CH. 6 - ENERGY & METABOLISM

          I. ENERGY = ABILITY TO DO WORK

            A. SUN is the ultimate source of almost all energy for the earth. 

      1. <1% is used for life.

            B. PSYN/RESPIRATION CYCLE

      1. Energy FLOWS from sun

      2. Nutrients CYCLED

C. KINETIC - energy of motion

D. POTENTIAL - stored energy

          II. OXIDATION/REDUCTION RXNS (Redox):  "LEO says GER" (p. 109)

            A. Reduction  =       1. gain an electron. 

                                                2. gain a H    

                                                3. gains/stores energy.

            B. Oxidation   =        1. lose an electron

                                                2. lose a H

                                                3. loses/releases energy

            C. When one compound is oxidized, another is reduced:

                        a. A^e- + B è A + B^e-  

                        b. AH + B è   A +BH

                        c. Psyn:   6CO₂  + 6H₂0 è C₆H₁₂O₆ + 60₂

           III. LAWS OF THERMODYNAMICS

A.   1st LAW OF THERMODYNAMICS:  Energy cannot be created or destroyed

            but can be converted from one form to another.     

            B. 2nd LAW OF THERMODYNAMICS: Every energy transformation

                              results in the loss of energy.

                  1. Entropy = loss of energy; no input è death (p. 110)

                  2. Sun = constant source of energy.

            C. METABOLISM - Gk:  "metabole" = to change

                        All enzyme-mediated chemical rxns that occur in a cell/organism.

                  1.  Anabolism - Endergonic (p. 111)

                        a. synthesis reactions, form bonds, small to large

                        b. requires & stores energy. 

                  2.  Catabolism - Exergonic

                        a. degredation reactions,  break bonds,  large to small

                        b. releases energy

          IV. ATP (p. 112)

            A. UNIVERSAL ENERGY CURRENCY OF CELLS

            B. NUCLEOTIDE

            C. PHOSPHORYLATION = add a phosphate group (P_i) (p. 113)

            ADP + P_i è ATP; STORES ENERGY

            D. DEPHOSPHORYLATION = remove a phosphate group

                        ATP è ADP + P_i; RELEASES ENERGY

            E. Energy for making ATP comes from:

                  1. Respiration (Ch. 7) = Substrate level & oxidative pp

                  2. Photosynthesis (Ch. 8) = Photophosphorylation & oxidative pp

            V. ENZYMES

            A. DEFN:

                  1.  Globular or 3^o proteins, lower ENERGY OF ACTIVATION (p. 111)

                  2.  Specific catalysts, "lock and key"

                  3.  Powerful - é rate up to 10,000,000,000X normal rate

                  4.  Recyclable & Reusable, efficient.

                  5.  Not used in reaction (don't become part of what the product is).

                  6.  Substrate - Compound(s) to be reacted on (p. 115)

                  7.  Cofactor - Non-protein required by some enzymes to function. 

                        a.   Ions - Mg²⁺, K⁺, Ca²⁺, Mn²⁺

                        b.  Coenzymes  -      i. vitamins 

                                                            ii. e^- acceptors in redox rxns

           B. ENZYME-MEDIATED BIOCHEMICAL PATHWAY (p. 118)

                              Enz #1       Enz #2         Enz #3        Enz #4

            1. Substrate è product 1è product 2è product 3è end product

            2. Reaction Rate Regulated by (p. 116):

                        a. Δ pH

                        b. Δ Temperature

                        c. Δ [substrate], [enz], other chemicals

            3. Denature - change in shape or ê fxn

           C. ENZYME REGULATION & INHIBITION - Model of enzyme (p. 117)

              - ACTIVE SITE: substrate normally fits here    

                  1. Competitive inhibition

                        a. another molecule similar to the substrate

                        b. reverse by adding more substrate (overwhelm the other)

                        c. some antibiotics - sulfa drugs

                  2. Irreversible inhibition  

                        a. another molecule similar to substrate

            b. irreversible, permanent binding to enzyme

                        c. Penicillin, nerve gas, chemical weap

              - ALLOSTERIC/2^ND SITE:

                  3. Allosteric activator

a.    molecules/ions other than substrate - often cofactor

b.    turns enzyme on - changes enzyme to correct shape

     4. Noncompetitive Inhibition = Allosteric inhibitor

a.    molecule other than substrate

b.    turns enzyme off - changes enzyme to wrong shape

c.    Lead & mercury poisoning

d.    FEEDBACK inhibition (p. 119)

e.    Reversible w/ certain chemicals