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B2 Exam Revision. Plant cells vs. Animal cells Both types of cell have these: Only plant cells have these: Nucleus This controls the cell Cytoplasm This.

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Presentation on theme: "B2 Exam Revision. Plant cells vs. Animal cells Both types of cell have these: Only plant cells have these: Nucleus This controls the cell Cytoplasm This."— Presentation transcript:

1 B2 Exam Revision

2 Plant cells vs. Animal cells Both types of cell have these: Only plant cells have these: Nucleus This controls the cell Cytoplasm This is the jelly like substance where chemical reaction take place Cell wall Gives support to the cell Large vacuole Large space filled with cell sap Cell membrane Controls what goes in and out of the cell 1) 2) 3) 6) 5) 7) Mitochondria Energy is released here by respiration 4) Chloroplasts Where photosynthesis takes place

3 Complete this definition of Diffusion using the key words: Diffusion is the _______ __________ of ______ from where there are lots of particles ( high __________) to where there are less particles. We say the particles diffuse down a concentration _________. In cells, the cell membrane has small holes that allow small particles through, but not large molecules. We call this membrane ________ ________. The bigger the difference in concentration, the faster the rate of ________. Partially permeable Diffusion Concentration Gradient Random movement Particles

4 Osmosis is diffusion but with … WATER

5 OSMOSIS IS THE MOVEMENT OF WATER PARTICLES FROM WHERE THERE ARE LOTS OF THEM (Dilute solutions) TO WHERE THERE ARE NOT VERY MANY OF THEM (concentrated solutions) THROUGH A SEMI-PERMEABLE MEMBRANE (LIKE A CELL WALL) OSMOSIS

6 Photosynthesis - The equation 1. What factors are needed to make glucose? 2. What products are made by photosynthesis?

7 Limiting factors If you alter the levels of light, carbon dioxide or change the temperature the rate of photosynthesis will change!

8 What happens to the glucose?

9 Mineral needs Can you fill in this table? MineralNeeded forDeficiency disease Nitrates Magnesium

10 Mineral needs MineralNeeded forDeficiency disease NitratesHealthy leaves Good all round growth Purple leaves, poor growth MagnesiumTo make chlorophyllYellow leaves

11 Food chains A food chain shows where the energy goes in a food chain (in other words, “what gets eaten by what”): Cabbage Rabbit Stoat Fox The arrows indicate where the energy is going Plants convert the sun’s energy into food

12 Pyramids of biomass In this food chain we can see that the mass of organisms in each stage is less than in the previous stage: CabbageRabbitStoatFox We can draw a “Pyramid of Biomass” to show this pattern: Mass of cabbages Mass of rabbits Mass of stoats Mass of foxes

13 Energy flow in a food chain Consider the energy flow in this food chain: CabbageRabbitStoatFox 100%10%1%0.1% Clearly, not all of the ___’s energy that becomes stored in the _______ will end up in the fox. Only around ______ is passed on to the next stage in each food chain. Energy is lost at each stage because of a number of reasons: 1)Each organism has to ____, keep warm etc 2)Energy is lost through faeces (______) Words – 10%, move, sun, waste, cabbage

14 Improving the efficiency of a food chain Clearly, food chains aren’t very efficient. How could the efficiency of a food chain be improved? 1) Reduce the number of stages in the chain: Cabbage Rabbit Stoat 2) Limit an animal’s movement or keep it warm: Fox 3) Use plant hormones to regulate the ripening of fruit

15 Energy in food production Biomass and energy is lost at each stage of a food chain. The efficiency of food production can be improved by reducing the number of stages in our food chains. It would be most efficient if we all ate just plants If you stop animals moving around and keep them warm they lose a lot less energy which makes food production more efficient

16 Decay Decay is carried out by micro- organisms which work faster in warm, moist conditions with a good supply of oxygen. The decay process releases substances that plants need to grow.

17 Carbon cycle The constant cycling of carbon is known as the carbon cycle Carbon dioxide is removed from the atmosphere by photosynthesis It is returned to the atmosphere by respiration and combustion Microbes that decay waste and dead matter respire and produce carbon dioxide

18 Map from memory

19 Enzymes Enzymes are biological catalysts, they increase the rate of reactions. Enzymes are protein molecules made up of long chains of amino acids. When enzymes are denatured the active site changes shape.

20 What happens at the active site? In the same way that a key fits into a lock, so a substrate is thought to fit into an enzyme’s active site. The enzyme is the lock, and the reactant is the key. + ↔↔ + enzyme reactant + enzyme-reactant complex ↔ products enzyme + ↔

21 Factors affecting enzymes If the temperature and pH changes sufficiently beyond an enzyme’s optimum, the shape of the enzyme irreversibly changes. normal denatured heat pH This affects the shape of the active site and means that the enzyme will no longer work. When this happens the enzyme is denatured.

22 Aerobic Respiration Oxygen + Glucose Carbon Dioxide + Water Energy + +

23 Amylase Protease Lipase Bile Hydrochloric acid Where are the enzymes found?

24 Enzymes of digestion

25 Homeostasis The internal conditions of your body need to be controlled to maintain a constant internal environment Waste products such as carbon dioxide and urea need to be constantly removed Urea is produced by your liver as you break down excess amino acids and is removed by your kidneys as urine

26 Five factors we need to keep constant. 1. temperature 2. water 3. sugar 4.waste products (need to remove) 5. ions B2 Homeostasis

27 Use these words to complete the notes. receptors brain receptors The thermo-regulatory centre of the ______ monitors and controls the temperature of blood as it passes through. This centre has __________which are sensitive to the temperature of the blood. The skin also has _________ sensitive to temperature. B2 Homeostasis

28 Glucose control Your blood glucose concentration is monitored and controlled by your pancreas Insulin and glucagon are the hormones involved in controlling blood sugar. Insulin converts glucose to glycogen and glucagon converts glycogen to glucose In diabetes the blood glucose may rise to fatally high levels because the pancreas does not produce enough insulin. It can be controlled by injections and diet

29 Chromosomes, Genes and Alleles 1. ………….. 2. ……… …………….. 4. ……………… B b 5. ……………. Nucleus, Gene, Chromosome, Allele, Cell (b)

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31 Why was his work not spread quickly? He was not a famous scientist – nobody knew about him at the time. His job as abbot stopped him giving lectures at universities. He published his work in an obscure journal that few people read. Biologists at the time did not think mathematics had anything to do with Biology. Gregor Mendel (The Pea Plant Man)

32 Disease Some disorders are inherited Huntington’s disease is caused by a dominant allele of a gene and can be inherited from only one parent Cystic fibrosis is caused by a recessive allele of a gene and so must be inherited from both parents

33 Cystic Fibrosis The treatment involves chest physiotherapy. They are very prone to chest infections and malnutrition. The mucus encourages the growth of pathogenic microbes that cause infection and cause long term lung damage.

34 PHEW! Good Luck


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