Cellular Respiration

Cell Metabolism Anabolic Reaction: Using energy to construct sugar molecules Photosynthesis Catabolic Reactions: Breaking down sugars to release energy Cellular Respiration

Photosynthesis & Cell Respiration Reverse energy flow in these two reactions Cell Respiration equation is the reverse of Photosynthesis equation Photosynthesis releases O2, Cell Respiration uses O2 Photosynthesis uses CO2, Cell Respiration releases CO2 Photosynthesis: Chloroplast Cellular Respiration: Mitochondria

Mitochondria & Respiration Mitochondria have both an inner membrane & outer membrane Cristae: folds of inner membrane Matrix: Fluid space of mitochondria Mitochondria & Respiration

Mitochondria vs. Chloroplasts

Cellular Respiration Goal: Convert food (C6H12O6) into energy (ATP) Overall Reaction: C6H12O6 + 6 O2  6 CO2 +6 H2O + 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

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

Glycolysis First step in releasing energy Whether oxygen is present or not Small amount of energy is released (only 2 ATP) Location: Cytoplasm (not in the mitochondria) Reactants: Glucose Products: 2 Pyruvate – 3 Carbon sugar 2 NADH (NAD+, e-, and H+) as electron carriers 4 ATP are made – 2 ATP are used = net 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, pyruvate will enter the mitochondria and cell respiration will continue

Krebs Cycle Named after Hans Krebs Also known as the Citric Acid Cycle Pyruvate is broken down into CO2 in a series of energy extracting reactions Takes place in the matrix (space) of the mitochondria

Krebs Cycle One carbon from Pyruvate attaches to an O2 molecule forming CO2 The remaining carbons go through a series of events to release more CO2 and add e- to NAD+  NADH, and FAD+  FADH2 to fuel the next cycle NADH and FADH2 are similar to NADPH Reactants: Pyruvate (3 carbon sugar) & Oxygen Products: CO2, NADH, FADH2, and 2 ATP

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 e- from glycolysis & Krebs Cycle to the ETC to convert ADP into ATP As e- are passed from carrier to carrier, energy is used to pump H+ across the membrane of the mitochondria. O2 acts as final carrier, adding e- to H+ forming H2O H+, now in high concentration, diffuse through ATP Synthase, converting ADP into ATP Form 34 ATP

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!