What is a Carbohydrate?

A carbohydrate is a compound with 1 or more sugars. The more complex the structure (the more sugars and the more branching) the more complex the carbohydrate. Simple carbohydrates are just that, simple. They have one or two sugars bound together. We call simple carbohydrates, simple sugars. Complex carbohydrates have many sugars linked together. This is the way we store sugar and the way plants store sugar and gain structure. CHO is a commonly used abbreviation for carbohydrate.

    carb = carbon     hydrate = water    saccharide = sugar                   
    mono = one or single    di = two or double    poly = many

Simple Carbohydrates

Structure of mono and disaccharides

Simple carbohydrates are simple sugars. There are 6 simple CHOs:
3 single sugars and 3 double sugars:

• Monosaccharides (single sugars)
  • fructose: fruit sugar
  • glucose: body’s blood sugar
  • galactose: part of milk sugar

• Disaccharides (double sugars)
  • maltose:  glucose + glucose = malt sugar
  • sucrose: fructose + glucose = table sugar
  • lactose: galactose + glucose = milk sugar
    

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Complex Carbohydrates

Complex carbohydrates, starch, glycogen and fiber

A complex carbohydrate is a polysaccharide. Poly means many and saccharide is sugar. In polysaccharides, the main sugar unit is glucose. Polysaccharides are made up of many glucose units, up to several thousand! There are 3 complex carbohydrates:

Starch

• Plant storage form of carbohydrate
• Repeating units of glucose with some branching
• An example is the starch stored inside a corn kernel      

Glycogen

• Animal storage form of glucose
• Repeating units of glucose, highly branched, very dense
  
• Glycogen is our (humans) storage form of carbohydrate
  
• There are very few carbohydrates in meat we eat (eg: chicken), because the glycogen breaks down rapidly once the animal is slaughtered.
  

Fiber

• Structural component in plants
• Repeating units of glucose linked together
• Bonds cannot be broken (digested) by humans
  
• Fiber passes through the digestive tract unabsorbed
  
• Cellulose, a type of fiber, makes up the cell wall of plants
  

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Types of Foods with Carbohydrates

Most whole carbohydrate foods have both simple and complex carbohydrates. Grains have starch and fiber and a small amount of naturally occurring sugar. Fruits have naturally occurring glucose, fructose, sucrose and fiber. Some fruits, such as bananas, also have starch. Vegetables have a small amount of glucose, fructose, sucrose along with fiber. Green vegetables have little to no starch, while root vegetables such as potatoes and carrots have more starch. Dairy has lactose. Nuts have fiber and a small amount of sucrose and starch.

Simple vs Complex Carbohydrate Video

< Digestion & Absorption

Carbohydrate Digestion >

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References

1. Groff. J, Gropper S. Chapter 4 Carbohydrates. In: Advanced Nutrition and Human Metabolism 3rd Ed. Belmont, CA. Wadsworth; 2000.
   
2. Carbohydrates. US National Library of Medicine. https://www.nlm.nih.gov/medlineplus/ency/article/002469.htm. Last updated February 2, 2016. Last accessed February 27, 2016.
3. Monoaccharide and disaccharide diagram by Christine Dobrowolski, CC BY-SA 2.0.
   
4. Starch, fiber and glycogen diagram by Christine Dobrowolski, CC BY-SA 2.0.
   
5. Wheat header image by Charles Knowles on FlickrCC, CC by 2.0. 

Last updated April 8, 2016.