Learning Objectives. Refer to objectives handout. Where does the energy our cells need come from?

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1 Learning bjectives Refer to objectives handout Biology 105: hapter 9 Energy Releasing athways: from Matter Why is energy necessary for living things? What types of activities in the cell require energy? Movement in/out of the cell (Active Transport) Building/replacing cell parts, reproduction, movement, extracting wastes, building polymers (Dehydration synthesis reactions), Where does the energy our body cells need come from? The break down (hydrolysis) of our food molecules. ow does our body extract/get the energy out of our food? A series of stepwise reactions (cellular respiration) What stores energy in our body? (what molecule holds it?) Adenosine Triphosphate () pp BIL 105 from Matter BIL 105 Where does the energy our cells need come from? Energy is needed to maintain life. rganisms are ordered; entropy tends to dismantle that order. Materials go in and out of cells against concentration gradients. Movement of muscles. ells need to be replaced. Build biomolecules (anabolism). Degrade molecules. (catabolism) eterotrophs get energy by eating other living things (cellular respiration). from Matter 4 BIL 105 as Energy Source from Matter 5 BIL 105 The energy carrying molecule of the cell. =a charged battery ready to supply energy to the cell molecules consist of: a) Adenine (amino ) b) Ribose (sugar) c) hosphate groups xidizing glucose in cells is same overall reaction as burning it in a fire. In fire, this energy is lost as heat in a single reaction. In cells, intermediate reactions occur to reduce loss as heat & capture energy in bonds. NAD and FAD are electron carriers. Exergonic removal of phosphate provides energy for endergonic reactions; energy coin for cells. E. coli anabolism example costs: olysaccharide: ~000 rotein: 1500 DNA: 10,000, million s/second needed for all biosynthesis. 6 Results: G= 870 kj/mol. s and reduced electron carriers gained instead of heat. ydrolysis of nly ~1 million s/cell from Matter Burning igh-energy bonds between phosphate groups. to AD: G = 7.5 kcal/mol Autotrophs get energy primarily from sunlight (photosynthesis). eterotrophs get energy by eating other living things (cellular respiration). hief Wiggum is a eterotroph who likes to eat doughnuts. Figure 9.1 BIL 105 Life is Work! Autotrophs get energy primarily from sunlight (photosynthesis). The giant panda btains energy for its cells by eating plants from Matter xidized states: NAD+ & FAD Regenerated quickly BIL 105 from Matter 7 BIL 105 from Matter 8 BIL 105 from Matter 9 1

2 The Big icture to be oxidized comes from food. From autotrophs. First step is glycolysis. (6) to yruvate (). not necessary. Next, yruvate xidation required. yruvate() to Acetyl o-a () and. Kreb s ycle follows. Acetyl o-a () to. Step 4: Electron Transport & hemiosmosis. Get s from e carriers SUN energy AUTTRS hotosynthesis Stored chemical energy Food AUTTRS AND ETERTRS resent Absent Aerobic Respiration yruvate xidation Kreb s ycle Electron Transport & chemiosmosis Fermentation Reactions or Anaerobic Respiration Energy Flows into an ecosystem as sunlight and leaves as heat Endergonic photosynthesis Exergonic cellular respiration Figure 9. Light energy ESYSTEM hotosynthesis in chloroplasts rganic + ellular molecules + respiration in mitochondria powers most cellular work eat energy ellular respiration Is the most prevalent and efficient catabolic pathway onsumes oxygen and organic molecules such as glucose Yields BIL 105 from Matter 10 BIL 105 from Matter 11 BIL 105 from Matter 1 To keep working ells must regenerate Redox Reactions: xidation and Reduction atabolic pathways yield energy Due to the transfer of electrons ow do eterotrophs get s? If so many s needed, how are they gained? Biomolecules are degraded by process called cellular respiration. ellular respiration phosphorylates (adds a phosphate group to) ADs. is primary biomolecule degraded by cellular respiration. Redox reactions oxidize glucose ( ) to form 6 molecules and gain energy as ; reduced to. Transferring hydrogen equivalent to transferring electrons. General Equation: BIL 105 from Matter 1 BIL 105 from Matter 14 xidation Reduction BIL 105 from Matter 15 The rinciple of Redox Redox reactions Transfer electrons from one reactant to another by oxidation and reduction In oxidation A substance loses electrons, or is oxidized In reduction A substance gains electrons, or is reduced Examples of redox reactions becomes oxidized (loses electron) Na + l Na + + l becomes reduced (gains electron) BIL 105 from Matter 16 BIL 105 from Matter 17 BIL 105 from Matter 18

