* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download cellular respiration - wlhs.wlwv.k12.or.us
Survey
Document related concepts
Mitochondrion wikipedia , lookup
Basal metabolic rate wikipedia , lookup
Metalloprotein wikipedia , lookup
Nicotinamide adenine dinucleotide wikipedia , lookup
NADH:ubiquinone oxidoreductase (H+-translocating) wikipedia , lookup
Phosphorylation wikipedia , lookup
Photosynthesis wikipedia , lookup
Evolution of metal ions in biological systems wikipedia , lookup
Microbial metabolism wikipedia , lookup
Electron transport chain wikipedia , lookup
Adenosine triphosphate wikipedia , lookup
Photosynthetic reaction centre wikipedia , lookup
Biochemistry wikipedia , lookup
Light-dependent reactions wikipedia , lookup
Transcript
NOTES: Ch 9 Cellular Respiration: Harvesting Chemical Energy Part 1: The Overview Overview: Life Is Work ● Living cells require energy from outside sources ● Some animals, such as the giant panda, obtain energy by eating plants; others feed on organisms that eat plants ● Energy flows into an ecosystem as sunlight and leaves as heat ● Photosynthesis generates oxygen and organic molecules, which are used in cellular respiration ● Cells use chemical energy stored in organic molecules to regenerate ATP, which powers work Light energy ECOSYSTEM Photosynthesis in chloroplasts Organic + O molecules 2 CO2 + H2O Cellular respiration in mitochondria ATP powers most cellular work Heat energy 9.1 - Catabolic Pathways & Production of ATP: ● The breakdown of organic molecules is EXERGONIC ● Fermentation is a partial degradation of sugars that occurs without oxygen ● Cellular respiration consumes oxygen and organic molecules and yields ATP Principles of Energy Harvest ● Although carbohydrates, fats, and proteins are all consumed as fuel, it is helpful to trace cellular respiration with the sugar glucose: Chemical Equation: C6H12O6 + 6O2 6CO2 + 6H2O + Energy (ATP + heat) Recall: the ATP cycle Redox Reactions: Oxidation and Reduction ● The transfer of electrons during chemical reactions releases energy stored in organic molecules ● This released energy is ultimately used to synthesize ATP ● REDOX REACTIONS: involve electron transfers from 1 substance to another The Principle of Redox ● OXIDATION: loss of electrons (“energy releasing”) ● REDUCTION: gain of electrons (“energy storing”) Example of Redox: Oxidation (loss of electrons) Na + Cl Na+ Reduction (gain of electrons) + Cl- ● The electron donor is called the reducing agent ● The electron receptor is called the oxidizing agent Example of Redox: Na is oxidized; it is the reducing agent Na + Cl Na+ + Cl is reduced; it is the oxidizing agent Cl- Oxidation of Organic Fuel Molecules During Cellular Respiration: ● During cellular respiration, the fuel (such as glucose) is oxidized and oxygen is reduced: Respiration: oxidized C6H12O6 + 6O2 6CO2 + 6H2O reduced *the transfer of electrons from 1 element to another, more electronegative element (e.g. from H to O) releases stored potential energy - - this chemical energy can be put to work! ● Glucose & other fuels are broken down gradually, in a series of steps ● at key steps, H atoms are stripped from glucose and passed to a coenzyme: NAD+ – (this is performed by enzymes: dehydrogenase) NAD+ + 2H NADH + H+ Stepwise Energy Harvest via NAD+ and the Electron Transport Chain ● As an electron acceptor, NAD+ functions as an oxidizing agent during cellular respiration ● Each NADH (the reduced form of NAD+) represents stored energy that is tapped to synthesize ATP 2 e– + 2 H+ NAD+ 2 e– + H+ H+ NADH Dehydrogenase + 2[H] (from food) Nicotinamide (oxidized form) + Nicotinamide (reduced form) H+ ● Respiration uses an ELECTRON TRANSPORT CHAIN to break the fall of electrons into several energyreleasing steps (instead of one explosive reaction) e- ● NADH passes the electrons to the electron transport chain ● Oxygen pulls electrons down the chain in an energy-yielding tumble ● The energy yielded is used to regenerate ATP H2 + 1/2 O2 + 2H 1 /2 O2 1/2 O2 (from food via NADH) Explosive release of heat and light energy Free energy, G Free energy, G 2 H+ + 2 e– Controlled release of energy for synthesis of ATP ATP ATP ATP 2 e– 2 H+ H2O Uncontrolled reaction H2O Cellular respiration ELECTRON TRANSPORT CHAIN: ● consists of molecules, mostly proteins, built into the inner membrane of mitochondria ● NADH carries the electrons to the “top” of the chain ● oxygen captures electrons at the “bottom” of the chain and combines with H+, forming water. Reduction of oxygen! SUMMARY OF ENERGY FLOW IN THE CELL: Food NADH E.T.C. oxygen (glucose) **oxygen is the final electron acceptor! The Stages of Cellular Respiration: A Preview ● Cellular respiration has three stages: 1) Glycolysis (breaks down glucose into two molecules of pyruvate) 2) The Citric Acid Cycle, a.k.a. Krebs Cycle (completes the breakdown of glucose) 3) E.T.C. & Oxidative phosphorylation (accounts for most of the ATP synthesis) Glycolysis Pyruvate Glucose Cytosol Mitochondrion ATP Substrate-level phosphorylation Glycolysis Pyruvate Glucose Cytosol Citric acid cycle Mitochondrion ATP ATP Substrate-level phosphorylation Substrate-level phosphorylation Electrons carried via NADH and FADH2 Electrons carried via NADH Glycolysis Pyruvate Glucose Cytosol Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis Mitochondrion ATP ATP ATP Substrate-level phosphorylation Substrate-level phosphorylation Oxidative phosphorylation ATP Synthesis: ● The process that generates most of the ATP is called oxidative phosphorylation because it is powered by redox reactions ● Oxidative phosphorylation accounts for almost 90% of the ATP generated by cellular respiration ATP Synthesis: ● A small amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation Enzyme Enzyme ADP P Substrate + Product ATP