energy types of potential energy -...
TRANSCRIPT
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Big Idea #2
�Biological Systems utilize
free energy and molecular
building blocks to grow, to
reproduce and to maintain
dynamic homeostasis
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� Life runs on chemical reactions
� rearranging atoms
� transforming energy
organic molecules →→→→
ATP & organic molecules
organic molecules →→→→ ATP & organic molecules
solar energy →→→→
ATP & organic molecules
Metabolism
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Energy
�Very difficult to define
quantity
�The ability to do something
(i.e. move)
�2 general types:
� Potential energy- stored energy
� Kinetic energy – moving energy3
Types of Potential Energy
� Gravitational
� Elastic
� Nuclear
� Electrical (separation of charges)
� Chemical (energy stored in chemical bonds)
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Chemical Potential Energy
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Kinetic Energy
� Moving objects
� Radiation (movement of light particles/waves)
� Thermal (heat, movement of particles)
� Electrical (movement of electrons)
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1st Law of Thermodynamics
�Energy is never created or destroyed
�Energy is, however, transformed from
one form to another
�i.e. wind’s motion is converted to
electricity, which is converted to heat
and light energy in a light bulb7
2nd Law of Thermodynamics
�The entropy of an isolated system is
always increasing
�Entropy is the amount of energy in
an unusable form – usually heat
�Systems are always losing usable
forms of energy8
What This Means
� In every conversion of energy- a lot of energy is lost as heat
� I.e. when you burn gas in your car- you lose a lot of energy as heat
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Put Another Way
�Energy will be spread from areas of high
energy to low energy
� I.e. heat will transfer from a hot pan to the air around it
� A moving object will lose its kinetic energy to other objects and heat
� Chemicals with a lot of potential energy tend to explode – releasing heat and movement of other objects
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Why Do Biologists Care About This Physics Stuff ?
�Because living
things obey these
laws!
�Living things are
always losing
energy to their
surroundings
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We Require an Energy Input
�For living things to
remain whole they
must have an
energy input
� I.e. organisms must
get energy from
sun, deep thermal
vents or eating14
Order and Organization Require Energy
�Things naturally break down – to keep them from breaking down or to put them together requires an input of energy
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Energy Coupling� Processes that release energy are coupled to ones
that require an input of energy
� More energy must be released than is required for
the next reaction due to entropy (energy loss)
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Example
� Flexing a muscle
requires an energy input
� Breaking down food
releases energy
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Exergonic Reactions
�Release free energy
�Used in living things to provide energy for other processes
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The Most Significant Exergonic Reaction
� ATP + H2O� ADP + Pi + Energy
� This is the main molecule the body
uses to transfer energy to where it is
needed
Hydrolysis of one of its phosphate bonds releases ADP, INORGANIC PHOSPHATE, AND FREE ENERGY
ATP drives endergonic reactions by transfer of the phosphate group to specific reactants.
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Making ATP is an Endergonic Reaction
� It requires an input of energy
� Made in cellular respiration (input of chemical
energy in food)
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Energy Rxns are Coupled
catabolic/anabolic endergonic/exergonic
ATP/ADP
oxidation/reduction (redox)
ADP
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ATP
� Metabolism fuels the body’s economy
� eat high energy organic molecules� carbohydrates, lipids, proteins, nucleic acids
� break them down� digest = catabolic; exergonic
� capture released energy in a form the cell can use
� Requires an energy currency
� a way to move energy around
� need a short term energy
carrier molecule
Living Energy Economy
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� A modified nucleotide� adenine + ribose + Pi → AMP
� AMP + Pi → ADP
� ADP + Pi → ATP
� Adding phosphates – phosphorylation is endergonic
� Removing phosphates is exergonic� energy available for cell work
ATP: Adenosine Triphosphate
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� Negative PO4 makes for unstable bonds� 3rd Pi is hardest to keep bonded to molecule
� most energy stored in 3rd Pi
� Pi group “pops” off easily, releasing energy
ATP is unstable
Instability of its Pi
bonds makes ATP an
excellent energy donor
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� ATP → ADP
� releases energy • 7.3 kcal/mole ATP
� Phosphorylation
� Pi transferred to other molecules • requires kinase
PO–
O–
O
–O PO–
O–
O
–O PO–
O–
O
–O Cal+P
O–
O–
O
–O
ADPATP
ATP transfers energy
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ATP/ADP are cycled� Energy transferred as ATP ->
ATP (redox)
� ADP is recycled via
monosaccharide metabolism
(respiration)
� polysaccharides, lipids, not
ATP, for storing energy
A working muscle
recycles over 10
million ATPs per
second!
Energy
for cell
work
Energy from
catabolism
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Uses of Free Energy
�Maintain body temperature
(some organisms)
�Reproduction
�Growth
�Movement
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Fuel for Life
reproduction
movement
…and more
Bulk transport
temperature
regulation
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Body Temperature Regulation
Endothermy
� Use heat released by
metabolic reactions to
keep a stable temp
� I.e. humans
Ectothermy
� Use external sources to
try to maintain body
temperature
� I.e. snakes/reptiles
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Reproduction
� Requires a huge amount of energy!