3 xidation of rganic Fuel Molecules During ellular Respiration During cellular respiration is oxidized and oxygen is reduced becomes oxidized becomes reduced Energy Stepwise Energy arvest via NAD + and the Electron Transport hain ellular respiration xidizes glucose in a series of steps Electrons from organic compounds Are usually first transferred to NAD +, a coenzyme NAD + N + N N N Nicotinamide (oxidized form) N N N + [] (from food) e + e + NAD Dehydrogenase Reduction of NAD + xidation of NAD N N + Nicotinamide (reduced form) Figure 9.4 BIL 105 from Matter 19 BIL 105 from Matter 0 BIL 105 from Matter 1 Where the Reactions ccur and Respiration In Action NAD, the reduced form of NAD + asses the electrons to the electron transport chain Mitochondria is location of the last steps in respiration. organelle in eukaryotic cells. Abundant in locations where lots of energy is needed. Sperm tails have many. System of membranes divide spaces. uter membrane Inner membrane NAD lasma membrane yruvate () NAD Acetyl-oA Krebs 6NAD FAD Electron transport Mitochondrion system Intermembrane space between them. ristae are folds in inner membrane. Matrix is space inside. Extracellular fluid ytoplasm BIL 105 from Matter BIL 105 from Matter BIL 105 from Matter 4 What To Keep Track f rocess (abbreviated) The Stages of ellular Respiration: A review Text goes in more detail than I will. For each stage know: Starting material ow many of them come from 1 glucose. ow many carbons in it. roducts made The biomolecules that continue in further reactions. # s produced # reducing compounds made (NAD & FAD ) Waste products ( & ) Energy inputs (s needed) 1 6-carbon glucose (Starting material) 6-carbon sugar diphosphate 6-carbon sugar diphosphate -carbon sugar hosphate (G) -carbon sugar hosphate (G) -carbon sugar phosphate NAD -carbon pyruvate -carbon sugar phosphate -carbon pyruvate NAD Respiration is a cumulative function of three metabolic stages The citric xidative BIL 105 from Matter 5 BIL 105 from Matter 6 BIL 105 from Matter 7

4 itric xidative NAD + NAD + 6 Triose phosphate dehydrogenase i 1, -Bisphosphoglycerate AD 7 hosphoglycerokinase -hosphoglycerate 8 hosphoglyceromutase -hosphoglycerate 9 hosphoenolpyruvate AD 10 yruvate kinase yruvate itric xidative Breaks down glucose into two molecules of pyruvate The citric ompletes the breakdown of glucose An overview of cellular respiration Electrons Electrons carried carried via NAD and via NAD FAD xidative itric Glycolsis : Glucos yruvate electron e transport and chemiosmosis ytosol Mitochondrion oncept 9.: harvests energy by oxidizing glucose to pyruvate Means splitting of sugar Breaks down glucose into pyruvate ccurs in the cytoplasm of the cell Figure 9.6 Substrate-level Substrate-level xidative BIL 105 from Matter 8 BIL 105 from Matter 9 BIL 105 from Matter 0 consists of two major phases Energy investment phase Energy payoff phase Gly coly si s Energy investment phase + used A closer look at the energy investment phase 1 exokinase AD -6-phosphate hosphoglucoisomerase Fructose-6-phosphate Energy payoff phase hosphof ructokinase 4 AD f ormed AD NAD e NAD y ruv ate + Fructose- 1, 6-bisphosphate 4 Aldolase Figure f ormed used NAD e + 4 y ruv ate + + NAD Figure 9.9 A 5 Isomerase Dihydroxyacetone Glyceraldehydephosphate -phosphate BIL 105 from Matter 1 BIL 105 from Matter BIL 105 from Matter A closer look at the energy payoff phase Enolase oncept 9.: The citric completes the energy-yielding oxidation of organic molecules The citric Takes place in the matrix of the mitochondrion Figure 9.8 B BIL 105 from Matter 4 BIL 105 from Matter 5 BIL 105 from Matter 6 4

