Photosynthesis, respiration and ATP

HideShow resource information

Biological processes need energy

Plants need energy for things like :

  • photosynthesis
  • active transport (to take in minerals via their roots)
  • DNA replication

Animals need energy for things like : 

  • muscle contraction
  • maintanence of body temperature
  • protein synthesis
1 of 6


  • photosynthesis is the process where energy from light is used to make glucose from water and carbon dioxide
  • photosynthesis occurs in a series of reactions, but the overall equation is

6CO2 + 6H2O + energy --> C6H12O6 (glucose) + 6O2

  • energy is stored in the glucose until the plant releases it by respiration
  • animals obtain glucose by eating plants (or other animals) then respire the glucose to release energy
2 of 6

Cells release energy from glucose by respiration

  • plant and animal cells release energy from glucose ; the process is called respiration
  • this energy is used to power all the biological processes in a cell
  • There are two types of respiration, aerobic (requires oxygen), and anaerobic (does not require oxygen) 
  • aerobic respiration produces carbon dioxide and water, and releases energy 
  • the overall equation is 

C6H12O6 (glucose) + ^O2 --> 6CO2 + 6H2O + energy

3 of 6

ATP is the immediate source of energy in a cell

  • a cell can't get its energy directly from glucose
  • in respiration, the energy released from glucose is used to make ATP (adenosine triphosphate)
  • ATP is made from the nucleotide base adenine, combined with a ribose sugar and the three phosphate groups 
  • ATP is synthesised from ADP and inorganic phosphate (Pi) using energy from an energy-release reaction (breakdown of glucose in respiration). This energy is stored as chemical energy in the phosphate bond. The enzyme ATP synthase catalyses this reaction
  • ATP diffuses to the part of the cell that needs energy
  • It's broken back down back into ADP and inorganic phosphate, chemical energy is released from the phosphate bond and used by the cell. ATPase catalyses this reaction
  • The ADP and inorganic phosphate are recycled and the process starts again
4 of 6

ATP's properties makes it a good energy source

  • ATP stores or releases only a small, managable amount of energy at a time, so no energy is wasted
  • It's a small, soluable molecule so can easily be transported around the cell
  • It's easily broken down so energy can easily be released 
  • It can transfer energy to another molecule by transferring one of its phosphate groups 
  • ATP can't pass out of the cell so the cell always has an immediate  supply of energy
5 of 6


  • a coenzyme is a molecule that aids the function of an enzyme
  • they work by transferring a chemical group from one molecule to another
  • NADP is used in photosynthesis --> transfers hydrogen from one molecue to another. This means it can reduce of oxidise a molecule
  • In respiration : NAD and FAD transfer hydrogen from one molecule to another. It can reduce or oxidise a molecule
  • Coenzyme A transferes acetate between molecules 
6 of 6


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Cellular processes resources »