AP Biology The Point is to Make ATP! ATP Cell Respiration – Part 1!

AP Biology Objectives:  Understand the transfer of energy in living systems  Explain how easily ATP’s energy can be transferred to do cell work.  Demonstrate the difference between anaerobic and aerobic respiration.  Observe why energy must be extracted in a step by step process rather than all at once.

AP Biology Energy needs of life  Organisms are endergonic systems  What do we need energy for?   synthesis (biomolecules)  reproduction  active transport  movement  temperature regulation

AP Biology First Law of Thermodynamics  The energy of the universe is constant  It can be transferred or transformed  It cannot be created or destroyed  Principle of Conservation of Energy

AP Biology Second Law of Thermodynamics  Every energy transfer or transformation increases the entropy of the universe.

AP Biology 3 Main types of work done by cells:  Mechanical work  Transport work  Chemical work

AP Biology Exergonic Reactions  Energy is released during the reaction  Free Energy -  G < 0 (neg)

AP Biology Endergonic Reactions  Energy is absorbed during the chemical reaction   G > 0 (positive)

AP Biology energy Where do we get the energy from?  Work of life is done by energy coupling  use exergonic (catabolic) reactions to fuel endergonic (anabolic) reactions ++ energy + +

AP Biology 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 energy currency  a way to pass energy around ATP Whoa! Hot stuff!

AP Biology ATP  Adenosine Triphosphate  modified nucleotide  adenine + ribose + P i  AMP  AMP + P i  ADP  ADP + P i  ATP an RNA nucleotide How efficient! Build once, use many ways

AP Biology Why does ATP store energy? P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O  Each P i group more difficult to add  a lot of stored energy in each bond  most stored in 3rd P i  ∆G = -7.3 kcal/mole  Close packing of negative P i groups I think he’s a bit unstable… don’t you?  spring-loaded instability of its P bonds makes ATP an excellent energy donor

AP Biology How does ATP transfer energy? P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O energy P O–O– O–O– O –O–O +  Phosphorylation  when ATP does work, it transfers its 3rd P i to other molecules  ATP  ADP  releases energy  ∆G = -7.3 kcal/mole  it destabilizes the other molecule Why is 3rd phosphate like a baaad boyfriend?

AP Biology it’s never that simple! An example of Phosphorylation…  Building polymers from monomers  need ATP for energy & to take the water out C H OH H OHOH C C H O H C + H2OH2O kcal/mol C H OH + C H P + ATPADP -7.3 kcal/mol H OHOH C C H O H C + + C H P PiPi -3.1 kcal/mol “kinase” enzyme

AP Biology glucose C-C-C-C-C-C fructose-6P P-C-C-C-C-C-C-P DHAP P-C-C-C PGAL C-C-C-P 2 ATP 2 ADP Another example of Phosphorylation…  The first steps of cellular respiration  beginning the breakdown of glucose  ATP those phosphates sure make it uncomfortable around here enzyme 1 enzyme 3enzyme 4 enzyme 5 enzyme 6 enzyme 2

AP Biology ATP / ADP cycle A working muscle recycles over 10 million ATPs per second Whoa! Pass me the glucose & oxygen! Can’t store ATP  too reactive  transfers P i too easily  only short term energy storage  carbs & fats are long term energy storage

AP Biology What’s the point?  Cells spend a lot of time making ATP!  ~ 1Billion ATP Molecules in every cell!! “The point is to make ATP!” I didn’t HEAR you! Make ATP! That’s all I do all day. And no one even notices!

AP Biology The Point is to Make ATP! ATP What’s the point?

