Chpt. 8 An Intro to Metabolism Metabolism - totality of an organism’s chemical reactions.
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Transcript of Chpt. 8 An Intro to Metabolism Metabolism - totality of an organism’s chemical reactions.
Chpt. 8
An Intro to Metabolism
Metabolism-
totality of an organism’s chemical
reactions
Metabolism-
totality of an organism’s chemical
reactionsmolecules are alteredmolecules are ateredmolecules are ateed
Metabolism-
molecules are altered molecules are atered molecules are ateed
Enzymes catalyze each step
Metabolic Reactions:Types:Catabolic-break down molecules
•release energyex. cellular respiration
Metabolic Reactions:Types:Anabolic-
consume energyex. making proteins from
amino acids
build molecules
Examples • dehydration synthesis (synthesis)
• hydrolysis (digestion)
+
H2O
+
H2O
enzyme
enzyme
Examples • dehydration synthesis (synthesis)
• hydrolysis (digestion)
enzyme
enzyme
HOW ORGANISMS MANAGE THEIR ENERGY
resources
capacity to do work: change in the state or motion of matter
Cells obtain chemical energy when molecules are
rearranged:
Therefore, a basic knowledge of ENERGY is necessary to understand how cells work…
Potential Energy •stored in molecules in the chem. bonds
…is converted to Kinetic Energy
Potential Energy - where is it in this picture?
Kinetic Energy
•(energy of motion)
• energy that “powers” the cell.
ex. cell respiration, releases energy stored in the bonds of sugar
molecules.
Kinetic Energy
Where is it here??? This one is easy to see!
energy transformat
ion
1st Law of Thermodynamics
chemical energy was not chemical energy was not created, and will not be created, and will not be destroyed… but it can destroyed… but it can
change formschange forms
A
B
C
Flow of energy through life• Life is built on chemical
reactions transforming energy from one form to another
organic molecules ATP & organic molecules
organic molecules ATP & organic molecules
sun
solar energy ATP & organic molecules
2nd Law of Thermodynamics
Every energy transfer or Every energy transfer or transformation, increases transformation, increases entropyentropy (disorder) in the (disorder) in the
UniverseUniverse
Christian Right Lobbies To Overturn Second Law Of ThermodynamicsSeptember 6, 2000 | Issue 36•31
TOPEKA, KS–The second law of thermodynamics, a fundamental scientific principle stating that entropy increases over time as organized forms decay into greater states of randomness, has come under fire from conservative Christian groups, who are demanding that the law be repealed.
"What do these scientists want us teaching our children? That the universe will continue to expand until it reaches eventual heat death?" asked Christian Coalition president Ralph Reed, speaking at a rally protesting a recent Kansas Board Of Education decision upholding the law. "That's hardly an optimistic view of a world the Lord created for mankind. The American people are sending a strong message here: We don't like the implications of this law, and we will not rest until it has been reversed in the courts."
The controversial law of nature, which asserts that matter continually breaks down as disorder increases and heat is lost, has long been decried by Christian fundamentalists as running counter to their religion's doctrine of Divine grace and eternal salvation.
"Why can't disorder decrease over time instead of everything decaying?"
2nd Law of Thermodynamics
Every energy transfer or Every energy transfer or transformation increases transformation increases entropy (disorder) in the entropy (disorder) in the
UniverseUniverse
HEAT is a very HEAT is a very DISORDERED form of DISORDERED form of
energyenergy
Chemical reactions & energy
• Some chemical reactions release energy– exergonic– breaking polymers– hydrolysis = catabolism
• Some chemical reactions require input of energy– endergonic– building polymers – dehydration synthesis = anabolism
digesting molecules= LESS organization=lower energy state
building molecules= MORE organization=higher energy state
Living cells,
unavoidable,
convert organized forms of energy to
heat
QuickTime™ and a decompressor
are needed to see this picture.
