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UNIT 2 Lecture 6 Metabolism Unit 2: Life’s Energy Sources and Conversions • Metabolism • Cellular Respiration: Sugar ATP • Photosynthesis: Light Sugar Key Themes • Energy acquisition & conversions in metabolism The Molecules of Life Structure-Function Relationship Life’s Energy Conversions Metabolism An organism’s metabolism is the total of the organism’s chemical reactions •Two types of reactions: – Big molecule Several small molecules • Releases energy – Small molecules • Requires energy Big molecule Metabolism An organism’s metabolism is total of the organism’s chemical reactions •Two types of reactions: – Big molecule Several small molecules • Releases energy • This sounds like: a) Cellular respiration b) Photosynthesis c) Neither Order and Chaos Energy Nature “wants” to be random/chaotic Energy Mydesigningsolutions.com; bedroomdisaster.blogspot.com; fritolay.com; slashfood.com Order and Chaos A complex, ordered molecule Energy Several small, disordered molecules Nature “wants” to be random/chaotic A complex, ordered molecule Energy Mydesigningsolutions.com; bedroomdisaster.blogspot.com; fritolay.com; slashfood.com Several small, disordered molecules CO2 Glucose Requires Energy Releases Newenergyandfuel.com; ualberta.ca; all-water.org H2O Fig. 8-6 Reactants Energy Amount of energy released Energy Products Progress of the reaction (a) Energy-releasing reactions Products Energy Amount of energy required Energy Reactants Progress of the reaction (b) Energy-requiring reactions Fig. 9.2 Light Ecosystem energy energy flow ECOSYSTEM ATP Photosynthesis in chloroplasts Organic + O CO2 + H2O 2 molecules Cellular respiration in mitochondria ATP ATP then powers cellular work Heat energy 1. Be able to link producers and consumers via cycles of energy and carbon flow Light energy ECOSYSTEM ATP Photosynthesis in chloroplasts Organic + O CO2 + H2O 2 molecules Cellular respiration in mitochondria ATP Fig. 9.2 Energy flow in ecosystems ATP then powers cellular work Heat energy 1. Be able to link producers and consumers via cycles of energy and carbon flow Light energy ECOSYSTEM ATP Photosynthesis in chloroplasts Organic + O CO2 + H2O 2 molecules Cellular respiration in mitochondria ATP Fig. 9.2 Energy flow in ecosystems ATP then powers cellular work Heat energy Chaos = Entropy CO2 Glucose H2O Requires Energy Releases Low Entropy System (less random, more ordered) High Entropy System (more random, less ordered) Newenergyandfuel.com; ualberta.ca; all-water.org CO2 Glucose Requires Energy Releases Potential energy is stored in chemical bonds (C-H especially) Newenergyandfuel.com; ualberta.ca; all-water.org H2O Heat Chemical energy CO2 + H2O Cells’ ability to store energy in chemical bonds is what makes organisms and ecosystems function Heat Chemical energy CO2 + H2O Cells’ ability to store energy in chemical bonds is what makes organisms and ecosystems function Without photosynthesis… There is no way to convert light energy into chemical energy Heat Chemical energy CO2 + H2O What about cellular respiration? Without cellular respiration: A. Nothing could live B. No animals could live C. Nothing nonphotosynthetic could live D. Everything could live Where does energy go? Where does energy go in an ecosystem? • Heat, growth, reproduction, etc. Heat Heat Heat Heat Trophic levels: Energy Flow Through Ecosystem http://www.britannica.com/EBchec ked/media/15/Transfer-of-energythrough-an-ecosystem 5 minute break A cell (in any organism) constantly performs work that requires energy: Energy for all cellular work is provided by the same energy-rich compound: ATP (adenosine triphosphate) Fig. 8.8 ATP ATP consists of three phosphate groups, a sugar, and a nitrogenous base. What does that sound like? A) a triglyceride B) a nucleotide C) a phospholipid D) a trisaccharide Each nucleotide is composed of: a monosaccharide sugar, a phosphate group, and a (N-containing) nitrogenous base Nitrogenous base A = adenine A + Ribose = adenosine adenosine mono-phosphate (AMP) adenosine di-phosphate (ADP) adenosine tri-phosphate (ATP) Phosphate Sugar group (b) Nucleotide Fig. 5.27 Fig. 8.8 ATP takes the energy released from the breakdown of energy-rich food molecules and does cellular work Energy loaded onto ATP Energy from breakdown of energy-rich molecules ATP + H2O Fig. 8.12 Energy released from ATP Energy for cellular work ADP + P i Fig. 8-9 P P P Adenosine triphosphate (ATP) H2O Pi + Inorganic phosphate P P + Adenosine diphosphate (ADP) Energy