genbio2

• Adenosine triphosphate (ATP)


  The energy molecule used by the cell
• ATP


  Analogy to money or currency of the cell, used to power cellular processes
• Triphosphate


  Three phosphates, energy is stored in the bonds between the second and third phosphate
• Hydrolysis of ATP


  ATP + water yields ADP + single phosphate + energy
• The energy released from ATP hydrolysis powers cellular processes
• Cellular respiration


  The process that creates ATP
• Mitochondria


  • The powerhouse of the cell, produces most of the ATP
• Cellular respiration


  1. Glycolysis

  2. Krebs cycle

  3. Electron transport chain
• Glycolysis


  Takes place in the cytoplasm, breaks down glucose to produce some ATP and NADH
• Glycolysis uses 2 ATP but produces 4 ATP, resulting in a net gain of 2 ATP
• Pyruvate is the end product of glycolysis
• Aerobic pathway


  Pyruvate enters the mitochondria and goes through the Krebs cycle and electron transport chain
• Anaerobic pathway


  Pyruvate is used in fermentation when oxygen is lacking
• Krebs cycle


  1. Pyruvate is converted to acetyl-CoA

  2. Acetyl-CoA enters the Krebs cycle

  3. Krebs cycle intermediates are broken down, producing NADH and FADH2
• The main products of the Krebs cycle are NADH and FADH2, not ATP
• Electron transport chain


  1. NADH and FADH2 from glycolysis and Krebs cycle provide electrons

  2. Electrons are passed through protein complexes, creating a proton gradient

  3. Protons flow through ATP synthase, driving the production of ATP
• Oxygen is used at the end of the electron transport chain to combine with hydrogen to form water
• Up to 34 ATP can be produced through the electron transport chain and ATP synthase
• Cellular respiration


  1. Derive energy from food

  2. One molecule of glucose (C6H12O6) reacts with six molecules of oxygen to produce six molecules of carbon dioxide and six molecules of water

  3. Release energy (exergonic)
• ATP


  Adenosine triphosphate, the energy currency of the cell
• ATP is used to


  Drive endergonic reactions, provide energy for movement, growth, and everyday activities
• ATP is formed by

  Converting ADP (adenosine diphosphate) to ATP by adding a phosphate group
• ATP releases energy when

  It loses a phosphate group (exergonic reaction)
• Efficiency


  Releasing energy from ATP is more efficient than directly using the energy from glucose, as it results in less energy loss as heat
• Cells use ATP instead of glucose because it is more efficient to convert that energy into useful work
• Structure of ATP


  Five-carbon ribose sugar, nitrogenous base adenine, three phosphate groups
• Stages of cellular respiration

  1. Glycolysis

  2. Pyruvate oxidation

  3. Krebs cycle

  4. Electron transport chain
• Glycolysis


  Glucose (6 carbons) is converted into two pyruvate molecules (3 carbons each), producing a net of 2 ATP molecules
• Glycolysis


  • Occurs in the cytosol
  • Involves an investment phase (2 ATP consumed) and a payoff phase (4 ATP produced)
  • Produces 2 NADH molecules
• Pyruvate oxidation


  Pyruvate is oxidized into acetyl coenzyme A, releasing CO2 and producing NADH
• Krebs cycle


  Acetyl coenzyme A is oxidized into CO2, producing 3 NADH, 1 FADH2, and 1 ATP (GTP)
• Krebs cycle


  • Occurs in the mitochondrial matrix
  • Involves dehydrogenase enzymes that transfer hydrogen atoms
• One glucose molecule yields 6 NADH, 2 FADH2, and 2 ATP from the Krebs cycle
• The electron carriers NADH and FADH2 produced in glycolysis, pyruvate oxidation, and the Krebs cycle will be used in the electron transport chain
• The terms "molecules" and "ions" are sometimes used interchangeably in this context, as the particles can carry a charge
• Krebs cycle


  1. One turn produces 3 NADH

  2. 1 FADH2

  3. 1 GTP
• GTP gains a phosphate to become ATP


  GTP then loses the phosphate, regenerating GDP and converting ADP to ATP
• One turn of the Krebs cycle produces 3 NADH, 1 FADH2, and a net of 1 ATP (GTP)
• Glucose generates 2 pyruvate and 2 acetyl CoA, so 1 glucose = 2 turns of the Krebs cycle
• 1 glucose yields 6 NADH, 2 FADH2, and 2 ATP from the Krebs cycle