Cell Energy: Cellular Respiration

Cellular Respiration Overview Cytoplasm Mitochondria Electrons [Inner membrane] Glycolysis Krebs Cycle Electron Transport Chain (ETC) [Matrix] Glucose Pyruvate 34 ATP 2 ATP Image modified from—Campbell Biology: Concepts and Connections, 5th ed. (Online textbook). Retrieved 30 March 2010 from: http://media.pearsoncmg.com/bc/bc_campbell_concepts_5/media/art/ch6/ir/imagelib_tab_1/14.htm

Comparing photosynthesis and cell respiration The energy flow in these reactions take place in opposite directions The equation for photosynthesis and cellular respiration are the reverse of each other Photosynthesis releases oxygen and cellular respiration uses the oxygen to release the energy in food Photosynthesis uses carbon dioxide and cellular respiration replaces it. Photosynthesis: Chloroplast Cellular Respiration: Mitochondria

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Cellular respiration overview Goal: Convert food (C6H12O6) into energy  ATP Overall Reaction: C6H12O6 + 6 02  6 CO2 +6 H20 + ENERGY (ATP) In the presence of oxygen: Aerobic- 34-38 ATP Glycolysis Krebs cycle ETC Without oxygen- Anaerobic- 2 ATP Fermentation: Alcoholic and Lactic Acid

Big Picture GLUCOSE Glycolysis Not a lot of ATP made Then With oxygen Aerobic Respiration Without oxygen Fermentation Alcoholic Lactic Acid Glycolysis Not a lot of ATP made

Glycolysis- the first step in releasing energy Only a small amount of energy is released in this step (2 ATP) Happens first whether oxygen is present or not Location: In the cytoplasm of the cell (not yet in the mitochondria) Reactants: Glucose Products: 2 Pyruvate 2 NADH (NAD+, Electrons, and Hydrogen) as an electron carrier 4 ATP are made – 2 ATP are used = 2ATP

Cellular Respiration Overview Cytoplasm Mitochondria Electrons [Inner membrane] Glycolysis Krebs Cycle Electron Transport Chain (ETC) [Matrix] Glucose Pyruvate 34 ATP 2 ATP Image modified from—Campbell Biology: Concepts and Connections, 5th ed. (Online textbook). Retrieved 30 March 2010 from: http://media.pearsoncmg.com/bc/bc_campbell_concepts_5/media/art/ch6/ir/imagelib_tab_1/14.htm

In the presence of oxygen the cycle will continue into the mitochondria!

Krebs Cycle Named after Hans Krebs- Also known as the Citric Acid Cycle Pyruvate is broken down into Carbon Dioxide in a series of energy extracting reactions Takes place in the matrix or space in the mitochondria Reactants: Pyruvate (3 carbon sugar) and oxygen Products: CO2, NADH, FADH2 (from FAD+), and 2 ATP One carbon from the Pyruvate attaches to an O2 molecule: CO2 The remaining carbons go through a series of events to release more CO2 and add electrons to NAD+  NADPH, and FAD+  FADH2 to fuel the next cycle

Image taken from www.sp.uconn.edu Chemically, this is how it all goes down. Image taken from www.sp.uconn.edu

Cellular Respiration Overview Cytoplasm Mitochondria Electrons [Inner membrane] Glycolysis Krebs Cycle Electron Transport Chain (ETC) [Matrix] Glucose Pyruvate 34 ATP 2 ATP Image modified from—Campbell Biology: Concepts and Connections, 5th ed. (Online textbook). Retrieved 30 March 2010 from: http://media.pearsoncmg.com/bc/bc_campbell_concepts_5/media/art/ch6/ir/imagelib_tab_1/14.htm

Electron Transport Chain (ETC) Takes place on the Cristae of the mitochondria The electron carriers FADH2 and NADH take the high energy electrons from the Krebs Cycle to the electron transport chain to convert ADP into ATP As electrons are passed from carrier to carrier, the energy is used to pump hydrogen ions (H+) across the membrane of the mitochondria. This high concentration of H+ flow through a protein, ATP Synthase, to convert ADP into ATP Forming 34 ATP Since oxygen is present, some of it will attach to the H+  H20

Cellular Respiration Overview Cytoplasm Mitochondria Electrons [Inner membrane] Glycolysis Krebs Cycle Electron Transport Chain (ETC) [Matrix] Glucose Pyruvate 34 ATP 2 ATP Image modified from—Campbell Biology: Concepts and Connections, 5th ed. (Online textbook). Retrieved 30 March 2010 from: http://media.pearsoncmg.com/bc/bc_campbell_concepts_5/media/art/ch6/ir/imagelib_tab_1/14.htm

Anaerobic conditions lead to . . . Fermentation What if after glycolysis, there is NO oxygen???? Anaerobic conditions lead to . . . Fermentation 1. Alcoholic 2. Lactic Acid ***No more ATP produced after glycolysis

Summary

Photosynthesis and Cellular Respiration “Cycle” Products of one become reactants of the other!