Biological molecules

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  • Created by: Dani41
  • Created on: 29-10-15 11:54


Covalent Bonding - Nonmetal atoms share a pair of electrons in their outer shells, resulting in both atoms having full outer shells and forming a molecule.


Ionic Bonding - Between a metal and a nonmetal atom whose opposite charges attract one another. This bond is weaker than a covalent bond


Hydrogen Bonding - Between polar molecules that have an electrostatic attraction which occurs when a H atom bound to a highly electronegative atom such as Nitrogen, Oxygen and Fluorine (N,O,F)




Carbohydrate - Contains Carbon Oxygen and Hydrogen


Organic Molecules - Carbon is an organic molecules as it can readily form bonds with other carbon atoms which builds up a ‘backbone’ in which other atoms can join too meaning that a large number of different shapes and sizes of molecules can be formed based on carbon meaning that carbohydrates can be large or small molecules.

Making of large molecules - monomers (individual molecules such as amino acids, monosaccharides and nucleotides) join together with other monomers in order to form long chains called polymers ( carbohydrates and proteins) and are normally based on a small number of chemical elements like C,H,O,N.

Monosaccharide - In carbohydrates the basic monomer unit is a sugar (saccharide) meaning therefore that a single monomer can be called a monosaccharide. They are sweet tasting and are soluble (able to be dissolved). They have the formula (CH²O)n, where n can be 3-7. I.e Glucose is a monosaccharide, which is a six-carbon or hexose sugar, so has the formula C6H12O6. Glucose has two isomers (contain the same number of atoms of each element, but have different arrangements of their atoms.)



Disaccharides - formed when two monosaccharides join by a glycosidic bond in a condensation reaction. They can be broken by the addition of water at the right conditions by hydrolysis.

There are three main types of disaccharides:

Maltose is glucose-glucose (formed on digestion of starch by amylase)

Sucrose is glucose-fructose (common in plants as less reactive than glucose - there main transport sugar)

Lactose is galactose-glucose (milk sugar)


Polysaccharide - formed by many monosaccharides joining together by glycosidic bonds in a condensation reaction. They are large molecules which are insoluble        (incapable of being dissolved) meaning that they are good for storage. Starch is a polysaccharide and so is Cellulose which is not used in storage but used to give structural support to plant cells.




Starch - A polysaccharide found in many parts of plants in the form of small grains or granules. It is made of two components - amylose (spiral - unbranched) and amylopectin (branched). Contains glycosidic bonds that are formed by condensation reactions. Must be fairly big so that it is insoluble and so it does not diffuse out of the cell. This prevents it from causing an osmotic effect in cells whereby water floods in. Molecules must be compact so that it can be stored





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