Transcript Lecture Chpt. 08 Metabol

Chpt. 8
An Intro
to
Metabolism
Metabolismtotality of an organism’s
chemical reactions
Metabolismtotality of an organism’s
chemical reactions
molecules are altered
molecules are atered
molecules are ateed
Metabolismmolecules are altered
molecules are atered
molecules are ateed
Enzymes catalyze
each step
Metabolic Reactions:
Types:
Catabolicbreak down molecules
•release energy
ex. cellular respiration
Metabolic Reactions:
Types:
Anabolicbuild molecules
consume energy
ex. making proteins from amino acids
Examples
• dehydration synthesis (synthesis)
+
enzyme
H2O
• hydrolysis (digestion)
enzyme
H2O
+
Examples
• dehydration synthesis (synthesis)
enzyme
• hydrolysis (digestion)
enzyme
HOW
ORGANISMS
MANAGE
THEIR
ENERGY
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
transformatio
n
1st Law of
Thermodynamics
chemical energy was not created, and
will not be destroyed… but it can
change forms
B
A
C
Flow of energy through life
• Life is built on chemical reactions
transforming energy from one form to another
organic molecules  ATP
& organic molecules
sun
solar energy 
ATP & organic molecules
organic molecules 
ATP & organic molecules
2nd Law of
Thermodynamics
Every energy transfer or
transformation, increases entropy
(disorder) in the Universe
Christian Right Lobbies To Overturn Second Law Of Thermodynamics
September 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Christian groups, who are demanding that the law be repealed.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?"
HEAT is a very
DISORDERED form of
energy
2nd Law of
Thermodynamics
Every energy transfer or
transformation increases entropy
(disorder) in the Universe
Chemical reactions & energy
• Some chemical reactions release energy
– exergonic
– breaking polymers
– hydrolysis = catabolism
digesting molecules=
LESS organization=
lower energy state
• Some chemical reactions require
input of energy
building molecules=
MORE organization=
higher energy state
– endergonic
– building polymers
– dehydration synthesis = anabolism
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Living cells,
unavoidable,
convert
organized
forms of
energy to
heat
Get it…
convert to HEAT
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Now, THAT’s some disordered
HEAT!!
changes that
occur on their
own…
•When spontaneous
processes occur in
a system (an
organism), stability
increases~ but in
terms of the
•Unstable systems
tend to become
more stable
spontaneously.
How can we predict
which changes occur
spontaneously, and
which require input of E.
from the outside?
ENERGY, in a
system,
THAT CAN
PERFORM
measure of
this free
energy
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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
Entropy = measure of
disorder
G=H-TS
free
total
=
energy potential
amount energy~
of useable total
E. to do
bond
work
energy
enthalpy
-
entropy
unuseable
energy
Not all of the energy in a
system is available for
We can use this to
predict which changes
occur
spontaneously, and
which require input of E.
from the outside?
G=H-TS
free
energy
=
total
energy
-
entropy
spontaneous changes,
decrease free energy
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
G = change in free energy = ability to do work
Chemical Reactions (2 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 positive
nonspontaneous
Chemical Reactions (2 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
digesting molecules=
LESS organization=
lower energy state
• Some chemical reactions require
input of energy
building molecules=
MORE organization=
higher energy state
– endergonic
– building polymers
– dehydration synthesis = anabolism
Cells “work” three ways:
•Mechanical work
•Transport work
•Chemical work
= muscle contraction
= pumping across membranes
= making polymers
ENERGY SOURCE for
the work is ATP
Adenine
Phosphates
Ribose
sugar
ATP
•Adenine (Nitrogen-base)
•Ribose (sugar) Phosphate
chain (3)
ATP
•Ribose (sugar)
•Phosphate chain (3)
ATP
•Phosphate chain (3)
Bond hold potential
energy!!!
ATP
•Phosphate chain (3)
Bond can be broken
via. hydrolysis
ATP
•Phosphate chain (3)
Unstable b/c three
negative charges
Label the three parts of the ATP molecule below:
ATP + H2O --->
ADP + P + ENERGY
release
the “P” flew off!!!!
-G
ATP + H2O --->
ADP + P + ENERGY
B/C moving to a
more stable condition
-G
ATP, when
hydrolysized, releases
free energy
(energy that is able
be used)
broken
to
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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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 o
Energy
released
Enzymes don’t change
G
Energy o
Substrate
Active Site
Conformational
Change
Energy
released
Energy
released
Energy
released
Energy
released
Enzymes are substrate
specific
Enzym
e
Enzymes are effected by
environmental factors:
Enzymes are affected by
environmental factors:
TOO MUCH Heat
disrupts H-bonds in the
protein
…remember, enzymes
are PROTEIN
However: Heat does
increase rate of rx….
TO A POINT
…remember, enzymes
are PROTEIN
Beyond that temp, speed
of reaction drops:
WHAT about pH
changes????
pH disrupts H-bonds in
the protein
…remember, enzymes
are PROTEIN
paperose
A
B
substrate
paperase
Sometimes enzymes
have “hitch hiker”
chemicals/molecules
that INHIBIT their
effectiveness
Sometimes enzymes
have “hitch hiker”
chemicals/molecules
that INHIBIT their
effectiveness
Competitive
Inhibitors
Molecules that are bound to the active site
“normal”
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“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
paperose
A
B
substrate
inhibitor
A
paperase
B
see
the
differ
ence
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IMPLICATIONS??
Turns out, the
pesticide DDT is a
noncompetitive
inhibitor
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paperose
A
B
substrate
inhibitor
A
paperase
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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Allosteric
Regulation
• The control of an enzyme complex by
the binding of a regulatory molecule.
• Regulatory molecule may stimulate
or inhibit the enzyme complex.
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”
Molecules that are bound to the active site
CoEnzymes
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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?