AP Biology Chapter 8. Cellular Respiration Harvesting Chemical Energy
AP Biology The Point is to Make ATP! ATP What’s the point?
AP Biology Harvesting stored energy Energy is stored in organic molecules heterotrophs eat food (organic molecules) digest organic molecules serve as raw materials for building & fuels for energy controlled release of energy series of step-by-step enzyme-controlled reactions “burning” fuels carbohydrates, lipids, proteins, nucleic acids
AP Biology Harvesting energy stored in glucose Glucose is the model catabolism of glucose to produce ATP glucose + oxygen carbon + water + energy dioxide C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP heat CO 2 + H 2 O + heat fuel (carbohydrates) combustion = making heat energy by burning fuels in one step respiration = making ATP (& less heat) by burning fuels in many small steps ATP CO 2 + H 2 O + ATP (+ heat) respiration
AP Biology Oxidation & reduction Oxidation adding O removing H loss of electrons releases energy exergonic Reduction removing O adding H gain of electrons stores energy endergonic C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP +++ oxidation reduction
AP Biology Moving electrons in respiration Electron carriers move electrons by shuttling H atoms around NAD + NADH (reduced) FAD +2 FADH 2 (reduced) + H reduction oxidation P O–O– O–O– O –O–O P O–O– O–O– O –O–O C C O NH 2 N+N+ H adenine ribose sugar phosphates NAD nicotinamide Vitamin B3 P O–O– O–O– O –O–O P O–O– O–O– O –O–O C C O NH 2 N+N+ H H NADH stores energy as a reduced molecule reducing power! How efficient! Build once, use many ways
AP Biology Overview of cellular respiration 4 metabolic stages Anaerobic respiration 1. Glycolysis respiration without O 2 in cytosol Aerobic respiration respiration using O 2 in mitochondria 2. Pyruvate oxidation 3. Kreb’s cycle 4. Electron transport chain C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP +++ (+ heat )
AP Biology Chapter 8. Cellular Respiration STEP 1: Glycolysis
AP Biology The Point is to Make ATP! ATP What’s the point?
AP Biology Glycolysis Breaking down glucose “glyco – lysis” (splitting sugar) most ancient form of energy capture starting point for all cellular respiration inefficient generate only 2 ATP for every 1 glucose in cytosol why does that make evolutionary sense? glucose pyruvate 2x2x 6C3C
AP Biology Glycolysis summary endergonic invest some ATP exergonic harvest a little more ATP & a little NADH
AP Biology Energy accounting of glycolysis Net gain = 2 ATP some energy investment (2 ATP) small energy return (4 ATP) 1 6C sugar 2 3C sugars 2 ATP2 ADP 4 ADP4 ATP glucose pyruvate 2x2x 6C3C All that work! And that’s all I get?
AP Biology The Point is to Make ATP! ATP What’s the point?
AP Biology Chapter 8. STEP 2 Cellular Respiration Oxidation of Pyruvate Krebs Cycle
AP Biology Cellular respiration
AP Biology Pyruvate oxidized to Acetyl CoA 1 pyruvate Yield = 2C sugar + CO NADH reduction oxidation
AP Biology Krebs cycle produces large quantities of electron carriers NADH FADH 2 stored energy! go to ETC a.k.a. Citric Acid Cycle What’s so important about NADH?
AP Biology Energy accounting of Krebs cycle Net gain=2 ATP = 8 NADH + 2 FADH 2 4 NAD + 1 FAD 4 NADH + 1 FADH 2 1 ADP1 ATP 3x3x pyruvate CO 2 ][ 2x 3C 1C
AP Biology So why the Krebs cycle? If the yield is only 2 ATP, then why? value of NADH & FADH 2 electron carriers reduced molecules store energy! to be used in the Electron Transport Chain
AP Biology The Point is to Make ATP! ATP What’s the point?
AP Biology Chapter 8. STEP 3: Cellular Respiration Electron Transport Chain
AP Biology Cellular respiration
AP Biology The Point is to Make ATP! ATP What’s the point?
AP Biology 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! There’s got to be a better way! What’s the Point?
AP Biology There is a better way! Electron Transport Chain series of molecules built into inner mitochondrial membrane mostly transport proteins transport of electrons down ETC linked to ATP synthesis yields ~34 ATP from 1 glucose! only in presence of O 2 (aerobic) That sounds more like it!
AP Biology Mitochondria Double membrane outer membrane inner membrane highly folded cristae* fluid-filled space between membranes = intermembrane space matrix central fluid-filled space * form fits function!
AP Biology Electron Transport Chain
AP Biology PGAL Glycolysis Kreb’s cycle 2 NADH 8 NADH 2 FADH 2 Remember the NADH?
AP Biology Electron Transport Chain NADH passes electrons to ETC H cleaved off NADH & FADH 2 electrons stripped from H atoms H + (H ions) electrons passed from one electron carrier to next in mitochondrial membrane (ETC) transport proteins in membrane pump H + across inner membrane to intermembrane space
AP Biology But what “pulls” the electrons down the ETC? electrons flow downhill to O 2
AP Biology Cellular respiration
AP Biology Summary of cellular respiration Where did the glucose come from? Where did the O 2 come from? Where did the CO 2 come from? Where did the H 2 O come from? Where did the ATP come from? What else is produced that is not listed in this equation? Why do we breathe? C 6 H 12 O 6 6O 2 6CO 2 6H 2 O~36 ATP +++
AP Biology Taking it beyond… What is the final electron acceptor in electron transport chain? O2O2 So what happens if O 2 unavailable for organisms that REQUIRE oxygen? ETC backs up ATP production ceases cells run out of energy and you die!
AP Biology THERE IS ANOTHER WAY ANAEROBIC RESPIRATION 1. Alcoholic Fermentation 2. Lactic Acid Fermentation Less efficient Original pathway in evolutionary history
AP Biology Anaerobic ethanol fermentation Bacteria, yeast 1C 3C2C pyruvate ethanol + CO 2 Animals, some fungi pyruvate lactic acid 3C beer, wine, bread at ~12% ethanol, kills yeast cheese, yogurt, anaerobic exercise (no O 2 ) NADHNAD + NADHNAD +
AP Biology Pyruvate is a branching point Pyruvate O2O2 O2O2 Kreb’s cycle mitochondria fermentation
AP Biology The Point is to Make ATP! ATP What’s the point?