Ch 6-Metabolism - Lecture notes 6 PDF

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Notes from Ch 6 lecture on Metabolism...

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Chapter 6: Metabolism  Energy and Metabolism  The Laws of Thermodynamics  Potential, Kinetic, Free, and Activation Energy  ATP: Adenosine Triphosphate  Enzymes I) Introduction  Living cells of every organism constantly use energy  Nutrients and other molecules are imported, metabolized (broken down) and possibly synthesized into new molecules, modified if needed, transported around the cell, and may be distributed to the entire organism  Cellular processes require a steady supply of energy II) Energy and Metabolism  Bioenergetics used to discuss the concept of energy flow through living systems (cells)  cellular processes that metabolize occur through stepwise chemical reactions  spontaneous: release energy  nonspontaneous: require energy  metabolism all the chemical reactions that take place within that cell that require energy or release energy III) Metabolism of Carbohydrates  Sugar molecules have a great deal of energy within their bonds  The breakdown of glucose C 6 H 12 O 6 +6 O 2 →6 C O 2 +6 H 2 O+ Energy

 Synthesis of glucose 6 C O 2 +6 H 2 O +Energy → C 6 H 12 O 6 +6 O 2

IV) Metabolic Pathways I  There are different ways but one simple way all interconnected  Reactions involved in the cell are part of the interconnecting ways V) Metabolic Pathways II  metabolic pathway begins with a specific molecule and ends with a product with each step being catalyzed by a specific enzyme

catabolic pathways

anabolic pathways

Release energy by breaking down complex molecules into simpler compounds  cellular respiration, the breakdown of glucose in the presence of oxygen

Consume energy to build complex molecules from simpler ones  the synthesis of protein from amino acids is an example of anabolism

VI) Metabolic Pathways III Evolution of Metabolic Pathways:  Probably evolved anaerobic metabolism to survive (living organisms came into existence about 3.8 billion years ago, when the atmosphere lacked oxygen)  All branches of life share some of the same metabolic pathways  All organisms must harvest energy from their environment and convert it to ATP to carry out cellular functions VII) Potential, Kinetic, Free, and Activation Energy Forms of Energy  Energy is the capacity to cause change  Energy exists in various forms, some which can perform work  Kinetic energy is energy associated with motion  Heat (thermal energy) is kinetic energy associated with random movement of atoms or molecules  Potential energy is energy that matter possesses because of its location or structure  Chemical energy is potential energy available for release in a chemical reaction VIII) Potential and Kinetic Energy IX) Chemical Energy X) The Laws of Thermodynamics Energy Transformations=Thermodynamics  Thermodynamics is the study of energy transformations  open systems energy and matter can be transferred between the system and its surroundings  organisms are open systems The First Law of Thermodynamics  first law of thermodynamics the energy of the universe is constant (principle of conservation of energy)

 energy can be transferred and transformed, but it cannot be created or destroyed The Second Law of Thermodynamics  during every energy transfer or transformation, some energy is unusable, and is often lost as heat  second law of thermodynamics every energy transfer or transformation increases the entropy (disorder) of the universe Cells, Organisms, and Thermodynamics  spontaneous processes occur without energy input, can happen slowly or quickly  in order for this to happen, must increase entropy of the universe Biological Order and Disorder  cells create ordered structures from less ordered materials  organisms also replace ordered forms of matter and energy with less ordered forms  energy flows into an ecosystem as light and exits as heat XI) Free Energy Change in Free Energy Determines Direction of Chemical Reaction  Total energy=usable energy + unusable energy  Energy transformations involve an increase in entropy  Free energy (G) = amount of energy available to do work  Gibbs free energy XII) Free-Energy Change, G  changes in free energy identify spontaneous reactions which is related to the change in  enthalpy/change in total energy (∆H)  entropy (∆S)  temperature in Kelvin (T)  processes with negative ∆G are spontaneous  ∆G=GFINAL STATE –GINITIAL STATE (a) ∆G0 (+) reaction occurs non-spontaneously XIII) Free Energy, Stability, and Equilibrium  Free energy a measure of a system’s instability, its tendency to change to a more stable state -> during a spontaneous change, free energy decreases and the stability of a system increases  Equilibrium is a state of maximum stability

XIV) Equilibrium and Metabolism  Cells are open systems  Closed systems eventually reach equilibrium and do no work XV) Free Energy and Metabolism  An exergonic (catabolic) reaction proceeds with a net release of free energy and is spontaneous  H (total energy/enthalpy) decreases  S (disorder/entropy) increases  ∆G...