Chemistry of life

 Metabolism  =  the totality of an organism’s chemical processes [Gr. metabole: change]

Catabolism    =  metabolic process release energy by breaking down complex molecules to simpler compounds (down hill reactions)

Anabolism     =  consume energy to build complicated molecules from simpler ones (uphill reactions)

Bioenergetic  =  study of how organisms manage their energy resources

Energy           =  capacity to do work

Kinetic energy    =  energy of motion

Potential energy  =  stored energy (example water behind  dam, food (chemical energy)      Thermodynamics   =  the study of the energy trasformations

System          =   the matter under study

Surroundings =    everything outside the system

Closed system =    isolated from surrounding

Open system    =    energy can be transferred between the system and its surroundings

                               organisms are open systems

Laws of thermodynamics

The first law of thermodynamics is conservation of energy

   = energy can be transferred and transformed, but it can be neither created nor destroyed

The second law of thermodynamics is every energy transfer or transformation increases the entropy of the universe

Entropy = randomness

@ 25% of chemical energy stored in fuel ® the motion of car (75%® heat)

@ the quantity of energy in the universe is constant, but its quality is not

@ organisms take organised forms of matter ® replaces with® less ordered   

    forms, for example  Proteins  ® ate by animals ® CO₂ + H₂O + related molecules   

Free energy available for work is the potion of a system’s energy that can perform work (temperature:T, constant)

   Free energy      =   G

            System’s total energy      =   H

            Its entropy                        =   S                 

                                               G   =   H-TS

                       (T= °C+273: standard for absolute temperature)

              Noted that systems tend to change spontaneously to more stable state.

              Therefore, in any spontaneous process, the free energy of a system decreases 

                     the change in free energy   = DG

                                                        DG  =  G_{final state} – G_{starting state}

                                              or       DG  =  DH- TDS

                              spontaneous process  =  decrease in H

                                                                =  increase in S

                                                                =  DG = negative

                DG is more negative (greater decrease), greater the maximum amount, so spontaneous        

                process can perform

               Chemical equilibrium = chemical reactions are reversible and proceed until the forward and                   backward reactions occur at the same rate

                Metabolic disequlibrium: DG = 0  (this state, a cell is dead)

               Exergonic reaction (energy outward) (downhill)

          ·       release free energy

          ·       DG = negative

          ·       occur spontaneously

           C₆H₁₂O₆ + 6O₂  ® 6CO₂ + 6H₂O

          DG = -686 kcal/mol (-2870 kJ/mol)

           Glucose  ® respiration® free energy = 686 kcal

                         180 g

                 Endergonic reactions (energy inward) (uphill)

                             ·     absorbs free energy from its surroundings

           ·     DG = positive

                ·     nonspontaneous reaction

           ·     DG = energy required to drive the reaction

        

                    Noted that  key strategy in bioenergetics is energy coupling

                                         

                      Noted that ATP is responsible for mediating most energy coupling in cells

  

Three main kinds of cell work

1.    Mechanical work: movement

2.  Transport work

3.  Chemical work  : pushing endergonic reactions to happen

The energy source that powers cellular work is ATP

 ATP = adenosine triphosphate  = adenine + ribose + phosphate groups

                                ATP + H₂O  ® ADP (more stable)+ Pi

                                    DG = - 7.3 kcal/mol (-31 kJ/mol)

                                           (in standard conditions)

                                    DG = -13 kcal/mol (78% greater)

                                          (in the cellular environment)

 Noted that phosphate bonds are unstable ® hydrolysis ® yields ® energy

Noted that it is not phosphate bonds that give energy

Triphosphate bonds are so fragile and charges are crowed together that is a loaded spring

How ATP performs work

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