution rises as the volume of sugar solution increases Capillary tube start Clicking the red boxes will reveal more information. Visking tube water The sugar molecules are too large to diffuse out through the visking tube pores Water diffuses into the sugar solution by osmosis,from a high concentration of water to a low concentration of water through a selectively permeable membrane Sugar solution

8. OSMOSIS EXPERIMENTS 2 In this experiment we measure the changes in length of potato cylinders placed in varying concentrations of sucrose solution for 6 hours. The graph produced will enable us to work out the concentration of the potato cells. Calculate the change in length, in the results table. At a sucrose concentration of 5.2% there is no change in length as there is no net flow of water in or out of the potato cells by osmosis. Both concentrations are equal. 0% 6% 8% 10% 2% 4% +2.0 Results +1.5 +1.0 +0.5 0.0 change in length/cm 2.0 4.0 6.0 8.0 10.0 +1.5 sucrose solution concentration/% -0.5 +1.2 -1.0 +0.5 We can also say that concentration of the water in the sucrose solution is equal to the concentration of the water in the cells. -1.5 -0.2 -1.0 -2.0 -1.5

9. ACTIVE TRANSPORT – higher tier Active transport is an active process whereby substances can enter cells against a concentration gradient. This requires energy in the form of ATP. Click on the buttons below to learn more. ATP ATP The blood contains a high concentration of glucose The small intestine lumen contains a low concentration ofglucose The cell contains a high concentration of ions e.g. Nitrate The soil water contains a low concentration of ions e.g. Nitrate SMALL INTESTINE ROOT HAIR CELL gut lumen Microvilli increase the surface area for absorption.. The cell has a large surface area for absorption of mineral ions Concentration gradient Concentration gradient Active transport Active transport Mitochondria provide energy as ATP. soil Mitochondria provide energy as ATP. blood stream

10. TEST YOUR UNDERSTANDING- FOUNDATION Click on the or buttons which match the statements. Can occur in the absence of a cell membrane Can occur in the absence of a cell membrane Responsible for maintaining plant cell shape Responsible for maintaining plant cell shape DIFFUSION DIFFUSION OSMOSIS OSMOSIS OSMOSIS OSMOSIS OSMOSIS DIFFUSION OSMOSIS OSMOSIS DIFFUSION DIFFUSION DIFFUSION DIFFUSION DIFFUSION OSMOSIS Occurs through a selectively permeable membrane Occurs through a selectively permeable membrane Diffusion of water across a membrane Diffusion of water across a membrane Movement of water molecules from high to low concentration of water Movement of water molecules from high to low concentration of water This is how gas exchange occurs in the lung’s alveoli This is how gas exchange occurs in the lung’s alveoli Movement of particles from high to low concentration Movement of particles from high to low concentration

11. TEST YOUR UNDERSTANDING - HIGHER Click on the buttons to show which picture matches the statement. No need for a selectively permeable membrane for particles to move down their concentration gradient No need for a selectively permeable membrane for particles to move down their concentration gradient OSMOSIS Particles are moving against their concentration gradient Particles are moving against their concentration gradient ACTIVE TRANSPORT ATP Many mitochondria are needed for this to happen Many mitochondria are needed for this to happen Diffusion of water from high water concentration to low water concentration through a selectively permeable membrane Diffusion of water from high water concentration to low water concentration through a selectively permeable membrane DIFFUSION This requires energy This requires energy

12. PRACTICE QUESTION 1 Click on the correct answers. Which solution has the highest water concentration? 1.Which way will water flow? 0.1% sucrose Distilled water B B A A visking tube visking tube A to B B to A A A B A B B 1.0% sucrose Sucrose solution 4. Which sentence is correct? 3. Which sentence is correct? A) All water molecules ( ) will diffuse from A to B by osmosis B) There is a net diffusion of water molecules from A to B by osmosis. A) Animal cells will swell and burst if placed in pure water because they do not have a cell membrane. B) Animal cells will swell and burst if placed in pure water because they do not have a cell wall. A B

13. PRACTICE QUESTION 2 Potato cylinders were left for 6 hours in sucrose solutions of varying concentration. The change in length was plotted on a graph. Study the graph, then try to answer the questions below. 1. Which sucrose concentration caused the potato cylinders to shrink the most? 4.5% 4.5% 5% 4.5% 5% 5% 7% 5% 10% 0% 0% 10% 0% 10% 0% 10% 2. Which sucrose concentration represents distilled water? 3. What is the concentration of the potato cells? 4. At which concentration is there no net flow of water in or out of the potato?

14. EXAM QUESTION 1 Click on the answers to see how many marks the examiner awarded each response: WJEC Biology 2 Summer 2014 (foundation) Q6 osmosis 0 marks The correct answer is ‘diffusion’ as the question refers to oxygen molecules, not the diffusion of water molecules 2 marks The first two answers are correct as the candidate has realised that the molecules diffuse from a high to low concentration in both cases. The third answer is incorrect as the candidate has not understood that the greater the difference in concentration, the faster diffusion occurs

15. EXAM QUESTION 2 Try to answer this exam question. Once you have had a go, click on the to see the answer the examiner was looking for. WJEC Biology 2 winter 2015 (foundation) Q4 high low Semi-permeable/ selectively permeable 3

16. EXAM QUESTION 2 20 24 20 2 20 no change in mass/the potato chip was still 20g after 30 minutes; NOT weight Water concentration was higher outside the chip; Water {passes in/is absorbed}/chip gains water by osmosis.

17. EXAM QUESTION 3 Try to answer this exam question Once you have had a go, click on the to see the answer the examiner was looking for. WJEC Biology unit 1 2018 (higher) Q5 -7.9 - 4.8 x 100 = -7.9 60.9

18. EXAM QUESTION 3 14 Point correctly plotted and line drawn ± 1 small square. Remember that the line must go exactly through the centre of each point In egg 3, the concentration of water is greater than inside and the water moves into the egg (1) by osmosis (1), through a selectively permeable membrane (1) In egg 5 the water concentration the egg is greater than outside the egg and the water leaves (1) 0/ 5/ 10