Chapter 9: Respiration
What you need to know: The summary equation of cellular respiration. The difference between fermentation and cellular respiration. The role of glycolysis in oxidizing glucose to two molecules of pyruvate. The process that brings pyruvate from the cytosol into the mitochondria and introduces it into the citric acid cycle. How the process of chemiosmosis utilizes the electrons from NADH and FADH2 to produce ATP.
Stages of Cellular Respiration Glycolysis Pyruvate Oxidation + Citric Acid Cycle (Krebs Cycle) Oxidative Phosphorylation (electron transport chain (ETC) & chemiosmosis)
Overview of Cellular Respiration
Cellular Respiration Stage 1: Glycolysis
Glycolysis 6C 3C Breaking down glucose glucose pyruvate 2x ancient pathway which harvests energy where energy transfer _______________________________________ transfer energy from organic molecules to ATP still is starting point for ________ cellular respiration but it’s _____________________________ generate only 2 ATP for every 1 glucose occurs in ___________________ glucose pyruvate 2x 6C 3C Why does it make sense that this happens in the cytosol? Who evolved first? That’s not enough ATP for me!
TURN & TALK Why does it make sense EVOLUTIONARILY that Glycolysis occurs in cytoplasm?
Evolutionary perspective Enzymes of glycolysis are “well-conserved” _____________________________ first cells had no organelles __________________________ atmosphere life on Earth first evolved without free oxygen (O2) in atmosphere energy had to be captured from organic molecules in absence of O2 Prokaryotes that evolved glycolysis are ________________ of all modern life ALL cells still utilize glycolysis The enzymes of glycolysis are very similar among all organisms. The genes that code for them are highly conserved. They are a good measure for evolutionary studies. Compare eukaryotes, bacteria & archaea using glycolysis enzymes. Bacteria = 3.5 billion years ago glycolysis in cytosol = doesn’t require a membrane-bound organelle O2 = 2.7 billion years ago photosynthetic bacteria / proto-blue-green algae Eukaryotes = 1.5 billion years ago membrane-bound organelles! Processes that all life/organisms share: Protein synthesis Glycolysis DNA replication You mean we’re related? Do I have to invite them over for the holidays?
Glycolysis Overview “sugar splitting” Believed to be ancient (early prokaryotes - no O2 available) Location: cytosol Reaction: Partially oxidizes glucose (___C) to 2 pyruvates (___C) Consumes: 2 ATP Net Yield: ___________+ ___________ Also makes _________________ (waste) No ________ required
Glycolysis Stage 1: Energy Investment Stage Cell uses ________ to phosphorylate compounds of glucose Stage 2: Energy Payoff Stage Two 3-C compounds oxidized For each glucose molecule: 2 Net _________ produced by substrate-level phosphorylation 2 molecules of NAD+ ______________
Substrate-Level Phosphorylation Generate small amount of ATP Phosphorylation: enzyme transfers a _______________________ to other compounds ADP (_______________) + Pi ATP P compound
Is that all there is? Not a lot of energy… for 1 billon years+ this is how life on Earth survived no O2 = ___________________________________________ only harvest 3.5% of energy stored in glucose more carbons to strip off = more energy to harvest O2 glucose pyruvate O2 So why does glycolysis still take place? 6C 2x 3C O2 Hard way to make a living! O2 O2
How is NADH recycled to NAD+? with oxygen aerobic respiration without oxygen anaerobic respiration “fermentation” Another molecule must accept H from NADH pyruvate H2O NAD+ CO2 recycle NADH NADH O2 NADH acetaldehyde acetyl-CoA NADH NAD+ NAD+ lactate lactic acid fermentation which path you use depends on who you are… Krebs cycle ethanol alcohol fermentation
Fermentation (anaerobic) ____________, ___________ 1C 3C 2C pyruvate _______ + CO2 NADH NAD+ back to glycolysis beer, wine, bread _____________, some fungi Count the carbons!! Lactic acid is not a dead end like ethanol. Once you have O2 again, lactate is converted back to pyruvate by the liver and fed to the Kreb’s cycle. pyruvate ____________ 3C NADH NAD+ back to glycolysis cheese, anaerobic exercise (no O2)
Alcohol Fermentation pyruvate ethanol + CO2 Dead end process bacteria yeast Alcohol Fermentation recycle NADH 1C 3C 2C pyruvate ethanol + CO2 NADH NAD+ back to glycolysis Dead end process at ~12% ethanol, kills yeast can’t reverse the reaction Count the carbons!
Lactic Acid Fermentation animals some fungi Lactic Acid Fermentation recycle NADH O2 pyruvate lactic acid 3C NADH NAD+ back to glycolysis Reversible process once O2 is available, lactate is converted back to pyruvate by the liver Count the carbons!
