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Metabolism (Fermentation (Lactic Acid Fermentation (pyruvate is reduced…

- - - - Pyruvate is converted to a two-carbon compound, acetaldehyde, by the removal of CO2
      - Acetaldehyde is reduced by NADH to ethanol. This process regenerates the supply of
        NAD+ needed for the continuation of glycolysis
- - - - Oxygen requirement: yes
      - Location: inner mitochondrial membrane
    - - Reactants
        
        10 NADH
        
        2 FADH2
        
        O2
        
        H+
        
        ADP, P
      - Products
        
        H2O
        
        32 or 34 ATP
        
        NAD+
        
        FAD
  - - - Location: mitochondrial matrix
      - Oxygen requirement: none
    - - Reactants
        
        2 Acetyl CoA
        
        6 NAD+ from ETS
        
        2 ADP + 2P
        
        2 FAD from ETS
      - Products
        
        4 CO2
        
        6 NADH go to ETS
        
        2 FADH2 go to ETS
        
        2 ATP
  - - - Location: cytoplasm--->mitochondria
      - Oxygen requirement: none
    - - Reactants
        
        2 pyruvic acid
        
        2 NAD+ from ETS
        
        2 Coenzyme A
      - Products
        
        2CO2
        
        2NADH-go to ETS
        
        2 Acetyl CoA
  - - - Location: occurs in the cytoplasm of the cell near the mitochondria
      - Oxygen requirement: none
    - - Reactants
        
        1 glucose
        
        2NAD+ from ETS
        
        2ADP + 2P
      - Products
        
        2 ATP
        
        2 pyruvic acid
        
        2 NADH go to ETS
        
        2H +
- - - - states: Every energy transfer or transformation
        increases the entropy of the universe
      - Entropy
        
        a measure of disorder or randomness: The more random a collection of matter, the greater its entropy
      - Although order can increase locally, there is an unstoppable trend toward randomization of the universe.
      - Much of the increased entropy of the universe takes the form of increasing heat, which is the energy of random molecular motion
    - - states that the energy of the universe is constant: Energy
        can be transferred and transformed, but it cannot be created or destroyed
      - principle of conservation of energy
      - During every transfer or transformation of energy, some energy is converted to heat
    - - the matter under study
        
        Surroundings
        
        include the rest of the universe—everything outside the system
      - open system
        
        energy and matter can be transferred between the system and its surroundings
      - isolated system
        
        approximated by liquid in a thermos, is unable to exchange either energy or matter with its surroundings
  - - - Cells manage their energy resources to do this work by energy coupling
      - using an exergonic
        process to drive an endergonic one
      - ATP is responsible for mediating most energy coupling in cells, and ATP mediates most energy coupling in cells
      - Phosphorylated Intermediate
        
        In the cell, the energy from the hydrolysis of ATP is directly coupled to endergonic processes by the transfer of the phosphate group to another molecule.
        
        ATP hydrolysis leads to a change in a protein’s shape and often its ability to bind another molecule
        
        This change may occur via a phosphorylated intermediate
        
        This recipient molecule with a phosphate group covalently bonded to it is called a phosphorylated intermediate.
        
        It is more reactive (less stable) than the original unphosphorylated molecule
    - - ATP is a renewable resource that can be regenerated by the addition of a phosphate group to ADP
      - The free energy to phosphorylate ADP comes from exergonic (catabolic) reactions in the cell
      - Regeneration of ATP is an endergonic process, requiring an investment of energy
    - - Transport work-- pumping substances across membranes against the direction of spontaneous movement
      - Mechanical work-- such as the beating of cilia, contraction of muscle cells, and movement of chromosomes during cellular reproduction
      - Chemical work-- pushing endergonic reactions such as the synthesis of polymers from monomers
    - - a nucleotide triphosphate consisting of the sugar ribose, the nitrogenous base adenine, and a chain of three phosphate groups
      - ATP acts as the immediate source of energy that powers cellular work
      - ATP + H2O ---> ADP + Pi, ∆G = -7.3 kcal/mol (-30.5 kJ/mol)
      - The release of energy during the hydrolysis of ATP comes from the chemical change to a state of lower free energy, not from the phosphate bonds themselves
        
        Why does the hydrolysis of ATP yield so much energy?
        
        Each of the three phosphate groups has a negative charge.
        
