Activating Strategy Belief or Disbelief 1. 1 st Law of thermodynamics states that energy can be created and destroyed. 2. Anabolic reactions are reactions that break bonds between molecules. 3. Exergonic chemical reactions release energy. 4. Chemical reactions occur spontaneously in living organisms because they have stable covalent bonds. 5. Activation energy is the amount of energy required to start a chemical reaction 6. Biological catalysts help divide chemical reactions into small steps, which increases their efficiency. AP Lesson #10 EQ: What is metabolism and what role does energy play in metabolism? How does energy move through an environment? Life is built on chemical reactions transforming energy from one form to another 1 st Law of Thermodynamics Energy can be transferred, but never created or destroyed organic molecules ATP & organic molecules sun organic molecules ATP & organic molecules solar energy ATP & organic molecules 1
So then what is metabolism? An emergent property of life that arises from interactions between molecules within the cell Chemical reactions of life forming bonds between molecules dehydration synthesis Ex. Protein Synthesis anabolic reactions breaking bonds between molecules Hydrolysis and digestion Ex. Cellular Respiration catabolic reactions Examples Anabolic Metabolism dehydration synthesis (synthesis) Catabolic Metabolism hydrolysis (digestion) What is the difference between chemical reactions in living things? Some chemical reactions release energy exergonic digesting polymers digesting molecules = LESS organization release of stored energy Some chemical reactions require input of energy endergonic building polymers building molecules = MORE organization stores energy 2
What is the difference between the two reactions? G = change in free energy = ability to do work exergonic - energy released - digestion endergonic - energy invested - synthesis + G - G So then why do we need chemical reactions? Organisms require energy to live where does that energy come from? coupling exergonic reactions (releasing energy) with endergonic reactions (needing energy) digestion synthesis If reactions are downhill, why don t they just happen spontaneously? Why don t stable polymers spontaneously digest into their monomers? because covalent bonds are stable bonds starch 3
We need activation energy! Breaking down large molecules requires an initial input of energy activation energy large biomolecules are stable must absorb energy to break bonds cellulose energy CO 2 + H 2 O + heat What is activation energy? amount of energy needed to destabilize the bonds of a molecule moves the reaction over an energy hill at temperatures typical of the cell, molecules don t make it over the hump of activation energy glucose How do we Reduce Activation Energy? Catalysts reducing the amount of energy to start a reaction uncatalyzed reaction catalyzed reaction NEW activation energy reactant product 4
So what s a cell got to do to reduce activation energy? Use Enzymes Requires less energy input for metabolism G Metabolic pathways A B C D E F G 1 2 3 4 Chemical reactions of life are organized in pathways divide chemical reaction into many small steps efficiency intermediate branching points control = regulation Feedback 5 6 Summarizing Strategy Belief or Disbelief 1. 1 st Law of thermodynamics states that energy can be created and destroyed. 2. Anabolic reactions are reactions that break bonds between molecules. 3. Exergonic chemical reactions release energy. 4. Chemical reactions occur spontaneously in living organisms because they have stable covalent bonds. 5. Activation energy is the amount of energy required to start a chemical reaction 6. Biological catalysts help divide chemical reactions into small steps, which increases their efficiency. 5
Assessment HW: Chapter 8.1 8.2 MC Wkst and Read Chapter 8.4 6