As you should recall, glucose is a reducing sugar. There are many chemical assay
ID: 32708 • Letter: A
Question
As you should recall, glucose is a reducing sugar. There are many chemical assays for reducing sugars such as using Nelsons alkaline copper reagent or 3,5 dinitrosalicylic acid (DNS). Why is an enzymatic assay the preferred method for blood glucose?
Convert a typical measurement of 95 mg/dL blood glucose into a mM amount.
The concentration of glucose inside a typical cell is about 1.0 mM. Why is the concentration of glucose inside the cell less than in the blood?
A typical red blood cell has a diameter of about 7 m. Although they are disk-shaped, lets assume they are a sphere and determine the number of glucose molecules in the cell?
Red blood cells are one of the few tissues that rely solely on glycolysis. How much ATP can be made from the amount of glucose in the red blood cell?
Based on questions 2-5, why is it important that the blood glucose concentration remain constant?
Explanation / Answer
The end point assay for glucose estimation keeps on varying depending on our activities affecting the glucose metabolism. Therefore the breakdown of glucose per min is the correct measure when the enzymatic conversion rate is linear. It should be avoided at initial and saturation phases.
The 95 mg/dl blood glucose can be converted into mM as follows:
For this conversion divide the mg/dl of glucose by 18 which gives the mM of glucose in the blood. For the given values the calculation is
95/18 = 5.27 mM.
It is a simple osmosis rule. High concentration in blood will try to ensure its movement towards lower concentration gradient. But the movement of glucose is tightly controlled over the cell surface but GLUT transporters, so that only the required amount may enter
The no. of molecules of glucose in a volume of RBC is approx. 3.17 x 10^20. Check the radius of cell mentioned in Q. Therefore considering the volume of a RBC to be average 90 femto litre and 3.34 x 10^18 molecules of glucose per mg of glucose using the moles concept it has been calculated.
4 molecules of ATP are produced per glucose molecule. Therefore, 12.68 x 10^20 molecules of ATP is produced in a typical cell. But in RBC ATP is not produced directly, rather NADH and Lactate is produced as a result of anaerobic glycolysis. The product is used in Pentose Phosphate Pathway to be further utilized for Energy production
Impotence of maintaining constant blood glucose levels:
The blood sugar levels must be maintained as to meet the requirements of the cell. When the blood sugar level gets low or sugar levels fall below the normal value it may lead to a hypoglycaemic condition. The hypoglycaemic condition may be due to low food intake, increase in the insulin levels etc.
When the blood sugar levels are high it may damage the blood vessels and also may lead to the diabetic condition. This causes hyperglycaemia. In this condition the insulin levels may be reduced in diabetic patients. It may happen due to eating of too much food, stress and illness etc. Hence, the blood glucose levels must be maintained to avoid from such complications.
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