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What is energy coupling AND what does that have to do with ATP? Think of energy as money…. ATP picks up the energy released from an exergonic reaction, and drops energy off to go into an endergonic reaction. ATP is the middle man. CELLULAR RESPIRATION YOU WOULD BE DEAD WITHOUT THIS PROCESS TOO! Cellular respiration is how we derive (harvest) energy from the food we eat. eh hem….what do you notice? •Reactants: C₆H₁₂O₆ + 6 O₂ •Products: 6 CO₂ + 6 H₂O + Energy ~ 38 ATP & Heat Aerobic Respiration has three stages… 1. 2. Also known as the ‘Citric Acid Cycle’ 3. GOOD NEWS!!! • Memorization of the steps of Glycolysis and the Krebs cycle, structures of molecules, and names of enzymes involved (except ATP Synthase) are beyond the scope of the course and the AP EXAM Besides glucose, other energyfilled molecules (other carbs, proteins, and lipids) can also be broken down for ATP during cellular respiration. Different types of molecules have different entry points into this process. Varied diet can be consumed without a loss of viable energy. FIRST STAGE: GLYCOLYSIS Think about the break-down of this word. The breaking down of sugar ‘related to’ To Break (glucose). SUGAR What goes in to the reaction: 1 Glucose (C₆H₁₂O₆) and 2 ATPs (used to break the glucose) Glycolysis takes place outside of the mitochondria in the cytoplasm. FIRST STAGE: GLYCOLYSIS The breaking down of sugar (glucose). What is created: 2 Pyruvate (3-carbon molecules), 2 Waters, 2 NADH (electron carriers), 4 ATPs (used to break the glucose) FIRST STAGE: GLYCOLYSIS The breaking down of sugar (glucose). FOR A NET OF: Begins With.. Glycolysis basically rearranges the glucose molecule and breaks it in half to make 2 Pyruvate Ends With.. , , 2 NADH Energy Input Steps Energy Releasing Steps Now Unstable Energy Releasing Steps, cont. Now Unstable SECOND STAGE: KREBS CYCLE Also called ‘Citric Acid Cycle’ Inside the INNER MEMBRANE OF THE MITOCHONDRIA SECOND STAGE: KREBS CYCLE Also called ‘Citric Acid Cycle’ What goes in to the cycle: 2 What’s created: The Krebs Cycle is a series of reactions that take place in the Mitochondria that synthesize 2 ATP and many energy-filled electron transport molecules. Carbon Dioxide is a waste product ATP Krebs Tally 6- CO2 8- NADH 2- ATP 2- FADH2 1. The 2 Pyruvates enter (3 carbon sugars) 2. ATP One carbon from each breaks off, attaches to an O₂, and is released as a waste (2 CO₂), 2 NAD swoop in and steal some energized electrons- creating 2 NADHs 3. What’s left is two 2-carbon molecules called Acetyl CoA ATP 1. Each Acetyl CoA combines with a 4 carbon oxaloacetate, creating citric acid 2. Citric acid is taken through many reactions that create 2 ATPs , 6 more NADHs, and 2 FADH₂ 3. 4 more CO₂ molecules are given off and in the end there are 2 oxaloacetate’s ready to do it all over again. Much like NADPH in photosynthesis, NADH and FADH₂ are simply carrier molecules of energized electrons and hydrogen ions. They take the energy from one place and drop it off at another. ATP accounting so far… • Glycolysis 2 ATP • Kreb’s cycle 2 ATP • Life takes a lot of energy to run, need to extract more energy than 4 ATP! I need a lot more ATP! A working muscle recycles over 10 million ATPs per second THIRD STAGE: Electron Transport Chain Phosphorylation 2 THIRD STAGE: Electron Transport Chain Instead of light energy like in Photosynthesis, this time excited electrons are being dropped off at the ETC by all of the electron carriers from Glycolysis and Krebs (in all 10 NADH and 2 FADH₂) Same as before, as the excited electrons travel from protein to protein their energy is used to pump H⁺ into the space between the inner and outer mitochondrial membranes. The FINAL ELECTRON ACCEPTOR IN CELLULAR RESPIRATION THAT PICKS UP THE EXCITED ELECTRONS IS A SINGLE OXYGEN ATOM. It also picks up two Hydrogen ions and becomes a water molecule! All the H+ H+ H+ H+ • Concentration is too high on one side of the membrane H+ H+ H+ H+ • The protons flow through ATP synthase - enzyme • Uses ‘proton motive force’ energy to Synthesizes ATP ADP + Pi ATP ADP + Pi ATP H+ H+ What can slow the rate of CR? • Decrease in breathing rate, pulse rate, or food in-take • Decrease in temperature