Nucleotides

• A Nucleotide is yet another type of Biological Molecule, it's made from a Pentose Sugar, a Nitrogenous Base and a Phosphate Group.
• All Nucleotides contain the elements, Phosphorus, Oxygen, Nitrogen, Carbon and Hydrogen 

• Nucleotides are the Monomers that make up DNA and RNA
• ADP and ATP are Special types of Nucleotides used to Store and Transport Energy in cells

Deoxyribose (Shown Above)

• The pentose sugar in a DNA nucleotide is 'Deoxyribose'
• Each DNA Nucleotide has the Same Sugar and Phosphate Group, it is the Base on each DNA nucleotide that Varies.
• There are 4 possible bases, Adenine (A), Thymine (T), Guanine (G) and Cytosine (C)
• Adenine and Guanine are a type of base called Purine.
• Thymine and Cytosine are a type of base called Pyrimidine.

• Purine: contains 2 Carbon-Nitrogen Rings joined together
• Pyrimidine: Only 1 Carbon-Nitrogen Ring - so it is Smaller than purine.
• A Molecule of DNA contains Two Polynucleotide Chains - each chain having lots of nucleotides joined together.

Ribose 

• RNA contains Nucleotides with a Ribose sugar instead of deoxyribose.
• An RNA molecule also has a Phosphate group, and one of four different bases.
• However, in RNA, Uracil (U), which is a Pyrimidine, Replaces Thymine as a base.
• An RNA molecule is made up of a Single Polynucleotide Chain

ADP and ATP

• To Phosphorylate a nucleotide, you Add One or More Phosphate Groups to it.
• ADP (Adenosine Diphosphate) contains the base Adenine, the sugar Ribose and Two Phosphate Groups.
• ATP (Adenosine Triphosphate) contains the base Adenine, the sugar Ribose, and Three Phosphate Groups.

ADP, ATP and Energy

• ATP provides Energy for Chemical Reactions in the Cell.
• ATP is Synthesised from ADP and Inorganic Phosphate (Pi) using the Energy From an Energy-Releasing Reaction, (e.g. the breakdown of glucose in respiration.
• The ADP is Phosphorylated to form ATP and a Phosphate Bond is formed.
• Energy is Stored in the Phosphate Bond. When this Energy is Needed by a cell, ATP is Broken Back Down into ADP and Inorganic Phosphate (Pi). The Energy is Released from the Phosphate Bond and Used by the Cell.