Koster

I. Energy of Reactions
 

    A. Thermodynamics =
 

        1. Energy exists in different forms:

                a. kinetic =

                b. potential =

                c. chemical =

                d. thermal =
 

2. Organisms transform energy from one form to another, according to the Laws of Thermodynamics.
 

    B. Laws of Thermodynamics

        1. First = "Conservation of Energy" = Total amount of energy in the universe is constant.
        Energy can be transferred and transformed, but it can be neither created nor destroyed.
 

        2. Second = "Law of Entropy" = Every energy transfer or transformation in universe
        increases the entropy or disorder of the universe.
 
 
 

        3. Free energy =
 
 

    C. Spontaneous reactions

.
 

        1. In any spontaneous process, the free energy of the system decreases.
 

            a. DG = change in free energy during reaction =

               G_products - G_reactants

            b. DG is negative for spontaneous reactions or processes.
                    DG < 0
 

        2. Loss of free energy often, but not always, occurs as a liberation of heat.

            a. Exergonic
 

            b.
 

        3. Spontaneous reactions can sometimes be reversed by putting free energy into the system.
 
 
 
 

    D. Equilibrium
 

        1. Chemical reactions are reversible.
               Reactants <--> Products

            a.
 
 
 
 

        2. At the equilibrium point, there is no further net change in the system, so DG = 0.
 

        3. Extent to which reactants are converted to products (NET change) depends on the
                initial DG of the reaction.

            a.
 

        4. Equilibrium =
 
 
 
 

            a. Metabolic pathways link multiple reactions together in series within cell so that
            the products of one reaction are used as reactants in the next. [Fig 6.5]
 
 
 
 

                i) Metabolism = totality of an organism's chemical processes.

                ii) Catabolic pathways = reactions that break down complex molecules to
                simpler molecules. These pathways usually result in the net release of energy.

                iii) Anabolic pathways = reactions that consume energy to build complex
                molecules out of simple ones.
 

    E. Energy Flow in Living Systems

        Bioenergetics = study of energy flow in living systems

        1. Why is energy needed for life? Because the reactions that characterize living
        systems often do not have DG < 0. Without inputs of energy, living organisms could not:

            a. synthesize complex molecules
            b. do mechanical work (muscle contraction, flagella beating, etc.)
            c. transport molecules across membranes against diffusion
            d. perform other types of work

        2. Energy in living systems is often carried within the structure of a molecule called
            ATP, adenosine triphosphate.

            a. Structure: adenosine (nucleotide) + 3 phosphates stuck together on one end.

                i) ATP hydrolysis:
                        ATP + H₂O --> ADP + Pi ,
                where ADP = adenosine diphosphate, P_i = inorganic phosphate
                DG = -7.3 kcal/mol
    (calorie = energy needed to raise temp of 1 g of water by 1°C; kcal = 1000
        cal = dietary Calorie)

        3. ATP can be used to fuel endergonic reactions in living systems through a process
            called energy coupling.

        Energy coupling =
 
 
 
 
 
 
 

        4. ATP contains
 
 

            a.

            b.

            c. to

Enzymes and Metabolism

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