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.