Where do we get the energy we need? Energy needs a source How much energy do we need? It all depends on what we are doing The Pathways of Metabolism http://www.sigmaaldrich.com/img/assets/4202/ MetabolicPathways_6_17_04_.pdf ATP: ADENOSINE TRIPHOSPHATE Structure Three phosphate groups Energy is stored in phosphate bond ATP: adenosine triphosphate When energy is required • ATP binds to enzyme • ATP ADP + Pi +Energy release energy to perform a needed function ADP gets recycled into ATP repeatedly ATP↔ ADP + (Pi) + Energy NADH/NAD+ REDOX R(X) Chemical energy Energy comes from electrons Glucose (and other molecules) store energy in chemical bonds • One glucose molecule contains 90 times the energy produced by 1 ATP • Remember last chapter…. The first steps are always the hardest…. (except for here) Movies are always better than the book (?!) http://henge.bio.miami.edu/mallery/movies/glyc olysis.mov GLYCOLYSIS: series of reactions in which a molecule of glucose is broken down “Sugar breaking” If this process shuts down, it cannot restart Always the first step to breaking down carbs Requires energy to get energy • Requires 2 ATP to get things started • Results in 4 ATP being produced Takes place in cytosol GLYCOLYSIS: series of reactions in which a molecule of glucose is broken down The steps • Two phosphate groups attach to glucose Phosphates are supplied by 2 ATP 2ADP Form a new 6-carbon compound • 6-carbon molecule splits Forms two 3-carbon molecules of PGAL GLYCOLYSIS: series of reactions in which a molecule of glucose is broken down The steps (cont.) • Two PGAL 2 molecules of a 3-carbon compound PGAL gets oxidized (loses an e-) Each PGAL gains a phosphate group NAD+ reduced to NADH + H+ • Phosphate groups are removed Two molecules pyruvic acid are made Phosphate groups attach to ADP 4 ADP + 4 phosphate groups 4 ATP GLYCOLYSIS: series of reactions in which a molecule of glucose is broken down Net production • Two molecules pyruvic acid • Two molecules ATP • Two pair high energy e- carried by NADH Energy from e- is used when O2 is not available 2Pi C-C-C-C-C-C Glucose 2 ATP P-C-C-C-C-C-C-P 6-C compound 2ADP P-C-C-C C-C-C-P 2 PGAL 2NAD+ P-C-C-C-P P-C-C-C-P C-C-C C-C-C 2 molec 3-C compound 2 molecules pyruvic acid 2NADH +2H+ 4ADP 4 ATP What is next? It all depends on the air Fermentation Glucose Cellular Respiration What is next? It all depends on the air Fermentation Glucose Cellular Respiration What is next? It all depends on the air Fermentation Glucose Cellular Respiration Or “What to do when you can’t get enough air….” FERMENTATION: regeneration of NAD+ when oxygen is unavailable Temporary solution Two types (each organism uses only one, but two are critical to our lives…) Electron gets passed back from NADH to C atoms Allows cell to recycle NAD+ Allows glycolysis to continue Cell accumulates compounds that accept electrons LACTIC ACID FERMENTATION Pyruvic acid lactic acid • Transfer of 2 H+ from NADH + H+ to pyruvic acid • NADH oxidized to NAD+ • NAD+ used in glycolysis Regeneration of NAD+ allows continuation of glycolysis LACTIC ACID FERMENTATION Occurs when you are very active (i.e.: running) • When there is insufficient oxygen to cells fermentation occurs • Lactic acid accumulates in cells decreasing pH of cell • Increased acidity reduces cell’s ability to contract results in muscle fatigue, pain, cramps eventually diffuses into blood stream and is processed by liver reverts to pyruvic acid when oxygen becomes available Used in cheese and yogurt industry Cheese is produced by lactic acid fermentation. (So is yogurt!) C-C-C-C-C-C Glucose C-C-C C-C-C Lactic acid C-C-C C-C-C Glycolysis NAD+ NADH Pyruvic acid ALCOHOLIC FERMENTATION Pyruvic acid – CO2 ethyl alcohol (ethanol) Two steps • Pyruvic acid 2-C compound + CO2 • 2-C compound + 2H+ ethyl alcohol H+ comes from NADH + H+ NAD+ ALCOHOLIC FERMENTATION Yeast utilizes alcoholic fermentation • beer and wine industry • yeast produces ethanol until [ethanol] is too high for yeast to survive wine: CO2 allowed to escape champagne & beer: CO2 is retained • bread CO2 that is released causes bread to rise Ethyl alcohol evaporates during baking Yeast undergoes alcoholic fermentation to produce…. Saccharomyces cerevisiae …a little beer,… …a lot of beer,… …Champagne,… … and wine. Released CO2 makes bread rise Alcoholic Fermentation C-C-C-C-C-C Glucose C-C-C C-C-C Glycolysis Pyruvic acid NAD+ 2 CO2 NADH C-C C-C Ethyl alcohol C-C C-C 2-C compounds Which is which? In what organisms do each occur? AEROBIC RESPIRATION Pyruvate Glucose ATP ATPATP ATP ATP ATP 7-2: AEROBIC RESPIRATION: release of energy from breakdown of food when oxygen is present CONVERSION TO ACETYLCOA: The beginning Occurs in mitochondria Pyruvic acid diffuses into mitochondria crossing both membranes Reactions occur within the mitochondrial matrix Space inside the inner mitochondrial membrane Contains enzymes needed for the Krebs Cycle Pyruvic acid + Coenzyme A AcetylCoA Conversion to Acetyl-CoA CO2 CoA C-C-C Pyruvic Acid C-C AcetylCoA NAD+ NADH KREBS CYCLE AcetylCoA CO2 + H+ + ATP Occurs in the matrix The steps • Step 1:AcetylCoA + oxaloacetic acid citric acid 2C + 4C = 6C • Step 2: Citric acid CO2 + H+ + a 5-C compound regenerates CoA citric acid is oxidized H+ atom transferred to NAD+ reducing it to NADH KREBS CYCLE AcetylCoA CO2 + H+ + ATP The steps (cont.) • Step 3: 5-C compound CO2 + H+ + 4-C compound (succinyl-CoA) NAD+ reduced to NADH ADP + phosphate ATP KREBS CYCLE AcetylCoA CO2 + H+ + ATP. The steps (cont.) • Step 4: 4-C compound different 4-C compound + H+ (maleate) FAD reduced to FADH2 FAD is similar to NAD+ - it accepts e- during redox reactions • Step 5: (new) 4-C compound H+ + oxaloacetic acid Regenerates oxaloacetic acid NAD+ reduced THE KREBS CYCLE Step 1 CoA Acetyl CoA Step 2 Citric Acid CO2 NAD+ Oxaloacetic acid NADH + H+ 5-C compound NADH + NAD+ NAD+ NADH + H+ ADP + Phosphate H+ 4-C compound ATP 4-C compound Step 5 FADH2 Step 4 FAD CO2 Step 3 KREBS CYCLE Because 1 glucose 2 pyruvic acid then 1 glucose 2 turns of Krebs cycle Final production of Krebs cycle • Six NADH continue on • Two FADH2 • Two ATP – used for energy • Four CO2 – given off by organism as waste KREBS CYCLE Totals so far from 1 glucose • NADH –10 (2 from glycolysis; 2 from AcetylCoA conversion) • FADH2 – 2 • ATP – 4 (2 from glycolysis; 2 from Krebs cycle) • CO2 – 6 (2 from AcetylCoA conversion; 4 from Krebs cycle) http://henge.bio.miami.edu/mallery/movies/krebs.mov ELECTRON TRANSPORT CHAIN (ETC) Occurs in cristae • H+ atoms contain high energy e- • e- transported from molecule to molecule along • • • • cristae losing energy each time Energy used to pump p+ of H atoms across matrix membrane [H+] increases between inner and outer membranes concentration gradient is created concentration gradient drives ATP production (chemiosmosis) Electron Transport Chain (ETC) Role of oxygen • e- produced above must be removed • O2 is final acceptor of e• O2 also accepts H+ protons • Result: O2 + 4e- + 4 H+ 2 H2O • http://www.johnkyrk.com/mitochondrion.swf Movie for your viewing pleasure… Electron Transport System and ATP Synthesis Harvard Cell Krebs Cycle From trucks to energy…. NADH + H+ + 3 ADP + 3 Pi + 1/2 O2 NAD+ + H2O + 3 ATP FADH2 + 2 ADP + 2 Pi + 1/2 O2 FAD+ + H2O + 2 ATP To sum it all up… The Final Yield: the complete oxidation of glucose in aerobic respiration can be summarized as: The end is near… Glucose 2 ATP produced directly Glycolysis Pyruvic Acid 2 NADH + 2 NADH 6 ATP through ETC + Acetyl CoA Krebs Cycle + 6 ATP through ETC* 2 ATP produced directly 6 NADH 2 FADH2 + 18 ATP through ETC + 4 ATP through ETC 38 ATP To really sum it up succinctly… What about everything else that we eat?