Respiration & Metabolism

• You need energy to keep your body alive. Energy comes from food, and it's transferred by respiration
• Respiration is not 'breathing in and out'
• Respiration involves many reactions. These are really important reactions, as respiration transfers the energy that the cell needs to do everything - this energy is used for all living processes
• Respiration is the process of transferring energy from the breakdown of glucose - and it goes on in every cell in the body continuously
• Respiration also happens in plants. All living things respire. It's how they transfer energy from their food to their cells
• Respiration is the process of transferring energy from glucose, which goes on in every cell
• Respiration is exothermic - it transfers energy to the environment
• 3 examples of how organisms use the energy transferred by respiration are:

  • To build up larger molecules from smaller ones (like proteins form animo acids)
  • In animals it's used to allow the muscles to contract (so they can move)
  • In mammals and birds the energy is used to keep their body temperature steady in colder surroundings. (Unlike other animals, mammals and birds keep their bodies constantly warm)
• Metabolism is all the chemical reactions in an organism
• In a cell there are lots of chemical reactions happening all the time, which are controlled by enzymes. Many of these reactions are linked together to form bigger reactions:

  reactant -(enzyme)-> product -(enzyme)-> product -(enzyme)-> product
• Enzymes are biological catalysts
• In some of these reactions, larger molecules are made from smaller ones:

  • Lots of small glucose molecules are joined together in reactions to form starch (a storage molecule in plant cells), glycogen (a storage molecule used in animal cells) and cellulose (a component of plant cell walls)
  • Lipid molecules are each made from one molecule of glycerol and 3 fatty acids
  • Glucose is combined with nitrate ions to make amino acids, which are then made into proteins
• In other reactions, larger molecules are broken down into smaller ones:

  • Glucose is broken down in respiration. Respiration transfers energy to power all the reactions in the body that make molecules
  • Excess protein is broken down in a reaction to produce urea. Urea is then excreted in urine
• The sum of all the reactions that happen in a cell or the body is called its metabolism