Good carbs / good carbs ?
Carbohydrates in one form or another are found in in very many foods.
Carbohydrates or "Carbs" are not only essential components of a balanced diet, providing energy and fibre, but can also provide the raw materials to produce useful, biodegradable "eco"polymers . Jayne explains..
Carbohydrates are an important source of energy. It is often thought that we should reduce our carbohydrate intake . However this is only really true if we are consuming too much of the wrong carb type.
Simpler carbohydrates, like glucose are broken down and release energy for essential chemical reactions in our cells.
Larger carbohydrate molecules like starch, which are made up of many glucose molecules joined together, are important energy storage molecules. They can be broken down to release simpler carbohydrates when required. Other large carbohydrates like cellulose are important sources of fibre in our diets and can be modified to produce polymers which can be used as alternatives to plastics derived from crude oil.
Simple sugar : a monosaccharide close up
A molecule of alpha glucose. Rotate and zoom into the model to view it.
These are single units of carbohydrates, sometimes commonly referred to as 'simple sugars.' Examples include, glucose, fructose and galactose. These three are hexose sugars with the chemical formula C6H12O6. This diagram is of alpha glucose. For simplification, only 5 of the carbons and only the OH and H groups around carbon 1 and 4 are shown in this diagram.
Can you identify carbon atoms 1 - 6 ?
Alpha glucose with numbered carbon atoms
Click to see and compare beta glucose.....
Look at carbon 1. These two forms of glucose are identical apart from the arrangement of the OH and H atoms on carbon 1. These two forms of the same molecule are isomers. This type of isomerism is known as stereoisomerism.
The slideshow here shows how two alpha glucose molecules join together via a condensation reaction to form a molecule of maltose. Many glucose molecules join to form a molecule of starch
Click to move through the slideshow and use it to answer the questions below:
- Why is the reaction joining to glucose molecules referred to as a condensation reaction?
- Describe the structure of amylose.
- What is the position of the glycosidic bonds in amylose?
- What bonds hold the alpha helix of amylose in place?
- Condensation reactions involve the joining of two molecules and release a small molecule in the process
- Amylose is a polymer made up of glucose monomers joined by glycosidic bonds
- The glycosidic bonds are on carbons 1 and 4 on the glucose rings
- The alpha helices in amylose are held in place by hydrogen bonds.
Maltose is found in grains
Sucrose is found in plants
These have molecules made up of two monosaccharide molecules joined by a glycosidic bond. Examples include Maltose, Sucrose and Lactose. Maltose is shown in the image above. It is made of two alpha glucose molecules, each with the formula C6H12O6 . A molecule of water is lost as the glycosidic bond between the two glucose molecules forms, making its chemical formula C12H22O11
Most crude oil derived polymers remain in the environment
The vast bulk of the modern man made polymers used in everyday life are derived from crude oil. Whilst properties like impermeability and insolubility in water are often what makes them useful, it is also these very properties that create a very large pollution problem . Many of nature's own polymers such as Chitin and Cellulose can be adapted to replace synthetic polymers and can also be made biodegradable.