Chapter 2 Cellular Respiration PDF

Chapter 2 CELLULAR RESPIRATION 1  LESSON LEARNING OUTCOMES Upon completion of this lecture, students should be able to: a) Define the principles of cellular respiration. b) Explain respiration as an oxidation-reduction process. c) Describe the structure and function of ATP. d)...

Chapter 2 CELLULAR RESPIRATION 1  LESSON LEARNING OUTCOMES Upon completion of this lecture, students should be able to: a) Define the principles of cellular respiration. b) Explain respiration as an oxidation-reduction process. c) Describe the structure and function of ATP. d) Explain the biochemical processes in cellular respiration: Glycolysis Kreb cycle Electron transport chain and oxidative phosphorylation e) Define aerobic and anaerobic respiration. f) Explain alcohol fermentation & lactic acid fermentation.2  Overview: Life Is Work Living cells require energy from outside sources. Energy is necessary for life processes: These include growth, transport & movement. Some animals, such as the chimpanzee, obtain energy by eating plants. Some animals feed on other organisms that eat plants. 3  Light energy Energy flows into an ECOSYSTEM ecosystem as sunlight and leaves as heat Photosynthesis generates Photosynthesis in chloroplasts Organic O2 and organic molecules, CO2 + H2O molecules+ O2 Cellular respiration which are used in cellular in mitochondria respiration Cells use chemical energy stored in organic molecules ATP powers and 02 to generate ATP ATP most cellular work (which powers work and Heat energy release CO2 and H2O) 4 CELLULAR RESPIRATION: AEROBIC HARVEST OF FOOD ENERGY A cell requires oxygen to break down its fuel So cellular respiration is an aerobic process Respiration requires a cell to exchange 2 gases – O2 and CO2 - with the surroundings (inside the body) Breathing requires body to exchange 2 gases with outside 5  Breathing and cellular respiration are closely related Breathing is necessary for exchange of CO2 produced during cellular respiration for atmospheric O2 Cellular respiration uses O2 to help harvest energy from glucose and produces CO2 in the process 6 CELLULAR RESPIRATION – HARVESTING CHEMICAL ENERGY 7  Cellular Respiration Defined as a complex process in which food molecules or organic molecules are broken down to harvest chemical energy which is then stored in the chemical bonds of adenosine triphosphate (ATP). C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy (ATP + Heat) The energy necessary for life is contained in the arrangement of electrons in chemical bonds in organic molecules. 8 How do cells extract this energy? Cellular respiration is the controlled breakdown of organic molecules When the carbon-hydrogen bonds of glucose are broken, electron are be transferred to oxygen. Transfer of electrons during chemical reactions releases energy stored in organic molecules. This released energy is ultimately used to synthesize ATP 9 Redox Reactions: Oxidation and Reduction The Principle of Redox Chemical reactions that transfer electrons between reactants are called oxidation-reduction reactions or redox reactions In oxidation, - a substance loses electrons or is oxidized In reduction, - a substance gains electrons or is reduced 10 becomes oxidized (loses electron) becomes reduced (gains electron) becomes oxidized becomes reduced 11  Oxidation of Organic Fuel Molecules During Cellular Respiration During cellular respiration, the fuel (such as glucose) is oxidized, and O2 is reduced Loss of hydrogen atom (oxidation) becomes oxidized becomes reduced Gain of hydrogen atom (reduction) Oxidation and reduction are coupled usually involved the transfer by hydrogen atom where electron will be moved with proton (H+). electron travel with a hydrogen atom. 12  Electron Carriers NAD+ In cellular respiration, glucose and other organic molecules are broken down in a series of steps Electrons (in H atom) from organic compounds are not transferred directly to oxygen but are passed to an electron carrier. NAD+, a coenzyme an electron carrier/ acceptor during cellular respiration NAD+ is reduced to NADH NADH must pass the electrons eventually so that it can be deoxidized to NAD+ and become available once again as a carrier 13 NAD+ NADH Dehydrogenase Reduction of NAD+ (from food) Oxidation of NADH Nicotinamide Nicotinamide (oxidized form) (reduced form) NAD+ as an electron shuttle. 