Energy & Metabolic Pathways 1

ATP Redox Electron Carriers 2

ATP What’s the Big Deal? What is ATP? How Do Cells “Run” on ATP? How Do Cells Make ATP? 3

ATP: What’s the Big Deal? Life = endergonic Organisms … 1.Require energy input Plants—sunlight Animals—food 2.Use this energy to maintain life Build & repair Reproduce Evidence? Without sunlight (plants) or food (animals), organisms die 4 P R EAEA ΔGΔG G Time Life

ATP: What’s the Big Deal? Where does ATP fit into this? Analogy: Just as … Vehicles run on Gasoline Household appliances run on Electricity Cells? How would this look on energy graph? Conclusion: 5 Life P R EAEA ΔGΔG G Time ATP ATP = general form of energy that cells use to maintain endergonic “lifestyle” run on ATP

ATP: What’s the Big Deal? Another analogy: ATP = energy “currency” of cell What does this mean? $, Electricity, ATP = all easily convertible $ = wealth Electricity = energy ATP = energy for cells 6 Food/Sunlight  ATP  Growth/Reproduction Work  $  Make Purchases Coal/Oil/Gas  Electricity  Run Machines Energy Flow Convert … To … To …

ATP: What’s the Big Deal? So … what’s the big deal? ATP is fundamental to life All cells run on ATP Without ATP, there is no life! OK, so ATP is important What, exactly, is ATP? 7

ATP What’s the Big Deal? What is ATP? How Do Cells “Run” on ATP? How Do Cells Make ATP? 8

ATP: What is ATP? What does ATP stand for? Biological molecule class: Monomer: What is a Nucleotide? Phosphate 5-Carbon Sugar Nitrogenous Base What is ATP? Nucleotide Nucleic Acid Adenosine Triphosphate 3 parts Nucleotide 9

ATP What’s the Big Deal? What is ATP? How Do Cells “Run” on ATP? How Do Cells Make ATP? 10

ATP: How Do Cells “Run” on ATP? We know … Life = endergonic ATP supplies energy to “run” endergonic “lifestyle” If ATP supplies energy, then ATP molecule must … Contain energy Transfer energy to endergonic reactions 3 questions: 1.Where is energy in ATP molecule? 2.How is energy in ATP released? 3.How is energy transferred to endergonic reactions to make them “run”? 11 Life P R EAEA ΔGΔG G Time ATP

ATP: How Do Cells “Run” on ATP? Energy! 1.Where is energy in ATP molecule? In bonds between phosphates How is energy stored here? (Hint: look at the 2 P i below) What do you notice? Phosphates negative How does this explain how energy stored? 3 repel each other To force 3 close together requires energy Covalent bond between holding these ions together contains this energy P P P P ( ) P 12

ATP: How Do Cells “Run” on ATP? 2.How is energy in ATP released? What do you notice? Bonds between broken by hydrolysis Energy released ATP hydrolysis ADP + P i + energy P P 13

ATP: How Do Cells “Run” on ATP? Can represent on energy graph … Graph: Include: axes labels, Reactants, Products, E A, Δ G Reaction = endergonic / exergonic Δ G = + / – Reaction = spontaneous / not spontaneous On graph, what represents energy ATP supplies to endergonic reaction to make it run? ATP hydrolysis ADP + P i + energy ADP + P i ATP EAEA ΔGΔG G Time 14 ΔGΔG

ATP: How Do Cells “Run” on ATP? We know: Can update our graph … 15 P R EAEA ΔGΔG G Time ADP + P i ATP Life P R EAEA ΔGΔG G Time ATP ATP hydrolysis ADP + P i + energy Life ↓ energy ↑ energy Energy transferred from ATP to R

ATP: How Do Cells “Run” on ATP? 3.How is energy transferred to endergonic reactions to make them “run”? Use energy graphs … G Time R P +  Couple Endergonic Reaction with ATP hydrolysis (= Exergonic) Overall reaction = Exergonic ATP ADP, P i Time R, ATP P, ADP, P i Time P R EAEA ΔGΔG G ADP + P i ATP Endergonic Reaction ATP Hydrolysis Coupled Reaction 16

ATP: How Do Cells “Run” on ATP? Example ATP making endergonic reaction “run” Label concentrations What process is occurring? How can you tell? Na + & K + moving up their gradients ATP supplying energy 17 ↑ [Na + ] ↓ [Na + ] ↓ [K + ] ↑ [K + ] Active Transport What is actually happening? How is energy from ATP moving ions up their gradients? Inside Cell Outside Cell ↓ energy ↑ energy Transport protein

ATP: How Do Cells “Run” on ATP? What do you notice? Na + moves out, up gradient K + moves in, up gradient ATP transfers P i to transport protein Transport protein changes shape What can you conclude? Energy in ATP transferred with P i Energy causes protein to change shape Shape change allows ions to move up their gradients 18 ↑ [Na + ], ↓ [K + ] ↓ [Na + ], ↑ [K + ] Transport Protein Outside Cell Membrane Inside Cell

ATP What’s the Big Deal? What is ATP? How Do Cells “Run” on ATP? How Do Cells Make ATP? 19

ATP: How Do Cells Make ATP? Average human Mass: 62 kg ( g) Amount of ATP: 51 g (0.08%) Amount of ATP used per day: kg ( g), about 2X body mass! What do you notice? You have very little ATP but use a HUGE amount every day How is this possible? ATP recycled Reverse reaction occurs also ADP + P i  ATP We know … 20 ATP hydrolysis ADP + P i + energy ADP + P i ATP EAEA ΔGΔG G Time ADP + P i ATP EAEA ΔGΔG G Time

