ATP

Many of the reactions carried out by living cells require ATP (adenosine triphosphate), which is an energy transfer molecule

ATP is a nucleotide consisting of adenine, ribose, three phosphate groups

During photosynthesis, plants use light to synthesise ATP to make food molecules

During respiration, energy is released from food molecules, which synthesises ATP

To drive these reactions, ATP is hydrolised (split up by addition of water) to ADP (adenosine diphosphate) and an inorganic phosphate group

This reaction gives out energy

Question:

What is ATP used for in plants and animals?

Photosynthesis and respiration are redox reactions (involves the transfer of electrons from one molecule to another)

Each stage of the is catalysed by enzymes, coenzymes help transfer the electrons

Coenzymes easily accept electrons and become reduced, then give them up again

Coenzymes have two forms: the oxidised form and the reduced form

Coenzymes are molecules that work alongside enzymes, transferring chemical groups or atoms between active sites of enzymes

Question:

What is the role of coenzymes in photosynthesis and respiration?

When a chemical reaction takes place, bonds within the reactant molecules are broken, atoms rearranged, and bonds reformed

The energy needed for the initial bond breaking is called the activation energy

Catalysts, including enzymes, lower the activation energy

This means that reactions can take place at lower temperatures

Some chemical reactions take in energy, when the energy needed to break the bonds is greater than the energy released when bonds form

Other reactions give out energy, when the energy needed to break the bonds is less than the energy released when bonds form

Question:

What is the role of catalysts in a chemical reaction?

Redox reactions involve the transfer of electrons, so reduction and oxidisation always go together

When oxygen reacts with magnesium, electrons are transferred from the magnesium to the oxygen

This results in a magnesium ion with a positive charge and an oxygen ion with a negative charge

Question:

What is a redox reaction?