Bioenergetics
Learning Objectives 1.Compare the difference between potential and kinetic energy. 2.Define the two laws of thermodynamics and explain how they relate to biological systems. 3.Explain how ATP functions as an energy shuttle. 4.Describe how enzymes speed up chemical reactions. Bioenergetics 5.Describe how cellular respiration produces energy that can be stored in ATP. 6.Describe the three main stages of cellular respiration. 7.Discuss the importance of oxidative phosphorylation in producing ATP. 8.Compare ATP generation from substrate level phosphorylation and oxidative phosphorylation. 9.Compare cellular respiration and fermentation.
Energy Transformation in cells Energy
• Cells are small units, a chemical factory, Energy is the capacity to cause change or to housing thousands of chemical reactions. perform work. • Cells use these chemical reactions for There are two kinds of energy: – cell maintenance, • Kinetic energy is the energy of motion. – manufacture of cellular parts, and • Potential energy is energy that matter – cell replication. possesses as a result of its location or structure.
Fuel Energy conversion Waste products Types of Energy used by Cells
Heat energy • Heat or thermal energy, is a type of kinetic
Gasoline Carbon dioxide energy associated with the random movement + + Combustion of atoms or molecules. Kinetic energy of movement • Light is kinetic energy, and can be harnessed to Oxygen Water Energy conversion in a car power photosynthesis. • Electrical energy used in the nervous system. Heat energy • Chemical energy is responsible for all the
Cellular respiration biochemical reactions in the cell like ATP Glucose Carbon dioxide + + ATP ATP
Oxygen Energy for cellular work Water
Energy conversion in a cell
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Thermodynamics
• “Thermodynamics, science of the relationship between heat, work, temperature, and energy. In broad terms, thermodynamics deals with the transfer of energy from one place to another and from one form to another. The key concept is that heat is a form of energy corresponding to a definite amount of mechanical work”. Encyclopedia Britannica
• Scientists use the word – system for the matter under study and – surroundings for the rest of the universe.
Biological Thermodynamics Energy Transformations • Quantitative study of the energy transductions Two laws govern energy transformations in that occur in and between living organisms, living organisms. structures, and cells and of the nature and – The first law of thermodynamics, energy in function of the chemical processes underlying the universe is constant, (statement of the these transductions. conservation of energy)and
• Biological thermodynamics may address the – The second law of thermodynamics, energy question of whether the benefit associated conversions increase the disorder of the with any particular phenotypic trait is worth universe. the energy investment it requires. • Entropy is the measure of disorder, or randomness.
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Energy Transforma on Energy Transformations in Cells
• Cells use oxygen in reactions that release energy from fuel molecules. • In cellular respiration, the chemical energy stored in organic molecules is converted to a form that the cell can use to perform work.
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Energy and Chemical reactions Exergonic reactions
• Chemical reactions either Exergonic reactions release energy. – release energy (exergonic reactions) – These reactions release the energy in covalent or bonds of the reactants – require an input of energy and store – Burning wood releases the energy in glucose as energy (endergonic reactions). heat and light – Cellular respiration • involves many steps, • releases energy slowly, and • uses some of the released energy to produce ATP.
Exergonic Reaction Endergonic Reactions
Endergonic reaction Reactants – requires an input of energy and – yields products rich in potential energy. Amount of energy released Endergonic reactions Energy – begin with reactant molecules that contain Products relatively little potential energy but – end with products that contain more chemical energy. Potentialenergy moleculesof
Endergonic Reaction Photosynthesis : endergonic reaction
Photosynthesis is a type of endergonic Products process. – Energy-poor reactants, carbon dioxide, and Amount of water are used. energy – Energy is absorbed from sunlight. Energy required – Energy-rich sugar molecules are produced. Reactants Potentialenergy moleculesof
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The Energy Cycle Metabolism
• A living organism carries out thousands of endergonic and exergonic chemical reactions. • Metabolism :The total of an organism’s chemical reactions. • Metabolism = Anabolism + Catabolism • A metabolic pathway is a series of chemical reactions that either – builds a complex molecule or – breaks down a complex molecule into simpler compounds.
Metabolic pathways Energy Coupling Breakdown Proteins to Amino Acids, Starch to Glucose • Energy coupling uses the – energy released from exergonic reactions to drive – essential endergonic reactions, – usually using the energy stored in ATP molecules.