14  NADH passes the electrons to the electron transport chain The electron transport chain passes electrons in a series of steps instead of one explosive reaction O2 pulls electrons down the chain in an energy- yielding tumble The energy yielded is used to regenerate ATP 15 Burning compared to cell respiration: The energy release is controlled by carries molecules in a series of steps. The one-step exergonic reaction of hydrogen with oxygen to form water releases large amount of energy in form 16 of heat and light.  Two common electron carrier are ❖ Nicotinamide adenine dinucleotide (NAD+) derivative of vitamin B3 (niacin) ❖ Flavin adenine dinucleotide (FAD) – derivative of vitamin B2 (riboflavin) 2H NAD+ ⇌ NADH + H+ 2H FAD ⇌ FADH2 NAD+ & FAD -> ‘e’ acceptor during respiration -→ represents stored energy that can tapped to make ATP when electron complete their fall down an energy gradient from NADH/FADH2 to oxygen. 17  Adenosine Triphosphate (ATP) ATP is a high-energy molecule that stores and transports energy within cells. ATP is the cell’s energy shuttle: Is a nucleotide with unstable phosphate bonds that the cell hydrolyses for energy. known as energy carrier or universal energy carrier. ATP powers cellular work by coupling exergonic reactions to endergonic reactions ATP is hydrolyzed –> energy of ATP is released 18  Chemical structure of ATP Nitrogenous base (Adenine) 5-Carbon sugar (Ribose) 3 Phosphate groups High energy bond 19 How Do We Get Energy from ATP? By breaking the high- energy bonds between the last two phosphates in ATP HYDROLYSIS 20  HYDROLYSIS OF ATP Thebonds between the phosphate groups of ATP can be broken by hydrolysis forming ADP and Pi The reaction is exergonic Releases 7.6 kcal of energy per mole of ATP hydrolyzed. 21  MECHANISMS TO GENERATE ATP 3 mechanism to generate ATP a) Substrate- level phosphorylation - Generates ATP by transferring a high – energy phosphate group from a substrate directly to ADP Enzyme Enzyme ADP P Substrate ATP Product 22 b) Oxidative phosphorylation (energy from food) - Food is oxidized and the energy is extracted from the electron by an electron transport chain. - The extracted energy is then used to make ATP by a process known as chemiosmosis. 23 c) Photophosphorylation (energy from sunlight) - Light energy used to generate electron and then the energy is extracted from electrons by an electron transport chain. - The extracted energy then used to make ATP by process known as chemiosmosis. STROMA (low H+ concentration) Cytochrome NADP+ Photosystem II complex Light Photosystem I reductase Light 4 H+ NADP+ + H+ Fd Pq NADPH 2 Pc H2O 1 1/ 2 O 2 THYLAKOID SPACE +2 H+ 4 H+ + (high H concentration) To Calvin Cycle Thylakoid membrane ATP synthase ADP STROMA + ATP (low H+ concentration) P i H+ 24  How ATP Performs Work As ATP is broken down, it gives off usable energy to power chemical work and gives off some non usable energy as heat. The energy released during ATP hydrolysis perform the few types of cellular work. 25  Living organisms require energy for the following activities [significance of ATP] a) Movement - Energy is required for the movement of cilia and flagella, muscle contraction and movement of chromosomes during cell division. 26 b) Anabolic processes - These are metabolic processes that consume energy to build molecules from simple molecules. 27 c) Secretion - In the cell, the packing and transport of secretory product require energy. 28 d) Active transport - energy is required to move substance such as ions across the plasma membrane against their concentration gradients. 