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| Frage | Antworten |
| What does the biuret test test for? | Proteins |
| What does the iodine test test for? | Starch |
| What does the emulsion test test for? | Lipids |
| What does the Benedict's test test for? | Reducing and non-reducing sugars |
| What do test strips test for? | Glucose |
| Outline the method of the biuret test | 1. Add NaOH solution (test solution must be alkaline) 2. Add copper (II) sulphate |
| What are the results of the biuret test? | POSITIVE = purple NEGATIVE = blue |
| Outline the method of the iodine test | Add iodine dissolved in potassium iodide solution |
| What are the results of the iodine test? | POSITIVE = dark, blue-black NEGATIVE = browny-orange |
| Outline the method of the emulsion test | 1. Shake the test substance with ethanol for a minute 2. Pour the solution into water |
| What are the results of the emulsion test? | POSITIVE = milky solution NEGATIVE = clear solution |
| Outline the method of the Benedict's test for reducing sugars | 1. Add Benedict's reagent (blue) 2. Heat in a water bath |
| What are the results of the Benedict's test for reducing sugars? | POSITIVE = green --> yellow --> orange --> brick red precipitate NEGATIVE = blue (non-reducing sugar may be present) |
| Outline the method of the Benedict's test for non-reducing sugars | 1. Add dilute HCl (breaks non-reducing sugar down to monosaccharides) 2. Heat in water bath 3. Add NaHCO₃ (neutralises solution) 4. Add Benedict's reagent 5. Heat in water bath |
| What are the results of the Benedict's test for non-reducing sugars | POSITIVE = green --> yellow --> orange --> brick red precipitate NEGATIVE = blue (no non-reducing or reducing sugar present) |
| Outline the method of using test strips | 1. Strips are dipped in test solution 2. Compare colour change to a chart |
| Complete the sentences: A ____________ is a device that measures the strength of a coloured solution by seeing how much _______ passes through it. It measures _______ (the amount of light absorbed by the solution). The more _______ the colour of the solution, the _______ the absorbance is. | A COLORIMETER is a device that measures the strength of a coloured solution by seeing how much LIGHT passes through it. It measures ABSORBANCE (the amount of light absorbed by the solution). The more CONCENTRATED the colour of the solution, the HIGHER the absorbance is. |
| Outline the method to find the glucose concentration of an unknown solution | 1. Make up several solutions of known glucose concentrations 2. Measure the absorbance of these solutions 3. Plot these absorbances on a graph to make a calibration curve |
| Outline the method of serial dilution (using 40mM sucrose solution) | 1. Line up 5 test tubes 2. Add 10 cm³ of the initial 40 mM sucrose solution tot he first test tube and 5 cm³ of distilled water to the other four test tubes 3. Using a pipette, draw 5 cm³ of the solution from the first test tube, add it to the second test tube and mix thoroughly 4. Repeat this process to create solutions of 10 mM, 5 mM and 2.5 mM |
| Outline the method for measuring the absorbance of known solutions | 1. Do a Benedict's test on each solution (plus a negative control of pure water) 2. Remove any precipitate (centrifuge or leave for 24 hours) 3. Switch the colorimeter on and allow 5 mins to stabilise 4. Set up the colorimeter with a red filter 5. Add distilled water to a cuvette 6. Put the cuvette into the colorimeter 7. Calibrate the machine to zero 8. Use a pipette to transfer a sample of the solution from the first test tube to a clean cuvette 9. Put the cuvette in the colorimeter and measure absorbance 10. Repeat steps 8-9 for the remaining solutions |
| What is a biosensor? | A device that uses a biological molecule (e.g. enzyme) to detect a chemical |
| How does a biosensor work? | The biological molecule produces a chemical signal, which is converted to an electrical signal by a transducer. The electrical signal is processed and can be used to work out other information. |
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