1. All living systems require constant input of free energy
All living systems require constant input of free energy. Metabolism and Energy

2. The First Law of Thermodynamics
Energy 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.

3. Flow of energy through life
Life is built on chemical reactions
transforming energy from one form to another
organic molecules  ATP & organic molecules
sun
organic molecules  ATP & organic molecules
solar energy  ATP & organic molecules

4. 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

5. Living Systems are “Open” Systems
Matter and energy move in to living systems from the environment. Living systems transform matter and energy and return it to the environment

6. Multi-Step Metabolism
To increase control, living systems produce free energy in multiple-step pathways, mediated by enzyme catalysts.

7. Metabolic Reactions Can form bonds between molecules
dehydration synthesis
synthesis
anabolic reactions
ENDERGONIC
Can break bonds between molecules
hydrolysis
digestion
catabolic reactions
EXERGONIC
building molecules= more organization= higher energy state
breaking down molecules= less organization= lower energy state

8. Endergonic vs. exergonic reactions
- energy released
- digestion
energy input
synthesis
+G
-G
G = change in free energy = ability to do work

9. Stable polymers don’t spontaneously digest into their monomers
What drives reactions?
If some reactions are “downhill”, why don’t they just happen spontaneously?
because covalent bonds are stable bonds
Stable polymers don’t spontaneously digest into their monomers
“spontaneous” does not imply that the change will happen quickly. Rusting is spontaneous under the right conditions and takes a long time.

10. 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
Need a spark to start a fire
Can cells use heat to break the bonds?
energy
cellulose
CO2 + H2O + heat

11. 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 expose living cells to!
2nd Law of thermodynamics
Universe tends to disorder
so why don’t proteins, carbohydrates & other biomolecules breakdown?
at temperatures typical of the cell, molecules don’t make it over the hump of activation energy
but, a cell must be metabolically active
heat would speed reactions, but… would denature proteins & kill cells

12. Catalysts So what’s a cell got to do to reduce activation energy?
get help! … chemical help…
ENZYMES
Call in the ENZYMES! G

13. Energy needs of life Organisms are endergonic systems
synthesis (biomolecules)
reproduction
active transport
movement
temperature regulation
Organisms are endergonic systems
What do we need energy for?
Which is to say… if you don’t eat, you die… because you run out of energy.
The 2nd Law of Thermodynamics takes over!

14. Metabolic pathways Work of life is done by energy coupling
use exergonic (catabolic) reactions to fuel endergonic (anabolic) reactions
energy + +
energy + +

15. Metabolic Strategies
Temperature must be maintained for metabolic reactions.
Ectotherms vs. endotherms
Body size vs. metabolic rate
Reproductive strategies optimized

16. Insufficient Free Energy Production
Individual = disease or death
Population = decline of a population
Ecosystem = decrease in complexity
Less productivity
Less energy moving
through system

17. ATP Living economy Fueling the body’s economy Uses an energy currency
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
ATP
Whoa! Hot stuff!

18. ATP Adenosine Triphosphate modified nucleotide
nucleotide = adenine + ribose + Pi  AMP
AMP + Pi  ADP
ADP + Pi  ATP
adding phosphates is endergonic
Marvel at the efficiency of biological systems!
Build once = re-use over and over again.
Start with a nucleotide and add phosphates to it to make this high energy molecule that drives the work of life.
Let’s look at this molecule closer.
Think about putting that Pi on the adenosine-ribose ==>
EXERGONIC or ENDERGONIC?
How efficient!
Build once, use many ways
high energy bonds