� Many species only reproduce when energy is available
� I.e. most plants flower in the spring when sunlight energy is abundant
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Growth
� Extra free energy not
needed for cellular
processes like
movement and
reproduction can be
put to growth
� I.e. extra calories
become stored fat
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Energy Deprivation
�Mass is broken down to provide
energy
�Eventually death will occur if there is
no energy input
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Smaller Organisms Require
More Food Per Body Mass
� Smaller organisms
have more surface
area relative to
volume, so they lose
more heat
� So they must replenish
that energy loss by
eating more (relative
to their body size)
than larger animals do33
QUANTIFYING ENERGY
total energy = useable energy* + unusable energyavailable for work random atomic motion
*point of interest for biologists
useable energy = total energy - unusable energyavailable for work random atomic motion
OR
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This relationship can be used to determine the
energy change of a rxn: exergonic or endergonic?
useable = total _ unuseable
energy energy energy
GIBBS
FREE ENERGY = ENTHALPY - ENTROPY
As entropy increases, free energy decreases
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To Know
Gibbs = entHalpy - (Temp K) diSorder
If G < 0, the reaction is exergonic; occurs
spontaneously; disorder is increased G is negative
If G > 0, the reaction is endergonic;
order/complexity is increased G is positive
requires coupling with an exergonic rxn* to drive the process
* usually ATP -> ADP + P
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Energy released
Spontaneous
Exergonic
G is negative
Energy required
Non-
spontaneous
Endergonic
G is positive
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2H2O2 -> 2H2O + 02
Catabolic or anabolic?
Endergonic or exergonic?
Increasing or decreasing disorder?
Spontaneous or coupled with ATP?
Energy stored or released?
Decreasing or increasing complexity?
Change in G positive or negative?
Building or breaking down molecules?
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Catabolic or anabolic?
Endergonic or exergonic?
Increasing or decreasing disorder?
Spontaneous or coupled with ATPrxn?
Energy stored or released?
Decreasing or increasing complexity?
Change in G positive or negative?
Building or breaking down molecules?
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Gibbs Free Energy Problems
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II. ENZYMES
♦ ENZYMES SPEED UP METABOLIC
REACTIONS BY LOWERING ENERGY
BARRIERS
♦ ENZYMES: PROTEINS THAT SERVE AS
BIOLOGICAL CATALYSTS
– SPEED REACTIONS BY LOWERING
ACTIVATION ENERGY
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ENZYMES ARE SUBSTRATE-SPECIFIC
� EACH TYPE OF ENZYME HAS A UNIQUE
ACTIVE SITE THAT COMBINES
SPECIFICALLY WITH ITS SUBSTRATE
� SUBSTRATE: THE REACTANT
MOLECULE ON WHICH AN ENZYME
ACTS UPON
� MECHANISM (INDUCED FIT): THE
ENZYME CHANGES SHAPE SLIGHTLY
WHEN IT BINDS THE SUBSTRATE44
THE ACTIVE SITE IS AN ENZYME’S
CATALYTIC CENTER
♦THE ACTIVE SITE CAN LOWER
ACTIVATION ENERGY BY
ORIENTING SUBSTRATES
CORRECTLY, STRAINING THEIR
BONDS, AND PROVIDING A
SUITABLE MICRO-ENVIRONMENT
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A CELL’S PHYSICAL AND CHEMICAL
ENVIRONMENT AFFECTS ENZYME
ACTIVITY
♦AS PROTEINS, ENZYMES ARE
SENSITIVE TO CONDITIONS THAT
INFLUENCE THEIR 3-D
STRUCTURE
♦EACH ENZYME HAS AN OPTIMAL
TEMPERATURE AND PH
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NOT ALL ENZYMES FUNCTION ALONE
♦COFACTORS: IONS OR MOLECULES FOR SOME ENZYMES TO FUNCTION PROPERLY
♦COENZYMES: ORGANIC COFACTORS
♦ INHIBITORS: REDUCE ENZYME FUNCTION
–COMPETITIVE: COMPETES AND BINDS TO ACTIVE SITE
–NONCOMPETITIVE: BINDS TO A DIFFERENT SITE, BUT STILL INHIBITS
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FIGURE 6.14 ENZYME INHIBITION
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III. THE CONTROL OF METABOLISM
♦ METABOLIC CONTROL OFTEN DEPENDS ON ALLOSTERIC REGULATION
♦ SOME ENZYMES CHANGE SHAPE, WHEN REGULATORY MOLECULES, EITHER ACTIVATORS OR INHIBITORS, BIND TO SPECIFIC ALLOSTERIC SITES
♦ ALLOSTERIC SITE: A SPECIFIC RECEPTOR SITE ON AN ENZYME REMOTE FROM THE ACTIVE SITE. MOLECULES BIND TO THE ALLOSTERIC SITE AND CHANGE THE SHAPE OF THE ACTIVE SITE, MAKING IT EITHER MORE OR LESS RECEPTIVE TO THE SUBSTRATE
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FIGURE 6.15 ALLOSTERIC REGULATION
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FIGURE 6.16 FEEDBACK INHIBITION
♦ FEEDBACK INHIBITION: THE END-
PRODUCT OF A METABOLIC PATHWAY
ALLOSTERICALLY INHIBITS THE ENZYME FOR
AN EARLY STEP IN THE PATHWAY
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6.17 COOPERATIVITY
♦ COOPERATIVITY: A SUBSTRATE MOLECULE BINDING
TO ONE ACTIVE SITE OF A MULTI-SUBUNIT ENZYME
ACTIVATES THE OTHER SUBUNITS
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THE LOCATION OF ENZYMES WITHIN A
CELL HELPS ORDER METABOLISM
♦ SOME ENZYMES ARE GROUPED INTO
COMPLEXES, SOME ARE INCORPORATED INTO
MEMBRANES, AND OTHERS ARE CONTAINED
IN ORGANELLES
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