Carbohydrates are the most important source of energy. They contain the elements Carbon, Hydrogen and Oxygen. The first part of the name "carbo-" means that they contain Carbon. The second part of the name "-hydr-" means that they contain Hydrogen. The third part of the name "-ate-" means that they contain Oxygen. In all carbohydrates the ratio of Hydrogen atoms to Oxygen atoms is 2:1 just like water.
We obtain most of our carbohydrate in the form of starch. This is found in potato, rice, spaghetti, yams, bread and cereals. Our digestive system turns all this starch into another carbohydrate called glucose. Glucose is carried around the body in the blood and is used by our tissues as a source of energy. Any glucose in our food is absorbed without the need for digestion. We also get some of our carbohydrate in the form of sucrose; this is the sugar which we put in our tea and coffee (three heaped spoonfuls for me!). Both sucrose and glucose are sugars, but sucrose molecules are too big to get into the blood, so the digestive system turns it into glucose.
When we use glucose in tissue respiration we need Oxygen. This process produces Carbon Dioxide and water and releases energy for other processes. Now try my starch test in the Virtual Laboratory.
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