ATP - topic 17
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
What is ATP used for in plants and animals?
Coenzymes - topic 18
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
What is the role of coenzymes in photosynthesis and respiration?
Energy transfer - topic 19
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
What is the role of catalysts in a chemical reaction?
Reduction and oxidisation - topic 20
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
What is a redox reaction?