Pyruvate is a branching point ____________ anaerobic respiration mitochondria __________________ aerobic respiration
Glycolysis (Summary) 2 NAD+ P ADP 2 NADH + 2H+ 2 ATP (3-C) C3H6O3
Stage 2: Pyruvate Oxidation + Citric Acid Cycle [Krebs Cycle] Cellular Respiration Stage 2: Pyruvate Oxidation + Citric Acid Cycle [Krebs Cycle]
Mitochondria — Structure ___________________ membrane energy harvesting organelle smooth ________________ membrane highly __________________ inner membrane Called _____________________ intermembrane space fluid-filled space between membranes _________________ inner fluid-filled space DNA, ribosomes enzymes free in matrix & membrane-bound intermembrane space inner membrane outer matrix cristae mitochondrial DNA What cells would have a lot of mitochondria?
Mitochondrion Structure Citric Acid Cycle (Krebs) (matrix) ETC (inner membrane)
Pyruvate Oxidation
Pyruvate Oxidation 2 Pyruvate 2 _______________________ (used to make citrate) Produces: 2)______ and 2NADH
[ ] Oxidation of pyruvate Pyruvate enters mitochondrial matrix 3 step oxidation process releases 2 CO2 (count the carbons!) reduces 2 NAD 2 NADH (moves e-) produces 2 acetyl CoA Acetyl CoA enters _________________ [ 2x ] pyruvate acetyl CoA + CO2 3C NAD 2C 1C Where does the CO2 go? Exhale! CO2 is fully oxidized carbon == can’t get any more energy out it CH4 is a fully reduced carbon == good fuel!!!
Krebs cycle 1937 | 1953 aka Citric Acid Cycle in _____________________________ 8 step pathway each catalyzed by specific enzyme step-wise catabolism of 6C citrate molecule Evolved later than glycolysis does that make evolutionary sense? bacteria 3.5 billion years ago (glycolysis) free O2 2.7 billion years ago (photosynthesis) eukaryotes 1.5 billion years ago (aerobic respiration = ________________ mitochondria) Hans Krebs 1900-1981 The enzymes of glycolysis are very similar among all organisms. The genes that code for them are highly conserved. They are a good measure for evolutionary studies. Compare eukaryotes, bacteria & archaea using glycolysis enzymes. Bacteria = 3.5 billion years ago glycolysis in cytosol = doesn’t require a membrane-bound organelle O2 = 2.7 billion years ago photosynthetic bacteria / proto-blue-green algae Eukaryotes = 1.5 billion years ago membrane-bound organelles! Processes that all life/organisms share: Protein synthesis Glycolysis DNA replication
Citric Acid Cycle (Krebs) Location: Occurs in mitochondrial matrix Reaction: Acetyl CoA Citrate released Net Yield: ___ATP, ___ NADH, ___ FADH2 (electron carrier) ATP produced by ___________________________ CO2
Count the carbons! x2 3C 2C 4C 6C 4C 6C 5C 4C 4C 4C pyruvate 3C 2C acetyl CoA citrate 4C 6C 4C 6C This happens __________ for each glucose molecule oxidation of sugars CO2 A 2 carbon sugar went into the Krebs cycle and was taken apart completely. Two CO2 molecules were produced from that 2 carbon sugar. Glucose has now been fully oxidized! But where’s all the ATP??? x2 5C 4C CO2 4C 4C
Count the electron carriers! pyruvate 3C 2C acetyl CoA NADH NADH citrate 4C 6C 4C 6C reduction of electron carriers This happens twice for each glucose molecule CO2 Everytime the carbons are oxidized, an NAD+ is being reduced. But wait…where’s all the ATP?? NADH x2 5C 4C FADH2 CO2 4C 4C NADH ATP
Whassup? So we fully oxidized glucose C6H12O6 CO2 & ended up with _______! What’s the point?
What’s so important about electron carriers? Electron Carriers = ___________ Carriers H+ Krebs cycle produces large quantities of electron carriers NADH FADH2 go to __________ _______________! ADP + Pi ATP What’s so important about electron carriers?
Energy accounting of Krebs cycle 2x 4 NAD + 1 FAD 4 NADH + 1 FADH2 pyruvate CO2 1 ADP 1 ATP 3C 3x 1C ATP Net gain = 2 ATP = 8 NADH + 2 FADH2
Value of Krebs cycle? If the yield is only 2 ATP then how was the Krebs cycle an adaptation? value of NADH & FADH2 electron carriers & H carriers reduced molecules move _____________________ to be used in the ___________________________ like $$ in the bank
Summary of Citric Acid Cycle
REVIEW: TURN & TALK Explain “glycolysis”. Where does it occur? How does it “work”? What is the chemical equation for cellular respiration? Which has more energy available: ADP or ATP? NAD+ or NADH? FAD+ or FADH2? Where does the Citric Acid Cycle occur in the cell?
