RP11 - Use Of Colormetric Techniques To Identify The Concentration Of Glucose In An Unknown Urine Sample

Question 1

Describe how a calibration curve could be produced for glucose (4)

Answer 1

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

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

3) Measure absorbance of each solution using a colorimeter

4) Plot a graph of absorbance against concentration of glucose solution and draw a line of best fit

Question 2

Describe how the concentration of glucose in an unknown urine sample can be identified using a calibration curve (30

Answer 2

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

Question 3

Give examples of variables that should be controlled (4)

Answer 3

1) Volume of sample used

2) Volume of Benedict’s solution

3) Temperature of water bath

4) Time samples were heated for in water bath

Question 4

Explain why a high blood glucose concentration can cause glucose to be present in the urine of a diabetic person (2)

Answer 4

1) Not all glucose re absorbed at proximal convoluted tubule

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