Carbohydrates
The Basics of Carbohydrates
Carbohydrates are the “fast fuel" of living things. Because very little energy is required to break down carbohydrates, they are the first macromolecules used to obtain energy for a living thing. Carbohydrates are sugar molecules made up of the base elements carbon, hydrogen, and oxygen in a 1:2:1 ratio (1 carbon atom, 2 hydrogen atoms, 1 oxygen atom).
Types of Carbohydrates
Carbohydrates are divided into four chemical groupings: monosaccharides, disaccharides, oligosaccharides, and polysaccharides.
A monosaccharide is the simplest of the saccharides, being a single, simple sugar molecule. These can be found in foods such as fruits.
Two monosaccharides that have covalently bonded, forming a pair, is called a disaccharide, or every day table sugar. Sugar beets, cane sugar, and lactose are examples of these. Disaccharides must be broken down into separate monosaccharides before living things can use their energy.
An oligosaccharide is a saccharide containing a three to six simple sugar molecules. Oligosaccharides are rarely found in natural sources and places, though some plants contain them.
Finally, a polysaccharide is composed of many molecules of one sugar. Polysaccharides make up the majority of carbohydrates, and vary greatly in size (number of linked monosaccharides, which can reach up to ten thousand), sugar content, and structure. The most common polysaccharide is cellulose, a complex polysaccharide, the main component in the structure of plants. Cellulose is made up of many glucose units linked together. Glycogen, found in animals, and starch, found in plants, are also complex glucose polysaccharides.
These polysaccharides have a molecular structure that is either branched or linear. An example of a linear polysaccharide is starch. Starch has just one long chain of monosaccharides. On the other hand, glycogen is a branched polysaccharide. Branched polysaccharides, like linear polysaccharides, are long chains of monosaccharides, but have other chains, or branches, connected to them. The more chains a polysaccharide has, the more energy it is able to store. So, a branched polysaccharide the same length as a linear polysaccharide is able to store more energy, like glycogen is able to more than starch.
Two monosaccharides that have covalently bonded, forming a pair, is called a disaccharide, or every day table sugar. Sugar beets, cane sugar, and lactose are examples of these. Disaccharides must be broken down into separate monosaccharides before living things can use their energy.
An oligosaccharide is a saccharide containing a three to six simple sugar molecules. Oligosaccharides are rarely found in natural sources and places, though some plants contain them.
Finally, a polysaccharide is composed of many molecules of one sugar. Polysaccharides make up the majority of carbohydrates, and vary greatly in size (number of linked monosaccharides, which can reach up to ten thousand), sugar content, and structure. The most common polysaccharide is cellulose, a complex polysaccharide, the main component in the structure of plants. Cellulose is made up of many glucose units linked together. Glycogen, found in animals, and starch, found in plants, are also complex glucose polysaccharides.
These polysaccharides have a molecular structure that is either branched or linear. An example of a linear polysaccharide is starch. Starch has just one long chain of monosaccharides. On the other hand, glycogen is a branched polysaccharide. Branched polysaccharides, like linear polysaccharides, are long chains of monosaccharides, but have other chains, or branches, connected to them. The more chains a polysaccharide has, the more energy it is able to store. So, a branched polysaccharide the same length as a linear polysaccharide is able to store more energy, like glycogen is able to more than starch.
Dehydration Synthesis
The monomers of organic compounds join together by a chemical reaction to create polymers is known as dehydration synthesis. Dehydration synthesis is a chemical reaction that involves the loss water from the reacting molecule. With carbohydrates, this process removes water from the monosaccharides and joins them together. Two monosaccharides can be joined together using dehydration synthesis. The new molecule is a disaccharide. In carbohydrates, an H from one carbohydrate and an OH from another are removed (combined, the removed elements form water; H2O). If dehydration synthesis continues for an extended period of time, a long and complex carbohydrate chain is formed, creating a polysaccharide.
Hydrolysis is simply the reverse of dehydration synthesis. Adding water to a molecule will break down the polysaccharide, eventually into individual monosaccharides.
Hydrolysis is simply the reverse of dehydration synthesis. Adding water to a molecule will break down the polysaccharide, eventually into individual monosaccharides.