Biochemistry

Biochemistry

Carbohydrates "2"
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Monosaccarides

monosaccarides are classified according to three different characteristics :

1- the placment of its carbonyl group.
2- the number of carbon atoms.
3- and its chiral handedness.
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1- the placment of its carbonyl group.

- If the carbonyl group is an aldehyde, the monosaccaride is an aldose.
- If the carbonyl group is an ketone, the monosaccaride is an ketose.

2- the number of carbon atoms.

- Monosaccarides with three carbon atoms are called trioses.
- those with four are called tetroses.
- five are called pentoses.
- six are hexoses, and so on.

These two systems of classification are often combined.
For example, glucose is an aldohexose (a six-carbon aldehyde).
ribose is an aldopentose (a five-carbon aldehyde).
and fructose is a ketohexose (a six-carbon ketone).


Use in living organisms :

Monosaccarides are the major source of fuel for metabolism, being
used both as an energy source (glucose being the most important in nature) and in biosynthesis.

this storage form is glycogen , especially in liver and muscle cells.

in plants, starch is used for the same purpose.