Synthesis Amino Acids to Proteins, Glucose to Starch
The Energy Currency of the Cell Renewable cellular energy: ATP
• ATP is a renewable source of energy • ATP, adenosine triphosphate, powers for the cell nearly all forms of cellular work. • In the ATP cycle, energy released in an exergonic reaction, such as the • ATP consists of breakdown of glucose,is used in an – the nitrogenous base adenine, endergonic reaction to generate ATP
– the five-carbon sugar ribose, and
– three phosphate groups.
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Figure 5.12A_s1 ATP: Adenosine Triphosphate ATP drives cellular work Phosphate group • Hydrolysis of ATP releases energy by transferring its third phosphate from ATP P P P Adenine to some other molecule in a process Ribose called phosphorylation.
• Most cellular work depends on ATP energizing molecules by phosphorylating them.
ATP: Adenosine Triphosphate ATP drives cellular work Phosphate group
P P P • There are three main types of cellular Adenine work: Ribose 1. chemical, 2. mechanical, and H O Hydrolysis 2 3. transport • ATP drives all three of these types of work
P P P Energy
Chemical work Mechanical work Transport work
ATP ATP ATP
Solute HOW ENZYMES FUNCTION
P Motor P protein P Reactants Membrane protein
P
P P Product Molecule formed Protein filament moved Solute transported
ADP P ADP P ADP P
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Biological Catalysts The Energy of Activation
• Although biological molecules possess • We can think of EA much potential energy, it is not – as the amount of energy needed for a reactant released spontaneously. molecule to move “uphill” to a higher energy – An energy barrier must be overcome but an unstable state before a chemical reaction can begin. – so that the “downhill” part of the reaction can begin. – This energy is called the activation • One way to speed up a reaction is to add energy (E ). A heat, – which agitates atoms so that bonds break more easily and reactions can proceed but – but could also kill a cell.
Reaction without enzyme Enzymes lower energy of activation Activation energy barrier Enzymes • are usually proteins, although some RNA molecules can function as enzymes. Reactant
• function as biological catalysts by lowering the
EA needed for a reaction to begin,
• increase the speed of a reaction without being Energy consumed by the reaction
Products
Reaction with enzyme Metabolic reaction in a cell with and without enzyme
Enzyme
Activation energy a barrier Reactant reduced by b
enzyme Reactants Energy Energy c
Products Products Progress of the reaction
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Figure 5.14_s2 1 Enzymes have a specific shape Enzyme available with empty active site • An enzyme Active site Substrate (sucrose) – is very selective in the reaction it catalyzes and 2 Substrate binds to enzyme with – has a shape that determines the induced fit enzyme’s specificity. Enzyme (sucrase) • The specific reactant that an enzyme acts on is called the enzyme’s substrate. • A substrate fits into a region of the enzyme called the active site. • Enzymes are specific because their active site fits only specific substrate molecules.
Figure 5.14_s3 1 Enzyme available 1 Enzyme available with empty active with empty active site site Active site Substrate Active site Substrate (sucrose) (sucrose)
2 Substrate binds 2 Substrate binds to enzyme with to enzyme with induced fit induced fit Enzyme Enzyme (sucrase) Glucose (sucrase)
Fructose
H2O H2O
4 Products are released 3 Substrate is 3 Substrate is converted to converted to products products
Some common enzymes Conditions for optimum enzyme activity
A my Every enzyme has optimal conditions under which it is l most effective. a s • Temperature affects molecular motion. e – An enzyme’s optimal temperature produces the highest rate of contact between the reactants and the enzyme’s active site. – Most human enzymes work best at 35–40ºC. – But high temperature disrupts the structure • The optimal pH for most enzymes is near neutrality.
catalase lactase http://mm.rcsb.org
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Enzyme activity Effect of heat on enzyme activity
Temperature
pH Four Variables Enzyme Concentration
Denaturing protein Substrate Concentration
IF ACTIVE SITE CHANGES SHAPE: SUBSTRATE NO LONGER FITS
Even if temperature lowered – enzyme cannot regain its correct shape
Temperature Environmental Conditions can Cause Changes in Shape (Denaturing) 5- 35oC Increase in Activity 40oC -denatures
RateReactionof
0 10 20 30 40 50 60 <5oC - inactive
pH Cofactors and coenzymes
• Many enzymes require nonprotein
Narrow pH optima helpers called cofactors, which
Disrupt Ionic bonds - Structure – bind to the active site and
Effect charged residues at active site – function in catalysis. • Some cofactors are inorganic, such as
RateReactionof zinc, iron, or copper. • If a cofactor is an organic molecule, 1 2 3 4 5 6 7 8 9 such as most vitamins, it is called a coenzyme.