19. How does ATP store energy?
I think he’s a bit unstable… don’t you?
How does ATP store energy? P O– O –O P O– O –O P O– O –O P O– O –O P O– O –O
ADP
AMP
ATP
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!
Not a happy molecule
Add 1st Pi  Kerplunk! Big negatively charged functional group
Add 2nd Pi  EASY or DIFFICULT to add? DIFFICULT takes energy to add = same charges repel  Is it STABLE or UNSTABLE? UNSTABLE = 2 negatively charged functional groups not strongly bonded to each other So if it releases Pi  releases ENERGY
Add 3rd Pi  MORE or LESS UNSTABLE? MORE = like an unstable currency • Hot stuff! • Doesn’t stick around • Can’t store it up • Dangerous to store = wants to give its Pi to anything
Instability of its P bonds makes ATP an excellent energy donor

20. How does ATP transfer energy?
7.3
energy P O– O –O P O– O –O P O– O –O P O– O –O +
ATP
ADP
ATP  ADP
releases energy (exergonic)
Phosphorylation (adding phosphates!)
released Pi can transfer to other molecules
destabilizing the other molecules
enzyme that phosphorylates = kinase
How does ATP transfer energy?
By phosphorylating
Think of the 3rd Pi as the bad boyfriend ATP tries to dump off on someone else = phosphorylating
How does phosphorylating provide energy?
Pi is very electronegative. Got lots of OXYGEN!! OXYGEN is very electronegative. Steals e’s from other atoms in the molecule it is bonded to. As e’s fall to electronegative atom, they release energy.
Makes the other molecule “unhappy” = unstable. Starts looking for a better partner to bond to. Pi is again the bad boyfriend you want to dump.
You’ve got to find someone else to give him away to. You give him away and then bond with someone new that makes you happier (monomers get together).
Eventually the bad boyfriend gets dumped and goes off alone into the cytoplasm as a free agent = free Pi.

21. An example of Phosphorylation…
Building polymers from monomers
need to destabilize the monomers
phosphorylate! H OH C H HO C
enzyme C H OH HO O +
H2O
+4.2 kcal/mol +
ADP C H OH
“kinase” enzyme C H P
Monomers  polymers
Not that simple!
H2O doesn’t just come off on its own
You have to pull it off by phosphorylating monomers.
Polymerization reactions (dehydration synthesis) involve a phosphorylation step!
Where does the Pi come from? ATP
It’s never that simple! +
ATP
-7.3 kcal/mol C H P H HO C + C H O + Pi
-3.1 kcal/mol

22. A working muscle recycles over 10 million ATPs per second
ATP / ADP cycle
Can’t store ATP
too reactive
transfers Pi too easily
only short term energy storage
carbs & fats are long term energy storage
A working muscle recycles over 10 million ATPs per second

23. Make ATP! That’s all I do all day. And no one even notices!
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!

24. 2. Math Skills: Gibbs Free Energy
3.1: All living systems require constant input of free energy.
2. Math Skills: Gibbs Free Energy

25. What You Have To Do
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 temperature
ΔS = change in entropy (+ = entropy increase, - = entropy decrease)

26. Spontaneity
Spontaneous reactions continue once they are initiated. Non-spontaneous reactions require continual input of energy to continue.

27. 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.

28. Sample Problem
Determine which of the following reactions will occur spontaneously at a temperature of 298K, justify your answer mathematically:
Reaction 1:
A + B → AB
Δ H: KJ/mol
Δ S: KJ / K
Reaction 2:
BC → B + C
Δ H: KJ/mol
Δ S: KJ/K

29. 4. Math Skills: Coefficient q10
3.1: All living systems require constant input of free energy.
4. Math Skills: Coefficient q10

30. What You Have To Do
Be able to use and interpret the Coefficient Q10 equation:
t2 = higher temperature
t1 = lower temperature
k2= metabolic rate at higher temperature
k1= metabolic rate at lower temperature
Q10 = the factor by which the reaction rate increases when the temperature is raised by ten degrees.

31. What It Means
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

32. Sample Problem
Data taken to determine the effect of temperature on the rate of respiration in a goldfish is given in the table below. Calculate the Q10 value for this data.
Temperature (°C)
Heartbeats per minute 20 18 25 42