respiration

• During fermentation in yeast, pyruvate can be converted into ethanol and carbon dioxide
• The energy released during cellular respiration is used to synthesise ATP, which fuels all other activities in the cell
• The first step in the breakdown of glucose is the conversion into pyruvate
• ATP is broken down to provide a fixed amount of energy for endothermic reactions in the cell
• When there is a lack of oxygen in muscle cells, pyruvate can be converted into lactic acid, causing muscle cramps
• Break-down of glucose

  1. Glucose, a six-carbon molecule, is broken down into a three-carbon molecule called pyruvate in the cytoplasm

  2. Pyruvate may be converted into ethanol and carbon dioxide in yeast during fermentation, known as anaerobic respiration

  3. Pyruvate breakdown using oxygen takes place in the mitochondria, breaking it into three molecules of carbon dioxide and water, known as aerobic respiration

  4. In the absence of oxygen, pyruvate can be converted into lactic acid, causing cramps in muscles
• Aerobic respiration takes place in the presence of air (oxygen) and produces more energy than anaerobic respiration
• When the terminal phosphate linkage in ATP is broken using water, the energy equivalent to 30.5 kJ/mol is released
• ATP


  Energy currency for most cellular processes
• Endothermic processes in the cell

  Use ATP to drive the reactions
• Process of respiration

  Energy is released to make an ATP molecule from ADP and inorganic phosphate
• Gases exchanged by diffusion in plants

  • Carbon dioxide
  • Oxygen
• Animals' organs for oxygen uptake and CO2 disposal

  • Terrestrial animals breathe oxygen in the atmosphere
  • Animals that live in water need to use the oxygen dissolved in water
• Requirements of the plant affecting gas exchange

  • Water
  • Nutrients
  • Growth stage
• Stomata


  Small openings on the underside of leaves that allow for gas exchange
• Aerobic organisms need to ensure sufficient intake of oxygen
• Places where gas exchange occurs in plants

  • Stomata
  • Large inter-cellular spaces
• Gas exchange in plants

  1. Exchange occurs through stomata

  2. Large inter-cellular spaces ensure all cells are in contact with air

  3. Gases can go into Life Processes 89 cells or away from them and out into the air

  4. Direction of diffusion depends on environmental conditions and requirements of the plant

  5. At night, CO2 elimination is the major exchange activity going on

  6. During the day, CO2 generated during respiration is used up for photosynthesis, hence there is no CO2 release

  7. Oxygen release is the major event at this time
• Aerobic respiration depends on oxygen
• Environmental conditions affecting gas exchange in plants

  • Light
  • Temperature
  • Humidity
  • Wind