This document discusses how organisms obtain and use energy. It explains that ATP is the main energy currency of cells, as it can easily store and transfer energy via phosphate bonds. The breakdown of glucose and other nutrients through cellular respiration releases energy to produce ATP from ADP and inorganic phosphate. This ATP is then used to drive energetic processes in the cell, as its phosphate bonds can be broken down to fuel other reactions. The proton gradient formed during respiration powers ATP synthase to regenerate ATP from ADP and phosphate. Overall, the document emphasizes that the main purpose of cellular energy metabolism is to continuously produce ATP to fuel the energy needs of life.

1. Making energy!
ATP
The point
is to make
ATP!
AP Biology
2008-2009

2. 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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3. 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
+
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+
energy
+
energy

4. 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


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a way to pass energy around
need a short term energy
storage molecule
Whoa!
Hot stuff!
ATP

5. 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

6. How does ATP store energy?
AMP
ADP
ATP
I think
he’s a bit
unstable…
don’t you?
O– O– O– O – O–
–
O P –O– P –O––P O––O– P O–
OP
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
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Instability of its P bonds makes ATP an excellent energy donor

7. How does ATP transfer energy?
ATP
ADP
O– O– O–
–
O P –O– P –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
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enzyme that phosphorylates = “kinase”

8. 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
OH that
+ ATP
simple!
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
P
H H
C C
O
H H
C C
HO
OH
+
+
H2O
ADP
+
Pi

9. 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

10. 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

11. Cells spend a lot of time making ATP!
The
point is to make
ATP!
What’s the
point?
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12. H+
ATP synthase
H+
 Enzyme channel in
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
change in shape of
ATP synthase enzyme
 powers bonding of
Pi to ADP:
ADP + P
ATP
ADP + Pi → ATP
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But…
catalytic
head
is the proton (H+) gradient formed?
H+

13. That’s the rest
of my story!
Any Questions?
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2008-2009