Lesson 13 diffusion
- 1. Discussion: How can a shark find injured prey so quickly?
- 3. Define and describe DIFFUSION Explain what affects the RATE of DIFFUSION To link diffusion with EXAMPLES in BIOLOGY Respiration Digestion Leaf Cells
- 4. Maybe you can smell your dinner cooking when you get home... This is due to diffusion.
- 5. Diffusion is the movement of particles from an area of HIGH concentration to an area of LOW concentration (down a concentration gradient) until there is an EQUAL spread of particles Diffusion only occurs in fluids. Why?
- 6. In which states are molecules able to diffuse? Molecules in liquids and gases are constantly moving and bumping into each other. This means that they tend to spread out. gas (e.g. steam)liquid (e.g. water)solid (e.g. ice)
- 7. The net movement of particles from an area of high concentration to an area of low concentration Due to the random movement of particles A passive process which means that no energy from respiration is needed
- 8. HIGH concentration LOW concentration A difference in concentration between 2 areas is called a CONCENTRATION GRADIENT. What effect might the gradient have on speed of diffusion?
- 9. Fast Steep concentration gradient Shallow concentration gradient Rate of Diffusion Draw both sets of diagrams, write how the rate of diffusion changes when the concentration gradient changes Slow
- 10. Concentration gradient Temperature Distance particles must travel Surface area Faster Diffusion When... Large concentration gradient Higher Temperature Short distance Larger surface area
- 11. Dissolved substances have to pass through the partially permeable cell membrane to get into or out of a cell. Diffusion is one of the processes that allows this to happen.. What substances are we talking about?
- 12. All living cells rely on diffusion to live. They use it for: Getting raw materials for respiration (dissolved substances and gases) Removing waste products (eg. from respiration) Plants use of photosynthesis (raw materials in, waste products out) Examples…
- 13. Oxygen in inhaled air diffuses through the lungs and into the bloodstream. The oxygen is then transported throughout the body. Carbon dioxide is the waste gas produced by respiration. Carbon dioxide diffuses from body tissues into the bloodstream and is exhaled via the lungs. Where does gas exchange take place in the lungs?
- 14. deoxygenated blood (from body tissues) oxygenated blood (to body tissues) Alveoli are the tiny air sacs at the end of the bronchioles, in which gas exchange occurs. alveolus capillary red blood cell CO2 O2
- 15. Alveoli have several adaptations that help to make gas exchange very efficient: They are very thin – only one cell thick. They are covered by a network of fine capillaries, enabling gases to pass almost directly between the lungs and bloodstream. They are moist, encouraging gas molecules to easily dissolve. They have a large combined surface area, allowing large amounts of gases to be exchanged with each breath.
- 17. Digestion breaks down large food molecules into smaller molecules such as glucose, amino acids and fatty acids that can be easily absorbed. Small food molecules are usually absorbed in the small intestine, diffusing across the intestine wall and into the bloodstream.
- 18. blood vessels capillary network Villi small intestine
- 19. The small intestine has these things called villi. The best way of explaining them, is that they look like millions of little sausages. The villi INCREASE THE OVERALL SURFACE AREA of the small intestine, thus increasing the volume of substances which can be absorbed by diffusion. The villi have a very GOOD BLOOD SUPPLY as each contains a capillary, which leads to the main blood supply, so when substances diffuse, they can go straight to the bloodstream. Attached to each villi are thousands and thousands of MICROVILLI. These are exactly the same as the villi, except a lot smaller. Again, the purpose of these is to further increase the surface area. Like before, as well, this increasing the volume of substances which can be absorbed. So, the main points to remember are: The villi and microvilli result in a LARGE SURFACE AREA, for maximum absorption. The villi also give a GOOD BLOOD SUPPLY to absorb the nutrients.
- 20. Carbon dioxide diffuses in through the stomata Oxygen and water diffuse out of the stomata carbon dioxide + water oxygen + glucose During photosynthesis, the level of CO2 is low inside the leaf This creates a big concentration gradient so CO2 diffuses into the cell