Cell Respiration

What happens to the sugars made in photosynthesis What happens to the sugars made in photosynthesis? Sugars can be broken down in cells to provide energy I. Cell respiration A. Process where mitochondria breaks down food molecules to produce ATP and CO2 B. Equation: C6H12O6 + 6O2 = 6H2O + 6CO2 + energy C. Three stage process: glycolysis, citric acid cycle (Krebs cycle), and the electron transport chain 1. glycolysis takes place in the cytoplasm of the cell, is considered anaerobic (doesn’t need oxygen), and takes place in plants, animals, and microorganisms a. breaks down glucose into pyruvic acid

b. 2 molecules of ATP are used, and 4 are produced (net gain of 2 ATP) c. 2 pyruvic acid molecules move into the mitochondria, and are converted in 2 molecules of acetyl-CoA 2. Citric Acid Cycle (Krebs Cycle)- series of chemical reactions that take place in the mitochondria a. uses the acetyl-CoA to form 2 ATP and 2 CO2 molecules (1 of each per molecule of a-CoA)

b. the electron carries pick up energized electrons and pass them to the electron transport chain in the inner mitochondrial membrane 3. Electron Transport Chain a. electrons are transported in the electron transport chain inside the mitochondria, and are passed from protein to protein b. energy released during this transport is used to make ATP

c. the final electron acceptor at the end of the chain is oxygen, which reacts with 4 hydrogen atoms to form two molecules of water d. aerobic process- need O2 present this is why we need oxygen! Without it, the proteins in the electron transport chain can’t pass electrons and ATP production stops e. Electron transport chain adds 32 ATP molecules

4. Fermentation- there are times when cells are w/o oxygen for a short time (heavy exercise) a. an anaerobic process called fermentation follows glycolysis and makes ATP until oxygen is available b. two types i. lactic acid fermentation: pyruvic acid are converted to lactic acid & ATP is formed - lactic acid builds up in muscle cells, resulting in soreness after exercise

ii. Alchololic fermentation: used by yeast cells and some bacteria - breaks down sugar to produce ethyl alcohol and CO2 - used to bake break and in brewing