Lecture 8: METABOLISM AND ENERGY• Know the difference between oxidation and reduction, and be able to identify if amolecule is being oxidized or reduced if given a reaction.

Oxidation and reduction are two types of chemical reactions that often occur together, known as redox reactions.

1. Oxidation: This is a process where a molecule, atom or ion loses electrons. In other words, it's the process of increasing the oxidation state of a molecule, atom or ion. Oxidation reactions are characterized by the loss of electrons or an increase in oxidation state by a molecule, atom, or ion.

2. Reduction: This is a process where a molecule, atom or ion gains electrons. In other words, it's the process of decreasing the oxidation state of a molecule, atom or ion. Reduction reactions are characterized by the gain of electrons or a decrease in oxidation state by a molecule, atom, or ion.

To identify if a molecule is being oxidized or reduced in a reaction, you need to look at the change in oxidation state of the molecule.

• If the oxidation state of the molecule increases, then the molecule is being oxidized.
• If the oxidation state of the molecule decreases, then the molecule is being reduced.

For example, consider the reaction: H2 + O2 -> H2O

In this reaction, hydrogen is being oxidized (from an oxidation state of 0 in H2 to +1 in H2O) and oxygen is being reduced (from an oxidation state of 0 in O2 to -2 in H2O).