Cellular Respiration Mitochondria Rule! Mr. Kurt Kristensen
Harvard Biovisions Mitochondria
Summer Session Week 1: Cellular Respiration Students should. 1) Understand the locations, and functions of the essential phases of cellular respiration. 2) Describe the connections between each phase of cellular respiration. 3) Understand how mitochondria work with the cell to harvest chemical energy. 4) Understand chemiosmosis and its central role in ATP production.
Cell Respiration Review Living is work. To perform work, cells require energy from outside sources In most ecosystems, energy enters as sunlight. Light energy trapped in organic molecules is available to both photosynthetic organisms and others that eat them.
Back to the big picture, Cell Respiration (CH 2 O CO 2 + H 2 O and ATP) We will be looking at three connected metabolic processes. The function of these processes is to make ATP.
Bioenergetics: The Big Picture The Equations: CH 2 O + O 2 CO 2 + H 2 O + Energy C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + ATP + Heat In general Organic Molecules Food Combustion or Oxidation of Glucose ( G) = -686 kcal/mole Number of ATP/Glucose Molecule Regeneration of ATP (from ADP & P i ) ( G) = +7.3 kcal/mol So. 38 ATP x 7.3 kcal/mol = 277 kcal 277 kcal/mol + (-686 kcal/mol) -409 kcal/mol lost as heat That s about 40% efficient!
Consumers (start with organic molecules, give off CO 2 ) Some Details: Glycolysis Fermentation Cellular Respiration These are re-dox reactions
Cellular Respiration Oxidation of Food Molecules in the presence of Oxygen Releases Chemical energy in food Converted to less stable, more useful Cumulative Function of 3 metabolic stages Glycolysis Citric Acid (Kreb s) Cycle Oxidative Phosphorylation (OXYPHOS) Glycolysis Kreb s OXYPHOS FOOD Pyruvate e- shuttles
Living organisms don t tolerate explosions too well..
Mitochondria Structure How many per cell?
Cellular Respiration Where How Connections
Our Objective Learn the important details about the 3 metabolic stages of cellular respiration Glycolysis, Citric Acid Cycle, Oxidative Phosphorylation Remember that the cell is using glucose to make ATP (it s harvesting energy) Remember these stages are connected!
SLP: Substrate Level Phosphorylation RBC s have no mitochondria Hard-working muscle Phospocreatine + ADP creatine phosphokinase ATP + creatine
Phase 1: Glycolysis Literally sugar break, the splitting of sugar Fig 9.8 (2 phases) Energy Investment Energy Return
Glycolysis 1: Energy Investment What happens, and why? 2 ATP molecules are spent to 1) Trap the glucose molecule in the cytosol 2) Destabilize the glucose molecule so it will break in half and more easily fit into the mitochondria or be used in fermentation What s the end product? The end product of the energy investment phase is 2 molecules of G3P (glyceraldehyde 3- phosphate) Glycolysis
Glycolysis 2: Energy Return G3P is a 3-carbon sugar that can be further rearranged to make Pyruvate 2 NET molecules of ATP are returned during this rearragement, but the real energy is in the The end product(s): NADH Pyruvate (> 75% of energy of glucose still remains in 2 pyruvate molecules)
Connections: Pyruvate is Oxidized In the presence of Oxygen, pyruvate is actively transported into mitochondria and 1) Pyruvate is converted to a 2-Carbon compound (CO 2 ) is released 2) This 2-Carbon compound is further oxidized (and NAD+ is reduced) 3) Coenzyme A is added to the 2-carbon compound, it s called Acetyl CoA, and this enters the Kreb s Cycle.
Citric Acid Cycle: It is a cycle! Where does it happen? What are the outcomes? Oxaloacetate (4-C) Citrate (6-C)
Citric Acid Cycle: The Bottom Line Pyruvate is completely oxidized and the energy is converted to NADH and FADH 2 (ETC) and ATP via S.L.P. 6 NADH and 2 FADH 2 per glucose molecule This is the intersection between Glycolysis and OXY PHOS You don t need to learn every step and every enzyme!
Oxidatative Phosphorylation Overview: During oxidative phosphorylation, chemiosmosis couples electron transport to ATP Synthesis. This may sound complicated, but it s something you need to know.
