What did you eat for breakfast? Chapter 6: Cellular Respiration. Is glucose likely to form spontaneously from water (H 2 O) and CO 2? Why or why not?

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1 hapter 6: ellular Respiration Why do we eat? What did you eat for breakfast? What types of macromolecules were in your breakfast? Where did the macromolecules (carbs, protein, fat) in your breakfast come from? Where do the producers get their breakfast? + sugar roducers and onsumers Autotrophs and Heterotrophs lants take in carbon dioxide (O ) at their leaves lants absorb water (H O) at their roots O Is glucose likely to form spontaneously from water (H O) and O? Why or why not? + The simple molecules O and H O have all of the atoms needed to form glucose ( 6 H 1 O 6 ), if rearranged O and H O Breakfast is served O H O 6 H 1 O 6 1

2 Fuel molecules are rich in hemical Energy (a form of otential Energy) Where does the energy come from? Glucose or Fuel Molecules + O H O 6 H 1 O 6 + O as waste hotosynthesis is an uphill climb! The energy of the sun is captured, or harnessed at the chloroplasts, and used to do work! Reminder What is work? What has been moved uphill in photosynthesis? There is more chemical energy in the products of photosynthesis than in the reactants! A little, green sugar producing factory All plants, some bacteria and some protisis, trap energy from sunlight and use it to build sugars, which they need to live and grow. This process is called photosynthesis. Nearly all life on Earth depends on photosynthesis. If plants stopped photosynthesising, animals would have no food, and the world would eventually run out of oxygen. Energy Flow and hemical ycling in Ecosystems Energy flows through the ecosystem, beginning as light energy from the sun Do animals take in all of this glucose, or do plants keep some for themselves? Why or why not? Light energy is transformed into chemical energy Some used to do work, and some transformed into heat Why heat?

3 O QUIZ Which living organisms have chloroplasts? All living things grow, and do cellular work, correct? We know that growth requires energy. All living things are capable of acquiring energy to do work. Tomorrow we will learn that cellular respiration has 3 major steps. The first step, glycolysis, occurs in the cytoplasm, and yields a little bit of AT. Hmm, then, do all living things undergo some form of cellular respiration. Yes or No? ellular Respiration The process by which energy is harvested from the breakdown of food and converted into the energy of AT This process is most efficient in the presence of oxygen (O ) but can occur in its absence Aerobic respiration Anaerobic respiration (fermentation) Burning Fuel Notice there are many arrows in this equation. ellular Respiration breaks down glucose in a highly regulated, multi-step process Why not just one step? Why not just light glucose on fire? H + During cellular respiration, the hydrogen from glucose (and an electron) is being transferred to oxygen This is also a transfer of electron(s), TO oxygen, from glucose. The electron(s) are moving to a MORE electronegative atom, Oxygen. Oxygen will hold on to these electrons(s) very tightly. H O H OXYGEN Recall that oxygen is a highly electronegative atom Energetically, it is much more difficult to move an electron (an electron and H) away from oxygen than it is to move an electron (and H) away from a carbon atom Thus, electrons held by oxygen are lower on the energy hill than electrons associated with carbon in a fuel molecule 3

4 Energy must be added to pull an electron away from an atom. The more electronegative the atom, the more energy is required to take an electron away from it H Less stable bond otential Energy H O Very stable bond H How great is this potential energy difference? An electron equally shared between Hydrogen and arbon vs. an electron being hogged when bound to Oxygen? otential Energy H Less stable bond H O H Very stable bond A LOT! A rapid electron fall A balloon is filled with HYDROGEN GAS H This is similar to the arrangement of -H A match is touched to the balloon (a catalyst to get the reaction going) Hydrogen gas reacts with Oxygen in the air and causes an explosiong. All of the energy is given off as HEAT. (think Hindenburg, except on a smaller scale). Energy is released when electrons are transferred from a less electronegative atom to a more electronegative atom (like from glucose to oxygen-to make water) The electrons are now in a more stable environment, as more energy would be needed to pull them away from their current arrangement ellular Respiration is a collection of controlled Redox Reactions ellular Respiration is a Stepwise Energy Harvest In cellular respiration, glucose is not burned in one step. Instead, the ELETRONS from glucose are transferred, step-by-step to increasingly more electronegative atoms. The final electron (and H) acceptor is oxygen. Water is formed as a byproduct. H O O Stepwise Energy Harvest via: Enzymes electron shuttlers (NADH) electron transport chain O 4

5 Electrons are passed in short energy steps, down to oxygen Electrons are passed in short steps from food (glucose) to electron shuttlers, and then to an electron transport chain oupled hemical Reactions Energy is harnessed along the way Which picture is similar to the balloon experiment? Which picture is analogous to an electron transport chain? Why? oupled hemical Reactions The Regeneration of AT AT AT AT synthesis requires Energy AT hydrolysis yields Energy AD Electron Transport hain How do reactions yield energy? Transfer of electrons during chemical reactions Relocation of electrons releases energy stored in organic molecules This energy is ultimately used to synthesize AT AT NH Redox Reactions are a form of Energy Transfer The term Redox is a combination and abbreviation of two words: 1. Reduction. Oxidation These two chemical reactions always happen together The coupled gain and loss of ELETRONS ( s) Electrons are negatively charged 5

6 LEO LEO the lion goes GER GER Loss of Electrons is Oxidation Gain of Electrons is Reduction Oxidation Is Loss Reduction Is Gain OIL RIG Bush and o. Redox Reactions Redox Reactions: Follow the electrons ( ) Redox Reactions In this example, ompound B is transformed into a new compound with a more negative charge. Its overall charge has been reduced. A Redox Reaction Na+ l Na + l - Which atom is reduced? Which atom is oxidized? Follow the electrons! 6

