1. Metabolism, ATP, & Energy
Big Idea #2: Energy is needed to do stuff.

2. 2A1: All living systems require constant input of free energy.
Essential Knowledge
2A1: All living systems require constant input of free energy.

3. From food webs to the life of a cell
energy
energy
energy

4. 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

5. Anabolic Reactions
Forming bonds between molecules  build things Ex: dehydration synthesis, photosynthesis

6. Catabolic Reactions Breaking bonds between molecules  break up things
Ex: Hydrolysis, digestion, cellular respiration

7. Examples dehydration synthesis (anabolic) hydrolysis (catabolic)
enzyme +
H2O
hydrolysis (catabolic)
enzyme +
H2O

8. In CR, 1st step: Break down glucose into 2 pyruvate molecules  2 ATPs
Example
In CR, 1st step: Break down glucose into 2 pyruvate molecules  2 ATPs

9. What types of reactions release energy?
Question 1!
What types of reactions release energy?
Exergonic reactions!

10. What types of reactions invest energy?
Question 2!
What types of reactions invest energy?
Endergonic reactions!

11. Energy and Life!!
Orgs couple exergonic reactions (releasing energy) w/ endergonic reactions (needing energy)
energy + +
digestion
synthesis
energy + +

12. Question 3! What is the first rule of thermodynamics?
Energy cannot be created nor destroyed

13. What is the second rule of thermodynamics?
Question 4!
What is the second rule of thermodynamics?
No reactions is 100% efficient  Every energy transfer or transformation increases entropy of universe

14. The Living Body
Fuel = eat high energy org. molecules and break down  catabolism  capture released energy in a form cell can use
Need an energy currency, a way to pass energy around  ATP = short term energy storage molecule
ATP

15. ATP Adenosine Triphosphate -Modified 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?

16. How does ATP store energy?
I think he’s a bit unstable… don’t you? 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
spring-loaded
Pi groups “pop” off easily & release energy
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