Energy and Respiration

• Energy


  Why we need it: Active transport, Anabolic reactions (protein synthesis), Movement (e.g. muscle contraction), Maintaining body temperature (for mammals and birds)
• Sources of energy


  • Photosynthesis: Where light energy is used to synthesize carbohydrates for autotrophs
  • Respiration: The process by which living cells break down to release energy
• Respiration equations


  1. C6H12O6 + 6O2 ⇒ 6CO2 + 6H2O (R)

  2. 6CO2 + 6H2O ⇒ C6H12O6 + 6O2 (P)
• ATP


  A universal short term energy store, considered as energy currency, which breaks down and releases energy - to form ADP, and then again to form AMP
• Glycolysis


  1. 1 - Glucose is phosphorylated to fructose bisphosphate (hexose) by 2 molecules of ATP

  2. 2 - Fructose bisphosphate splits into two triose phosphate

  3. 3 - 2 molecules of TP are oxidised to two pyruvate

  4. Net gain of two reduced NAD and two ATP per glucose molecule
• Link reaction


  1. 1 - Oxidative decarboxylation and dehydrogenation of pyruvate occur to form acetate

  2. Net gain of CO2 and two NADH

  3. 2 - Acetate combines with coenzyme A to form acetyl coA
• Role of coA


  Basically, its a molecule that helps an enzyme carry out its function but its not used in the reaction itself
• Krebs cycle


  Series of redox reactions that produce: 1 - ATP by substrate level phosphorylation, 2 - Reduced coenzymes, 3 - CO2 from decarboxylation
• NAD and FAD


  Coenzymes that accept hydrogen atoms at different points during respiration and transfer the hydrogen ions and electrons to the electron transport chain
• Oxidative phosphorylation


  1. Hydrogen atoms are donated by reduced NAD and FAD

  2. Hydrogen atoms split into protons and electrons

  3. The released energy is used to transport protons across the inner mitochondrial membrane from the matrix into the intermembrane space

  4. A concentration gradient of protons is established between the intermembrane space and the matrix

  5. The protons return to the matrix via facilitated diffusion through the channel protein ATP synthase

  6. The movement of protons down their concentration gradient provides energy for ATP synthesis

  7. Oxygen combines with protons and electrons at the end of the electron transport chain to form water
• Anaerobic respiration


  This occurs when there is not enough oxygen in the cell. The consequences are: The ETC stops functioning, ATP is not produced from Oxidative Phosphorylation, NAD and FAD aren't oxidised, The Krebs Cycle stops
• Ethanol fermentation


  1. Glucose turns to pyruvate

  2. ADP is turned to ATP

  3. NADH is reduced to NAD

  4. Pyruvate turned to Ethanal

  5. CO2 is produced

  6. Ethanal turn to Ethanol

  7. Hydrogen is taken from NADH
• Lactate fermentation


  1. Glucose turns to pyruvate

  2. ADP is turned to ATP

  3. NADH is reduced to NAD

  4. Pyruvate turned to Lactate

  5. Hydrogen is taken from NADH
• Metabolism of Lactate


  • Lactate can oxidise back into Pyruvate - which is then taken to the Krebs cycle for ATP production
  • It can be converted into Glycogen for storage in the liver
• Comparison between Aerobic and Anaerobic Respiration


  • Aerobic Respiration: Complete oxidation of glucose, Total ATP produced ≈36 (high), Occurs in cytoplasm and mitochondria, Products: CO2 and H2O
  • Anaerobic Respiration: Incomplete oxidation of glucose, Total ATP produced 2 (low), Occurs in cytoplasm, Products: Yeast - CO2 and Ethanol, Mammals - Lactate
• Adaptations of rice plants for aerobic respiration


  • Increased rate of upward growth - away from the waterline
  • Possess Aerenchyma tissue in the stem that contains air spaces for gas diffusion
  • Can store gases in the Aerenchyma tissue even when leaves are underwater
• Adaptations of rice plants for anaerobic respiration


  • Use Ethanol Fermentation
  • Tolerate higher levels of Ethanol compared to other plants
  • Produce Ethanol Dehydrogenase enzyme to break down Ethanol
  • Can carry out Anaerobic Respiration for longer to produce more ATP
• Using DCPIP and Methylene Blue to investigate respiration


  1. They are redox indicators that change colour when reduced or oxidised

  2. They are added to a suspension of living yeast cells

  3. The faster the rate of respiration, the faster the rate of hydrogen release, and the faster the colour change
• Mechanism of using DCPIP and Methylene Blue

  1. The hydrogen molecules are transferred to the final stage of Aerobic Respiration (Oxidative Phosphorylation) via NAD and FAD

  2. This reaction is called 'Dehydrogenation'
• Investigating the effect of temperature and substrate concentration

  1. Use different test tubes with yeast mixture at different temperatures (30°C, 35°C, 40°C, 45°C)

  2. Use a stopwatch to calculate the time taken for colour change

  3. Repeat with different substrate concentrations
• Respirometers


  • Used to measure and investigate the rate of oxygen consumption during aerobic respiration
  • Can be used to investigate the effect of temperature on the rate of respiration
• Calculating the rate of oxygen consumption

  Using the diameter of the capillary tube and the distance moved by the fluid: Πr^2 * h
• The rate of oxygen consumption is often taken as the rate of respiration for organisms
• What is the relationship between rate of respiration & rate of hydrogen release?

  The faster the rate of respiration, the faster the rate of hydrogen release
• How many ATPs are produced in Aerobic & Anaerobic respiration?
• What are the stages of respiration?


  • Glycolysis, Link Reaction, Krebs Cycle, Oxidative Phosphorylation
• Substrate linked phosphorylation


  The process where ATP is produced directly from ADP and inorganic phosphate during the Krebs Cycle
• Name one of the types of anaerobic pathways


  • Ethanol Fermentation, Lactate Fermentation
• NAD and FAD


  Coenzymes that accept hydrogen atoms during respiration
• Write down the equation of respiration


  C6H12O6 + 6O2 ⇒ 6CO2 + 6H2O
• DCPIP and Methylene Blue


  Redox indicators used to investigate respiration