5 itric xidative phosphorylatio n itric NAD xidative NAD+ S oa oa S oa S S oa oa S + Results Thus Far xidation of yruvate Keeping tally after each stage should help make sense of it all. : Starting Material Ending -source Energy (6) yruvates () s +4 s + NADs No produced; still 6 carbons present. ccurred in cytoplasm of cell outside mitochondria. Next step, oxidation of pyruvate, occurs inside mitochondria. yruvates must enter mitochondria. s produced in this stage produced by substrate-level, not chemiosmosis. Before the citric can begin yruvate must first be converted to acetyl oa, which links the to glycolysis Figure 9.10 yruv ate YTSL Transport protein 1 NAD oenzy me A MITNDRIN S o A Acetyle oa ne of pyruvate s carbons is oxidized to form. diffuses out of mitochondrion. rovides enough energy to reduce an NAD + to NAD. yruvate changed to acetyl group () when removed. Acetyl group binds with oenzyme A forming Acetyl o-a. After Acetyl o-a formed, further respiration can occur or fats can be synthesized. BIL 105 from Matter 7 BIL 105 from Matter 8 BIL 105 from Matter 9 itric /Krebs An overview of the citric yruvate (from glycolysis, molecules per glucose) Figure 9.11 BIL 105 from Matter 40 FAD NAD + FAD Acetyle oa itric oa oa oa AD + i NAD + NAD + Figure 9.1 FAD Malate Fumarate FAD Acetyl oa + 1 NAD + 8 xaloacetate 7 6 Figure 9.1 itrate Isocitrate 5 itric Succinate i GT GD Succinyl oa AD a-k etoglutarate BIL 105 from Matter 41 4 NAD + NAD + NAD + NAD Tally ontinues After pyruvate oxidation there ar less carbons and more NADs. : Starting Material Ending -source Energy roducts (6) yruvates () s +4 s + NADs xidation of yruvate: yruvates ( ) Acetyl o-a () + NADs Acetyl group from acetyl o-a enters a cyclic biopathway, Krebs the, to be further oxidized. BIL 105 from Matter 4 Krebs ycle Details Another Tally 1 trips through necessary because Acetyl o-a present. oa (Acetyl-oA) 4-carbon molecule (xaloacetate) 6- molecule (itrate) 4-carbon molecule itrate 5-carbon molecule NAD NAD BIL 105 from Matter 4 NAD FAD xaloacetate (Starting material) 4-carbon molecule After Krebs all s oxidized, only energy compounds left. : Starting Material Ending -compounds Energy (6) yruvates () s +4 s + NADs xidation of yruvate: yruvates ( ) Acetyl o-a () + NADs Krebs ycle: Acetyl o-a ( ) 4 +6 NADs + FAD s + s nly 4 s from glucose at this point. More s come from electron transport and chemiosmosis. BIL 105 from Matter 44 The electron transport chain asses electrons in a series of steps instead of in one explosive reaction Uses the energy from the electron transfer to form BIL 105 from Matter 45 5

6 xidative. electron transport and c hemiosmosis The athway of Electron Transport In the electron transport chain Electrons from NAD and FAD lose energy in several steps Electron Transport Details Free energy, G 1 / (from food via NAD) ontrolled + e release of energy for synthesis of Electron transport chain e Electrons in NAD and FAD passed to electron carrier molecules in enzyme complexes; protons pumped into intermembrane space. final electron acceptor, makes. No s yet, but proton gradient built up in intermembrane space. Figure 9.5 B 1 / (b) ellular respiration BIL 105 from Matter 46 BIL 105 from Matter 47 BIL 105 from Matter 48 hemiosmosis Details roton (+) gradient provides energy to bind phosphate group to AD. Entropy gained by + leaving concentrated area. yields: s from NAD. sfrom FAD. hemiosmosis: The Energy- oupling Mechanism synthase Is the enzyme INTERMEMBRANE SAE that actually A rmakes otor w ithin the + membrane spins clockw ise w hen f low s past it dow n the gradient. A s tator anchored in the membrane holds the knob stationary. A r od (for stalk ) extending into the knob also spins, activating catalytic sites in the knob. The resulting gradient Stores energy Drives chemiosmosis in synthase Is referred to as a proton-motive force Figure 9.14 AD + i MITNDRIAL MATRIX Three catalytic sites in the stationary knob join inorganic hosphate to AD to make. BIL 105 from Matter 49 BIL 105 from Matter 50 BIL 105 from Matter 51 Final Energy Tally Inner hemiosmosis and the electron transport chain Gly coly sis Intermembrane space Inner mitochondrial membrane Mitochondrial matrix rotein complex of electron carners NAD (arrying electrons from, food) I + Q II FAD III yt c IV NAD + FAD / Electron transport chain Electron transport and pumping of protons (), w hich create an gradient across the membrane AD + i Mitochondrial membrane hemiosmosis synthesis pow ered by the flow f back across the membrane synthase There are three main processes in this metabolic Electron shuttles YTSL MITNDRIN enterprise span membrane NAD or NAD xidativ e : Acetyl electron transport oa and chemiosmosis FAD NAD 6 NAD FAD itric yruvate about or 4 by substrate-level by substrate-level by oxidative, depending on w hich shuttle transports electrons from NAD in cytosol About Maximum per glucose: 6 or 8 All the energy from glucose that can be captured by cell has been gained. : Total s NAD 6 ( / NAD) xidation of yruvate: NAD 6 ( / NAD) Krebs ycle: 6 NAD 18 ( / NAD) FAD 4 ( / FAD ) Total 8 x 7.5kcal /mol = 70 kcal/mol Figure 9.15 xidative Figure 9.16 BIL 105 from Matter 5 BIL 105 from Matter 5 BIL 105 from Matter 54 6

