Required practical 11

Question 1

How can the Benedict’s solution be used to measure the concentration of glucose in a solution?

Answer 1

Use a colorimete to measure in absorbance of a series of solutions known concentrations to create a calibration curve.

Compare the absorbance of an unkown sample to calibration curve.

Question 2

What is a serial dilution?

Answer 2

A dilution where successive concentrations increase/decrease in a logarithmic fashion.

Question 3

Outline the procedure of this practical

Answer 3

1. Make a serial dilution of glucose, ranging from 0 to 10 mmol dm-3.
2. Placce 2cm3 of each of the unkown sample in a seperate boling tubes.
3. Add 2cm3 of Benefict’s solution to all boiling tubes.
4. Place boiling tubes in a water bath at 90 degrees for 4 mins
5. Zero the colorimeter using a cuvette with distilled water and set to red filter.
6. Place known samples into cuvette and measure the absorbance of each using colorimeter then make a calibration curve.
7. Measure the absorbance of the unkown samples using the colorimter. Use the calibration curve to determine glucose concentrations

Question 4

What are the axes in a calibration curve

Answer 4

y = Absorbance agaisnt glucose concentration = x

Question 5

What would a high glucose concentration suggest?

Answer 5

It may suggest diabetes. Lack of insulin leads to high blood glucose concentration, hence high concentration in the glomerular filtrate, so not all glucose can be reabsorbed in the proximal convoluted tubule

Question 6

Stae the hazards and precautions of this practical

Answer 6

Benedict’s solution is a irritant, wear eye protection, avoid contact with skin.

Handle the hot water bath with care

Question 7

How can you increase the accuracy of the estimate of the unkown glucose solution?

Answer 7

Increase the number of concentration (at smaller intervals) for the calibration curve within the range of concentrations that the unkown solution belongs in.