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What is cellular metabolism?
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It is the sum of all chemical reactions that take place in the cell
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What are these reactions generally categorized as?
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Anabolic or catabolic
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Which requires energy?
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Anabolic requires energy
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What does it involve?
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It is the biosynthesis of complex organic compounds from simpler molecules
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What is catabolism?
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It releases energy as they break down complex organic compounds into smaller molecules
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What are autotrophic organisms?
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They convert sunlight into bond energy
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What is an example?
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Green plants
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What type of bond energy is sunlight converted into?
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It is converted into the bond energy in the bonds of organic compounds like glucose
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When does this occur?
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During the anabolic process of photosynthesis
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Because of this, what do autotrophs not need?
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They do not need an exogenous supply of organic compounds
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What are heterotrophic organisms?
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They obtain their energy catabolically, via the breakdown of organic nutrients that must be ingested
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What is the net reaction of photosynthesis?
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6CO2 + 6H20 + Energy à C6H12O6 + 6O2
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Why do heterotrophic organisms metabolize glucose and other organic molecules?
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They do it to release the stored bond energies
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What is the net reaction of glucose catabolism?
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C6H12O6 + 6O2 à 6CO2 + 6H20 + Energy
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What is interesting about this reaction?
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It’s basically the backward reaction of Photosynthesis!
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What are some of the various molecular carriers used to shuttle energy between reactions?
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ATP is one of them, along with the coenzymes NAD+, NADP+, and FAD
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What is ATP?
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Adenosine triphosphate is the cell’s main energy currency
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What happens through its formation and degradation?
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Cells have a quick way of releasing and storing energy
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How is ATP synthesized?
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It occurs during glucose catabolism
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What is ATP composed of?
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It has the nitrogenous base adenine, the sugar ribose, and three weakly linked phosphate groups
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Where is the energy of ATP stored?
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In the covalent bonds attaching the phosphate groups
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What are they often referred to as?
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High-energy bonds
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What does hydrolysis of ATP to ADP and Pi release?
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It releases stored bond energy that the cell can use in metabolic processes
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How many kcal of energy are released per mole of ATP?
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Approximately 7kcal of energy
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What does this energy provide for?
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Endergonic (endothermic) reactions such as muscle contraction, motility, and the active transport of substances across plasma membranes
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What can ATP be hydrolyzed into?
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AMP and PPi
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What do ADP and Pi combine to form?
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ATP
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What is the purpose of this?
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To regenerate its ATP supply
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Does this process require energy?
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Yes
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Where does the necessary input of energy come from?
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It comes from the degradation of glucose
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What is a second mechanism by which the cell stores chemical energy?
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It stores energy in the form of high potential electrons
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What are electrons transferred as?
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Hydride ions (H:-) or as pairs of hydrogen atoms
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What happens during glucose oxidation?
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Hydrogen atoms are removed
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What happens to these hydrogen atoms?
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They are accepted by NAD+, FAD, and NADP+
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What do these molecules do?
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They transport the high-energy electrons of the hydrogen atoms to a series of carrier molecules on the inner mitochondrial membrane
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What are the carrier molecules known as?
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The electron transport chain
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What is oxidation?
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It is the loss of an electron
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What are NAD+, NADP+, and FAD referred to as?
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Oxidizing agents
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Why?
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Because they cause other molecules to lose electrons and undergo oxidation
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In the process what do they themselves undergo?
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Reduction
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What does this mean?
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They gain electrons
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What do NADH, NADPH, and FADH2 all behave as?
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Reducing agents
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What does NADH transfer its electrons to?
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Another electron acceptor, thereby reducing it, and in the process NADH is oxidized back to NAD+
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So, what do these coenzymes ultimately do?
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They temporarily store and release energy in the form of electrons through their successive oxidations and reductions
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What are the two stages of the degradative oxidation of glucose?
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Glycolysis and cellular respiration
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What is the first stage of glucose catabolism?
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Glycolysis
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What is glycolysis?
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A series of reactions that lead to the oxidative breakdown of glucose into two molecules of pyruvate
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What else is produced besides pyruvate?
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ATP
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What is reduced?
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NAD+ becomes NADH
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Where do all of these reactions take place?
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In the cytoplasm
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