Get it… convert to HEAT
Now, THAT’s some disordered HEAT!!QuickTime™ and a
decompressorare needed to see this picture.
changes changes that occur that occur on their on their
own…own…
•When When spontaneous spontaneous
processes occur processes occur in a system (an in a system (an
organism), organism), stabilitystability
increasesincreases~ but ~ but in terms of the in terms of the universe, it universe, it decreasesdecreases
•Unstable Unstable systems tend to systems tend to become more become more stable stable spontaneously.spontaneously.
How can we predict How can we predict which changes occur which changes occur
spontaneously, and spontaneously, and which require input which require input
of E. from the of E. from the
outsideoutside? ?
ENERGY, in a system, THAT CAN PERFORM WORK
measure of this free energy
Yale scientist featured in stamp series Gibbs received the first Ph.D. in engineering in the U.S. from Yale in 1863. He later became a
member of the Yale faculty.
G = H - T S free energy
total energy
temp*entropy change
= -
EntropyEntropy = measure of = measure of disorderdisorder
G = H - T S free energy amount
of useable E. to
do work
total potential
energy~
total bond
energy enthal
py
entropy
= -unuseable energy
Not all of the energy Not all of the energy in a system is in a system is
available for workavailable for work
We can use this to We can use this to predict which predict which
changes occur changes occur spontaneously, and spontaneously, and which require input which require input
of E. from the of E. from the
outsideoutside? ?
G = H - T S free energy
total energy
entropy
= -
spontaneous changes, spontaneous changes, decreasedecrease free free energyenergy
Unstable Systems - change
spontaneously, becoming stable systems, and Free Energy Decreases
Endergonic vs. exergonic reactions
exergonic endergonic- energy released- digestion
- energy invested- synthesis
-G
G = change in free energy = ability to do work
+G
Chemical Reactions (2 Chemical Reactions (2 types):types):
Exergonic- proceeds with a net release of free E. G is negative spontaneous
Endergonic- proceeds with a net gain of Energy/ absorbs it
G is positivenonspontaneous
Chemical Reactions (2 Chemical Reactions (2 types):types):
Exergonic- proceeds with a net release of free E.
exergonic- energy released- digestion
-G
Chemical reactions & energy
• Some chemical reactions release energy– exergonic– breaking polymers– hydrolysis = catabolism
• Some chemical reactions require input of energy– endergonic– building polymers – dehydration synthesis = anabolism
digesting molecules= LESS organization=lower energy state
building molecules= MORE organization=higher energy state
Cells “work” three Cells “work” three ways: ways:
•Mechanical work = muscle
contraction
•Transport work = pumping across
membranes
•Chemical work = making polymers
ENERGY SOURCE for the work is ATPATP
Adenine
Ribose sugar
Phosphates
ATP•Adenine (Nitrogen-base)
•Ribose (sugar) Phosphate chain (3)
ATP•Ribose (sugar)
•Phosphate chain (3)
ATP•Phosphate chain (3)
Bond hold Bond hold potential potential energy!!!energy!!!
ATP•Phosphate chain (3)
Bond can be Bond can be broken via. broken via. hydrolysishydrolysis
ATP•Phosphate chain (3)
Unstable b/c Unstable b/c three negative three negative chargescharges
Label the three parts of the ATP molecule below:
ATP + H2O --->
ADP + P + ENERGY
release
- G
the “P” flew off!!!!
ATP + H2O --->
ADP + P + ENERGY
- G
B/C moving to a more stable condition
ATP, when hydrolysized, releases free
energy (energy that is able
to be used)broken
ATP, when hydrolysized,
releases free E. Cell
takes the energy and transfers the
Phosphate to another molecule.
ATP, when hydrolysized, releases free E.
Cell takes the E. and transfers the Phosphate to another molecule.
Phosphorylation!
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are needed to see this picture.
Cell takes the E. and transfers the Phosphate to another molecule.This molecule is less
stable than the original molecule.
WHAT DOES A graph HAVE TO DO WITH BIOLOGY ???????