29 30  The ATP cycle ATP synthesis from ATP hydrolysis to ADP + Pi requires ADP + Pi yields energy energy ATP Synthetase ATPase + H2O exergonic endergonic Energy released by breakdown reactions (catabolism) in the cell is used to phosphorylate ADP, regenerating ATP. 31 More about Cellular Respiration ❖ Metabolic Pathway that breaks down glucose ❖ Glucose is oxidized/breakdown into CO2 and H2O ❖ Process is also Catabolic because larger Glucose breaks into smaller molecules ❖ Exergonic reaction - Breakdown of one molecule glucose result in 30 or 32 ATP 32  The Stages of Cellular Respiration Harvesting of energy from glucose has three stages – Glycolysis (breaks down glucose into two molecules of pyruvate) – Kreb cycle/Citric acid cycle (completes the breakdown of glucose) – Oxidative phosphorylation (accounts for most of the ATP synthesis) 33  An overview of cellular respiration (aerobic respiration) - Metabolic pathway of aerobic respiration can be divided into three main stages Electrons Electrons carried carried via NADH and via NADH LINK FADH2 REACTION Pyruvate Oxidative Glycolysis Citric phosphorylation: oxidation acid electron transport Glucose Pyruvate Acetyl CoA cycle and chemiosmosis CYTOSOL MITOCHONDRION ATP ATP ATP Substrate-level Substrate-level Oxidative phosphorylation phosphorylation phosphorylation Phosphate group from a substrate 34 Where Does Cellular Respiration Take Place? takes place in two parts of the cell: Krebs Cycle & Oxidative phosphorylation take place in Glycolysis occurs in the the Mitochondria Cytoplasm 35 Glycolysis harvests chemical energy by oxidizing glucose to pyruvate Glycolysis (“splitting of sugar”) breaks down glucose (6-carbon sugar) into two molecules of pyruvate (3-carbon sugar) Involve 10 steps, each of the ten steps in glycolysis is catalyzed by a specific enzyme. Glycolysis occurs in the cytoplasm and has two major phases – Energy investment phase – Energy payoff phase Glycolysis occurs whether or not O2 is present 36 Glycolysis occurs whether or not O2 is present Glycolysis 37  INVESTMENT PHASE In the energy investment phase, ATP provides activation energy by phosphorylating glucose. 38  PAYOFF PHASE In the energy payoff phase, ATP is produced by substrate-level phosphorylation and NAD+ is reduced to NADH. 39  GLYCOLYSIS Takes place in the Cytoplasm Anaerobic (absence of O2) or Aerobic (present of O2) Requires input of 2 ATP Glucose split into 2 molecules of Pyruvate (with the presence of O2 will enter Kreb cycle) Net yields 2 ATP molecules for every one glucose molecule broken down (4 ATP in payoff phase) – (2 ATP used in investment phase) Yields 2 NADH per glucose molecule (will enter electron transport chain) 40 Presence of O2, pyruvate enters the mitochondrion (in eukaryotic cells) where the oxidation of glucose is completed O2 in cell Electrons Electrons carried carried via NADH and via NADH FADH2 Glycolysis Pyruvate Citric oxidation acid Glucose Pyruvate Acetyl CoA cycle CYTOSOL MITOCHONDRION LINK REACTION ATP ATP Substrate-level Substrate-level phosphorylation phosphorylation 41  Pyruvate to Acetyl CoA (LINK REACTION) Before the kreb cycle/citric acid cycle can begin, pyruvate must be converted to acetyl Coenzyme A (acetyl CoA), Links glycolysis to the Krebs cycle/citric acid cycle Carried out by a multienzyme complex that catalyses 3 - reactions CYTOSOL MITOCHONDRION Coenzyme A, sulfur containing compound attached to acetate by unstable bond that makes acetyl group (the attached Pyruvate’s carboxyl is CO2 Coenzyme A acetate) very reactive. removed as CO2 1 3 2 2 NAD+ NADH + 2 H+ Acetyl CoA Pyruvate Remaining 2-carbon fragment is oxidized to forming acetate Transport protein 42  Citric Acid Cycle (Kreb cycle) Pyruvate Glycolysis Citric Oxidative acid (from glycolysis, cycle phosphorylation 2 molecules per glucose) Named after Hans Kreb ATP ATP ATP CO2 Acetyl CoA produced from link CoA reaction enter Krebs cycle. Also NADH +H + Acetyle CoA known as the citric acid cycle or the CoA tricarboxylic acid cycle. CoA A series of enzymatic reaction occur in matrix of mitochondrial. Kreb cycle/ Most of the reaction are Citric acid 2 CO2 oxidation/reduction reactions and cycle FADH 3 NAD+ decarboxylation reactions. 