Required Practical 11 - producing dilution series of glucose solution and use colormetric techniques to produce a calibration curve (identifying concentration of glucose in an unknown 'urine' sample

producing a calibration curve for glucose

use distilled water and glucose solution of known concentration to produce a dilution series

heat a set volume of each solution with a set volume of quantitative Benedict’s solution

measure absorbance (of light) of each solution using a colorimeter

plot a graph of absorbance (y axis) against concentration of glucose solution (x axis) and draw a line/ curve of best fit

Finding the glucose concentration in an unknown sample of urine using a calibration curve

perform benedict’s test on sample using same volumes of solutions used in producing calibration curve

measure absorbance using a colorimeter

absorbance value for ‘urine’ sample read off calibration curve to find associated glucose concentration

Variables which should be controlled

Volume of sample used

Volume of Benedict’s solution

Temperature of water bath

time samples were heated for in water bath

Why a high blood glucose concentration causes glucose to be present in the urine of a diabetic person

not all glucose reabsorbed at proximal convoluted tubule

as glucose co transporter proteins are saturated/ working at maximum rate