RP 11 - Dilution Series Of Glucose

Question 1

Describe how a calibration curve could be produced for glucose

Answer 1

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

Question 2

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

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.

Answer 3

• volume of sample used
• volume of Benedict solution
• temperature of water bath
• 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

Answer 4

• not all glucose reabsorbed in the proximal convuluted tubule
• as glucose carrier/co transporter proteins are saturated/ working at max rate