2 FAD 3 NADH + 3 H+ ADP + P i ATP Substrate level phosphorylation 43 Krebs cycle/Citric acid cycle Step 1 - 2C (acetyl CoA) enter cycle - CoA is stripped from AcetylCoA and recycled. STEP 8: Oxidation - 2C (acetyl) combine 4C (oxaloacetate) Malate oxidized, NAD+ Acetyl CoA forms a 6C (citrate). reduced to NADH and CoA-SH - Enzyme Citrate synthase regerate oxaloacetate. Enzyme Malate NADH 1 H2O STEP 2: Isomerisation dehydrogenase + H+ NAD+ Citrate are rearranged by 8 Oxaloacetate the removal and addition of 2 STEP 7: Hydration water molecule. Fumarate converted Malate Citrate - Enzyme Aconitase to malate by addition Isocitrate of H2O. Citric NAD+ Enzyme Fumarase acidFigure.12 3 NADH 7 + H+ H2O cycle STEP 3: : Oxidation and CO2 decarboxylation STEP 6: Oxidation Fumarate Isocitrate is oxidized and loses CoA-SH 2H transferred to FAD CO2 - form 𝛂 – ketoglutarate and and form FADH2. NAD+ reduced to NADH. 6 4 Enzyme succinate CoA-SH - Isocitrate dehydrogenase dehydrogenase -Ketoglutarate FADH2 5 CO2 NAD+ FAD STEP 5 : Substrate level Succinate Pi NADH phosphorylation GTP GDP Succinyl +H + CoA displaced by Pi, then transferred to CoA STEP 4 : Oxidation and decarboxylation GDP to form GTP. Pi from GTP transfer toADP 𝛂 – ketoglutarate is oxidized and loses CO2 and ADP and form ATP. ATP combine with Coenzyme A to form succinyl CoA. - Enzyme Succinyl-CoA synthetase - Enzyme α-ketoglutarate dehydrogenase  Krebs Cycle/ Citric Acid Cycle Requires Oxygen (Aerobic) Series of reactions that give off CO2 and produce one ATP per cycle. Each turn of the Krebs Cycle 3NADH, 1FADH2, and 2CO2 Cycle turns twice per glucose molecule For each Glucose molecule, need 2 turn of kreb cycle to produce 6NADH, 2FADH2, 4CO2, and 2ATP 2 ATP (substrate level phosphorylation) 45 Overall Process 46  Oxidative Phosphorylation Generates the majority of ATP in aerobic respiration. (in glycolysis & kreb cycle – only 2 ATP) Involve electron transport chain, chemiosmosis and ATP synthesis. III IV I II FADH2FAD Chemiosmosis and ATP synthesis Oxidative phosphorylation 47  ELECTRON TRANSPORT CHAIN Last step in aerobic respiration Occur in cristae (inner membrane of mitochondria) Uses high energy of electron to generate ATP ▪ Electrons drop in free energy as they pass down the electron transport chain. ▪ Electrons carried by NADH and FADH2 are transferred along a series of 9 carriers until they are ultimately donated to an O2 molecule. ▪ NADH and FADH2 -Energy rich molecule, contain a pair electron with high potential energy. 48  ELECTRON TRANSPORT CHAIN 1. Integral membrane protein complex (multiprotein complexes) (act as carrier protein as well as proton pump) 1. NADH dehydrogenase (complex I) 2. Succinate dehydrogenase (complex II) 3. Cytochrome reductase/ Cytochrome bf complex (complex III) 4. Cytochrome oxidase (complex IV) 2. Mobile carrier (shuttle electron between three proton pump) 1. Ubiquinone or coenzyme Q (Q) 2. Cytochrome C (cyt C) 49  REMEMBER The electron transport chain generates no ATP directly The movement of electrons along the electron transport chain will contribute to chemiosmosis and ATP synthesis. 50  Electron Transport Chain and Chemiosmosis Inner Mitochondrial Glycolysis Oxidative phosphorylation. membrane electron transport and chemiosmosis ATP ATP ATP H+ H+ H+ H+ Cyt c Protein complex Intermembrane of electron space carners Q IV I III ATP Inner II synthase mitochondrial FADH2 H2O membrane FAD+ 2 H+ + 1/2 O2 NADH+ NAD+ ADP + Pi ATP (Carrying electrons from, food) H+ Mitochondrial Electron transport chain Chemiosmosis matrix ATP synthesis powered by the flow Electron transport and pumping of protons (H+), which create an H+ gradient across the membrane Of H+ back across the membrane Oxidative phosphorylation 51 Electron from NADH Complex I accepts “e” from NADH. NADH oxidized to NAD+. Complex I reduced. Mobile carrier ubiquinone (Q) accepts the “e” from Complex I and Q is reduced. Complex I is oxidized. Oxidation of Complex I release energy and this energy is used to pump H+ from mitochondria matrix into intermembrane space. Q then carry the “e” to Complex III. The “e” from complex III then transferred to cyt C (mobile carrier). Complex III oxidized. Oxidation of Complex III is coupled with pumping of H+ from matrix into intermembrane space. 