Page 90 - Demo 1

CARBOHYDRATES

Carbohydrates are ulized by living organisms as an immediate energy source,
but they also have other important funcons in humans, animals, plants, and
fungi. Carbohydrates can be represented by the formula (CH2O)n, where n is
the number of carbon atoms in the molecule. In other words, the rao of carbon
to hydrogen to oxygen is 1:2:1 in carbohydrate molecules.

Carbohydrates are classified into three subtypes: monosaccharides, which are
single sugar molecules; disaccharides, which are bonds of two sugar
molecules; and polysaccharides, which are bonds of more than two sugar
molecules.

Monosaccharides: Ready Energy

Monosaccharides are also called simple sugars. Depending on the number of
carbon atoms in the sugar, they may be classified as trioses, pentoses, and
hexoses. Trioses have three carbon atoms, pentoses have five carbon atoms,
and hexoses have six carbon atoms.

Pentoses such as ribose and deoxyribose, are important because they form
part of nucleic acids.

Glucose, with six carbon atoms, has a molecular formula of C6H12O6. In most
living species, glucose is the preferred immediate source of energy. During
cellular respiraon, energy is released from glucose and that energy is used to
help make adenosine triphosphate (ATP). Plants synthesize glucose using
carbon dioxide and water by the process of photosynthesis, and the glucose,
in turn, is used for the energy requirements of the plant. The excess
synthesized glucose is oen stored as starch that is broken down by other
organisms that feed on plants.

Figure 42. Structures of Common Monosaccharides
Source: http://www.sarahkayhoffman.com/wp-content/uploads/2013/02/Monosaccharide-Structure.png

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