Cells Need Energy 1. Organisms obtain energy from food Slide # 2 Cells Need Energy 1. Organisms obtain energy from food 2. Glucose is main source of food for cells 3. Cells break chemical bonds of glucose; energy released Go to Section:

Respiration *** We DON’T have to teach super specific processes of glycolysis, fermentation, just the reactants and products of each of those and that NADH is an electron carrier just like ATP (they are all energy molecules)

Cellular Respiration If cellular respiration took place in just one step: All of the energy would be released at once Most would be lost in the form of light and heat. Instead, a living cell has to release chemical energy in food molecules a little bit at a time. Must trap those little bits of energy by using them to make ATP.

Cellular Respiration Cellular Respiration - Process that releases energy by breaking down glucose and other food molecules in the presence of oxygen

Cellular Respiration Requires (Reactants): Gives Off (Products): Glucose Oxygen Gives Off (Products): Water Carbon Dioxide Energy

3 Stages of Cellular Respiration Glycolysis Krebs Cycle Electron Transport Chain Each stage captures some of the chemical energy available in food molecules and uses it to produce ATP.

First Stage: Glycolysis Glycolysis –A molecule of glucose is broken into two molecules of pyruvic acid. Occurs in the cytoplasm Does not require oxygen (anaerobic) 1 Glucose 2 Pyruvic Acid C-C-C-C-C-C C-C-C C-C-C

TO THE ELECTRON TRANSPORT CHAIN Glycolysis Glucose C-C-C-C-C-C C-C-C C-C-C 2 Pyruvic Acid C-C-C C-C-C 2 ATP 2 ADP 2 NAD+ 4 ADP TO THE ELECTRON TRANSPORT CHAIN 2 NADH 4 ATP

Products of Glycolysis NET Gain 2 ATP (Major Energy molecule) 2 NADH (Minor Energy molecule) 2 Pyruvic Acid Molecules http://www.youtube.com/watch?v=C78BMJ7D68I (Glucose – Sugar Sugar Song)

Fermentation Krebs Cycle Glycolysis Fermentation Krebs Cycle Anaerobic (no oxygen) Aerobic (oxygen)

Second Stage: Fermentation or Krebs Cycle Glycolysis can be followed by fermentation or the Krebs cycle depending if oxygen is present. Fermentation will occur if no oxygen is present. Krebs Cycle will occur if oxygen is present.

Second Stage: Fermentation Fermentation - Releases energy from food molecules by producing ATP in the absence of oxygen. Anaerobic - Does not require oxygen Occurs in the cytoplasm (cytosol)

Fermentation Two types of Fermentation: Alcoholic Fermentation Lactic Acid Fermentation

Alcoholic Fermentation Produces: Ethyl alcohol Carbon dioxide Examples: Used to produce beer and wine Causes bread dough to rise Carried out by yeasts and a few other microorganisms

Lactic Acid Fermentation Produces: Lactic Acid Examples: Produced in your muscles during rapid exercise Buildup of lactic acid causes a painful, burning sensation…why muscles feel sore Used in production of cheese, sour cream, yogurt, and pickles. Carried out by animals and some unicellular prokaryotes (bacteria).

At the End of Glycolysis 90% of the chemical energy that was available in glucose is still unused Locked in the high-energy electrons of pyruvic acid Oxygen is required for the final steps of cellular respiration. Oxygen is the world's most powerful electron acceptor. Therefore, cellular respiration is aerobic (requires oxygen).

Second Stage: Krebs Cycle Krebs Cycle - Pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions. Occurs in the mitochondrion.

Krebs Cycle Starts: Pyruvic Acid Produces: Carbon Dioxide Source of all the carbon dioxide in your breath. Energy Tally - Each Molecule of Pyruvic Acid Produces: 1 ATP (and NADH/FADH2) All energy molecules!

Third Stage: Electron Transport Chain The electron transport chain uses the high-energy electrons from the Krebs cycle to convert ADP into ATP. Oxygen serves as the final electron acceptor. Occurs in the mitochondrion.

ATP Glycolysis: 2 ATP molecules per glucose molecule Needs 2 ATP (Investment) Produces 4 ATP Net gain of 2 ATP molecules. Krebs Cycle and Electron Transport: 34 ATP molecules per glucose molecule Total = 36 ATP

Black eyed peas review respiration song http://www.youtube.com/watch?v=3aZrkdzrd04&feature=email

Exercise: Quick Energy Muscles only contain enough ATP for a few seconds of intense activity Then, muscle cells produce their ATP by lactic acid fermentation. Lasts only about 90 seconds or about 200 - 300 meters. Produces lactic acid, which requires oxygen debt (must repay after the race with plenty of heavy breathing).

Exercise: Long-Term Energy (Longer than 90 seconds) Cellular Respiration is the only way to generate a continuing supply of ATP Releases energy slowly (why athletes must pace themselves) Body stores energy in muscle and other tissues in the form of the carbohydrate glycogen (usually enough to last for 15 - 20 min.) After that, your body begins to break down other stored molecules, including fats, for energy

Photosynthesis vs. Respiration Photosynthesis and cellular respiration take place in opposite directions! Photosynthesis: Use light energy to build a sugar. carbon dioxide + water + light energy → sugars + oxygen Respiration: Break down sugar to release energy. oxygen + sugars → carbon dioxide + water + energy

Respiration: Break Down Glucose Photosynthesis: Build Glucose

Photosynthesis vs. Respiration Cellular Respiration Occurs In: All eukaryotes Some prokaryotes Photosynthesis Occurs In: Plants Algae Some bacteria

F. Review 1. What is the source of carbon for cellular respiration? Glucose (C6H12O6) is the carbon source.

F. Review 2. Where do Stages 2 and 3 of cellular respiration take place? in mitochondria