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Plants have the ability to make their own food by a process called photosynthesis.
- H2O is absorbed via the roots.
- CO2 (from air) is absorbed visa stomata in the leaves.
- Sunlight (energy) is absorbed by chlorophyll in the leaves.
- The plant produces food (C6H12O6)
- The plant food is also known as simple sugars called monosaccharides.
- They are hexose sugars
Chemical Equation for Photosynthesis
6CO2 + 6H2O
> C6H12O6 + CO2
Elemental Composition of Carbohydrates
H:O = 2:1
The most common monosaccharide is Glucose. It has the following structure
Note: The only difference between monosaccharides is their molecular arrangement (i.e. the position of Carbon, Hydrogen and Oxygen differs with each hexose sugar.)
Monosaccharides are also known as simple sugars (they cannot be broken down any further and they are absorbed easily by the villi in the small intestine).
In some plants the products of photosynthesis (i.e. monosaccharides) are arranged in pairs. Two monosaccharides link together.
As the chemical link is formed one molecule of water is eliminated in a condensation reaction (H from one monosaccharide and OH – hydroxyl group from the other monosaccharide.
Chemical formula for disaccharides C12H22O11 (Note: H:O=2:1)
C6H12O6 + C6H12O6 - H2O
Example of Disaccharide
Formation of Maltose
- Two glucose units (monosaccharides) link together.
- H2O (one molecule of water) is eliminated as H from one glucose joins with OH from the second glucose, i.e. condensation reaction.
OH= Hydroxyl group.