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.