Carbohydrate, hydrocarbon

What is the difference between the two chemicals — carbohydrate and hydrocarbon, while both are fuels — one for humans and the other for engines?

V.K. PRAHLADA RAO

Bangalore

Carbohydrates and hydrocarbons are two different classes of organic compounds. Though the names appear to be similar, there is a vast difference in their basic chemical composition. Carbohydrates contain Carbon (C), Hydrogen (H), Oxygen (O). Whereas hydrocarbons contain only Carbon (C) and Hydrogen (H).

Both liberate energy in presence of oxygen and get converted to carbondioxide and water.

Carbohydrates include starch, sugars, cellulose glycogen etc., and they are basically polyhydroxy aldehydes, polyhydroxy ketones or compounds that can be hydrolysed to them. These carbohydrates are the ultimate source of most of our food because we eat grain or we feed to animals to be converted into meat and fat which we then eat.

These carbohydrates thus formed during photosynthesis in the plants in the form of starch, sugar are converted to glucose in our body through complex enzymatic catalysis. This glucose is finally converted to carbondioxide and water liberating energy in the form of ATP at cellular level during respiration.

These reactions take place in our body during respiration, wherein the oxygen required for the conversion is supplied during inhaling and the liberated carbondioxide is expelled during exhaling. During the metabolism, this energy is used by the muscles in the form of mechanical energy, used for maintaining the body temperature, stored in the form of ATP for future use and utilized in the body for various metabolic activities.

In our body also the conversion of carbohydrates takes place with the release of energy but through complex biochemical pathway and these reactions take place in the mitochondria present in the cells. Conversion of carbohydrates liberates approximately 4.1Kcal or 17kJ of energy per gram of carbohydrate consumed.

When it comes to the case of hydrocarbons they are combustible fuels. i.e, they liberate enormous amount of energy on burning in the presence of oxygen. Burning of hydrocarbons is an exothermic reaction, which means a lot of heat is liberated which is used to drive engines, motors, power plants and others. Basically these compounds contain only carbon and hydrogen in their structure. Common examples for this class of compounds are gasoline, kerosene, cooking gas, coal gas, naphtha and such other fuels.

Dr. T. BHAVANI

Bangalore

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