A chemical reaction will occur spontaneously if it releases free energy , but the process may be too slow to be effective, in living cells…
A chemical reaction will occur spontaneously if it releases free energy , but the process may be too slow to be effective, in living cells…
ex. hydrolysis of sucrose: Does occur
spontaneously….
But it would take way too long….
ex. hydrolysis of sucrose:
Energy of Activation - energy required to break bonds (EA) barrier is EXTREMELY high - the reaction will occur only if reactants are heated:
ex. hydrolysis of sucrose:
Energy of Activation EA barrier is EXTREMELY high - the reaction will occur only if reactants are heated:
Enzymes lower EA-
But do not change G
Energy of Activation EA barrier is EXTREMELY high - the reaction will occur only if reactants are heated:
Energy Energy releasereleasedd
Enzymes don’t change
Energy of Activation EA barrier is EXTREMELY high - the reaction will occur only if reactants are heated:
G
Substrate
Active Site Conformational Change
Energy Energy releasereleasedd
Energy Energy releasereleasedd
Energy Energy releasereleasedd
Energy Energy releasereleasedd
Enzymes are substrate specific
Enzyme
Enzymes are effected by environmental factors:
Enzymes are affected by environmental factors:
TOOTOO MUCHMUCH HeatHeat disrupts H-bonds disrupts H-bonds in the protein in the protein
……remember, remember, enzymes enzymes are PROTEINare PROTEIN
However:However: HeatHeat does does increaseincrease rate of rxrate of rx…. TO A …. TO A POINT POINT
……remember, remember, enzymes enzymes are PROTEINare PROTEIN
Beyond that temp, speed of reaction drops:
WHAT about pH changes????
pH disrupts H-pH disrupts H-bonds in the bonds in the protein protein
……remember, remember, enzymes enzymes are PROTEINare PROTEIN
paperosesubstrate
paperase
A B
Sometimes enzymes have “hitch hiker” chemicals/molecules that INHIBIT their effectiveness
Molecules that are bound to the active site
Competitive Competitive InhibitorsInhibitors
Sometimes enzymes have “hitch hiker” chemicals/molecules that INHIBIT their effectiveness
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“normal”
“competative”
WHAT does this to to the RX.
RT???
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How can we “get around” the lower RX RATE???
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How can we “get around” the lower RX RATE??? ADD more
substrate
paperosesubstrate
paperase
inhibitor
A B
A B
see the difference
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IMPLICATIONS??
Turns out, the pesticide DDT is a noncompetitive inhibitor
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paperosesubstrate
paperase
inhibitor A B
A B
“A cell is not just a bag of chemicals with thousands of
different kinds of enzymes and substrates
wandering about randomly.”
Chaos would result if all of a cell’s metabolic pathways were open at the same time… must be regulated
Allosteric
Regulation
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• The control of an enzyme complex by the binding of a regulatory molecule.
• Regulatory molecule may stimulatestimulate or inhibitinhibit the enzyme enzyme complexcomplex.
Allosteric Regulation
Allosteric Regulation
enzyme complex
Allosteric Regulation
regulatory
molecule may
stimulate or
inhibit the
complex
Allosteric Regulation-•allosteric enzymes have 2 or more polypeptides.
•Oscillates between active and inactive.
•activator keeps it “on” - active
•inhibitor keeps it “off” - inactive
Cooperativity-•Enzyme having many subunits
•Binding of one substrate to the active site causes all active sites to “run”
Feedback Inhibition-•pathways are switched on and off by the end product.
•the end product acts as an inhibitor of an enzyme within the pathway.
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Sometimes enzymes require nonprotein “helpers”
CoEnzymesCoEnzymes
Molecules that are bound to the active site
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Summary of chpt. 8
•Recognize that Life must follow the Laws of Thermodynamics.
•The role of ATP in cell energy.
•How enzymes work & all senarios in which they can be placed… what is the result?