Respiration and Biotechnology (2.34-2.39), (5.5-5.8)

what is respiration

a chemical reaction that takes place in all living cells, releasing energy from glucose to power other life processes

ATP

adenosine triphosphate

during cellular respiration, glucose is broken down and molecules of ATP are produced

the energy required by organisms is released via these molecules

aerobic respiration vs anaerobic respiration

aerobic

• needs oxygen

• high production of ATP

• happens in mitochondria and cytoplasm

• waste products: H₂O and CO₂

• highly efficient

• slower

aerobic respiration vs anaerobic respiration

anaerobic respiration

• doesn’t need oxygen

• lower production of ATP

• happens in cytoplasm

• waste products: lactic acid and (sometimes) ethanol

• less efficient

• faster

equation for aerobic respiration

glucose + oxygen → carbon dioxide + water

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

equation for anaerobic respiration

glucose → lactic acid

C₆H₁₂O₆ → 2C₃H₆O₃

role of lactobacillus in yoghurt

• lactobacillus is added to cooling homogenised milk at optimum temperature

• mixture is incubated in an oxygen-free environment, ensuring the bacteria respires anaerobically

• lactobacillus produces lactic acid via anaerobic respiration which lowers the pH

role of yeast in food production

• yeast produces enzymes that break down the starch in flour, releasing sugars that can be used by the yeast in respiration

• yeast begins to respire aerobically but will switch to anaerobic when oxygen runs out

• when yeast respires anaerobically it produces ethanol and carbon dioxide

• the CO₂ produced is trapped in small air pockets in the dough, causing it to rise

• during baking any ethanol produced by yeast evaporates in the heat, so the bread doesn’t contain any ethanol

• the yeast is killed by the high temperatures in the oven, ensuring there is no further respiration

suitable conditions in an industrial fermenter

• aseptic precautions - fermenter is steamed to kill microbes and prevent contamination

• nutrients - needed for organisms to release energy via respiration

• optimum temperature/pH - temperature/pH probes are used to maintain an optimum environment for enzymes

• oxygenation - oxygen needed for organisms to release energy via aerobic respiration

• agitation - stirring paddles ensure that microorganism, nutrients, oxygen, temperature and pH are evenly distributed