Oxidative Phosphorylation1: E.T.C. Where?: Along the inner membrane of the mitochondria 1000 s What? Proteins with prosthetic groups (co factors, that alternatively oxidize their uphill neighbors, and then get oxidized by their down hill neighbors P.C. How? Each Protein in the ETC is more electronegative (better at pulling electrons) from it s uphill neighbor. Oxygen drives the whole thing, because oxygen is the most electronegative element in the chain. What else happens? Oxygen is reduced to water Hydronium ions ( protons, H+) are pumped across the inner membrane into the intermembrane space of the mitochondria.
Oxidative Phosphorylation 2 So What? E.T.C. sets up a proton gradient across the innner membrane of mitochondria Higher [H+] in the intermembrane space compared to the matrix ATP Synthase This is a protein complex that allows H+ to diffuse back across the membrane and makes ATP as the H+ flow through (much like a turbine generates electricity as water flows through it)
Oxidative Phosphorylation 3: Putting it all together 1) e- flow down the electron transport chain 2) as e- flow, H+ are pumped against their concentration gradient 3) ATP synthase couples the flow of H+ with ATP synthesis [ ] 2) 1) [ ] 3)
Oxidatative Phosphorylation Overview: During oxidative phosphorylation, chemiosmosis couples electron transport to ATP Synthesis. Chemiosmosis! An energy-coupling mechanism that uses energy stored in the form of a H+ gradient across a membrane to drive cellular work.
Cellular Respiration: Review (F9.16) (don t look at the book, let s work this out together.) Reactants, Products, major intermediates, processes, specific locations Net ATP Production Mode of ATP Production Get to know this figure it s great review.
ATP Accounting? Catabolism of Glucose, G = -686 kcal/mol Anabolism of ATP from ADP + P i, G = 7.3 kcal/mol About 36-38 mol ATP/mol glucose ATP synthesis is roughly 40% efficient. Compare that cars 25% efficient Where does the rest of the energy go? It generates body heat (e.g. 37 C)
If you didn t eat pure sugar today Have I got a deal for you.
What about Fermentation?
Fermentation: an alternate pathway for energy production (ATP synthesis) Fermentation is further oxidation of pyruvate in an anoxic environment fermentation starts with... Glycolysis F.A Facultive Anaerobes (mammals, some bacteria) O.A Obligate Anaetobes (e.g. Botulism)
Fermentation: (2 processes) What do these pathways have in common? start with glycolysis generate ATP through reduction of NAD+ to NADH What s different? alcohol fermentation = 2 steps Lactate fermentation = 1 step What s the significance of alcohol fermentation? Downfall of Western Civilization What s the significance of lactic acid fermentation? fatigue What else do these pathways have in common? Both keep glycolysis going! Both have by products the cell has to export, and that slow down glycolysis.
Comparing Fermentation and Cellular Respiration Commonalities: Both are energy-yielding pathways that convert chemical energy in organic molecules to ATP Differences: Cellular respiration requires Oxygen. Cellular respiration is 16-18x more efficient than fermentation! That s 18x more ATP from the same amount of food. That s huge! Oxidative Phosphorylation
Glycolysis is ancient How old is it? Est. to be 3 billion years old What else do we know Is found in prokaryotes and eukaryotes Does not require membranes Does not require organelles therefore evolved before eukaryotes, but has been conserved b/c it is still useful
Video Review http://www.suman asinc.com/webco ntent/animations/ content/cellularre spiration.html http://www.brooks cole.com/chemistr y_d/templates/stu dent_resources/s hared_resources/ animations/oxidati ve/oxidativephosp horylation.html
Cellular Respiration: Critical Thinking 1. In what part of the cell does glycolysis take place? 2. List the reactants and products of glycolysis. 3. Describe the event that occurs when pyruvate enters the mitochondria? 4. In what major area of the mitochondria does the Krebs Cycle take place? 5. List the reactants and products of the Krebs Cycle. 6. Identify the major structure or area where the Electron Transport System (ETS) take place. 7. What is/are transferred from the Krebs Cycle to the Electron Transport System? 8. What reactant molecule is essential for electron transport to occur? 9. What molecule is the final electron acceptor of the ETS? 10. Describe two main functions of the ETS.
Cell Respiration Application Problems: 1. If a person moved from San Diego, CA (sea-level) to Estes Park, CO (elevation 7500 ft.), what would be the effect on cellular respiration for this person? 2. In terms of cellular respiration, why is it necessary to incorporate plants into a terrarium along with fauna (animals)? 3. What effect might smoking cigarettes have on cellular respiration? 4.Describe any disease symptoms that might be related to the interference or interruption of the processes of cellular respiration. 5. According to your model of cellular respiration, what could be happening when a runner must revert to walking?