1. Metabolism: fueling the body
Life is an economy of chemical reactions
rearranging atoms
transforming energy
organic molecules  ATP & organic molecules
organic molecules  ATP & organic molecules
solar energy  ATP & organic molecules

2. Fuel for This Bulk transport movement reproduction
Which is to say… if you don’t eat, you die… because you run out of energy.
The 2nd Law of Thermodynamics takes over!
reproduction
temperature regulation
…and more

3. ATP ATP is the Fuel ‘Currency’ of Life Required to live:
Metabolize organic molecules
Capture free energy product
Requires an energy currency
to move energy around the cell
to get cell work done
Cells earn ATP in exergonic rxns, spend it in endergonic rxns that drive cellular activities
ATP
Economy – earn money in your job, or buy your business; spend it on new goods, services, etc.

4. Energy moved between rxns via ATP
Energy released from exergonic reactions…
…drives essential endergonic reactions
ATP
Which is to say… if you don’t eat, you die… because you run out of energy.
The 2nd Law of Thermodynamics takes over!
ATP

5. ATP ‘coupled’ reactions
higher lower energy energy
Which is to say… if you don’t eat, you die… because you run out of energy.
The 2nd Law of Thermodynamics takes over!
lower energy higher energy

6. ATP? Adenosine Triphosphate
A modified nucleotide!
adenine + ribose + 3 Pi
Adding phosphates (phosphorylation) is an endergonic process
Removing phosphates is exergonic
makes energy available for cell work
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?

7. ATP is unstable Negative charge of PO4- makes for unstable bonds
3rd Pi is hardest to keep bonded /most energy needed
3rd Pi group “pops” off easily, releasing energy
This ‘dollar’ is useless if you do not use it immediately
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

8. Instability means energy transferP O– O –O
Cal P O– O –O P O– O –O P O– O –O +
ATP
ADP
ATP  ADP
Releases energy : 7.3 kcal/mole of ATP
G = -7.3C/mole
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. Δ

9. ADP is phosphorylated, recycled
Energy, inorganic P (Pi), transferred between ATP & ADP
ADP is recycled via glucose metabolism (respiration)
A working muscle recycles over 10 million ATPs per second!

10. Quiz yourself
From Hillis, 6.1