Chapter 8: Intro To Metabolism

• What is the totality of an organism’s chemical reactions called?

  Metabolism
• What is metabolism an emergent property of?

  Life
• What is a metabolic pathway?

  • A series of chemical reactions
  • Builds (anabolic) or breaks down (catabolic) complex molecules
  • Converts starting molecules into products through intermediates
• What type of pathway builds complex molecules from simpler ones?

  Anabolic pathway
• What is an example of an anabolic pathway?

  Building glucose from carbon dioxide
• What do catabolic pathways do?

  They break down complex molecules into simpler ones
• What is released during catabolic pathways?

  Energy
• How is energy harvested in catabolic pathways?

  In forms that can power the work of the cell, such as ATP
• What facilitates each reaction step in a metabolic pathway?

  An enzyme
• What does thermodynamics in biology study?

  • Energy transfers in molecules
  • Energy transfers in collections of molecules
• What is an open system in thermodynamics?

  A system that can exchange both energy and matter with its surroundings
• What is a closed system in thermodynamics?

  A system that can exchange only energy with its surroundings
• What is an isolated system?

  A system that cannot exchange either matter or energy with its surroundings
• What does the First Law of Thermodynamics state?

  Energy cannot be created or destroyed, only transformed or transferred
• What does the Second Law of Thermodynamics state?

  Every energy transfer increases the entropy of the universe
• What happens to usable energy during energy transfers according to the Second Law of Thermodynamics?

  It reduces
• What is the structure of ATP?

  • An RNA nucleotide
  • Contains a five-carbon sugar (ribose)
  • Attached to a nitrogenous base (adenine)
  • Has a chain of three phosphates
• What are the three phosphate groups in ATP called?

  Alpha, beta, and gamma
• What are phosphoanhydride bonds?

  Bonds between the phosphate groups in ATP
• What happens during the hydrolysis of ATP?

  Energy is released
• What is reaction coupling in cells?

  • Linking an energetically favorable reaction (exergonic) with an unfavorable reaction (endergonic)
  • Often involves a phosphorylated molecule when ATP is used
• What is a phosphorylated molecule?

  A molecule to which one of the phosphate groups of ATP has been attached
• Cellular respiration, the breakdown of glucose in the presence of oxygen, is an example of a pathway catabolism
• Anabolic pathways consume energy to build complex molecules from simpler ones
• Catabolic pathways are downhill

  Anabolic pathways are uphill
• The cell uses ATP as its primary source of chemical energy because it can be easily broken apart into ADP + Pi by adding a phosphate group to another molecule.
• What is activation energy?

  The minimum energy required for a chemical reaction to occur
• Why does an energy-releasing reaction with a negative ∆G need energy to proceed?

  Because reactant molecules must reach an unstable transition state
• What happens to reactant molecules during a chemical reaction?

  Some or all chemical bonds in the reactants must be broken
• What is the transition state in a chemical reaction?

  An unstable high-energy state that reactants must reach to proceed
• What is the relationship between the transition state and activation energy?

  The transition state is always at a higher energy level than reactants or products
• How does the activation energy change when a reaction proceeds in reverse?

  The activation energy is larger because products are lower-energy
• What is the typical source of activation energy for reactions?

  Heat
• How does thermal energy affect reactant molecules?

  It speeds up their motion and increases collision frequency
• What happens once a reactant molecule absorbs enough energy?

  It can proceed through the remainder of the reaction
• How is the activation energy related to the rate of a chemical reaction?

  The higher the activation energy, the slower the reaction rate
• What happens to reactions with high activation energies at room temperature?

  They do not proceed significantly without an input of energy
• What is an example of a reaction that has a high activation energy?

  The combustion of propane
• What initiates the combustion of propane?

  A spark providing enough energy to overcome the activation energy barrier
• What is catalysis?

  The process of speeding up a reaction by reducing its activation energy