52  Cyt c carry the “e” to Complex IV. Then, the “e” unites with H+ and O2 in the matrix to form H2O. Complex IV oxidized. Oxidation of Complex IV is coupled with pumping of H+ from matrix into intermembrane space. Electron from FADH2 FADH2 donates its “e” to Complex II. FADH2 oxidized to become FAD. Mobile carrier ubiquinone (Q) accepts the “e” from Complex II and Q is reduced. Complex II is oxidized. Oxidation of Complex II do not pump H+ because contain less energy for pump H+ from matrix to intermembrane space 53  Q then carry the “e” to complex III. The “e” from complex III then transferred to Cytochrome c. Complex III oxidized. Oxidation of Complex III release energy which is then used to pump H+ from matrix into intermembrane space. Cyt c carry the electrons to Complex IV. Then, the electrons unites with H+ and O2 in the matrix to form H2O. Complex IV oxidized. Oxidation of Complex IV is coupled with pumping of H+ from matrix into intermembrane space. 54  NADH 50 2 e− The “e” move along NAD+ FADH2 series of electron 2 e− I FAD Multiprotein carriers because each Free energy (G) relative to O2 (kcal/mol) 40 FMN complexes Fe S II Fe S Q carrier has a higher III Cyt b Fe S electronegativity 30 Cyt c1 Cyt c IV than the carrier Cyt a Cyt a3 before. 20 Thus, the “e” are pulled downhill 2 e− 10 (originally from NADH or FADH2) towards oxygen which has the highest 0 2 H+ + 1/2 O2 electronegativity H2O 55  NADH 50 Complex I (NADH 2 e− NAD+ dehydrogenase) Complex II (succinate FADH2 - FMN (flavoprotein) dehydrogenase) 2 e− FAD Multiprotein (flavin - Iron-sulfur I Free energy (G) relative to O2 (kcal/mol) 40 FMN complexes mononucleotide) Fe S II Fe S - Iron-sulfur protein Q III Cyt b Fe S 30 Ubiquinone (Q) Cyt c1 IV Cyt c Mobile carrier - Cyt a lipid Cyt a3 20 Complex III (Cytochrome bf complex) - Cyt b 2 e− - Iron-sulfur 10 (originally from - Cyt c1 NADH or FADH2) Cyt c 0 2 H+ + 1/2 O2 Complex IV (Cytochrome oxidase) - Cyt a H2O - Cyt a3 56  Chemiosmosis The Energy- Coupling Mechanism Pumping of H+ (proton) from matrix into intermembrane space creates proton concentration gradient. ❖ [H+] in intermembrane space is higher than [H+] in matrix So, H+ (proton) from intermembrane space will diffuse back into matrix through ATP synthase down their concentration gradient. This process known as Chemiosmosis. The flow of H+ down their concentration gradient will release energy (proton motive force) which is used to combine ADP + P → ATP (synthesis of ATP). 57  INTERMEMBRANE SPACE A protein complex, ATP H+ H+ H+ A rotor within the membrane spins clockwise when synthase, in the cristae H+ H+ flows past H+ it down the H+ actually makes ATP from gradient. ADP and Pi. H+ H+ A stator anchored in the membrane holds the knob ATP used the energy of stationary. an existing proton gradient to power ATP synthesis. A rod (for “stalk”) extending into the knob also spins, activating This proton gradient catalytic sites in the knob. develops between the H+ intermembrane space Three catalytic and the matrix ADP sites in the stationary knob + join inorganic Pi ATP Phosphate to ADP to make ATP. MITOCHONDRIAL MATRIX 58  Electron Transport Chain H2O Produced Occurs Across Inner Mitochondrial membrane Final electron acceptor oxygen NADH = 2.5 ATP’s 8 NADH = 20 ATP FADH2 = 1.5 ATP’s 2 FADH2 = 3 ATP 2 NADH from glycolysis if NADH = 5 ATP or CYTOSOL if FADH2 = 3 ATP IN MITOCHONDRIA 28 ATP or 26 ATP 59  NADH FROM GLYCOLYSIS IN CYTOSOL (2NADH) Most of NADH produced comes from Kreb cycle in the mitochondrial matrix – direct accessible to electron transport chain Inner mitochondrial membrane is not permeable (impermeable) to NADH from cytosol. Malate –aspartate shuttle (used liver, kidney, heart) So, electron from NADH is - Electron from NADH (cytosol) transfer transfer to ETC through to NAD+ in matrix of mitochondrial shuttle system. 