Making energy!
ATP
The point
is to make
ATP!
AP Biology
2008-2009
AP Biology
Chemical
energy
First Law
Of Thermodynamics
(a)
First law of thermodynamics: Energy
can be transferred or transformed but
Neither created nor destroyed. For
example, the chemical (potential) energy
in food will be converted to the kinetic
energy of the cheetah’s movement in (b).
Figure 8.3
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Heat
Second Law
co2
+
H2O
(b)
Second law of thermodynamics: Every energy transfer or transformation increases
the disorder (entropy) of the universe. For example, disorder is added to the cheetah’s
surroundings in the form of heat and the small molecules that are the by-products
of metabolism.
Figure 8.3
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Free Energy
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Reactions in a Closed System:
∆G < 0
∆G = 0
What would happen
To a living
System if it were closed?
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Body Cells:
∆G < 0
What do we
Need to
Stay alive?
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The energy needs of life
 Organisms are endergonic systems

What do we need energy for?
 synthesis
 building biomolecules
 reproduction
 movement
 active transport
 temperature regulation
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Where do we get the energy from?
 Work of life is done by energy coupling

use exergonic (catabolic) reactions to
fuel endergonic (anabolic) reactions
digestion
+
synthesis
+
AP Biology
+
energy
+
energy
Living economy
 Fueling the body’s economy

eat high energy organic molecules
 food = carbohydrates, lipids, proteins, nucleic acids

break them down
 digest = catabolism

capture released energy in a form the cell can use
 Need an energy currency


a way to pass energy around
need a short term energy
storage molecule
Whoa!
Hot stuff!
AP Biology
ATP
ATP
 Adenosine TriPhosphate

modified nucleotide
 nucleotide =
adenine + ribose + Pi  AMP
 AMP + Pi  ADP
 ADP + Pi  ATP
 adding phosphates is endergonic
How efficient!
Build once,
use many ways
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high energy bonds
How does ATP store energy?
ADP
AMP
ATP
I think
he’s a bit
unstable…
don’t you?
O– O– O – O– O–
–O P –O
O– P –O
O––P
OO
P––O
O– P O–
O 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


spring-loaded
Pi groups “pop” off easily & release energy
AP Biology
Instability of its P bonds makes ATP an excellent energy donor
How does ATP transfer energy?
ADP
ATP
O– O– O –
–O P –O
O– P –O
O– P O–
O O O
O–
–O P O – +
O
7.3
energy
 ATP  ADP

releases energy
 ∆G = -7.3 kcal/mole
 Fuel other reactions
 Phosphorylation

released Pi can transfer to other molecules
 destabilizing the other molecules
AP Biology
enzyme that phosphorylates = “kinase”
An example of Phosphorylation…
 Building polymers from monomers
need to destabilize the monomers
 phosphorylate!

H
C
OH
+
H
C
HO
H
C It’s
never that
OH
simple!
+ ATP
H
C
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+
P
H
C
HO
synthesis
+4.2 kcal/mol
“kinase”
enzyme
-7.3 kcal/mol
-3.1 kcal/mol
enzyme
H H
C C
O
H
C
H H
C C
OHHO
+
+
H2O
ADP
P
H H
C C
O
+
Pi
Another example of Phosphorylation…
 The first steps of cellular respiration

beginning the breakdown of glucose to make ATP
Those
phosphates
sure make it
uncomfortable
around here!
glucose
C-C-C-C-C-C
hexokinase
phosphofructokinase
P
2 ATP
C
C
2 ADP
fructose-1,6bP
P-C-C-C-C-C-C-P
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DHAP
P-C-C-C
G3P
C-C-C-P
H
C
P
activation
energy
ATP / ADP cycle
Can’t store ATP
cellular
 good energy donor,
not good energy storage respiration
 too reactive
 transfers Pi too easily
 only short term energy
storage
 carbohydrates & fats are
long term energy storage
Whoa!
Pass me
the glucose
(and O2)!
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ATP
7.3
kcal/mole
ADP + Pi
A working muscle recycles over
10 million ATPs per second
Cells spend a lot of time making ATP!
The
point is to make
ATP!
What’s the
point?
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How is ATP Made in a Cell?
Substrate Level
Phosphorylation
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Chemiosmosis
Start with a mitochondrion or
chloroplast
Trap H+ in the
intermembrane space
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Chemiosmosis
Start with a mitochondrion or
chloroplast
Trap H+ in the
intermembrane space
How can this
lead to
ATP production?
AP Biology
H+
ATP synthase
 Enzyme channel in
H+
H+
H+
H+
H+
H+
H+
rotor
mitochondrial membrane


permeable to H+
H+ flow down
concentration gradient
rod
 flow like water over
water wheel
 flowing H+ cause
ADP + P
change in shape of
ATP synthase enzyme
 powers bonding of
ATP
Pi to ADP:
ADP + Pi  ATP
APBut…
Biology How
is the proton (H+) gradient formed?
catalytic
head
H+
That’s the rest
of my story!
Any Questions?
AP Biology
2008-2009