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Transcript
Photosynthesis (briefly) and Cellular Respiration (aerobic respiration) • Capturing Energy • Sun is primary source of energy • Energy flows through life systems – Producers – Primary consumers – Secondary consumers • What this means… • On Land, most energy needs come from the plant kingdom • This energy originally comes from the sun • Photosynthesis converts the energy in sunlight into chemical energy (sugar) • Energy in the Cell • Photosynthesis transforms kinetic energy (light) into potential energy (chemical bonds in glucose) • Cellular respiration moves energy stored in glucose into ATP, which can be used for cellular work • Cellular Respiration • Think of what happens when you breathe – closely related to CR • Cellular Respiration and Gasses • Breathing brings O2 into the body • O2 is distributed to cells by the blood • In cellular respiration, mitochondria use O2 & glucose to generate ATP • In converting E (sugar -> ATP), heat is generated (2nd Law of Thermodynamics) • Breathing disposes of the waste product CO2 produced from cellular respiration • ATP – An Energy Carrier • Temporarily stores & transfers energy • ATP stores energy in phosphate bonds • Other Energy Carriers In Cells • NADP+ & NAD+ • Pick up electrons NADPH and NADH • Donate these electrons and energy • NAD+ shown • Aerobic respiration burns sugar • Electrons move from carbon in glucose to oxygen in water • Energy released rapidly as light and heat • Cellular Respiration • Electron movement is carefully controlled • Energy is released in small amounts; stored in ATP • Oxidation – Reduction Reactions • Oxidation: loss of electrons from an atom (or loss of a H atom from a molecule) • Reduction: addition of electrons to an atom (gain of a H atom to a molecule) – Think: reduction in CHARGE due to more e- • Always paired (one loses an e-, one gains) • What molecule gets OXIDIZED (loses e-)? • What molecule gets REDUCED (gains e-)? • Redox Reactions in Cellular Respiration • Glucose loses electrons (in H atoms) and becomes oxidized • Redox Reactions Continued • Glucose loses electrons (in H atoms) and becomes oxidized • O2 gains electrons (in H atoms) and becomes reduced • Along the way, energy is released • Cellular Respiration • Electrons are transferred to the coenzyme NAD+, which is converted to NADH – Is this oxidation or reduction? • NADH shuttles electrons in to another part of Cellular Respiration • Cellular Respiration: Big Picture • Electron transfer to NAD+ is the first step in an ELECTRON TRANSPORT CHAIN – Series of redox reactions – Pass from different carrier molecules eventually to O2 • Cellular Respiration • STEP 0: Eat to get glucose – Glucose is absorbed by cells in small intestine – Glucose enters the bloodstream and is transported to all the cells in your body – How is this different in a plant? • Cellular Respiration: Inside a Cell • STEP 1: Glycolysis • STEP 2: Prep. Step & Citric Acid Cycle • STEP 3: Oxidative Phosphorylation (Electron transfer chain) • Cellular Respiration • STEP 1: Glycolysis • Occurs in CYTOPLASM • Glucose is split into 2 molecules of pyruvate • 2 ATP and 2 NADH are made for each pyruvate • STEP 1: Glycolysis • STEP 1: Glycolysis Summary • Glucose is split into 2 three-carbon molecules called pyruvate (pyruvic acid) • 2 net ATP molecules are generated • Redox reaction generates 2 NADH • So far… • Glycolysis Prepatory Step Citric Acid (Krebs) Cycle • Mitochondria Structure • Two membranes – Outer membrane – Inner membrane • – Matrix inside the inner membrane – Intermembrane space • • Folded into cristae STEP 2: The Prepatory Step & the Citric Acid Cycle (TCA) In the prepartory step, Pyruvate (x2) is prepared for TCA cycle: – 1 Carbon atom released as CO2 – 1 NADH is made – Coenzyme A joins 2C which then enters TCA – STEP 2: The Citric Acid Cycle • Occurs inside matrix of MITOCHONDRIA • Completes breakdown of glucose to CO2 • Makes 1 ATP per pyruvate • Generates several NADH & FADH2 • STEP 2: Citric Acid Cycle • Also called TCA (The Citric Acid cycle) • Also called the Krebs Cycle • Note: There’s TWO pyruvates, so the TCA runs 2x!! • STEP 2: The Prep Step & TCA Summary • Completes oxidation of glucose: – Releases 3 CO2 molecules per pyruvate (1 fr/ Prep step) – Net yield/pyruvate – • 1 ATP, • 4 NADH (1 fr/ Prep step) • 1 FADH2 There are 2 pyruvates per glucose! • So far… • TCA Electron Transport Chain • Step 3: Electron Transport Chain • Complicated process, see my html page. • Step 3: Electron Transport Chain • Electrons passed down from NADH to ETC • H+ ions pumped inside inner mitochondrial membrane • Electrons passed down ETC to O2 which accepts electrons & 4H+ to become 2 H2O (decreases H+ inside) • So far… • Cellular Respiration Review • Occurs in all eukaryotes • Generates ATP • Involves oxidation – reduction reactions – Oxidation = loss of electron / H atom; charge is more positive – Reduction = gain of electron / H atom; charge is more negative • STEP 3: ETC Summary • Electons passed from NADH and FADH to proteins in ETC to O2 – • Transports H+ into inner membrane space in mitochondria creating a gradient – • STEP 3: ETC Summary Energy from H+ flowing downhill is stored in bond of ATP – • STEP 3: ETC Summary CHEMIOSMOSIS: H+ flowing (downhill) from high to low concentration releases KINETIC energy – • STEP 3: ETC Summary H+ gradient is POTENTIAL energy – • STEP 3: ETC Summary STEP 3: CHEMIOSMOSIS Generates majority of ATP (34) – Cellular Respiration Organizer • Cellular Respiration Animations • Cellular Respiration • Aerobic metabolism: three steps – Glycolysis, Citric Acid Cycle, & Oxidative Phosphorylation – Releases LOTS of energy – typically 36 ATP per molecule of glucose