1) All living systems require a constant input of free energy which is obtained from food and transformed through a series of chemical reactions from one form to another. 2) Energy is released through exergonic (catabolic) reactions like cellular respiration which break bonds, while endergonic (anabolic) reactions like synthesis require energy to form bonds. 3) ATP acts as a short-term energy storage molecule, transferring energy between reactions by having a phosphate bond that is easily broken to drive endergonic reactions in cells.

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

2. 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
organic molecules →
ATP
& organic molecules
sun
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)
enzy+me
H2O
 hydrolysis (catabolic)
+
H2O
enzyme

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

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

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

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

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

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

14. AT
P
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

15. ATP
•Adenosine
Triphosphate
-Modified nucleotide
•adenine + ribose +
Pi
→ AMP
•AMP + Pi → ADP
•ADP + Pi → ATP
-Adding phosphates

16. How does ATP store energy?
• 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
O– O– O– O– O–
–O P –O– P –O –PO OP –
O– P O– O O O
O O
Instability of its P bonds makes ATP an excellent energy donor
I think
he’s a bit
unstable…
don’t you?
AA
DTP
P