AP Biology Harvesting stored energy  Energy is stored in organic molecules  heterotrophs eat food (organic molecules)  digest organic molecules  serve as raw materials for building & fuels for energy  controlled release of energy  series of step-by-step enzyme-controlled reactions  “burning” fuels  carbohydrates, lipids, proteins, nucleic acids

AP Biology Harvesting energy stored in glucose  Glucose is the model  catabolism of glucose to produce ATP glucose + oxygen  carbon + water + energy dioxide C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP  heat CO 2 + H 2 O + heat fuel (carbohydrates) combustion = making heat energy by burning fuels in one step respiration = making ATP (& less heat) by burning fuels in many small steps ATP CO 2 + H 2 O + ATP (+ heat) respiration

AP Biology How do we harvest energy from fuels?  Digest large molecules into smaller ones  break bonds & move electrons from one molecule to another  as electrons move they carry energy with them  that energy is stored in another bond, released as heat, or harvested to make ATP + e-e- + e-e- +– loses e-gains e-oxidizedreduced oxidationreduction

AP Biology How do we move electrons in biology?  Moving electrons  in living systems, electrons do not move alone  electrons move as part of H atom + H + H +– loses e-gains e-oxidizedreduced oxidationreduction C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP  +++ oxidation reduction H

AP Biology Coupling oxidation & reduction  Redox reactions in respiration  release energy as breakdown molecules  break C-C bonds  strip off electrons from C-H bonds by removing H atoms  C 6 H 12 O 6  CO 2 = fuel has been oxidized  electrons attracted to more electronegative atoms  in biology, the most electronegative atom?  O 2  H 2 O = oxygen has been reduced  release energy to synthesize ATP C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP  +++ oxidation reduction  O2 O2

AP Biology Oxidation & reduction  Oxidation  adding O  removing H  loss of electrons  releases energy  exergonic  Reduction  removing O  adding H  gain of electrons  stores energy  endergonic C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP  +++ oxidation reduction

AP Biology How is the energy obtained from Glucose??  Watch the Video:  Gummy Bear Gummy Bear  Is it better to obtain energy from molecules all at once – or little by little??  Why??

AP Biology  If the energy is obtained all at once – the product is a thermodynamically unstable molecule  Energy obtained little by little will produce more stable products

AP Biology  The process of Cellular Respiration is a step by step process to extract energy from glucose while producing stable molecules  If it happened quickly – all energy would be lost as heat and light.

AP Biology Glycolysis:  First Step in Cellular Respiration  Takes place in the cytoplasm  One molecule of glucose is broken down into two molecules of pyruvic acid

AP Biology Energy from Glycolysis:  4 ATP are produced; however, it takes 2 ATP to start the process.  Therefore, the net gain is 2 ATP

AP Biology Glycolysis and Oxygen  Does not require Oxygen = anaerobic  Therefore, can provide some energy during times when oxygen is not available.

AP Biology Evolutionary perspective  Life on Earth first evolved without free oxygen (O 2 ) in atmosphere  energy had to be captured from organic molecules in absence of O 2  Organisms that evolved glycolysis are ancestors of all modern life  all organisms still utilize glycolysis You mean, I’m related to them?!

AP Biology Anaerobic Situation:  During times when oxygen is not available – the Kreb’s cycle and Electron Transport Chain cannot proceed  Energy from Glycolysis is used  Energy from Fermentation (Lactic acid or Alcoholic) is used if needed.

AP Biology Lactic Acid Fermentation:  Used by body to produce more energy during times of less oxygen = anaerobic  Pyruvic Acid (from glycolysis) is converted into Lactic Acid  A steady supply of ATP is produced.

AP Biology  During times of rapid exercise (less oxygen) the body uses lactic acid fermentation for energy  Lactic acid build up causes your muscles to burn.

AP Biology Energy tally so far???  2 ATP were produced from glycolysis.  90% of the energy in a glucose molecule still remains.

AP Biology Is that all there is?  Not a lot of energy…  for 1 billon years + this is how life on Earth survived  only harvest 3.5% of energy stored in glucose  slow growth, slow reproduction Heck of a way to make a living!

AP Biology In the Presence of Oxygen:  Pyruvic Acid will goes on to the Krebs Cycle – to squeeze more energy out.  To Be Continued………..

AP Biology  Glucose…glucose Glucose…glucose