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Step
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Practical
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1. Add a drop of water to the middle of a clean slide.
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Microscopy
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9. Adjust the focus with the fine adjustment knob until you get a clear image of the specimen.
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Microscopy
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4. Place a cover slip atop your slide, ensuring there are no air bubbles present that could obstruct your view of the specimen.
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Microscopy
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5. Use a dropping pipette to take a fresh sample from the boiling tube every 30 seconds and drop into a well; starch is no longer present when the iodine solution remains browny-orange.
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Investigating Enzymatic Reactions
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7. Use the coarse adjustment knob to move the stage up to just below the objective lens.
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Microscopy
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1. Place a source of white light a specific distance away from the pondweed.
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Photosynthesis
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2ii. Add a few drops of biuret solution and shake the contents; if the sample contains protein, it will change from blue to lilac (pink/purple).
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Food Tests
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1. Decontaminate your cultures (sterilise inoculating loop and petri dish, lightly tape petri dish and leave upside-down).
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Culturing Microorganisms
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1. Cut up a potato into cylinders, ensuring they're identical by measuring their mass.
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Osmosis
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6. Select the lowest-poweredobjective lens (lowest magnification).
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Microscopy
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You will need: a petri dish, an inoculating loop, agar jelly/nutrient broth solution, your antibiotic(s).
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Culturing Microorganisms
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3. Leave one potato cylinder in each beaker for 24 hours (or so).
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Osmosis
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You will need: a microscope, a slide, an onion, a cover slip, iodine solution, tweezers.
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Microscopy
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2. Place paper discs soaked in different types/different concentrations of antibiotics the agar plate.
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Culturing Microorganisms
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4i. Place the test tube in the water bath for 5 minutes.
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Food Tests
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3. Ensure you use a control disc (soaked in sterile water) to identify differences/ensure the inhibition zone had been created by the antibiotic alone.
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Culturing Microorganisms
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2. Put the beaker of water over the bunsen burner until it reaches 35 degrees celsius.
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Investigating Enzymatic Reactions
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4. Leave the plate for 48 hours at 25 degrees celsius.
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Culturing Microorganisms
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11. Draw what you see under the microscope - your diagram should be labelled, free of colour/shading, and titled with the magnification it was observed under.
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Microscopy
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2. Collect some beakers of different sugar solutions; one should be pure water whilst the other is very concentrated, with some being at equal intervals between (e.g. 0.2, 0.4, 0.6, 0.8, 1mol/dm³)
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Osmosis
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7. Calculate the size of the inhibition zones using πr².
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Culturing Microorganisms
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5. Clip your prepared slide onto the stage.
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Microscopy
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2iiii. Add a few drops of iodine solution and shake the contents; if the sample contains starch, it will change from browny-orange to blue-black.
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Food Tests
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You will need: potato cylinders, different concentrations of sugar solutions, beakers, scales.
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Osmosis
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1. Put a drop of iodine solution into every well of a spotting tile.
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Investigating Enzymatic Reactions
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Step
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Practical
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2iii. Add a few drops of Sudan III solution and shake the contents; of the sample contains lipids, the mixture will separate into two layers, with the top one being bright red.
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Food Tests
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8. Look down the eyepiece, using the coarse adjustment knob to move the stage.
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Microscopy
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3. Add a drop of iodine solution to stain the onion layer, highlighting the sub-cellular structures by adding colour to them.
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Microscopy
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4. Dry with a paper towel and measure the mass of the cylinders again once the 24 hours has passed.
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Osmosis
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6. The more effective the antibiotic against the bacteria, the larger the inhibition zone will be.
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Culturing Microorganisms
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You will need: amylase solution, starch solution, buffer solution, iodine solution, dropping pipette, spotting tile, bunsen burner, tripod, gauze, heat-proof mat, beaker of water, thermometer, syringe, boiling tube, stop clock.
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Investigating Enzymatic Reactions
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5. Repeat the entire experiment with the light at different distances from the pondweed.
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Photosynthesis
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1. Prepare a food sample and transfer 5cm³ to a test tube.
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Food Tests
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4. Use a different syringe to add 5cm³ of starch solution to the test tube, immediately stirring and starting the stop clock.
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Investigating Enzymatic Reactions
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10. Swap to a high-powered objective lens if a greater magnification is needed, and refocus.
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Microscopy
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2. Separate an onion into layers and peel off a section of epidermal tissue using tweezers, placing it onto the slide.
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Microscopy
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6. Repeat the entire experiment with buffer solutions of different pH values to identify how pH affects the time taken for starch to be broken down.
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Investigating Enzymatic Reactions
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2. Leave the pondweed to photosynthesise for a set amount of time; this allows the oxygen that's released to be collected in the capillary tube.
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Photosynthesis
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2i. Prepare a water bath set to about 60 degrees celsius.
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Food Tests
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4. Repeat the experiment twice more with the light source at the same distance to calculate the mean volume of oxygen.
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Photosynthesis
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5. An increase in mass means water has been drawn in, and a decrease in mass means water has been drawn out; you should find the higher the concentration of the sugar solution, the more water that's drawn out of the potato (and the higher the decrease of it's mass).
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Osmosis
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5. Antibiotic should diffuse into the agar jelly; non-resistant strains of bacteria will die, however resistant will continue growing on the agar around the paper discs. A clear area will be left around the bacteria that died (inhibition zone).
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Culturing Microorganisms
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6. Put your results into the equation 'light intensity ∝ 1/d²'.
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Photosynthesis
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You will need: 5cm³ of your food samples, iodine, Benedict's, Sudan III and Biuret solution, test tubes, waterbacth.
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Food Tests
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You will need: Canadian pond weed, syringe, two rulers, clamp, capillary tube, water, test tube, light source.
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Photosynthesis
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3. Use a syringe to add 1cm³ of amylase solution and buffer solution (pH 5) to a boiling tube, putting it in the beaker of water and leaving for 5 minutes.
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Investigating Enzymatic Reactions
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3i. Add some Benedict's solution to the test tube using a pipette (about 10 drops).
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Food Tests
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3. Draw up the gas bubble using a syringe alongside the ruler at the end of the experiment; the length of the bubble measured is proportional to the volume of oxygen produced.
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Photosynthesis
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5i. If the reducing sugars are present in the sample, the solution will change from blue to green/yellow/brick-red, depending on how concentrated the food is with sugar.
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Food Tests
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