Ch. 8: METABOLISM Cell = chemical factory Thousands of reactions per second  Synthesis of polymers  Digestion of polymers  Production/transfer of energy to work Very small space ( euk. Compartmentalize )

Chemical Pathways Anabolism is the building of new polymers from monomers “assembly” Catabolism is the break down of large molecules into smaller parts “digest” Metabolism is the sum of all the chemical reactions occurring in the cell  Metabolism = catabolism + anabolism Reactions often occur as a series of steps

Energy Energy is the ability to do work. Kinetic energy = energy of motion Potential energy = nrg of position, “possible” Chemical energy = energy that is stored in molecules as a result of the arrangement of their atoms. A form of potential energy. Chemical potential energy drives metabolism.

Laws of Thermodynamics First Law – Conservation  Energy can not be created or destroyed but must be transferred and transformed from one form to another. Second Law – Entropy Rules!  Every energy transfer increases the entropy of the universe. (can’t get more energy out than in)  Entropy is a measure of randomness / chaos  Even if polymers are more ordered it cost you valuable forms of energy (kinetic,mechanical,chemical) and left you with less usable forms (heat) overall.

Free Energy Free energy is the portion of a systems energy that is available to perform work when the temperature is consistent in the system. G = H – T S Free energy = total energy – (temp)(entropy) temperature is in Kelvin (absolute, C+273)  G should be < 0 for spontaneous reaction

Free Energy and Metabolism Exergonic reactions = proceeds with net release of free energy “energy exits”  Digestion of sugar to ATP to muscle contraction to body heat Endergonic reactions = absorb free energy from surroundings “energy enters”   G > 0  Photosynthesis of glucose needs input of solar energy COUPLE exergonic reactions with endergonic reactions.  universe total decreases ( More Chaos !!!)

ATP ATP powers cellular work  Mechanical  Transport  chemical Structure  ATP is adenosine triphosphate  ATP + H 2 O -> ADP + P i   G = -7.3 kcal/mol Performance  Break down is hydrolysis = heat,  Enzymes create using phosphorylation Regeneration  10 million molecules per second per cell – WOW  Continuous recycling process that COUPLES reactions

Adenosine Triphosphate…..ATP

Enzymes Catalysts are substances that change the rate of a chemical reaction with out being consumed in the reaction If the catalyst is a protein and is part of a biological reaction then it is an ENZYME Enzymes (catalysts) decrease the energy of activation required to start the reaction Heat and stirring are bad for cells, change in conc. isn’t usually good either.

Enzyme activity AB + CD = AC + BD AC and/or BD have less free energy  G would be spontaneous after activation allows reaction at moderate temperature Sucrose + water ===(sucrase)=  glucose + fructose

Enzyme specificity Enzyme names end in –ase (lactase needs to break down lactose) Enzyme is specific to one substrate (shape) Combine in area called active site with correct  Shape and  Chemical environment Actual connection/bonding causes shape change called induced fit  E + S  ES  E + P

Regulation of Enzymes Cofactors – nonprotein helper Allosteric regulation – enzymes with multiple subunits may need to change to an active shape  Activator  inhibitor Inhibition  Competitive – blocks site  Noncompetitive – sits elsewhere but changes enzyme  Feedback – a product comes back as an inhibitor