Metabolism Part 1

• Thermodynamics

  The study of energy flow in physical and biological processes
• Living things continually capture, store and use energy for their survival
• Examples of energy use in living things: movement, growth, reproduction, digestion, heat, movement across cells
• Metabolism

  Refers to all the chemical reactions that change or transform matter and energy in cells
• The main function of metabolism is to breakdown energy-rich compounds (e.g. glucose) and convert the energy into a useable form (e.g. ATP)
• Coupled reactions

  Energy from catabolic reactions is used to power anabolic reactions
• Anabolic

  Small molecules are assembled into large ones. Energy is required.
• Catabolic

  Large molecules are broken down into small ones. Energy is released.
• ATP

  Adenosine Triphosphate, the primary source of free energy in living cells
• ATP structure

  • Nitrogenous base adenine attached to 5-carbon sugar ribose which is attached to a chain of 3 phosphate groups
• How energy is obtained from ATP

  1. Enzyme ATPase catalyzes hydrolysis of terminal phosphate, releasing inorganic phosphate and energy

  2. The released phosphate can then phosphorylate other molecules, changing their shape and making them more active (e.g. in active transport)
• Electron carriers

  Compounds that pick up electrons from energy-rich compounds and then donate them to low-energy compounds, being recycled in the process
• How electron carriers work

  1. Compound accepts electrons - reduced

  2. Compound loses electrons - oxidized
• LEO GER: Lose Electrons Oxidation, Gain Electrons Reduction
• Electrons that pass from one atom to another carry energy with them
• Reducing power

  Electrons are said to carry reducing power
• Photoautotrophs transform light energy into chemical potential energy (glucose and other carbohydrates)
• Heterotrophs rely on autotrophs for energy
• Glucose is the primary energy source for (almost) all organisms
• Energy is extracted from glucose by enzymes doing redox reactions, and the released energy is trapped and stored as ATP
• Aerobic cellular respiration

  Oxygen is used, accomplished by 20 chemical reactions summarized as C6H12O6 + 6O2 → 6CO2 + 6H2O
• Glucose and oxygen don't just react together spontaneously, the activation energy barrier must be overcome by enzymes
• Endergonic reaction


  Chemical reaction that requires energy and does not proceed spontaneously
• Exergonic reaction

  Chemical reaction that releases energy and tends to proceed spontaneously
• Examples of endergonic and exergonic reactions

  • Endergonic: Photosynthesis
  • Exergonic: Cellular Respiration
• NADH


  Nicotinamide Adenine Dinucleotide, reduced form of electron carrier
• FADH2


  Flavin Adenine Dinucleotide, reduced form of electron carrier
• NAD+


  Nicotinamide Adenine Dinucleotide, oxidized form of electron carrier
• FAD


  Flavin Adenine Dinucleotide, oxidized form of electron carrier
• The 4 stages of cellular respiration

  1. Glycolysis

  2. Pyruvate Oxidation

  3. Krebs Cycle

  4. Electron Transport Chain
• Substrate level phosphorylation

  ATP is formed through the direct transfer of inorganic phosphate to ADP using an enzyme, resulting in less energy generation than oxidative phosphorylation
• Structure of mitochondria

  • Double membrane (inner folded into cristae, outer smooth)
  • Intermembrane space
  • Matrix
  • mtDNA
• Mitochondria are often described as the powerhouses of the cell because of their central role in ATP synthesis
• Mitochondrial membranes

  • Outer membrane - smooth
  • Inner membrane - convoluted with cristae, houses the electron transport chain
• Intermembrane space

  Location of a proton gradient
• Mitochondrial matrix contains mtDNA and ribosomes responsible for synthesis of 15% of mitochondrial proteins, the rest are encoded in the nucleus and transported in
• Glucose activation

  1. Glucose (6 carbon sugar) is phosphorylated by 2 ATPs to become a diphosphate molecule

  2. Diphosphate molecule is split into two 3-carbon molecules (G3P)

  3. Everything from this point on happens twice
• G3P formation

  1. Inorganic phosphate (P) is added

  2. Electrons are transferred to NAD to make NADH
• ATP production

  1. 4 ATP are made (2 per 3-carbon molecule)

  2. Net profit of 2 ATP
• Pyruvate

  Final 3-carbon molecule product of glycolysis