Glucose: A monosaccharide carbohydrate. When combined with fructose (a glucose isomer), produces sucrose (C12H22O11), and water (H2O). This is because of dehydration synthesis, which allows carbohydrates, amino acids, and lipids to combine into polymers, while producing a water molecule for each bond formed.

AKA blood sugar, and corn sugar.

Glucose is our body's primary source of energy. When we digest carbohydrates, our stomach breaks them down into glucose, which is carried throughout the body by our blood stream. Insulin binds with the glucose, making it available for our cells to use; what is not used immediately is stored in the liver as glycogen. (If your body cannot regulate your blood sugar levels correctly, this may result in diabetes.)

Every carbohydrate is originally formed through photosynthesis. The most common model of photosynthesis is:

6 (CO2) + 12 (H2O) + light energy = 1 (C6H12O6) + 6 (O2) + 6 (H2O)

The glucose (C6H12O6) then stores the energy (Chemical energy at this point) in the plant until it is needed. It may be stored as a simple sugar or as a starch, or even used as a structural component of the plant, such as cellulose. It is then broken down, releasing the energy. Humans use glucose and other forms of sugar coming from plants to provide all of their energy. As only plants (and some protists) make glucose, they are the base of all food chains.

Glucose is also used as a component in the synthesis of some amino acids and fatty acids.

See ATP.

Some isomers of glucose include dextrose, galactose, fructose, and mannose.

Glucose (also called dextrose or cerelose) is a six-carbon monosaccharide which is the major sugar in the blood and is an important intermediate molecule in metabolic processes. It is often given intravenously to replenish fluids and provide energy. Glucose is measured in routine blood and urine tests to detect diabetes.

The normal ranges for glucose are ...

  • in blood after fasting overnight: 3.5 - 6 mmol/L
  • in blood two hours after a meal: less than 8 mmol/L
  • in urine: none

In glycolysis, all six-carbon intermediates are derived from glucose and fructose. In the first step of glycolysis, hexokinase catalyzes the conversion of glucose and ATP into glucose 6-phosphate. Also, in the conversion of one molecule of glucose into two molecules of pyruvate, two molecules of ATP are also generated.

From the science dictionary at

Placement of the hydroxyl (OH) group in the structural formula for glucose is very important. For example, the structural difference between glucose and galactose are the turning up (or down) of the hydroxyl group for only one of the carbons. The correct structural formula for glucose is shown below as well as the structural formula for galactose to show the very slight difference in organization.

          H                        H
          |                        |
        H-C-OH                   H-C-OH
          |                        |
          C -- O                   C -- O
       H /|     \ H            HO /|     \ H
       |/ H      \|             |/ H      \|
       C          C             C          C
       |\ OH   H /|             |\ OH   H /|
      HO \|    |/ OH            H \|    |/ OH
          C -- C                   C -- C
          |    |                   |    |
          H    OH                  H    OH
        Glucose                  Galactose

Glu"cose` (?), n. [Gr. sweet. Cf. Glycerin.]


A variety of sugar occurring in nature very abundantly, as in ripe grapes, and in honey, and produced in great quantities from starch, etc., by the action of heat and acids. It is only about half as sweet as cane sugar. Called also dextrose, grape sugar, diabetic sugar, and starch sugar. See Dextrose.

2. Chem.

Any one of a large class of sugars, isometric with glucose proper, and including levulose, galactose, etc.

<-- ?Now only one is called glucose -- when did this usage diappear? = hexose-->


The trade name of a sirup, obtained as an uncrystallizable reside in the manufacture of glucose proper, and containing, in addition to some dextrose or glucose, also maltose, dextrin, etc. It is used as a cheap adulterant of sirups, beers, etc.


© Webster 1913.

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