rp11 Production of a dilution series of a glucose solution and use of colorimetric techniques to produce a calibration curve with which to identify the concentration of glucose in an unknown ‘urine’ sample.

how a calibration curve could be produced

1. Use distilled water and a glucose solution of known concentration to produce a dilution series (of glucose solutions of known concentrations)

2. Heat a set volume of each solution with a set volume of Benedict’s solution

3. Measure absorbance (of light) of each solution using a colorimeter

4. Plot a graph of absorbance (y axis) against concentration of glucose solution (x axis) and

draw a line / curve of best fit

how the concentration of glucose in an unknown ‘urine’ sample can be identified using a calibration curve

1. Perform Benedict’s test on sample using same volumes of solutions used in producing calibration curve

2. Measure absorbance using a colorimeter

3. Absorbance value for ‘urine’ sample read off calibration curve to find associated glucose concentration

Give examples of variables that should be controlled.

● Volume of sample used

● Volume of Benedict’s solution

● Temperature of water bath

● Time samples were heated for in water bath

Explain why a high blood glucose concentration can cause glucose to be present in the urine of a diabetic person.

● Not all glucose reabsorbed at proximal convoluted tubule

● As glucose carrier / cotransporter proteins are saturated / working at maximum rate