Transcript Energy

METABOLISM
Cell = chemical factory
Thousands of reactions per second
Synthesis of polymers
Digestion of polymers
Production/transfer of energy to work
Very small space
Eukaryotic cells “Compartmentalize”
 Compartmentalization 20 letters
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–TS
Free energy = total energy – (temp)(entropy)
temperature is in Kelvin
(absolute, C+273)
D 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”
D 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
 D 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
D G would be spontaneous after activation
allows reaction at moderate temperature
(sucrase)
Sucrose + water
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