7 A Redox Reaction becomes oxidized Na+ l Na + l - becomes reduced Redox Reactions Loss or gain of electrons does not need to be complete Which atom is reduced? l- Which atom is oxidized? Na+ ellular Respiration is a collection of Redox Reactions ellular Respiration is a collection of Redox Reactions becomes oxidized 6 H 1 O 6 + 6O 6O + 6H O + E 6 H 1 O 6 + 6O 6O + 6H O + E becomes reduced During cellular respiration: Glucose is oxidized and Oxygen is reduced. Glucose lost electrons, while oxygen gained electrons as water. ellular Respiration: A 3-part story ellular Respiration: A 3 part story 7

8 Glycolysis: the splitting of First step in cellular respiration sugar Occurs in the cytoplasm The enzymes involved are dissolved in cytoplasm! INUT: glucose, a 6 carbon sugar Small amount of AT added to start reaction OUTUT: molecules of pyruvic acid (a 3 carbon molecule) small amount of AT NADH! yruvic Acid AT NADH Glycolysis splits a six-carbon glucose into threcarbon molecules AT AD Glucose is first energized with a phosphate. It has become momentarily less stable, energized. Glycolysis splits a six-carbon glucose into threcarbon molecules AT Small amount of energy INUT A high-energy 6 carbon, glucoslike molecule AD enzyme Glycolysis splits a six-carbon glucose into NADH threcarbon molecules AT AD enzyme Small amount of energy INUT What is the cab carrying? AT yruvic Acid YIELDS: NADH AT Glycolysis Occurs in the ytosol and does not require oxygen! Glycolysis yruvic Acid YIELDS: NADH AT Glycolysis generates a small amount of AT Direct phosphate transfer, enzyme mediated 8

9 Glycolysis generates NADH NADH Later! What is meant by a high energy electron? The book s version If an electron was swiped or transferred to NADH from glucose, what happened to glucose during glycolysis? Was it oxidized or reduced? Glucose yruvic acid High Energy Electrons in the form of NADH and FADH ellular Respiration NAD+ reduced NAD H + NADH FADH art : Krebs ycle art : Krebs ycle Where is this occuring? What is a cycle? Scary picture! Focus on outputs!! = 6 4 9

10 art : Krebs ycle NUMEROUS OXIDATION STES 6 arbon molecule is oxidized to molecules of O 6 art : Krebs ycle Oxidiation steps produce energy in the form of AT, NADH, FADH And the starting material (4 carbon molecule) is regenerated 4 Where are the cabs (with s) going?? NADH and FADH shuttle high energy electrons to an Electron Transport hain art 3: Electron Transport hain Where is this located, EXATLY?? What molecule sits at the bottom of the chain? Hint: the molecule at the bottom is waiting, and is very hungry for electrons Electron Transport hain in the Inner Mitochondrial Membrane? 10

11 OXYGEN Why is oxygen so important for cellular respiration? What function does the oxygen we BREATHE in have in this process? High energy electrons When high energy electrons are obtained by a protein, the protein may become energized These energized proteins have the capacity to do work! The work they will do? Transport against its concentration gradient Before receiving I m feeling low on energy. I couldn t possibly do any WORK Intermembrane Space Mitochondrial matrix I m energized, and ready to do some WORK Intermembrane Space AFTER receiving Mitochondrial matrix empty The work that is done is the pumping of ions across the inner mitochondrial membrane AGAINST a concentration gradient! As electrons are passed along the ET, is pumped into the intermembrane space 11

12 This cellular work, has set up a gradient across the inner mitochondrial membrane Which way (into the matrix, or into the inner membrane space) do the ions NOW want to diffuse? AT Synthase The hydrogen ions will diffuse (rapidly) down their concentration gradient diffuses through AT Synthase, a membrane protein that functions like our paddle wheel The paddle wheel, and Star of the show!! AT Synthase is a mini-machine! htm AT Synthase captures the kinetic energy of diffusion, and transforms it to synthesize AT from AD and. MOVIE TIME Energetic Summary of ellular Respiration an we generate AT under anaerobic conditions? How? Aerobic= oxygen present Anaerobic= without oxygen 1

13 Does glycolysis require oxygen? Krebs ycle Does glycolysis produce AT? If so, how much? Without oxygen, NADH cannot drop off its high energy electrons at the ET Since oxygen is not pulling electrons down the ET, NADH (the electron carrier) fills up Anaerobic Respiration: Lactic Acid Fermentation In the absence of oxygen, NADH donates its high energy electrons to alternate substrates Why do we continue to breath heavily even after we ve STOED exerting ourselves? Anaerobic Respiration: Alcohol Fermentation Aerobic cellular respiration utilizes OXYGEN as the final electron acceptor Anaerobic Respiration Are you thankful for yeast now?? Anaerobic respiration can occur with an alternate electron acceptor! 13

14 Evolutionary Implications of Anaerobic Respiration Glycolysis is the most widespread metabolic pathway on Earth Glycolysis evolved very early eople can t live on glucose alone!! OUT? 3.5 bya= bacterial fossils.7 bya= O accumulates Does glycolysis require membrane bound organelles? Eukaryotic cells?? arbon fuel can come from macromolecules other than glucose Food cyanide olysaccharides Fats roteins Sugars Glycerol Fatty acids Amino acids Glycolysis Acetyl- oa Krebs ycle Amino groups Electron Transport Why is cyanide poisonous? How does cyanide actually KILL people, at the molecular level?? 14