CH6

• Energy

  Ability to do work or bring about change
• Forms of Energy

  • Kinetic Energy
  • Potential Energy
• First Law of Thermodynamics

  Energy can change from one form to another but can't be created or destroyed, not all captured solar energy is converted to carbohydrates, some is lost as heat
• Second Law of Thermodynamics

  Energy transformation efficiency, when energy transforms from one form to another, there's always a loss of usable energy
• No process achieves 100% efficiency, even gasoline engines are only 20-30% efficient
• Entropy

  Measure of disorder or randomness in a system, it is used to indicate the relative amounts of disorganization
• Every process in cells increases the total entropy in the universe, therefore less energy is available to do useful work
• Metabolism

  The sum of all the biochemical reactions in a cell
• Two main types of metabolism

  • Anabolism - complex molecules are synthesized from simpler substances (requires energy)
  • Catabolism - larger molecules are broken down into smaller ones (releases energy)
• Exergonic reactions

  Products have less free energy than reactants, release energy, they occur spontaneously, ΔG has a negative value
• Endergonic reactions

  Products have more free energy than reactants, require energy, are nonspontaneous, ΔG has a positive value
• ATP

  Adenosine triphosphate, high energy compound used to drive metabolic reactions
• Coupled reactions

  Energy released by an exergonic reaction is captured in ATP, ATP is then used to drive an endergonic reaction
• Biological advantages of ATP

  It's the universal energy currency used in many types of reactions, when ATP becomes ADP it releases energy about 7.3 kcal per mole, the energy is used for biological functions, ATP breakdown can be coupled to endergonic reactions that prevents energy waste
• How ATP acts as carrier of chemical energy

  ATP breakdown is coupled to the energy-requiring reaction which ensures favorable and unfavorable reactions to occur simultaneously, ATP can energize or change the shape of a reactant, both can be achieved by phosphorylation
• Enzymes

  Protein catalysts that speed chemical reactions without the enzyme being affected by the reaction
• Ribozymes

  RNA molecules that function as biological catalysts, involved in RNA and protein synthesis
• Substrates

  The reactants of an enzymatically accelerated reaction
• Each reaction requires a unique and specific enzyme, the end product will not appear unless ALL enzymes are present and functional
• Metabolic pathway

  Linked reactions where the products of an earlier reaction become the reactants of a later reaction
• Induced fit model

  Enzyme slightly changes in shape to fit the substance
• Synthesis (Anabolism)

  Enzyme complexes with two substrate molecules, which are joined together and released as single product molecule
• Degradation (Catabolism)

  Enzyme complexes with one substrate molecule, it breaks into two product molecules, only a small amount of enzyme is needed because enzymes are not consumed during catalysis
• Energy of activation (Ea)

  Energy that must be added to cause molecules to react
• Enzyme operation: enzymes operate by lowering the energy of activation, brings the substrates together and even join the reaction, this speeds up the reaction and is why enzymes are chemical catalysts
• Factors affecting enzymatic speed

  • Substrate concentration
  • Temperature
  • Denaturation
  • Optimal pH
  • Cofactors
• Reversible enzyme inhibition

  An inhibitor binds to an enzyme and decreases its activity
• Examples of irreversible enzyme inhibitors

  • Cyanides
  • Penicillin
  • Heavy metals
  • Nerve gas (Sarin)
• Oxidation-reduction (redox) reactions

  Reactions that involve the gain and loss of electrons
• Kinetic energy (mechanical energy)

  Energy of motion
• Potential energy (chemical energy)

  Stored energy
• The 2 laws of thermodynamics

  -Law of conservation of energy

  -Energy transformation efficiency
• Reactants

  Substance that participate in a reaction
• Product

  Substances that form as a result of a reaction
• Free energy

  Energy that is free to do work after a chemical reaction
• The ATP cycle

  Glucose and other biomolecules break down in cellular respiration so according to the 2 law of thermodynamics the process isn’t efficient on 39% of the energy stored in glucose is transformed to ATP rest is loss heat
• The 2 ways to couple ATP to energy requiring reaction

  ATP can reenergize and change the shape of the reactants, both can be achieved by phosphorylation
• Chemical work

  ATP uses energy to build macromolecules in cells
• Transport work

  ATP use energy to pump substances across the plasma membrane
• Mechanical work

  ATP provides energy to permit muscle contraction, cilia beating and chromosomes movement