HOMEWORK Watch the video “Cellular Respiration” from Bozeman Science http://www.bozemanscience.com/cellular-respiration Take detailed notes
POGIL: Glycolysis and Krebs Cycle
Stage 3: Oxidative Phosphorylation Cellular Respiration Stage 3: Oxidative Phosphorylation
Oxidative Phosphorylation Electron Transport Chain Chemiosmosis Occurs in inner membrane of mitochondria Produces 26-28 ATP by oxidative phosphorylation via chemiosmosis H+ ions pumped across inner mitochondrial membrane H+ diffuse through ATP synthase (ADP ATP)
Electron Transport Chain (ETC) Collection of molecules embedded in inner membrane of mitochondria Tightly bound protein + non-protein components Alternate between reduced/oxidized states as accept/donate e- Does not make ATP directly Ease fall of e- from food to O2 2H+ + ½ O2 H2O
As electrons move through the ETC, proton pumps move H+ across inner mitochondrial membrane
Chemiosmosis: Energy-Coupling Mechanism Chemiosmosis = H+ gradient across membrane drives cellular work Proton-motive force: use proton (H+) gradient to perform work ATP synthase: enzyme that makes ATP Use E from proton (H+) gradient – flow of H+ back across membrane
Chemiosmosis couples the ETC to ATP synthesis
H+ pumped from matrix to intermembrane space oxidative phosphorylation uses generates chemiosmosis which couples proton gradient ATP uses E to produce called redox reactions H+ pumped from matrix to intermembrane space proton motive force of ETC drives in which H+ e- passed down E levels through ATP synthase to final e- acceptor O2 H2O
ATP yield per molecule of glucose at each stage of cellular respiration
BioFlix: Cellular Respiration
Anaerobic Respiration: generate ATP using other electron acceptors besides O2 Final e- acceptors: sulfate (SO4), nitrate, sulfur (produces H2S) Eg. Obligate anaerobes: can’t survive in O2 Facultative anaerobes: make ATP by aerobic respiration (with O2 present) or switch to fermentation (no O2 available) Eg. human muscle cells
Fermentation = glycolysis + regeneration of NAD+
Glycolysis Fermentation Respiration Without O2 O2 present Fermentation Respiration Keep glycolysis going by regenerating NAD+ Occurs in cytosol No oxygen needed Creates ethanol [+ CO2] or lactate 2 ATP (from glycolysis) Release E from breakdown of food with O2 Occurs in mitochondria O2 required (final electron acceptor) Produces CO2, H2O and up to 32 ATP
Types of Fermentation Pyruvate Ethanol + CO2 Ex. bacteria, yeast Alcohol fermentation Lactic acid fermentation Pyruvate Ethanol + CO2 Ex. bacteria, yeast Used in brewing, winemaking, baking Pyruvate Lactate Ex. fungi, bacteria, human muscle cells Used to make cheese, yogurt, acetone, methanol Note: Lactate build-up does NOT causes muscle fatigue and pain (old idea)
Various sources of fuel Carbohydrates, fats and proteins can ALL be used as fuel for cellular respiration Monomers enter glycolysis or citric acid cycle at different points
Phosphofructokinase: Allosteric enzyme that controls rate of glycolysis and citric acid cycle Inhibited by ATP, citrate Stimulated by AMP AMP+ P + P ATP
Respiration: Big Picture
aerobic cellular respiration ENERGY aerobic cellular respiration (with O2) anaerobic (without O2) glycolysis (cytosol) mitochondria Fermentation (cytosol) pyruvate oxidation ethanol + CO2 (yeast, some bacteria) citric acid cycle substrate-level phosphorylation lactic acid (animals) ETC oxidative phosphorylation chemiosmosis
Glycolysis & Citric Acid Cycle
Oxidative Phosphorylation Electron Transport Chain Chemiosmosis
What’s the Difference? Substrate-level phosphorylation Oxidative phosphorylation Add Pi from one compound to ADP directly Energy comes from the chemical reaction itself “no middle man” Uses: Glycolysis Krebs Cycle Uses a “middle man” = NADH and FADH and the pumping of electrons to generate an electrochemical gradient to make ATP Pi come from a pool of phosphates Uses: ETC + Chemiosmosis
Worksheet Practice
Quizlet https://quizlet.com/_3whks7 Play/Review with the flashcards first Then select 1 game to play either alone or with a partner Record your time: ______
Bean Brew…an Investigative Case Close Read ? And ! Highlight key vocab terms Work to complete the questions throughout the investigation (Parts I-II)in your lab groups. Answer in complete sentences in the packets. Use the textbook to refer to the indicated diagrams in ch. 7, 8, and 9. Choose either Part IV or V to complete at home. Due date = Monday Nov. 6
“The Mystery of the Seven Deaths” Read the Case Study and answer the questions. Discuss with someone near you if you aren’t sure! Write your answers in the white space but be sure to use COMPLETE sentences that clearly address the question.