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