Biology I Chapter 8 MY notes
Biology I Chapter 8 MY notes BSC 2010
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This 3 page Class Notes was uploaded by Marla Notetaker on Saturday October 8, 2016. The Class Notes belongs to BSC 2010 at University of South Florida taught by Dr Daniel in Summer 2015. Since its upload, it has received 24 views. For similar materials see Cellular processes in Biology at University of South Florida.
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Date Created: 10/08/16
Chapter 8 – An introduction to Metabolism Yellow: Vocabulary GREE: Key concepts Concept 8.1 Metabolism: all the chemical reactions undergoing in a living system I. Organization of the Chemistry of Life into Metabolic Pathways Metabolic pathways: some molecule triggers a first reaction which will trigger another ones Catabolic pathways: degradation of a molecule. o Cellular respiration: glucose is broken down. Anabolic (biosynthetic) pathways: build up molecule. Bioenergetics: “study of how energy flows through living organisms” II. Forms of Energy Energy: capacity to cause change Kinetic energy: movement o Thermal energy: movement of particles o Heat: the transfer of thermal energy... entropy Potential energy: stored energy (inanimate object) o Chemical energy: “term used by biologists to refer to the potential energy available for release in a chemical reaction” III. The Law of Energy Transformation Thermodynamics: “study of energy transformations” o Isolated system: matter nor energy can go in or out of the system o Open system: matter and energy CAN go in and out of the system o Closed system: Energy can come into the system but matter CANNOT a. The 1 Law of Thermodynamics Energy cannot be created nor destroyed, only transferred b. The 2 law of Thermodynamics Whenever energy is transferred heat is lost to the system, increasing entropy, the “disorder” in the system Spontaneous process: process that requires no energy to be done Nonspontaneous process: more likely requires energy to be done Universe: system + surrounding Concept 8.2 I. FreeEnergy Change ΔG Free energy (ΔG): energy in the that can be used to do work Enthalpy (ΔH): Heat in the system ∆ G=∆H−T ∆S o Change in Entropy (ΔS) o Temperature in Kelvin (K) o Processes with NEGATIVE ΔG are spontaneous II. Free Energy, Stability, and Equilibrium’ ∆ G=∆G final state initialstate The HIGHER the ΔG the more UNSTABLE the system is (p. 146) o This usually makes them change for it to LOWER the ΔG = more STABLE Equilibrium: the forward and backward reaction occur at the same rate If there is NO equilibrium ΔG increases. Changing the equilibrium would require energy, which wouldn’t be a spontaneous reaction which means ΔG is POSITIVE. “A process is spontaneous and can perform work only when it is moving TOWARDS equilibrium” III. Free Energy and Metabolism a. Exergonic and Endergonic Reactions in Metabolism Exergonic (exothermic): releases free energy…. ΔG is NEGATIVE…spontaneous o The more – ΔG the more work can be done Endergonic (endothermic) absorbs free energy… ΔG is POSITIVE… nonspontaneous b. Equilibrium and Metabolism When the reaction reaches equilibrium there is NO work… therefore if a cell cannot do WORK it is DEAD Concept 8.3 Types of work a cell does: Chemical work: “pushing of endergonic reactions that would not occur spontaneously Transport work: passive transport of chemicals across membranes Mechanical work: “muscle contraction” Energy coupling: using the energy created by an exergonic reaction (which released energy) for an endergonic reaction (which TAKES energy). I. The Structure and Hydrolysis of ATP Adenosine Triphosphate (ATP) : basic unit of energy Components: o Sugar ribose o Adenine nitrogenous base o 3 Phosphates Adenosine diphosphate (ADP): when inorganic phosphate is broken down (by hydrolysis) Why does ATP holds so much energy? o The Phosphates are negatively charged (ALL of them) and same charges repel and since all of them are negative it takes a lot of energy to keep them together, so when they are broken down by hydrolysis they release all that energy II. How the Hydrolysis of ATP Performs Work? Heat is not sufficient to drive the work necessary by the cell During ATP hydrolysis the cell tries to do everything necessary by coupling Use the energy of ATP hydrolysis (exergonic) to perform the others (endergonic) Phosphorylation: o Activate a molecule (reactant probably) with a phosphate o Said phosphate comes from the ATP hydrolysis o Phosphorylated intermediated: “recipient molecule with the phosphate group covalently bonded to it Motor proteins: ATP binds to it to move it and once it hydrolyses ANOTHER ATP binds III. The Regeneration of ATP The ATP cycle: ATP by hydrolysis goes to ADP and then by phosphorylation back to ATP Concept 8.4 Enzymes: act as a catalysis in reactions to speed them up I. The Activation Energy Barrier Activation energy (E )A the amount of energy needed to break up the bond… energy that needs to get absorbed to “agitate” the bond and make it break (up lift) Transition state: peak of the graph where there is enough energy but it’s not broken yet II. How Enzymes Speed Up Reactions: They lower the Activation Energy of the reaction III. Substrate Specify of Enzymes Substrate: reactant which hooks up with the enzyme EnzymeSubstrate Complex: when the substrate actually going INTO the enzyme Most enzymes end with –ase Enzymes are very specific because most enzymes are proteins and with proteins (amino acids) shape determines function so only a specific reactant would fit in the active site Active Site: specific part of the enzyme that can accept the substrate Induced Fit: when the enzyme closes tightly around the substrate IV. Effects of Local Condition on Enzyme Activity What can affect an enzyme? o Temperature o pH a. Effects of Temperature and pH As the temperature increases the reaction will occur faster because “substrates collide with active sites more frequently” o TOO HIGH temperature can denature the protein o Most proteins in the human body have an optimal temperature of 35 – 40*C Most have an optimal pH of about 68 o Exceptions like digestive enzymes in the stomach of pH 2 b. Cofactors Help with the catalysis…. They are NOT proteins Cofactors (Inorganic) Coenzymes (Organic) – vitamins c. Enzyme Inhibitors If the inhibitor binds to the enzyme with a covalent bond is likely NONreversible Many of these inhibitors are done by noncovalent bonds Types of inhibitors (p.156): o Competitive: blocks the active site o Noncompetitive: blocks somewhere OTHER than the active site. TOXINES AND POISONS are usually PERMANENT inhibitors Concept 8.5 I. Allosteric Regulation of Enzymes Allosteric regulation: activates and deactivate the enzyme Feedback inhibition: when the final product inhibits the reactant that started the pathway
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