Presentation on theme: "How can a shark find injured prey so quickly?"— Presentation transcript:
1 How can a shark find injured prey so quickly? Diffusion & LifeB2 Additional
2 Learning Objectives To describe DIFFUSION To explain what affects the RATE of DIFFUSIONTo link diffusion with EXAMPLES in BIOLOGYRespirationDigestionPlacentaLeaf CellsNerve Impulses
3 DiffusionStarter:Explain in terms of particles how the smell of the perfume gets from one side of the class to the other
4 When you have just sprayed perfume, the concentration of perfume particles in that area is very high.Diffusion is the movement of the ‘smelly’ particles, through particles of air, to an area where they are at a LOWER concentration.
5 Maybe you can smell your dinner cooking when you get home Maybe you can smell your dinner cooking when you get home... This is due to diffusion.
6 Moving moleculesIn which states are molecules able to diffuse?gas (e.g. steam)liquid (e.g. water)solid (e.g. ice)Molecules in liquids and gases are constantly moving and bumping into each other. This means that they tend to spread out.
7 DiffusionThe net movement of particles from an area of high concentration to an area of low concentrationDue to the random movement of particlesA passive process which means that no energy is needed
8 What effect might the gradient have on speed of diffusion? LOW concentrationHIGH concentrationA difference in concentration between 2 areas is called a CONCENTRATION GRADIENT.What effect might the gradient have on speed of diffusion?
9 Rate of Diffusion Steep concentration gradient Draw both sets of diagrams, write how the rate of diffusion changes when the concentration gradient changesRate of DiffusionFastSteep concentration gradientSlowShallow concentration gradient9
11 When will diffusion stop? Think – Pair - Share?
12 Has diffusion stopped completely? Draw the diagrams next to each other and copy the captionsThe particles are fully diffuse.The particles are separate when first put together.They slowly start to mix due to their random motion.The particles are now nearly fully diffuse.Has diffusion stopped completely?Explain your answer12
13 Diffusion in action: one gas Teacher notesThis activity could be used as a starter exercise to work on diffusion.
14 Diffusion in action: two gases Teacher notesThis activity could be used as a starter exercise to work on diffusion.
15 What substances are we talking about? Biological diffusionDissolved 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?
16 Why is diffusion important? All living cells rely on diffusion to live.They use it for:Getting glucose and oxygen needed for respirationRemoving waste products (eg. from respiration)Examples…
17 1. Diffusion and breathing 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?
18 Cross-section through an alveolus Alveoli are the tiny air sacs at the end of the bronchioles, in which gas exchange occurs.air in/outdeoxygenated blood (from body tissues)alveoluscapillaryTeacher notesAlveoli = plural; alveolus = singularoxygenated blood (to body tissues)red blood cell
19 2. Diffusion and digestion 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.
20 3. Diffusion and nerves impulses A synapse is a junction between two neurones across which electrical signals must pass.synaptic cleftneurotransmitterneurotransmitter receptornerve impulseNeurotransmitter molecules diffuse from vesicles towards the neurotransmitter receptors, moving from an area of high concentration to low concentration.
21 4. Diffusion and the placenta The placenta is an organ that develops in the uterus during pregnancy.The umbilical cord connects the placenta to the foetus.It enables nutrients and oxygen to pass from the mother to the foetus by diffusion, and waste substances to diffuse from the foetus back to the mother.
22 Finally… Diffusion happens in gases as well as liquids. Draw an advert for a perfume or air freshener and explain how you would be able to smell it from the other side of a room.You can choose what your product smells of!