View
219
Download
1
Category
Preview:
Citation preview
The pointis to make
ATP!
Life and Thermodynamics(Ch. 8)
The energy needs of life• Organisms are endergonic systems
– What do we need energy for?• synthesis
–building biomolecules• reproduction• movement• active transport• temperature regulation
Food = Fuel = Energy
Transformations between kinetic and potential energy
More potential energy.Potential energy converted
to kinetic energy.
Kinetic Energy Converted toPotential Energy
Less potential energy
The two laws of thermodynamics
(a) First law of thermodynamics: Energy
can be transferred or transformed but
neither created nor destroyed.
Second law of thermodynamics: Every energy transfer or transformation increases the disorder (entropy) of the universe.
(b)
Chemicalenergy
Heatco2
H2O+
H2 + 1/2 O2 2 H 1/2 O2
(from food via NADH)
2 H+ + 2 e–
2 H+
2 e–
H2O
1/2 O2
Controlled release of energy for synthesis of
ATPATP
ATP
ATP
Electro
n tran
spo
rt chain
F
ree
ener
gy, G
(b) Cellular respiration(a) Uncontrolled reaction
Fre
e en
ergy
, G
H2O
Explosiverelease of
heat and lightenergy
+
How Food Becomes Energy
(a) A closed hydroelectric system
∆G < 0 ∆G = 0
(b) An open hydroelectric system
∆G < 0
∆G < 0
∆G < 0
A multistep open hydroelectric system (c)
∆G < 0
Open Systems and Equilibrium
Where do we get the energy from?• Work of life is done by energy coupling
– use exergonic (catabolic) reactions to fuel endergonic (anabolic) reactions
+ + energy
+ energy+
digestion
synthesis
ATP
Living economy• Fueling the body’s economy
– eat high energy organic molecules – break them down– 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!
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
How does ATP store energy?
PO–
O–
O
–O PO–
O–
O
–O PO–
O–
O
–OPO–
O–
O
–O PO–
O–
O
–OPO–
O–
O
–O PO–
O–
O
–O PO–
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
Instability of its P bonds makes ATP an excellent energy donor
I thinkit’s a bit
unstable…don’t you?
AMPADPATP
How does ATP transfer energy?
PO–
O–
O
–O PO–
O–
O
–O PO–
O–
O
–O7.3
energy+PO–
O–
O
–O
• ATP ADP– releases energy
• ∆G = -7.3 kcal/mole• Fuel other reactions• Phosphorylation
– released Pi can transfer to other molecules• destabilizing the other molecules
– enzyme that phosphorylates = “kinase”
ADPATP
Can’t store ATP good energy donor,
not good energy storagetoo reactivetransfers Pi too easilyonly short term energy
storagecarbohydrates & fats
are long term energy storage
ATP / ADP cycle
A working muscle recycles over 10 million ATPs per second
Whoa!Pass me
the glucose(and O2)!
ATP
ADP Pi+
7.3 kcal/mole
cellularrespiration
Cells spend a lot of time making ATP!
What’s thepoint?
Thepoint is to make
ATP!
H+
catalytichead
rod
rotor
H+H+
H+
H+ H+
H+H+H+ATP synthase
ATP
But… How is the proton (H+) gradient formed?
ADP P+
• Enzyme channel in mitochondrial membrane– permeable to H+ – H+ flow down
concentration gradient• flow like water over
water wheel• flowing H+ cause
change in shape of ATP synthase enzyme
• powers bonding of Pi to ADP:ADP + Pi ATP
That’s the rest of my
story!Any
Questions?
Review Questions
1. Which of the following reactions could be coupled to the reaction ATP + H2O → ADP + Pi (-7.3 kcal/mol)?
A. A + Pi → AP (+10 kcal/mol) B. B + Pi → BP (+8 kcal/mol) C. CP → C + Pi (-4 kcal/mol) D. DP → D + Pi (-10 kcal/mol) E. E + Pi → EP (+5 kcal/mol)
2. Assume that the reaction has a ∆G of -5.6 kcal/mol. Which of the following would most likely be true? * A. The reaction could be coupled to power an endergonic
reaction with a ∆G of +6.2 kcal/mol. B. The reaction could be coupled to power an exergonic
reaction with a ∆G of +8.8 kcal/mol. C. The reaction would result in a decrease in entropy (S) and
an increase in the total energy content (H) of the system. D. The reaction would result in an increase in entropy (S) and
a decrease in the total energy content (H) of the system. E. The reaction would result in products (C + D) with a greater
free-energy content than in the initial reactants (A + B).
3. A particularly obnoxious acquaintance claims that since life is able to spontaneously create more ordered structures and systems from less ordered structures and systems, that the laws of thermodynamics are wrong, or at the very least do not apply to living systems, and implies that this observation means that a higher power has created life.
Briefly explain why this person is an idiot, and where the flaw(s) in his logic lie.
Recommended