AP Biology Cellular Respiration Harvesting Chemical Energy Adapted from Ms. Lisa Miller’s AP Biology Notes.

AP Biology Harvesting Stored Energy  Energy is stored in organic molecules.  Glucose: C 6 H 12 O 6  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.

AP Biology Harvesting Energy Stored in Glucose  Glucose is the ideal molecule.  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 adenine 3 Phosphate groups ribose Cell Energy: needed for active transport, making proteins and nucleic acids, chemical signals.  Cells usable source of energy – ATP.  ATP stands for adenosine triphosphate.

AP Biology  All energy is stored in the bonds of the compound.  Breaking the bond releases energy.  When cell has energy available it can store this energy by adding a phosphate group to ADP, producing ATP.

AP Biology

Stage 1 Glycolysis: Breaking Down Glucose  “glyco – lysis” (splitting sugar)  Most ancient form of energy capture.  Starting point for all cellular respiration.  Occurs with or without oxygen.  Inefficient: generates only 2 ATP for every 1 glucose.  Location: in the cytoplasm. glucose      pyruvate 2x2x 6C3C

AP Biology Glycolysis Summary Invest some ATP Harvest a little more ATP and a NADH (electron carrier). ***NADH accepts a hydrogen (which has an electron) from glucose.

AP Biology Pyruvate is a Branching Point Pyruvate O2O2 O2O2 Kreb’s Cycle in Mitochondria Rermentation

AP Biology Don’t forget the Mito!  Double membrane  Outer membrane  Inner membrane  highly folded cristae*  fluid-filled space between membranes = intermembrane space  Matrix (Kreb’s here!)  central fluid-filled space * form fits function!

AP Biology 4C6C4C 2C6C5C4C CO 2 citrate acetyl CoA Stage 2: Krebs Cycle (Citric Acid Cycle) x2x2 3C pyruvate NADH FADH 2 NADH ATP This happens twice for each glucose! Occurs in the mitochondrial matrix and requires oxygen. ***First: pyruvate broken down into acetyl CoA.

AP Biology  Krebs cycle produces:  8 NADH  2 FADH 2  2 ATP Let’s go to ETC… NADH & FADH 2 What’s so important about NADH?

AP Biology So why the Krebs cycle?  If the yield is only 2 ATP, then why?  Value of NADH & FADH 2  Electron carriers (electron in hydrogen atom from pyruvate molecules).  Molecules store energy!  Used in the Electron Transport Chain (stage 3).

AP Biology ATP accounting so far…  Glycolysis  2 ATP  Kreb’s cycle  2 ATP  Life takes a lot of energy to run, need to extract more energy than 4 ATP! Why stop here… There’s got to be more to life than this.

AP Biology Stage 3: Electron Transport Chain  Last stop and most important!  Series of molecules built into inner mitochondrial membrane  mostly transport (integral) proteins  Transport of electrons down ETC linked to ATP synthesis.  Yields ~34 ATP from 1 glucose!  Only in presence of O 2 (aerobic) That sounds more like it!

AP Biology Electron Transport Chain

AP Biology Glycolysis Kreb’s cycle 2 NADH 8 NADH 2 FADH 2 Remember the NADH?

AP Biology NADH Passes Electrons to ETC  H cleaved off NADH & FADH 2.  Electrons stripped from H atoms  H + (H ions).  Electrons passed from one electron carrier to next in mitochondrial membrane (ETC).  Transport proteins in membrane pump H + across inner membrane to intermembrane space (creates a gradient).

AP Biology But what “pulls” the electrons down the ETC? electrons flow downhill to O 2

AP Biology Why the build up H + ?  ATP Synthase: enzyme in inner membrane of mitochondria. ADP + P i  ATP  Channel permeable to H +.  H + flow down concentration gradient = provides energy for ATP synthesis.  Molecular power generator!  Powers bonding of P i to ADP.

AP Biology Summary of cellular respiration  Where did the glucose come from?  Where did the O 2 come from?  Where did the CO 2 come from?  Where did the H 2 O come from?  Where did the ATP come from?  What else is produced that is not listed in this equation?  Why do we breathe? C 6 H 12 O 6 6O 2 6CO 2 6H 2 O~36 ATP  +++

AP Biology Taking it beyond…  What is the final electron acceptor in electron transport chain? O2O2  So what happens if O 2 unavailable?  ETC backs up  ATP production ceases  cells run out of energy  and you die!

AP Biology What if you do not have oxygen? FERMENTATION

AP Biology Anaerobic Fermentation  Bacteria, yeast 1C 3C2C pyruvate  ethanol + CO 2  Animals, some fungi pyruvate  lactic acid 3C  beer, wine, bread  at ~12% ethanol, kills yeast  cheese, yogurt, anaerobic exercise (no O 2 ) NADHNAD + NADHNAD +

AP Biology Lactic Acid Fermentation  No oxygen, so glycolysis is the only step performed.  NADH  NAD +.  Pyruvate  lactic acid  Example: human muscle cells. Alcohol Fermentation  No oxygen, so glycolysis is the only step performed.  NADH  NAD +.  Pyruvate  ethanol and carbon dioxide.  Example: Bacteria and yeast.