Respiration in Cells (Cambridge (CIE) IGCSE Combined Science): Revision Note

Uses of energy in living organisms

What is respiration?

• Respiration is a chemical process that involves the breakdown of nutrient molecules (specifically glucose) in order to release the energy stored within the bonds of these molecules

  • Respiration is enzyme-controlled

• Respiration can take place with oxygen (aerobically) or without oxygen (anaerobically).

  • Much less energy is released for each glucose molecule broken down anaerobically compared to the energy released when it is broken down aerobically

• Respiration occurs in all living cells; most of the chemical reactions in aerobic respiration take place in the mitochondria

Uses of energy released in respiration

• Humans need the energy released during respiration to carry out many processes

  • Muscle contraction

  • Protein synthesis

  • Cell division (to make new cells)

  • Growth

  • Active transport across cell membranes

  • Generation of nerve impulses

  • Maintaining a constant internal body temperature