Principles of Biochemistry

3.1.1 Carbohydrates

Carbohydrates are the most abundant class of macromolecule on earth. They constitute about 75% by mass of dry plant material. The plants produced carbohydrate via photosynthesis. In this process, glucose is synthesized from carbon dioxide and water by photosynthesis and stored as starch or converted to cellulose in the plant framework. Animals can synthesize some carbohydrate from fat and protein, but the bulk of animal carbohydrate is derived ultimately from plants.

They are organic compounds that contain carbon, hydrogen, and oxygen. Generally the hydrogen and oxygen in carbohydrates are present in the ratio of two hydrogen to one oxygen (2:1) as in water H₂O hence the term carbohydrates (carbon hydrate) were derived. But all compounds grouped under this heading have a similar structure. 

 

The simple sugar glucose contains 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms giving the molecular formula C₆H₁₂O₆. Carbohydrates are derivatives of polyhydoxy aldehydes or ketone.

Functions: Carbohydrate oxidation provides energy. They are stored as glycogen in animal tissues and   serve as short-term energy reserve. They supply carbon atoms for the synthesis of other biochemical compounds- proteins, lipids and nucleic acids. Carbohydrate form part of the structural component of DNA and RNA molecule.