• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

To compare quantitatively the concentrations of glucose and other reducing sugars in samples of fresh orange, lemon and grapefruit juice. The standard test for glucose (and other reducing sugars) is to use Benedict's reagent

Extracts from this document...


Glucose concentrations in orange, lemon and grapefruit juice Introduction In this experiment, I am going to have to compare quantitatively the concentrations of glucose and other reducing sugars in samples of fresh orange, lemon and grapefruit juice. The standard test for glucose (and other reducing sugars) is to use Benedict's reagent. Benedict's reagent is copper (II) sulphate in an alkaline solution, and so has a blue colour to it. If it is added to a reducing agent, its Cu2+ ions will be reduced to Cu+, resulting in the precipitant changing colour to the red of copper (I) sulphate. Reducing sugars have this effect on Benedict's reagent because they have a -C=O group somewhere in their molecules which can contribute an electron to the copper, hence the name "reducing sugars" (1). If a reducing sugar is present when Benedict's solution is added, the solution will change colour through green, yellow and orange, to brick red as the copper (I) sulphate forms a precipitant. All fruit contains the sugars glucose and fructose. Fructose is an isomer of glucose, so both sugars have the molecular formula: C6H12O6. Both are monosaccharides, and are hexoses (they both have 6 carbon atoms in each molecule). ...read more.


5. Repeat this operation for tubes 3, 4, 5, 6 and 7. Once the solution has been mixed in test tube 7, I will remove 1 cm3 of the solution so that there is an equal volume of test solution in each test tube - this will make the test fair. 6. I will now have glucose concentrations of 4%, 2%, 1%, 0.5%, 0.25%, 0.125% and 0.0625%. These are known as serial concentrations. This is a good range of test solutions, as I would have a strong solution, a very weak solution and a lot of concentrations in the middle so that I can draw an accurate line of best fit, and so that my calibration curve is generally as accurate as possible. In previous work, I found out that Benedict's solution stops detecting glucose between 0.1% and 0.01% glucose concentration, so it should still detect glucose at my lowest test concentration of 0.0625%. 7. Add 10 cm3 of Benedict's solution to each test tube using a 10 cm3 syringe (I will use the same concentration of Benedict's with each test solution in order to keep the test fair). The reason for using excess Benedict's solution is so that all of the sugar present will have definitely reacted (1). ...read more.


5. Filter each fruit juice into clean test tubes. 6. Using a clean syringe, add equal volumes of each filtered juice into separate cuvettes so that the cuvettes are more than half full. 7. Check that filter no 7 (orange) is in place in the colorimeter, and take one colorimeter reading for each cuvette. 8. Repeat this part of the experiment three times as well in order to get a mean transmission of light for each fruit juice. 9. Estimate the concentration of each juice by reading off the concentration at each average transmission of light. I will record my results on a similar table to the one on which I will record my test solutions on, but instead of having a column with known concentrations in, I will have the column with the name of the fruit juice. Prediction I predict that the lemon juice will have the smallest concentration of glucose, and the orange juice will have the largest. In previous research involving orange and lemon flavoured drinks, I have found out that the orange drink had a higher concentration of glucose than the lemon drink. The only problem that may occur in using this method is the colour of the fruit juices may affect the colorimeter reading, but as there will be a very large volume of Benedict's solution used compared to fruit juice volume, these effects should be kept to a minimum. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Exchange, Transport & Reproduction section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Exchange, Transport & Reproduction essays

  1. Marked by a teacher

    Aim: To test for reducing sugars using glucose, sucrose and lactose to see which ...

    3 star(s)

    First test a sample for reducing sugars, to see if there are any present before hydrolysis. Then, using a separate sample, boil the test solution with dilute hydrochloric acid for a few minutes to hydrolyse the glycosidic bond.

  2. Peer reviewed

    The comparison of antibacterial properties of herbal products and standard antibiotics

    5 star(s)

    Changing bacteria would make the results void as the structures vary in different types of bacteria. * The amount of bacteria on each agar plate- it is not known of how many bacteria are within the broth but the amount (ml)

  1. To find out the factors affecting the refractive index of liquid by using different ...

    The refractive index remained unchanged with increased temperature from 20 degree Celsius to 80 degree Celsius. This is different from what I predicted. When I did more research on this, I found that at liquid state, the molecule moved around randomly.

  2. Why did the colour leak out of cooked beetroot?

    Results: TEMPERATURE OF WATER IN DEGREE CELSIUS AVERAGE COLORIMETER READING OF THE RED PIGMENT IN COLORIES IN % ABSORBANCE 0C 0.12 10C 0.27 20C 0.67 30C 1.06 40C 1.2 50C 1.32 60C 1.44 70C 1.56 These are the results which I obtained after taking the reading in the calorie meter.

  1. You are required to plan a procedure that will allow you to compare quantitatively ...

    Also I have taken into account that Benidict's only produces semi-quantitative results. Therefore will use colorimeter to make it quantitative. A colorimeter can be used to show absorbance readings of different solutions. The way it is that the solution is placed into a cuvette, which then is placed in the

  2. Determine which of the three sugars tested (Glucose, Fructose and Sucrose) is a reducing ...

    The general formula for a disaccharide molecule is 2[(CH2O) n] - H2O. The properties of disaccharides are: o Small molecules o Low molecular mass o Sweet tasting o Crystalline o Soluble in water, but less readily soluble in water. An example of a disaccharide molecule is sucrose. Sucrose is formed by a condensation reaction between glucose and fructose (see below).

  1. A Colorimetric method for the estimation of glucose (or reducing sugars) in solution.

    After each minute allocated time record how long it takes the solution which contains 10cm3 sugar solution, 5cm3 sulphuric acid and 2cm3 potassium manganate to become colourised in each test. 4. Then the results of phase tow of the experiment will be recorded and plotted on a graph.

  2. The purpose of the activity was to make standard 1% solution of glucose in ...

    Tap water contains various chemicals and may have affected the result. Evaluation After finding out that my 1% glucose solution did contain glucose, I tested for glucose in the other two solutions A and B. I did this so I could then find out which of the two solutions matched my 1% glucose solution.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work