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Enzyme inhibitors Enzyme inhibitors
• Noncompetitive inhibitors • A chemical that interferes with an – bind to the enzyme somewhere other enzyme’s activity is called an inhibitor. than the active site, – change the shape of the active site,
• Competitive inhibitors and – prevent the substrate from binding. – block substrates from entering the active site and
– reduce an enzyme’s productivity.
Enzyme inhibi on Enzyme inhibitors regulate cell metabolism Substrate Active site • Enzyme inhibitors are important in Enzyme regulating cell metabolism. Allosteric site • In some reactions, the product may act Normal binding of substrate as an inhibitor of one of the enzymes in
Competitive Noncompetitive the pathway that produced it. This is inhibitor inhibitor called feedback inhibition.
Feedback Inhibition Some drugs, pes cides and poisons are enzyme inhibitors
• Many beneficial drugs act as enzyme inhibitors, including Feedback inhibition – Ibuprofen, inhibiting the production of prostaglandins, – some blood pressure medicines, Enzyme 1 Enzyme 2 Enzyme 3 – some antidepressants, A B C D Reaction 1 Reaction 2 Reaction 3 – many antibiotics, and Starting Product – protease inhibitors used to fight HIV. molecule • Enzyme inhibitors have also been developed as pesticides and deadly poisons for chemical warfare.
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The Marathoners and the Sprinters
Cellular respiration is the process by which cells produce energy aerobically The Marathoner and the Sprinter The different types of muscle fibers use different processes for making ATP • Slow-twitch fibers undergo aerobic respiration
(in the presence of O2) respiration are reddish in color as it contains myoglobin • Fast-twitch fibers undergo anaerobic respiration
(in the absence of O2) respiration
Breathing and Cellular Respiration Connecting breathing and cellular respiration
O CO2 2 Breathing Breathing and cellular respiration are closely related
• Breathing brings O2 into the body from the Lungs environment
• O2 is distributed to cells in the bloodstream
• In cellular respiration, mitochondria use O2 to Bloodstream O CO2 2 harvest energy and generate ATP
• Breathing disposes of the CO2 produced as a waste product of cellular respiration. Muscle cells carrying out Cellular Respiration
Glucose + O2
CO2 + H2O + ATP
Cellular respiration and ATP molecules The human energy requirement
The human body uses energy from ATP for all its • Cellular respiration is an exergonic process that activities transfers energy from the bonds in glucose to – The body needs a continual supply of energy to form ATP. maintain basic functioning: to breathe, to keep ▪ Cellular respiration heart pumping and maintain body temperature. – Can produce up to 32-34 ATP molecules from – The brain requires 120 gm of glucose/day! each glucose molecule and – ATP supplies energy (kilocalories) for voluntary – captures only about 34% of the energy activities originally stored in glucose. – An average adult human needs about 2,000 kcal of ▪ Other foods (organic molecules) can also be used energy each day. as a source of energy.
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What is kcal? Breaking down Glucose
• A kilocalorie (kcal) is – the quantity of heat required to raise the temperature of 1 kilogram (kg) of water by 1oC, C6H12O6 6 O2 6 CO2 6 H2O ATP – the same as a food Calorie, and Glucose Oxygen Carbon Water + Heat dioxide – used to measure the nutritional values indicated on food labels.
How can energy be released from glucose? Activity kcal consumed per hour by a 67.5-kg (150-lb) person*
Running (8–9 mph) 979 Dancing (fast) 510 • Energy can be released from glucose by Bicycling (10 mph) 490 simply burning it. Swimming (2 mph) 408 • The energy is dissipated as heat and Walking (4 mph) 341 Walking (3 mph) 245 light and is not available to living Dancing (slow) 204 organisms. Driving a car 61 Sitting (writing) 28
*Not including kcal needed for body maintenance
How do cells tap energy from glucose? The redox reaction in cells
• Movement of electrons from one molecule to • On the other hand, cellular respiration is another is an oxidation-reduction reaction, the controlled breakdown of organic or redox reaction. In a redox reaction, molecules. – the loss of electrons from one substance is • Energy is called oxidation, – gradually released in small amounts, – the addition of electrons to another substance – captured by a biological system, and is called reduction, – stored in ATP. – a molecule is oxidized when it loses one or more electrons, and – reduced when it gains one or more electrons.
