Cellular Respiration and Fermentation

Review The purpose of photosynthesis is to take kinetic light energy and convert it into potential chemical energy in the form of GLUCOSE In order to build glucose, low energy CO2 and H20 molecules are built up using light energy.

Chloroplasts  fix carbon which requires energy input Mitochondria  release energy from organic molecules

Cellular Respiration  Goal – To BREAK DOWN glucose and use energy to produce ATP Can happen WITH oxygen present  Aerobic  Can happen WITHOUT oxygen present  Anaerobic

Two Routes an organism can release energy Fermentation (aka anaerobic respiration) Takes place entirely in the cytoplasm (no mitochondria necessary) Only nets 2 ATP (inefficient) per glucose No oxygen necessary! Aerobic Cellular Respiration Takes place mostly in mitochondria Nets 36 ATP per glucose Oxygen necessary! Either way, both start with the same process, Glycolysis, which means “glucose splitting”

Overview of Cell Respiration and Fermentation Glucose Krebs cycle Electron transport Glycolysis Alcohol or lactic acid Fermentation (without oxygen) IT ALL STARTS WITH GLYCOLYSIS!!!!

To the electron transport chain Glycolysis Glucose To the electron transport chain

Glycolysis Summary One molecule of glucose split in half  two molecules of pyruvic acid Uses 2 ATP to start the process but gets 4 ATP back in the end. (Net 2 ATP!) 4 high energy electrons are removed from the carbon compounds and passed to an electron carrier 2 NAD+  2 NADH Electrons carriers will take high energy electrons to the electron transport chain for later use!

What happens after glycolysis? Depends on who you are and what your oxygen availability is. In order to move forward with cell respiration, you must have the following; Mitochondria Available Oxygen If an organism does not have one or more of these, big problem as all available NAD+ molecules will be used-up. Without available NAD+, glycolysis shuts down and now not even 2 ATP generated from glucose via glycolysis Enter fermentation AKA anaerobic respiration.

Fermentation Release of energy from food molecules in the absence of oxygen AKA: Anaerobic respiration Two forms: Alcoholic fermentation Lactic acid fermentation NADH reverts back to NAD+ in both types by dropping back off their electrons and H ions. With NAD+ freed up again, ATP production can continue via glycolysis  

Lactic Acid Fermentation Occurs in many cells Both eukaryotic and prokaryotic Pyruvic acid + NADH  lactic acid + NAD+ In foods, production of acid results in characteristic flavors of cheeses and yogurt This is what happens in our muscles when we exercise heavily “feel the burn”

Lactic Acid Fermentation Point of this happening is so the NADH can go back to NAD+ and keep glycolysis going! Glucose Pyruvic acid Lactic acid

Alcoholic Fermentation Occurs in yeast and a few other microorganisms Pyruvic acid + NADH  alcohol + CO2 + NAD+ Bread dough rising Wine and Beer fermentation

Alcohol Fermentation (same as pyruvate)

Uses – producing alcohol

Uses – producing CO2 Bubbles

3 Possible Pathways Fermentation Aerobic Cellular Respiration

Aerobic Cellular Respiration THE PROCESS BY WHICH CELLS UTILIZE OXYGEN TO BREAK DOWN ORGANIC MOLECULES INTO WASTE PRODUCTS, WITH THE RELEASE OF ENERGY THAT CAN BE USED FOR BIOLOGICAL WORK. Using energy from glucose into ATP! Equation 6O2 + C6H1206  6CO2 + 6H20 + Energy (ATP)

Cellular Respiration - 3 Main Steps 1.Glycolysis (same process as in fermentation) Occurs in cytoplasm of cell Net 2 ATP per glucose 2. Krebs Cycle Occurs in mitochondria 3. Electron Transport Chain Net 32 ATP per glucose

Electron Transport Chain Cellular Respiration Glucose (C6H1206) + Oxygen (02) Glycolysis Krebs Cycle Electron Transport Chain Carbon Dioxide (CO2) + Water (H2O)

Electron Transport Chain Cellular Respiration Electrons carried in NADH Electrons carried in NADH and FADH2 Pyruvic acid Glucose Electron Transport Chain Krebs Cycle Glycolysis Mitochondrion Cytoplasm

Overview of Aerobic Respiration 2 2 32 Glucose Glycolysis Acetyl CoA Krebs cycle Electron transport 6 NADH 2 FADH2 2 NADH 2 NADH Alcohol or lactic acid Fermentation (without oxygen)

