Cell respiration

• The electron transport chain is the final step in cellular respiration, where electrons are passed from one carrier molecule to another.
• Oxygen acts as an acceptor at the end of the electron transport chain.
• Electron carriers include cytochromes (proteins with iron atoms) and flavoproteins (containing riboflavin).
• ATP synthase uses energy released by protons moving through it to synthesize ATP.
• Oxygen acts as an acceptor of electrons during aerobic respiration.
• NADH and FADH2 donate their electrons to the electron transport chain at different points.
• Electron carriers transfer high-energy electrons along the electron transport chain.
• NADH donates its two electrons to the first protein in the electron transport chain (complex I).
• Proton gradient across membrane drives ATP production.
• Chemiosmosis involves the movement of H+ ions down their concentration gradient through the inner mitochondrial membrane.
• This process generates a proton motive force that powers the synthesis of ATP via oxidative phosphorylation.
• Proton gradient across inner mitochondrial membrane drives production of ATP via chemiosmosis.
• Cellular respiration pathway

  
• The Krebs cycle occurs in the matrix of the mitochondria.
• Pyruvate produced by glycolysis can be converted into lactate or ethanol if no oxygen is available.
• Glycolysis is anaerobic, meaning it does not require oxygen.
• Glycolysis is anaerobic, while cellular respiration requires oxygen.
• Anaerobic glycolysis produces only two molecules of pyruvate per glucose molecule.
• Anaerobic fermentation produces less energy than cellular respiration because it does not involve the electron transport chain.
• Anaerobic respiration produces only two molecules of ATP per glucose molecule compared to aerobic respiration which produces 36-38 molecules of ATP per glucose molecule.
• The 4 stages of aerobic cell respiration include:

  • glycolysis (cytoplasm)
  • link reaction (matrix)
  • Krebs cycle (matrix)
  • oxidative phosphorylation (cristae)
• Cell respiration is the controlled release of energy from organic compounds to form ATP
• ATP from cell respiration is immediately available as a source of energy in the cell
• Energy from ATP is mainly needed for:

  • Synthesizing large molecules (anabolism)
  • Pumping molecules and ions across membranes in the process of active transport
  • Moving things around the cell, such as chromosomes, vesicles, or in muscle cells (tissues) the protein fibres that cause muscle contraction
• Energy from ATP is obtained by splitting the ATP molecules into ADP and phosphate, which can be reconverted back by cell respiration
• Cell respiration can be divided into two types:

  • Anaerobic (no oxygen): Glucose is broken down without using oxygen, yielding a relatively small amount of ATP quickly. Conditions include short rapid burst of energy, oxygen depletion, and oxygen-deficient environments. Products vary by organism, e.g. in humans, glucose is converted to lactic acid
• Aerobic (with oxygen): Requires oxygen and yields a large number of ATP molecules. Glucose is more fully broken down with oxygen available, producing more energy. Aerobic respiration yields more than 30 ATP molecules and occurs in the mitochondrion, producing CO2 and water
• Cellular respiration breaks down organic molecules, like glucose, to produce energy in the form of ATP. It occurs in three main stages: glycolysis, the citric acid cycle, and oxidative phosphorylation
• Glycolysis:

  • Location: cytoplasm
  • Glucose is broken down into two molecules of pyruvate, requiring 2 ATP but generating 4 ATP (net gain of 2 ATP)
  • NAD+ is reduced to NADH
• Krebs Cycle (citric acid cycle):

  • Location: mitochondrial matrix
  • Pyruvate is converted to Acetyl CoA, initiating the cycle
  • Each turn produces: 1 ATP, 3 NADH, 2 CO2, 1 FADH2
  • One glucose molecule generates 2 turns of the cycle, producing a total of 2 ATPs, 6 NADH, 2 FADH2, 4 CO2
• Oxidative phosphorylation:

  • Location: Inner mitochondrial membrane
  • NADH and FADH2 donate high-energy electrons in the electron transport chain
  • Electrons lose energy, pumping protons into the intermembrane space, creating a proton gradient
  • ATP synthase drives ATP synthesis from ADP and Pi
  • Oxygen acts as the final electron acceptor, forming water
  • Produces 28-34 ATP molecules
• Total ATP yield from cellular respiration is approximately 32-38 ATP molecules per glucose molecule