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The Process The Redox Reaction in Cells • A cellular respiration equation is helpful to show the changes in hydrogen atom distribution. Loss of hydrogen atoms • Glucose (becomes oxidized)
– loses its hydrogen atoms and C6H12O6 6 O2 6 CO2 6 H2O ATP
– becomes oxidized to CO2. Glucose + Heat • Oxygen Gain of hydrogen atoms (becomes reduced) – gains hydrogen atoms and
– becomes reduced to H2O.
Mitochondria in Action Where does Cellular Respiration Occur?
Occurs across Cristae
Occurs in Cytoplasm
Occurs in Matrix
What are the three phases of Cellular Respiration ?
• Glycolysis • Citric Acid Cycle Oxidation • Oxidative Phosphorylation Glucose loses electrons (and hydrogens)
C6H12O6 + 6 O2 6 CO2 + 6 H2O
Glucose Oxygen Carbon Water dioxide
Reduction Oxygen gains electrons (and hydrogens)
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The role of Oxygen in Cellular Respiration 1 H O 2 2 2 • Cellular respiration can produce up to 38 ATP molecules for each glucose molecule consumed. • During cellular respiration, hydrogen and its bonding electrons change partners.
– Hydrogen and its electrons go from glucose Release to oxygen, forming water. of heat energy – This hydrogen transfer is why oxygen is so vital to cellular respiration.
H2O
Glucose and Oxygen Controlled breaking of the glucose molecule to release energy
• Glucose
– loses its hydrogen atoms and Loss of hydrogen atoms (becomes oxidized) – becomes oxidized to CO2.
• Oxygen C6H12O6 6 O2 6 CO2 6 H2O ATP – gains hydrogen atoms and Glucose + Heat Gain of hydrogen atoms – becomes reduced to H2O. (becomes reduced)
The controlled breakdown of glucose The molecules in the process
• There are other electron “carrier” molecules that I. Enzymes are necessary to oxidize function like NAD+. glucose and other foods. – They form an energy ‘staircase’ where the + electrons pass from one to the next down the II.NAD next level. – is an important enzyme in oxidizing – These electron carriers collectively are called glucose, the electron transport chain. – accepts electrons, and – As electrons are transported down the chain, – becomes reduced to NADH. ATP is generated.
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+
NAD ATP and oxidative phosphorylation
NADH passes electrons to the electron + • NAD picks up one hydrogen atom and another transport chain. single electron from carbohydrate, becoming – As electrons “move” from carrier to NADH. carrier and finally to O2, energy is • It will retain this form until it drops off its released in small quantities. energetic electrons (and a proton) in a later stage – The energy released is used by the cell to make ATP. of the energy-harvesting process.
+ The Electron Carrier NAD The energy gradient NADH
ATP NAD+
2e− Controlled empty loaded empty H+ release of energy for goes to pick synthesis proton up more electrons of ATP (oxidized)
used in later Electron transport stage of respiration (reduced) chain used in later stage of respiration 2e− NAD1. + within a cell, 2.NAD + is reduced to NAD NADH carries the 2 + O2 along with two by accepting an electron electrons to a later H 1/2 hydrogen atoms that from a hydrogen atom. It stage of respiration are part of the also picks up another then drops them off, food that is supplying hydrogen atom to becoming oxidized to energy for the body. become NADH. its original form, NAD H2O +.
Figure 6.7A
Glycolysis: substrate level phosphorylation Glucose
• Uses two ATP molecules per glucose to split 2 ADP 2 NAD+ the six-carbon glucose. 2 P • Makes four additional ATP directly when enzymes transfer phosphate groups from fuel molecules to ADP. 2 NADH Glycolysis produces a net of two 2 ATP 2 H+ molecules of ATP per glucose molecule.
2 Pyruvate
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Glycolysis harvests chemical energy by oxidizing glucose to Substrate Level Phosphorylation pyruvate
• ATP is formed in glycolysis by • substrate-level phosphorylation Enzyme Enzyme • during which – an enzyme transfers a phosphate group from a P ADP substrate molecule to ADP and
– ATP is formed. ATP • two NADH molecules are produced for each initial glucose molecule and P P • ATP molecules are generated. Substrate Product • The compounds that form between the initial reactant, glucose, and the final product, pyruvate, are called intermediates.
