Metabolism and Energy

1. Metabolism and Energy

2. digesting molecules= less organization=lower energy state building molecules= more organization=higher energy state Metabolic reactions & energy • Some chemical reactions release energy • exergonic • breaking polymers • hydrolysis = catabolism • Some chemical reactions require input of energy • endergonic • building polymers • dehydration synthesis = anabolism

3. Examples • dehydration synthesis • hydrolysis

4. Endergonic vs. exergonic reactions exergonic endergonic energy released energy invested G G = change in free energy = ability to do work

5. Energy & life • Organisms require energy to live • where does that energy come from? • coupling exergonic reactions (releasing energy) with endergonic reactions (needing energy) energy + + energy + +

6. Spontaneous reactions? • If reactions are “downhill”, why don’t they just happen spontaneously? • because covalent bonds are stable Why don’t polymers (carbohydrates, proteins & fats) just spontaneously digest into their monomers

7. energy Activation energy • Breaking down large molecules requires an initial input of energy • activation energy • large biomolecules are stable • must absorb energy to break bonds cellulose CO2 + H2O + heat

8. Activation energy • the amount of energy needed to start the reaction. • moves the reaction over an “energy hill”

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

10. Energy needs of life • Organisms are endergonic systems • What do we need energy for? • synthesis (biomolecules) • reproduction • active transport • movement • temperature regulation

11. Whoa! Hot stuff! Living economy • Fueling the economy • eat high energy organic molecules (food) • break them down = catabolism(digest) • capture energy in form cell can use • Need an energycurrency • a way to pass energy around ATP

12. How efficient! Build once,use many ways an RNA nucleotide ATP • Adenosine Triphosphate • modified nucleotide • adenine + ribose + Pi AMP • AMP + Pi ADP • ADP + Pi ATP

13. Why is the 3rd phosphate like a bad boyfriend? O– O– O– O– O– O– O– O– P P P P P P P P –O –O –O O– O– O– –O –O –O O– O– O– –O –O O– O– O O O O O O O O Why does ATP store energy? • Each Pi group more difficult to add • a lot of stored energy in each bond • most stored in 3rd Pi • Phosphorylation... • Storing energy with ATP • spring-loaded instability of its P bonds makes ATP an excellent energy donor

14. + + H H H H H H H H H2O C C C C C C C C OH OH OH OH O O H ATP ADP + + C -7.3 kcal/mol P H + + Pi C -3.1 kcal/mol P An example of Phosphorylation… • Building polymers from monomers • need ATP for energy & to take the water out +4.2 kcal/mol “kinase”enzyme

15. 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 • Coupling of exergonic and endergonic reactions. A working muscle recycles over 10 million ATPs per second

16. I didn’t HEAR you! What’s the point? • Cells spend a lot of time making ATP! “The point is to make ATP!” For chemical, mechanical, and transport work Make ATP! That’s all I do all day. And no one even notices!