The Structure and Function of Carbohydrates

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The Structure and Function of Carbohydrates

Large biological molecules are called macromolecules, there are giant

molecules (polymers) made up of repeating units (monomers).

Carbohydrates are one of the main classes of biological molecules.

Macromolecule units (monomers) are joined together by condensation

reactions and hydrolysis reactions split macromolecules down into

their individual units. Carbohydrates are molecules that contain

elements of carbon, hydrogen, and oxygen. Carbohydrates have a 2:1

hydrogen to oxygen ratio, there are twice as many hydrogen atoms as

oxygen atoms (the same proportion as in water). Carbohydrates are

categorised in three many groups:

Ø Monosaccharide – monomers and therefore contain single surgar.

Ø Disaccharide – contain double sugars.

Ø Polysaccharide – are large molecules containing many complex sugars.

The general formula for carbohydrates is Cx(H20)y.

Monosaccharides are white crystalline solids with low molecular mass

and sweet tasting. All monosaccharides are reducing sugars because

they all aldehydes. Different monosaccharides contain different number

of carbon atoms. There are three types of monosaccharides, trioses,

pentose and hexose. They generally contain three (trioses), five

(pentoses) or six (hexoses) carbon atoms. Triose is used as a product

in biochemical pathways of respiration and photosynthesis. An example

of pentoses is ribsomes and deoxyribsome. These sugars are found in

the nucleic acid of DNA and RNA. Examples of hexoses are glucose and

fructose. It is an important source of energy in respiration found in

many sweet tasting fruits. There are four different types of hexose

sugars. The slight differences in the way their atoms are arranged

give them slightly different properties. These are shown below:

α-glucose: β-glucose: Galatose: Fructose:



The main function of monosaccharide is that they are able to move

through bodies, gut walls and therefore important as a source of

energy. All other carbohydrates have to be converted to

monosaccharides before energy can be released and its is due to itÂ’s

small size they are very soluble and it is the form of monosaccharides

that all carbohydrates are carried in the blood.
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