From Glycolysis to Citric Acid Cycle Making Acetyl CoA
Pyruvate is chemically processed to enter the citric acid cycle – A large, multienzyme complex catalyzes three + + reactions in the mitochondrial matrix NAD NADH H
• A carbon atom is removed from pyruvate and 2 released in CO2 CoA • The remaining two-carbon compound is Pyruvate Acetyl coenzyme A oxidized, 1 + 3 • molecule of NAD is reduced to NADH CO2 Coenzyme A • Coenzyme A joins with the 2-carbon group to produce acetyl CoA
Acetyl CoA The citric acid cycle CoA CoA • The citric acid cycle – is also called the Krebs cycle (after the German- British researcher Hans Krebs, who worked out much of this pathway in the 1930s),
2 CO2 • Citric acid cycle processes two molecules of Citric Acid Cycle acetyl CoA for each initial glucose.
• Thus, after two turns of the citric acid cycle, + FADH 3 NAD the overall yield per glucose molecule is 2 – 2 ATP, FAD 3 NADH + – 6 NADH and 3 H
– 2 FADH2. ATP ADP P
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Figure 6.9B_s1 Figure 6.9B_s2 Acetyl CoA CoA Acetyl CoA CoA CoA CoA
2 carbons enter cycle 2 carbons enter cycle Oxaloacetate Oxaloacetate 1 1
Citrate NAD+
NADH H+ 2 Citric Acid Cycle Citric Acid Cycle
CO2 leaves cycle
Alpha-ketoglutarate 3 CO2 leaves cycle
NAD+
ADP P NADH H+
Step 1 Step 1 Steps 2 – 3 ATP Acetyl CoA stokes Acetyl CoA stokes NADH, ATP, and CO2 the furnace. the furnace. are generated during redox reactions.
Figure 6.9B_s3 Acetyl CoA CoA CoA INPUT OUTPUT Citric acid 2 carbons enter cycle Oxaloacetate 1
Citrate Acetic NADH H+ acid NAD+ 2 CO2 5 NAD+ NADH H+ 2 Citric Acid Cycle ADP + P ATP Citric CO2 leaves cycle Malate Acid Cycle 3 NAD+ 3 NADH FADH Alpha-ketoglutarate 2 4 3 FAD CO2 leaves cycle FAD FADH2 NAD+ Succinate ADP P NADH H+ Acceptor Step 1 Steps 2 – 3 Steps 4 – 5 ATP molecule Acetyl CoA stokes NADH, ATP, and CO2 Further redox reactions generate the furnace. are generated during redox reactions. FADH2 and more NADH.
Phase 3: Oxidative phosphorylation Making ATP in Bulk
• Occurs in the cristae of mitochondria • Electrons from NADH and FADH2 travel down the • The molecules of the electron transport chain are electron transport chain to O2. built into the inner membranes of mitochondria. • Oxygen picks up H+ to form water. • Uses the energy released by electrons “falling” down the electron transport chain to pump H+ across a membrane • Energy released by these redox reactions is used to • Harnesses the energy of the H+ gradient through pump H+ from the mitochondrial matrix into the chemiosmosis, producing ATP – These ions store potential energy. intermembrane space. + – requires an adequate supply of oxygen. • In chemiosmosis, the H diffuses back across the inner membrane through ATP synthase complexes, driving the synthesis of ATP.
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The Electron Transport Chain Oxidative Phosphorylation
H+ + + H H H+ H+ H+ H+ H+ + + Mobile H + Protein H H H+ + + + Mobile + electron H H Intermem- Protein H H complex ATP electron H+ + carriers brane complex H ATP carriers of electron synthase space of electron synthase carriers III carriers III IV IV I I
Inner mito- chondrial II II membrane FADH FAD Electron 2 Electron FADH2 FAD flow 2 H+ 1 H O flow 1 NADH NAD+ O2 2 2 H+ O H O 2 NADH NAD+ 2 2 2 Mito- H+ chondrial H+ matrix ADP P ATP H+ ADP P ATP H+ Electron Transport Chain Chemiosmosis Electron Transport Chain Chemiosmosis Oxidative Phosphorylation Oxidative Phosphorylation
ATP synthase Interrupting cellular respiration can have both harmful and beneficial effects http://www.mrc-mbu.cam.ac.uk/research/atp- synthase Three categories of cellular poisons obstruct the • ATP synthase is a huge molecular complex (>500,000 daltons) process of oxidative phosphorylation. These poisons embedded in the inner membrane of mitochondria. 1. block the electron transport chain (for • Its function is to convert the energy example, rotenone, cyanide, and carbon of protons (H+) moving down their monoxide), concentration gradient into the synthesis of ATP. 2. inhibit ATP synthase (for example, the • 3 to 4 protons moving through this antibiotic oligomycin), or machine is enough to convert a molecule of ADP and Pi (inorganic 3. make the membrane leaky to hydrogen ions phosphate) into a molecule of ATP. (called uncouplers, examples include • One ATP synthase complex can generate >100 molecules of ATP dinitrophenol). http://mm.rcsb.org each second.