After Glycolysis……. With free 02 and mitochondria, a cell can release even more energy from pyruvic acid. Only 10% of total energy of glucose released in glycolysis! We already know how glycolysis “splits” a glucose molecule into 2 pyruvic acid, so lets pick up with what happens AFTER glycolysis

Structure of the Mitochondria Outer membrane Inner membrane Inter-membrane space Cristae Projections of the inner membrane Contain the enzymes of the ETS, ATP synthase Matrix Inside area of the mitochondria Cells can contain 10 – 1000s of Mitochondria

Kreb’s Cycle Big Picture Further break-down of pyruvic acid molecules into CO2 via series of energy releasing reactions. Energy which is released is used to generate ATP (one per pyruvic acid molecule) Electrons released during cycles used to make; NAD+  NADH FAD  FADH2 Will be used later in electron transport (check to be cashed!)

Before Pyruvic Acid enters the Kreb’s cycle, it get modified; Carbon removed  C02 Electrons removed  NADH Coenzyme A joins the remaining 2-carbon molecule  acetyl-CoA Acetyl-CoA joins up with a 4-carbon compound already in the cycle and forms………… Citric Acid (6 carbon molecule)! Equation: Pyruvic acid  Acetyl Co A + CO2 + NADH Entry into Krebs Cycle Acetyl CoA + 4-C (oxaloacetate)  Citric Acid (6-C)

Kreb’s Cycle (aka Citric Acid Cycle Citric Acid Production Mitochondrion IMPORTANT! This cycle is repeated twice for each glucose molecule!

Results of Krebs Cycle Per Glucose molecule (2 cycles) 2 ATP 6 NADH  To electron transport chain 2 FADH2  To electron transport chain 6 CO2 (waste product) (4 in Krebs 2 in shuttle step) Also, 2 NADH were generated just before Kreb’s Cyles started when pyruvic acid was converted to Acetyl-CoA!

Electron Transport Big Idea All those high energy electrons which have been saved-up until now can be “cashed-in” for some big ATP gains! Electron transport links the movement of these high-energy electrons with the formation of ATP!

Electron Transport Electrons passes along an “electron transport chain” Prokaryotes Chain is a series of carrier proteins on cell membrane Eukaryotes (one we really care about) Chain is a series of carrier proteins located on inner membrane of mitochondria.

Electron Transport High Energy electrons passed along transport chain At end of chain, electrons passed to H+ and Oxygen to form H20. Oxygen is final electron acceptor Oxygen is important for the main reason that it accepts the low energy electrons and hydrogen ions which are wastes of cellular respiration!

Electron Transport and ATP production The movement of electrons down transport chain is coupled to the movement of hydrogen ions across inner membrane into the intermembrane space Hydrogen ion gradient established Special transport proteins along inner membrane called ATP synthases. As hydrogen moves through ATP synthase, ADP and P joined to form ATP! CALLED CHEMIOSMOSIS

Electron Transport Chain Hydrogen Ion Movement Channel ATP synthase ATP Production

The importance of oxygen Must be present to accept electrons and protons of hydrogen. Becomes WATER! Krebs and ETS cannot function without O2 Photosynthesis and respiration Products of Photosynth. are the raw materials for cellular respiration and vice versa Both utilize ETS Krebs and Calvin are similar, both involve rearrangements of carbon compounds Krebs forms ATP, NADH and FADH2 while Calvin uses ATP and NADPH

Grand Totals  Net 36 ATP per glucose 38% efficiency Exceeds efficiency of gas combustion in a car.

Totals: Step ATP NADH FADH2 Total ATP (net) Glycolysis 2 (net) 2* 6 6 Prep Step 2 Krebs Cycle 24 *energy is expended to get NADH (glycolysis) to ETS Only 2 ATP per NADH from glycolysis 3 ATP per NADH (prep and Krebs); 2 ATP per FADH2

Energy and Exercise Quick energy After that: ATP contained in muscles used in a few seconds After that: Anaerobic (weight lifting, sprinting – high ATP demands short term) Most ATP through lactic acid fermentation (90 seconds) Lots of oxygen required to get rid of buildup (oxygen dept) Sore muscles – caused by tissue damage

(cont.) Aerobic (jogging, light weights, - med ATP demands long term) First use ATP/glucose in blood Glycogen Lasts for 15-20 minutes Body breaks down fats after that