7 The Versatility of atabolism About 40% of the energy in a glucose molecule Is transferred to during cellular respiration, making approximately 8 atabolic pathways Funnel electrons from many kinds of organic molecules into cellular respiration The catabolism of various molecules from food roteins Amino s arbohydrates Fats Sugars Glycerol Fatty s Gly ceraldehy de-- N yruvate Acetyl oa itric Figure 9.19 xidativ e BIL 105 from Matter 55 BIL 105 from Matter 56 BIL 105 from Matter 57 Biosynthesis (Anabolic athways) The body Uses small molecules to build other substances These small molecules May come directly from food or through glycolysis or the citric Regulation of ellular Respiration via Feedback Mechanisms ellular respiration Is controlled by allosteric enzymes at key points in glycolysis and the citric Feedback inhabition The control of cellular respiration Inhibits Fructose-6-phosphate Stimulates + hosphofructokinase Fructose-1,6-bisphosphate yruvate Acetyl oa AM Inhibits itrate itric Figure 9.0 xidativ e BIL 105 from Matter 58 BIL 105 from Matter 59 BIL 105 from Matter 60 During oxidative, chemiosmosis couples electron transport to synthesis NAD and FAD Donate electrons to the electron transport chain, which powers synthesis via oxidative an produce with or without oxygen, in aerobic or anaerobic conditions ouples with fermentation to produce Fermentation enables some cells to produce without the use of oxygen ellular respiration Relies on oxygen to produce In the absence of oxygen ells can still produce through fermentation BIL 105 from Matter 61 BIL 105 from Matter 6 BIL 105 from Matter 6 7

8 Types of Fermentation Fermentation consists of plus reactions that regenerate NAD +, which can be reused by glyocolysis In alcohol fermentation yruvate is converted to ethanol in two steps, one of which releases During lactic fermentation yruvate is reduced directly by NAD to form lactate as a waste product BIL 105 from Matter 64 BIL 105 from Matter 65 BIL 105 from Matter 66 Fermentation and ellular Respiration ompared Both fermentation and cellular respiration Use glycolysis to oxidize glucose and other organic fuels to pyruvate yruvate is a key juncture in catabolism YTSL No present Fermentation Ethanol or lactate yruvate present ellular respiration Acetyl oa MITNDRIN itric In the Absence of xygen is not readily available in all environments. ellular energy () is still needed. Two alternatives catabolic pathways can be used. Fermentation: occurs, but NAD transfers electrons to pyruvate BIL 105 from Matter 67 Figure 9.18 BIL 105 from Matter 68 BIL 105 from Matter 69 Fermentation Reactions Alcohol Fermentation: used in brewing and baking process involving yeast. yruvate ( ) + + NAD yruvate Ethyl Alcohol ( ) + + NAD + Lactate Fermentation: occurs in fungi, bacteria, and animals (if is absent) yruvate + + NAD yruvate Lactate ( ) + NAD + AD + 1 Ethanol (a) Alcohol fermentation NAD + NAD yruvate Acetaldehyde If electron transfer is not stepwise A large release of energy occurs As in the reaction of hydrogen and oxygen to form water + 1 / AD + 1 NAD + NAD Free energy, G Explosive release of heat and light energy (a) Uncontrolled reaction Lactate (b) Lactic fermentation Figure 9.17 Figure 9.5 A BIL 105 from Matter 70 BIL 105 from Matter 71 BIL 105 from Matter 7 8

9 Both glycolysis and the citric an generate by substrate-level Enzyme Enzyme hemiosmosis Is an energy-coupling mechanism that uses energy in the form of a gradient across a membrane to drive cellular work The Evolutionary Significance of ccurs in nearly all organisms robably evolved in ancient prokaryotes before there was oxygen in the atmosphere AD Substrate + Figure 9.7 roduct BIL 105 from Matter 7 BIL 105 from Matter 74 BIL 105 from Matter 75 9