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