2 types of shuttle mechanisms. Glycerol -phosphate shuttle (used in skeletel muscle, brain) - Electron from NADH (cytosol) transfer to FAD in matrix of mitochondria 60 SUMMARY OF ATP PRODUCTION IN CELLULAR RESPIRATION SOURCE ATP yield (process) Glycolysis 2 ATP substrate level phosphorylation 2 NADH 3 ATP or 5 ATP oxidative phosphorylation Formation of Acetyl CoA ▪ 2 NADH 2X 2.5ATP 5 ATP oxidative phosphorylation Krebs cycle 2 GTP 2 ATP substrate level phosphorylation 6 NADH 6X2.5 ATP 15 ATP oxidative phosphorylation 2X1.5ATP 2 FADH2 3 ATP oxidative phosphorylation TOTAL 30 or 32 ATP 61 ATP Yield per molecule of glucose at each stage of cellular respiration + 2 ATP + 2 ATP + 26 or 28 ATP 30 or 32 ATP 62  Cellular respiration: Which details to know Molecular inputs and outputs from each stage. How many ATP molecules are produced from each stage. How many NAD+ and FAD molecules are reduced at each stage. 63  TUTORIAL 1. Draw the basic structure of ATP and give two function of ATP in cells. 2. Define cellular respiration. Give the equation for cellular respiration. 3. Explain the statement respiration as an oxidation-reduction process. 4. Sum up the total number of ATP molecules produced from the complete oxidation of one molecule of glucose during aerobic respiration (glycolysis, the formation of acetyl CoA and citric acid cycle). 64  TUTORIAL 5. Explain the chemiosmotic production of ATP during electron transport chain. (6 MARKS) 6. Define (6 MARKS) - Reduction - Oxidative phosphorylation - Substrate level phosphorylation 65  Anaerobic Respiration Breakdown of food without 0xygen Most cellular respiration requires O2 to produce ATP Without O2, the electron transport chain will stop to operate In that case, glycolysis couples with fermentation or anaerobic respiration to produce ATP Happen in cytosol 66  Anaerobic Respiration Anaerobic respiration uses an electron transport chain with a final electron acceptor other than O2, for example sulfate. Facultative anaerobes - organism that makes ATP with present of O2 and capable to switch to fermentation when no O2 Obligate anaerobes - organism will die in the presence of oxygen (use sulfate as final electron acceptor) Fermentation (anaerobic respiration) uses substrate- level phosphorylation instead of an electron transport chain to generate ATP. 67 68  Fermentation Fermentation consists of glycolysis plus reactions that + regenerate NAD , which can be reused by glycolysis Two common types are alcohol fermentation and lactic acid fermentation 69 Alcohol Fermentation Alcohol fermentation, pyruvate is converted to ethanol in two steps, with the first releasing CO2 then acetaldehyde reduced by receiving “e” from NADH. USED BY Yeast & many bacteria Bakery product (cake, bread) Beer, wine Local food (tempe, tapai budu) 70 Lactic Acid Fermentation Lactic acid fermentation, pyruvate is reduced by NADH, forming lactate as an end product, with no release of CO2 USED BY Lactobacillus bacteria Cheese & yogurt ( lactic acid -> sour taste) Human For quick ATP - during intense activity (running) - present of lactate muscle -> fatique and mucle cramp 71 Under aerobic conditions, the pyruvate is further oxidized to yield more ATP and under anaerobic conditions, the pyruvate is converted into lactic acid or ethanol. 72 Glycolysis and the citric acid cycle connect to many other metabolic pathways Glycolysis and the citric acid cycle are major intersections to various catabolic and anabolic pathways Proteins must be digested to amino acids; it can feed glycolysis or the citric acid cycle Fats are digested to glycerol (used in glycolysis) and fatty acids (used in generating acetyl CoA) Fatty acids are broken down by beta oxidation and yield acetyl CoA (2C – fragment) An oxidized gram of fat produces more than twice as much ATP as an oxidized gram of carbohydrate  Proteins Carbohydrates Fats Amino Sugars Glycerol Fatty acids acids Glycolysis 𝛃–oxidation Glucose - Breakdown of fatty acid into 2-C fragment Glyceraldehyde 3-P (acetyl group) NH3 Pyruvate Deamination - Amino group from amino acid Acetyl CoA been removed before enter glycolysis or kreb Citric cycle acid cycle Oxidative phosphorylation