Ch. 8: METABOLISM
Cell = chemical factoryThousands 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 motionPotential 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 + H2O -> ADP + Pi
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