Essential Molecules
Essential Molecules
Some important elements
Biological MoleculesOrganisms are made from a huge variety of organic
and inorganic compounds.
The most important inorganic molecule is WATER.
The main organic molecules are:
1. Carbohydrates2. Proteins3. Lipids4. Nucleic Acids
1. Carbohydrates
• These include sugars, starches, cellulose and glycogen.
• Carbohydrates always contain the elements carbon, hydrogen and oxygen.
one sugar molecule
carbohydratemolecule
They are divided into 3 categories, according to size:
– Monosaccharides – ‘simple sugars’, eg. glucose and fructose
– Disaccharides – ‘double sugars’,eg. sucrose and maltose
– Polysaccharides – ‘multiple sugars’, eg. starch, glycogen and
cellulose
Size and Function• Sugars - are small molecules,
soluble in water, easy to transport, making them ideal sources of energy
• Polysaccharides – giant molecules
eg. Starch and Glycogen have compact, coiled and branched molecules, making them ideal stores of energy
Size and Function cont’d
eg. Cellulose molecules have long straight molecules, perfect for forming structural fibres
Uses of Carbohydrates in Living Organisms
2. ProteinsProteins, like carbohydrates, are made of long
chains of small molecules. In proteins, these small molecules are not identical.
Proteins are made up of chains of small molecules called amino acids. There are over 20 different kinds of amino acid.
protein molecule
one amino acid
Structure of Proteins
They contain the elements carbon, hydrogen, oxygen and nitrogen (also often sulfur and phosphorus).
The subunits – amino acids – can be joined in any order and are key to the large variety of proteins.
Two amino acids join together to form a
dipeptide. A chain of amino acids is known as
a polypeptide.
Functions of Proteins in the Human Body
• Enzymes are proteins that control metabolism (body chemistry). There is a different enzyme for every reaction.
• Antibodies are proteins that help us to fight disease
• Collagen and other strong proteins effectively hold us together – connective tissues i.e. tendons, cartilage and bones all owe their strength to collagen
• Blood clotting involves many different proteins
• Keratin is the protein that gives strength to hair, skin and nails
3. Lipids
Lipids are a group of compounds that include fats, oils and waxes. They all contain the elements carbon, hydrogen and oxygen. Importantly, they do not mix with water.
There are 2 main types – Triglycerides and Phospholipids.
TriglyceridesTriglycerides are made up of fat
molecules which contain fatty acids and glycerol.
Triglycerides molecules have to be broken down by the body so that they can be used for energy storage.
fat molecule
glycerol
fatty acids
PhospholipidsAre important in Biology as they form
cell membranes, which surround all cells. A phospholipid molecule is similar to a triglycerides except one fatty acid is replaced by a phosphate group.
Functions of Lipids
• Source of energy• Insulation• Protection• Buoyancy• Waterproofing• Cell membranes
4. Nucleic Acids
Are made up of chains of individual units called nucleotides. These are comprised of:
1. A Phosphate group2. A sugar3. A base – there are 5 of these:
CYTOSINE THYMINE ADENINEGUANINE URACIL
Structure and Function
The main function of nucleotides is the formation of nucleic acids RNA and DNA, which play vital roles in protein synthesis and heredity.
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