Cellular Respiration Cellular respiration is the process by which cells make energy. They use glucose and oxygen to produce carbon dioxide, water and ATP (usable energy)

A common misconception Many people think “respiration” refers specifically to “breathing” Actually respiration refers to the processes of getting energy from food. All large animals (including humans) need to use oxygen to fully release the energy from food. That’s why the word respiration has also come to refer to breathing.

The Summary Formula: C 6 H 12 O O 2  6 CO H 2 O + energy Glucose + oxygen  carbon dioxide + water Enough energy is released during cellular respiration to produce up to 38 molecules of ATP 38 ADP + 38 PO 4  38 ATP Energy

cell Glucose Oxygen Carbon dioxide Water mitochondrion Energy (ATP)

Where it all happens: Mitochondiron Glucose ATP Oxygen CO 2

Stages of Respiration: Stage 1. Glycolysis (The splitting of sugars) Stage 1. Glycolysis (The splitting of sugars) Stage 2. Anaerobic (The fermentation of Pyruvic Acid) Stage 2. Anaerobic (The fermentation of Pyruvic Acid) Pyruvic Acid (CH 3 COCOOH) Pyruvic Acid (CH 3 COCOOH) No oxygen available Lots of oxygen available A little energy (2 ATP / glucose molecule) A lot of energy (38 ATP / glucose) Stage 2a. Aerobic (the Krebs Cycle) Stage 2b. Aerobic (Electron Transport) Stage 2a. Aerobic (the Krebs Cycle) Stage 2b. Aerobic (Electron Transport)

Glycolysis: Splitting the sugar Glucose is split into two 3-carbon molecules called pyruvic acid The Steps in Glycolysis are: Phosphate from ATP is joined to glucose, making a 6-carbon phosphate The 6-C phosphate breaks into 2 PGAL Hydrogen is removed and phosphate added to make two 3-carbon phosphates The two 3-C phosphates are converted to pyruvic acid, giving off enough energy for 4 ATP

Glycolysis Diagram 2 Pyruvic Acid (pyruvate) CH 3 COCOOH Glucose C 6 H 12 O 6 CCCCCC CCC 6 carbon-phosphate 2 PGAL 3 carbon-phosphate P-CCCCCC-P P-CCC P-CCC-P 2 ATP 2 ADP+P Energy “used” 2 NAD and 2P 2 NADH + H 4 ADP+P 4 ATP Energy “gained”

Uses of Pyruvic Acid The Pyruvic acid can be used for one of several different pathways, depending on the organism and the circumstances: 1. For alcoholic fermentation (in yeasts) 2.For lactic acid fermentation (in milk bacteria, and emergency systems in animals) 3.For aerobic respiration (the Krebs’ cycle) in most eukaryotes (plants and animals)  In most animals, the pyruvic acid is first changed to Acetyl Co-A before being used in Krebs’ cycle

Uses of Pyruvic Acid Pyruvic Acid Krebs Cycle Alcoholic Fermentation Lactic Acid Fermentation Ethyl Alcohol Lactic Acid Acetyl Co-A Co enzyme A Enzyme Reaction CO 2 NAD NADH+H Anaerobic RespirationAerobic Respiration 2 CO 2 Electron Transport Glycolysis 6 H 2 O

Lactic Acid Fermentation in Humans Humans normally undergo aerobic respiration (we use oxygen) Under extreme exertion (or when suffocating) we don’t get enough oxygen. Then we use lactic acid fermentation to produce some energy without oxygen. Build-up of lactic acid in muscles can cause pain and cramps. Runners sometimes can’t breath fast enough to supply their bodies with oxygen Lactic acid build-up causes pain, fatigue, and cramps

Steps in aerobic respiration 1. Pyruvic acid is converted to acetyl Co-A 2. 2 carbons from Acetyl Co-A join onto a 4C compound (oxaloacetic acid) to make citric acid, a 6C compound (citric acid) 3. Citric acid gives off one carbon dioxide to make a 5C compound (α-ketoglutaric acid) 4. This gives off another carbon dioxide to make a 4C compound (succinic acid) 5. The 4C compound rearranged (back into oxaloacetic acid), through two intermediate steps (fumaric acid and malic acid). 6. Captured hydrogen used to make energy Krebs cycle

The Enzyme Reaction Pyruvic acid + Co-enzyme A CO 2 + Acetyl Co-A Acetyl Co-A carries two carbon atoms to the Krebs cycle, before being turned back into co-enzyme A

Simplified Krebs Cycle Diagram Citric Acid C 6 5-carbon compound C 5 (α-ketoglutaric acid) 4 Carbon compound C 4 (Succinic acid) 4 Carbon compounds (fumaric acid & malic acid) Oxaloacetic Acid C 4 Acetyl Co-A CO 2 NADH+H FAD FADH 2 NAD H2OH2O H2OH2O C2C2 C4C4

Advanced Krebs cycle (Optional Enrichment) Co2Co2 CO 2 Given off Hydrogen Stored (NADH, FADH 2 )

The Electron Transport Chain AKA: cytochrome system During the reactions of aerobic respiration, lots of Hydrogen has been captured in hydrogen storing compounds, including: 2 NADH from Glycolysis 2 NADH from conversion of Pyruvic Acid 6 NADH from the Krebs cycle 2 FADH 2 from the Krebs cycle Many of the hydrogens have lost electrons Now the energy of those electrons & hydrogen ions are used to make ATP

The Electron Transport Chain

Along the inner membrane of the mitochondrion, electrons are passed from molecule to molecule The energy from these electrons is used to “pump” hydrogen ions (H + ) into the space between the membranes The hydrogen ions diffuse back in, producing ATP by chemiosmosis (similar to photosynthesis) The hydrogen ions and electrons are combined with oxygen to form water.

The Electron Transport Chain The simplified outcome of electron transport: The hydrogen atoms join with oxygen to make water. Lots of ATP is produced 4 H + + O 2 + 4e-  H 2 O + Energy ENERGY ATP ADP + P

Remember, up to 38 ATP molecules can be produced from the complete respiration of a single glucose molecule. Other organic molecules, such as starches and lipids, can produce even more ATP if they undergo complete respiration. ATP is the energy exchange medium of the cell. It provides the energy for most cellular activity.

Cellular Respiration Videos Cellular Respiration (Overview Lecture) Cellular Respiration Sugar Goes to ATP (Hey There Delilah) Sugar Goes to ATP Cellular Respiration Song ( I Gotta Feeling) Cellular Respiration Song Cellular Respiration (Californication: too long for class) Cellular Respiration Student Made Respiration video (not too bad) Student Made Respiration video Student-made Respiration song (dreadful and full of spelling mistakes, but mercifully short ) Student-made Respiration song

Assignments on Respiration. Read Chapter 7, pp. 127 to 138. Read carefully the chapter summary on page 139. Do exercises on page 140 # 1 to 20 Draw a diagram to represent the Krebs’ cycle