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

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

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

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

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

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

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

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

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

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

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

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

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

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

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?

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