        These three like charges are crowded together, and their mutual repulsion contributes to the instability of this region of the ATP molecule
        
        The triphosphate tail of ATP is the chemical equivalent of a compressed spring
  - - - the energy that matter possesses because of its location or structure
      - Chemical energy
        
        the potential energy available
        for release in a chemical reaction
    - - the energy associated with the relative motion of objects
      - Heat or thermal energy
        
        kinetic energy associated with the random movement of atoms or molecules
  - - - Catalyst
        
        a chemical agent that speeds up the
        rate of a reaction without being consumed by the reaction
        
        works to speed reactions by lowering EA
        
        activation energy (EA)
        
        The initial investment of energy for starting a reaction is the free energy of activation
        
        often supplied in the form of thermal energy from surroundings
    - - substrate
        
        The reactant that an enzyme acts on
        
        enzyme-substrate complex
        
        The enzyme binds to a substrate, or substrates, to form the complex
    - - Only a restricted region of the enzyme binds to the substrate
      - active site
        
        typically a pocket or groove on the surface of the protein
        where catalysis occurs
        
        usually formed by only a few amino acids. The rest of the protein
        molecule provides a framework that determines the configuration of the active site
        
        The active site is not a rigid receptacle for the substrate
        
        induced fit
        
        This change leads to an induced fit that brings the chemical groups of the active site into position to catalyze the reaction
        
        As the substrate enters the active site, interactions between the chemical groups on the substrate and those on the side chains of the amino acids that form the active site cause the enzyme to change shape slightly
      - cofactors
        
        nonprotein helpers required for catalytic activity
        
        bind permanently or reversibly to the enzyme
        
        coenzymes
        
        organic cofactors
    - - competitive inhibitors
        
        Some reversible inhibitors resemble the substrate and compete for binding to the active site
      - noncompetitive inhibitors
        
        impede enzymatic reactions by binding to another part of the
        molecule
    - - Temperature: Most human enzymes have optimal temperatures of about 35–40°C
      - pH: optimal pH falls between 6–8 for most enzymes
    - - a protein’s function at one site is affected by the binding of a regulatory molecule to a separate site
      - may result in either inhibition or stimulation of an enzyme’s activity
      - Cooperativity
        
        In enzymes with multiple catalytic subunits, binding by a substrate molecule to one active site in a multisubunit enzyme triggers a shape change in all the subunits
        
        amplifies the response of enzymes to substrates,
        priming the enzyme to accept additional substrates
        
        Cooperativity is considered to be “allosteric” regulation because binding of the substrate to one active site affects catalysis in a different active site
      - Feedback inhibition
        
        An early step in a metabolic pathway is switched off by inhibitory binding of the pathway’s final product to an enzyme acting early in the pathway
        
        Feedback inhibition prevents a cell from wasting chemical resources by synthesizing more
        product than is needed
  - - - ex: an explosion, the rusting of a car
    - - The concept of free energy (symbolized by the letter G) is useful for measuring the spontaneity of a system.
        
        Free energy
        
        the portion of a system’s energy that can perform work when temperature and pressure are uniform throughout the system, as in a living cell.
        
        The change in free energy, ∆G, can be calculated for any specific chemical reaction by applying the following equation:
        
        ∆G = ∆H – T∆S
        
        ∆S is the change in the system’s entropy
        
        T is the absolute temperature in Kelvin (K) units (K = °C + 273)
        
        ∆H symbolizes the change in the system’s enthalpy (in biological systems, equivalent to total energy)
        
        Calculating ∆G
        
        ∆G must have a negative value (∆G < 0) in order for a process to be spontaneous
        
        In any spontaneous process, the free energy of a system decreases (∆G is negative)
        
        For a process to occur spontaneously, the system must give up enthalpy (H must decrease),
        give up order (T∆S must increase), or both
        
        A system at equilibrium is at maximum stability
        
        equilibrium
        
        In a chemical reaction at equilibrium, the rates of forward and backward reactions are equal, and there is no change in the relative concentrations of products or reactants
        
        At equilibrium, ∆G = 0, and the system can do no work
        
        A process is spontaneous and can perform work only when it is moving toward equilibrium
        
        Movements away from equilibrium are nonspontaneous and will have a positive ∆G
- - - - the study of how energy flows through living organisms
  - - - store energy in molecules; ∆G is positive
      - one that absorbs free energy from its surroundings
      - nonspontaneous, and the magnitude of ∆G is the quantity of
        energy required to drive the reaction
      - For the conversion of carbon dioxide and water to sugar, ∆G = +686 kcal/mol
        
        If cellular respiration releases 686 kcal/mol, then photosynthesis, the reverse reaction, must require an equivalent investment of energy
        
        Photosynthesis is strongly endergonic, powered by the absorption of light energy
  - - - proceeds with a net release of free energy; ∆G is negative
      - The magnitude of ∆G for an exergonic reaction is the maximum amount of work the reaction can perform
      - The greater the decrease in free energy, the greater the amount of work that can be done
      - Overall reaction of cellular respiration: C6H12O6 + 6O2 ---> 6CO2 + 6H2O, ∆G = -686 kcal/mol
        
        For each mole (180 g) of glucose broken down by respiration under standard conditions (1 M of each reactant and product, 25°C, pH 7), 686 kcal of energy are made available to do work in the cell.
        
        The products have 686 kcal less free energy per mole than the reactants