ATP: Energy carrier Higher Energy Fig. 8.8 “Phosphorylated” (=energized!) molecule + Lower Energy High-energy P transferred to motor proteins for mechanical work ADP + ATP P Vesicle Cytoskeletal track i ATP Motor protein Protein moved ATP transfers phosphate group to motor protein (phosphorylated motor protein = energized) Fig. 8.11 (b) See Campbell Figures 50.27 & 50.29 for additional details on muscle contraction. High-energy P transferred to transport proteins for transport work Membrane protein (Na+/K+ pump) P Na+ P i Na+ moved uphill ADP ATP Fig. 8.11 (a); see also Fig. 7.16 for more detail + P i Na+/K+ Pump Na+ ATP K+ • Cells want to pump Na+ out • Cells want to pump K+ in 8. Be able to apply the principal features and functions of an ATP-fueled ion pump to the Na+/K+ pump Active transport and the sodium-potassium pump Both Na+ and K+ are moved AGAINST their concentration gradient See Fig. 7.16 for a six panel, blow-by-blow description of the sodium-potassium pump. http://www.colorado.edu/ebio/genbio/07_16ActiveTransport_A.html http://onlinephys.com/circuit1.html Fig.8.7 http://onlinephys.com/circuit1.html Cotransport: Using potential energy Na+ ATP fuels the Na+/K+ pump Na+ accumulates “on top of the hill” (against its concentration gradient) Na+ flows downhill again ATP Releasing useful energy Cotransport: Using potential energy Na+ ATP fuels the Na+/K+ pump Na+ accumulates “on top of the hill” (against its concentration gradient) POTENTIAL ENERGY Na+ flows downhill again ATP Releasing useful energy 35 Cotransport: Using potential energy This potential energy can be used… To transport other molecules AGAINST their concentration gradient The Na+ gradient built up by the Na+/K+ pump also fuels the secondary active transport of glucose (& other substances) AGAINST their concentration gradient In Na+/glucose co-transport, Na+ flows back downhill & drags glucose uphill AGAINST its concentration gradient What provides the energy for the uphill transport of Na+ against its concentration gradient? A)No energy is needed. B)the Na+/K+ transport protein itself C)ADP and Pi D)ATP What provides the energy for the Na+/glucose cotransporter? A)No energy is needed. B)the Na+ gradient C)ATP as a direct energy source D)ATP as an indirect energy source E)B and D High-energy P transferred to transport proteins for transport work Membrane protein (Na+/K+ pump) P Na+ P i Na+ moved uphill ADP ATP + Fig. 8.11 (a); see also Fig. 7.16 for more detail 41 P i High-energy P transferred to reactant molecules for chemical work (ATP adds phosphate group to glutamic acid, making it less stable.) P + Glu ATP Glu + ADP NH2 (Ammonia displaces phosphate group, forming the amino acid glutamine.) Fig. 8.10 (b) P Glu + NH3 + P Glu i Summary: To stay alive, living cell performs 3 kinds of work that require energy: 1. Mechanical work 2. Transport work 3. Chemical work Energy for all 3 types of work provided by: ATP (adenosine triphosphate) • ATP is too unstable to serve as an actual storage form of energy. • Therefore, C-H bonds in macromolecules (e.g. sugars) are instead used for energy storage. Since ATP is too unstable, C-H bonds in sugars are used for energy storage. Converts solar energy to ATP and uses ATP to make sugars Photosynthesis: Light (energy) CO2 + H20 ATP Sugar [CH2O]x + O2 ATP Respiration: Converts the energy of sugars back to ATP as needed. Hank’s crash course in ATP 0-3:30 http://www.youtube.com/watch?v=00jbG_cfGuQ&feature=relmfu Key Themes (2) “Think Like a Biologist”: Understand What Life Is. “Unity” of life: What are common features of eukaryotes? Energy conversions: Sugar breakdown & mitochondrial ATP formation Fig. 9.1 Respiration Food-to-Energy Fig. 8.3 Cellular respiration breaks down energy-rich molecules to CO2 & water, extracting their energy. Light energy ECOSYSTEM Low energy Photosynthesis in chloroplasts CO2 + H2O Cellular respiration in mitochondria Organic+ O molecules 2 High energy C-H bond! ATP ATP powers most cellular work Heat energy “burned” with O2 to form H2O + CO2 Fig. 9.2 Since ATP is too unstable, C-H bonds in sugars are used for energy storage. Converts solar energy to ATP and uses ATP to make sugars Photosynthesis: Light (energy) CO2 + H20 ATP Sugar [CH2O]x + O2 ATP Respiration: Converts the energy of sugars back to ATP as needed. Today’s Exit Ticket • In a few sentences: – Describe energy-releasing and energyrequiring reactions. – Use the creation and use of ATP for cellular work as examples of these reactions. – Be sure to use the word “entropy.”