Poisons of the Cellular Respiration Review: Each molecule of glucose yields many molecules of ATP
Cyanide, Oligomycin Rotenone H+ H+ carbon monoxide + ATP H H+ • The total yield is about 32 ATP molecules per synthase H+ H+ H+ glucose molecule. • This is about 34% of the potential energy of a DNP glucose molecule.
• In addition, water and CO2 are produced.
FADH2 FAD 1 O 2 H+ NADH NAD+ 2 2
H+ H2O ADP P ATP
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The overview of cellular respiration Energy Harvest
(b) In schematic terms NADH reactants products High-energy electrons carried by NADH (a) In metaphorical terms glycolysis NADH FADH 2 ATP 2 insert 1 glucose and glucose 2 NADH cytosol glucose derivatives glycolysis 2 energy CO GLYCOLYSIS OXIDATIVE tokens 2 NADH 2 Glucose Pyruvate PHOSPHORYLATION CITRIC ACID (Electron Transport CYCLE and Chemiosmosis) 2 energy CO2 tokens 6 NADH Krebs 2 ATP Krebs cycle cycle 2 FADH Cytoplasm Mitochondrion 2 32 energy tokens electron CO CO 2 2 transport chain ATP O electron 2 34 ATP ATP ATP transport Substrate-level Substrate-level Oxidative chain mitochondrion H2O phosphorylation phosphorylation phosphorylation 38 ATP maximum per glucose molecule
The Energy Harvest
Each molecule of glucose yields many FERMENTATION: ANAEROBIC molecules of ATP – Glycolysis and the citric acid cycle together HARVESTING OF ENERGY yield four ATP per glucose molecule – Oxidative phosphorylation, using electron transport and chemiosmosis, yields 34 ATP per glucose – These numbers are maximum – Some cells may lose a few ATP to NAD+ or FAD shuttles
Fermentation enables cells to produce ATP Fermentation enables cells to produce ATP without oxygen without oxygen • Fermentation is a way of harvesting chemical energy • Your muscle cells and certain bacteria can that does not require oxygen. Fermentation oxidize NADH through lactic acid – takes advantage of glycolysis, fermentation, in which – produces two ATP molecules per glucose, and – NADH is oxidized to NAD+ and + – reduces NAD to NADH. – pyruvate is reduced to lactate. • The trick of fermentation is to provide an anaerobic path for recycling NADH back to NAD+.
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Fermentation enables cells to make ATP without Lactic acid Glucose Fermentation oxygen 2 ADP +
2 NAD • Lactate is carried by the blood to the liver, where it 2 P is converted back to pyruvate and oxidized in the 2 ATP Glycolysis mitochondria of liver cells. 2 NADH • The dairy industry uses lactic acid fermentation by bacteria to make cheese and yogurt.
• Other types of microbial fermentation turn 2 Pyruvate – soybeans into soy sauce and 2 NADH – cabbage into sauerkraut.
2 NAD+
2 Lactate
Alcohol Glucose Alcohol Fermentation Fermentation
+ 2 ADP 2 NAD 2 P • The baking and winemaking industries have Glycolysis used alcohol fermentation for thousands of 2 ATP 2 NADH years. • In this process yeasts (single-celled fungi) + – oxidize NADH back to NAD and 2 Pyruvate
2 NADH – convert pyruvate to CO2 and ethanol. 2 CO2
2 NAD+
2 Ethanol
Food
Polysaccharides Fats Proteins
Sugars Glycerol Fatty acids Amino acids
Citric Glycolysis Acetyl CoA Acid Electron Cycle Transport
ATP
Sengupta 19 Figure 6.UN02 Cellular respiration
generates has three stages oxidizes uses (a) glucose and produce organic fuels some
(b) produces (d) energy for many to pull to (c) electrons down cellular work (f) by a process called uses (g) H+ diffuse through chemiosmosis ATP synthase (e)
uses pumps H+ to create
H+ gradient