ATP: How Do Cells Make ATP? Remember, we said … Life = endergonic Organisms … 1.Require energy input Plants—sunlight Animals—food 2.Use this energy to maintain life Build & repair Reproduce Where does energy to make ATP come from? How would this look on the graph? 21 P R EAEA ΔGΔG G Time Life Food or Sunlight Food/ Sunlight

ATP: How Do Cells Make ATP? Consider food Burn food Releases energy Capture energy to make ATP Can represent on energy graph Conclusion: Couple reactions so energy Released from burning food added to ADP + P i to synthesize ATP Overall reaction = exergonic 22 + O 2 CO 2 + H 2 O Food (carbs, fats) Energy ADP + P i ATP +  Coupled Reaction Time ADP, P i, Food, O 2 ATP, CO 2, H 2 O ATP ADP, P i Time ATP Synthesis Time Food, O 2 CO 2, H 2 O Burn Food G

ATP: Overview Covered 2 reactions: ATP  ADP + P i + energy ADP + P i + energy  ATP Both reactions occur in cycle Here, emphasis on ATP Shift focus to surrounding reactions 23 ATP ADP + P i Energy released to drive endergonic reaction Energy absorbed from food/sunlight to synthesize ATP Exergonic Endergonic High Energy Low Energy

ATP: What’s the Big Deal? Another analogy: ATP = energy “currency” of cell 24 Food/Sunlight  ATP  Growth/Reproduction Work  $  Make Purchases Coal/Oil/Gas  Electricity  Run Machines Energy Flow Convert … To … To …

ATP: Overview Energy output from catabolic reactions Energy input to anabolic reactions ATP connects reactions, shuttling energy from catabolic to anabolic pathways CO 2, H 2 O Food, O 2 EAEA G Time ΔGΔG 25 P R EAEA ΔGΔG Time Catabolism: Exergonic Reactions Anabolism: Endergonic Reactions ADP + P i ATP Food/Sunlight  ATP  Growth/Reproduction

If ATP captures & holds energy, why don’t organisms use ATP for energy storage? What molecules do cells use for energy storage? Carbohydrates (polysaccharides) Lipids (fats) Why not use ATP? Not stable Only useful for short-term storage (immediate energy transfer) How much ATP do you use per day? Twice your mass! ATP: Overview 26

Energy & Metabolic Pathways ATP Redox Electron Carriers 27

Redox: What is it? Oxidation/Reduction How to identify oxidation & reduction? Oxidation Loss of electrons Often: gain of O / loss of H Reduction Gain of electrons Often: gain of H / loss of O How to remember oxidation & reduction? OIL—Oxidation Is Loss (of electrons) RIG—Reduction Is Gain (of electrons) 28

Redox: How does it work? Oxidation & Reduction = coupled reactions 1 atom loses an e - (= ) Another atom gains e - (= ) NaCl = ionic compound Define: But organisms made of covalent compounds Define: Do redox reactions occur in covalent compounds? oxidation reduction Na Na + Cl Cl - e-e- Na is gaining / losing e - oxidized / reduced Cl is gaining / losing e - oxidized / reduced 29 ionic bond Atoms gain/lose electrons = Redox Reaction Atoms share electrons

Redox: Does it occur in reactions with covalent compounds? Add electrons What do you notice? 1.Bonds Reactants = nonpolar covalent Products = polar covalent 2.Redox C, H losing electrons = oxidation O gaining electrons = reduction Conclusion: Covalent compounds undergo redox reactions 30 nonpolar covalent bonds polar covalent bonds O gaining e - = reduction H losing e - = oxidation C losing e - = oxidation Reactants Products methane

Redox: Is redox related to energy? Burning methane releases energy Energy release related to redox? What do you notice? Nonpolar covalent bond = high energy e - Polar covalent bond = low energy e - As e - transition from nonpolar to polar covalent bond e - lose energy Energy released Energy lost from system How much energy released? Conclusion: energy C H C O Time G nonpolar covalent bond polar covalent bond high energy e - low energy e - = electron Energy changes in reactions are related to redox 31 CH 4 + 2O 2  CO 2 + 2H 2 O + energy covalent bond energy in bond ΔGΔG ΔGΔG

Energy & Metabolic Pathways ATP Redox Electron Carriers 32

Electron Carriers: What are they? Compounds that transfer (“carry”) e - from 1 compound to another compound Ex. NAD + (nicotinamide adenine dinucleotide; main electron carrier in cellular respiration) (Neither full name nor structure required … whew!) 33

Electron Carriers: How do they carry electrons? Equation: NAD +  NADH How are electrons carried? Look at how get from NAD + to NADH Add H, but H (or H 2 ) not present, only H + ; Result? But want NADH, not NADH 2+ ; How to fix? Add 2 e - ; Result? Overall reaction? Is NAD + being oxidized or reduced? How do you know? Gaining 2 e - /Gaining H, so reduced Which compound carrying electrons, NAD + or NADH ? Another way to look at this reaction NAD + + H +  NADH 2+ NADH + 2e -  ( ) Summary: NAD + + H + + 2e -  NADH NAD + NADH H e - oxidation reduction 34

Electron Carriers: How do they carry electrons? Let’s look at actual compound Relevant portions shaded What do you notice when NAD +  NADH? Added H + & 2 e - New covalent bond (attached to H) Where are electrons “carried”? In new covalent bond (Remember: 1 covalent bond = 2 e - ) Are these low or high energy electrons? How can you tell? High energy because 2 e - in nonpolar covalent bond Remember: vertices = C, so C—H bond new covalent bond Summary: NAD + + H + + 2e -  NADH 35