Download - AP Biology All living systems require constant input of free energy. Metabolism and Energy
AP Biology
The First Law of ThermodynamicsEnergy cannot be created or destroyed, only transformed.Living systems need to continually acquire and transform energy in order to remain alive. “Free energy”: The energy available in a system to do work.
AP Biology
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
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The 2nd Law of Thermodynamics
Every time energy is transformed, the entropy (“disorder”) of the universe increases.
In order to increase/maintain their internal order, living systems must process more ordered forms of matter in to less ordered ones
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Living Systems are “Open” SystemsMatter and energy move in to living systems from the environment. Living systems transform matter and energy and return it to the environment
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Multi-Step Metabolism
To increase control, living systems produce free energy in multiple-step pathways, mediated by enzyme catalysts.
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Metabolic Reactions Can form bonds between molecules
dehydration synthesis synthesis anabolic reactions ENDERGONIC
Can break bonds between molecules hydrolysis digestion catabolic reactions EXERGONIC
breaking down molecules= less organization=lower energy state
building molecules= more organization=higher energy state
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Endergonic vs. exergonic reactionsexergonic endergonic- energy released- digestion
- energy input- synthesis
-G
G = change in free energy = ability to do work
+G
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What drives reactions? If some reactions are “downhill”, why
don’t they just happen spontaneously? because covalent bonds are stable bonds
Stable polymersdon’t spontaneously
digest into theirmonomers
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Getting the reaction started… Breaking down large molecules
requires an initial input of energy activation energy large biomolecules are stable must absorb energy to break bonds
energycellulose CO2 + H2O + heat
Can cells use heat to break the bonds?
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Too much activation energy for life The amount of energy needed to
destabilize the bonds of a molecule moves the reaction over an “energy hill”
Not a match!That’s too much energy to exposeliving cells to!
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Catalysts So what’s a cell got to do to reduce
activation energy? get help! … chemical help… ENZYMES
G
Call in the ENZYMES!
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Energy needs of life Organisms are endergonic systems
What do we need energy for?
synthesis (biomolecules) reproduction active transport movement temperature regulation
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Metabolic pathways
Work of life is done by energy coupling use exergonic (catabolic) reactions to
fuel endergonic (anabolic) reactions
+ + energy
+ energy+
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Metabolic Strategies Temperature must be maintained for
metabolic reactions. Ectotherms vs. endotherms Body size vs. metabolic rate
Reproductive strategies optimized
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Insufficient Free Energy Production Individual = disease or death Population = decline of a population Ecosystem = decrease in complexity
Less productivity Less energy moving
through system
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ATP
Living economy Fueling the body’s economy
eat high energy organic molecules food = carbohydrates, lipids, proteins, nucleic acids
break them down catabolism = digest
capture released energy in a form the cell can use Uses an energy currency
a way to pass energy around need a short term energy
storage molecule
Whoa! Hot stuff!
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ATP
high energy bondsHow efficient!Build once,use many ways
Adenosine Triphosphate modified nucleotide
nucleotide = adenine + ribose + Pi AMP
AMP + Pi ADP ADP + Pi ATP
adding phosphates is endergonic
AP Biology
How does ATP store energy?
P
O–
O–
O
–O P
O–
O–
O
–O P
O–
O–
O
–OP
O–
O–
O
–O P
O–
O–
O
–OP
O–
O–
O
–O P
O–
O–
O
–O P
O–
O–
O
–O
Each negative PO4 more difficult to add a lot of stored energy in each bond
most energy stored in 3rd Pi
3rd Pi is hardest group to keep bonded to molecule
Bonding of negative Pi groups is unstable Pi groups “pop” off easily & release energy Spring Loaded!
Instability of its P bonds makes ATP an excellent energy donor
I thinkhe’s a bitunstable…don’t you?
AMPADPATP
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How does ATP transfer energy?
P
O–
O–
O
–O P
O–
O–
O
–O P
O–
O–
O
–O7.3energy
+P
O–
O–
O
–O
ATP ADP releases energy (exergonic)
Phosphorylation (adding phosphates!) released Pi can transfer to other molecules
destabilizing the other molecules enzyme that phosphorylates = kinase
ADPATP
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It’snever thatsimple!
An example of Phosphorylation… Building polymers from monomers
need to destabilize the monomers phosphorylate!
C
H
OH
H
HOC C
H
O
H
C+ H2O++4.2 kcal/mol
C
H
OHC
H
P+ ATP + ADP
H
HOC+ C
H
O
H
CC
H
P+ Pi
“kinase” enzyme
-7.3 kcal/mol
-3.1 kcal/mol
enzyme
H
OHC
H
HOC
AP Biology 2005-2006
ATP / ADP cycle
A working muscle recycles over 10 million ATPs per second
Can’t store ATP too reactive transfers Pi too
easily only short term
energy storage carbs & fats are
long term energy storage
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What’s the point? Cells spend a lot of time making ATP!
“WHY?”For chemical, mechanical,
and transport work
Make ATP! That’s all I do all day. And no one
even notices!
AP Biology
2. MATH SKILLS: GIBBS FREE ENERGY
3.1: All living systems require constant input of free energy.
Be able to use and interpret the Gibbs Free Energy Equation to determine if a particular process will occur spontaneously or non-spontaneously.
ΔG= change in free energy (- = exergonic, + =
endergonic) ΔH= change in enthalpy for the reaction
(- = exothermic, + = endothermic)T = kelvin temperatureΔS = change in entropy
(+ = entropy increase, - = entropy decrease)
What You Have To Do
Spontaneity
Spontaneous reactions continue once they are initiated. Non-spontaneous reactions require continual input of energy to continue.
Using the Equation
To use the equation, you’ll need to be given values.
Exothermic reactions that increase entropy are always spontaneous/exergonic Endothermic reactions that decrease entropy are always non-spontaneous/endergonic. Other reactions will be spontaneous or not depending on the temperature at which they occur.
Sample ProblemDetermine which of the following reactions will occur spontaneously at a temperature of 298K, justify your answer mathematically:Reaction 1:
A + B → ABΔ H: +245 KJ/molΔ S: -.02 KJ / K
Reaction 2:BC → B + C
Δ H: -334 KJ/molΔ S: +.12 KJ/K
Be able to use and interpret the Coefficient Q10 equation:
t2 = higher temperaturet1 = lower temperaturek2= metabolic rate at higher temperaturek1= metabolic rate at lower temperatureQ10 = the factor by which the reaction rate increases when the temperature is raised by ten degrees.
What You Have To Do
Q10 tells us how a particular process will be affected by a 10 degree change in temperature.
Most biological processes have a Q10 value between 2 and 3
What It Means