Glucose

Glucose comes from the Greek word for "sweet." It's a type of sugar you get from foods you eat, and your body uses it for energy. As it travels through your bloodstream to your cells, it's called blood glucose or blood sugar.

Glucose is initially synthesized by chlorophyll in plants using carbon dioxide from the air and sunlight as an energy source. Glucose is further converted to starch for storage.

Steps in the ring closure :

The electrons on the alcohol oxygen are used to bond the carbon #1 to make an ether (red oxygen atom).

The hydrogen is transferred to the carbonyl oxygen to make a new alcohol group .

The chair structures are always written with the orientation depicted below to avoid confusion.

Preparation Of Glucose (C6H12O6)

Sucrose (cane sugar) and starch are the two major sources of Glucose.

Preparation from sucrose or cane sugar:

Sucrose is a disaccharide with the formula C12H22O11. On boiling an aqueous solution of sucrose with dilute HCl or dilute H2SO4, Glucose and Fructose are formed in equimolar proportions.

   C12H22O11 + H2O → C6H12O6 + C6H12O6

Sucrose                               Glucose     Fructose

Preparation from starch: 

It is a polysaccharide that when boiled with dilute H2SO4 at 393 K under 2 to 3 atmosphere pressure, gives glucose.

    ( C6H12O5)n + n H2O → nC6H12O6  

         Starch                               Glucose

Uses Of Glucose (C6H12O6)

It is used in the treatment of hypoglycemia (low blood sugar)

It is given to patients who are very sick and cannot eat as it provides carbohydrate calories

It is used in the treatment of increased potassium levels in the blood (hyperkalemia)

It is used as a precursor for the synthesis of substances.