CHAPTER 4 Cellular Respiration: Harvesting Chemical Energy

The Big Picture EQUATION FOR PHOTOSYNTHESIS 6CO 2 + 6H 2 O + ENERGY C 6 H 12 O 6 + 6O 2 C 6 H 12 O 6 + 6O 2 Carbon Dioxide Water Glucose Oxygen EQUATION FOR RESPIRATION C 6 H 12 O 6 + 6O 2 C 6 H 12 O 6 + 6O 2 Carbon Dioxide Water ATP 6CO 2 + 6H 2 O + LIGHT Glucose Oxygen

Metabolism The sum of all the chemical processes occurring in an organism at one time Management of material and energy resources within the cell Catabolic – break down big molecules into smaller ones Anabolic – build larger molecules from smaller components

The Big Picture Important points to remember:  Energy enters the food chain through autotrophs  Heterotrophs must take in energy from organic sources  Carbohydrates, proteins, and fats do not come to us the way our cells can use them.  So…how do organisms change the food into energy to fuel their bodies?

Cellular Respiration How do we get from THIS To THIS

Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings ATP Energy molecule used to shuttle energy between catabolic and anabolic reactions Energy is released from ATP through the loss of phosphate groups

Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings What is Cellular Respiration? Cellular Respiration = making ATP through the breakdown of foods Aerobic Cellular Respiration Fermentation

Where Does Cellular Respiration Take Place? Glycolysis and Anaerobic Respiration occurs in the Cytoplasm of the cell Aerobic Respiration takes place in the Mitochondria

Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Overview of Cellular Respiration Pyruvic Acid Glycolysis OxygenAerobic No OxygenAnaerobic Krebs Cycle ETS Fermentation Lactic Acid Alcohol Glucose All of the reactions involved in cellular respiration can be grouped into these stages:

Three Stages of Aerobic Cellular Respiration  Glycolysis in cytoplasm  Kreb’s cycle in mitochondrial matrix  Electron Transport Chain at inner membrane of mitochondria C 6 H O 2  6CO 2 +6H ENERGY

Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Glycolysis This part of cellular respiration takes place in the cell cytoplasm Each Glucose molecule gets converted into 2 pyruvate molecules Energy requiring and energy releasing steps Energy net yield is 2 ATP and 2 NADH Enzymes help along the way

Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Krebs Cycle Each pyruvate (carbohydrate) molecule is completely oxidized into carbon dioxide Energy released from these reactions results in the formation of 1 ATP molecule and 3 NADH molecules Collectively, 2 ATP and 6 NADH are made from the 2 pyruvates. NADH will be used in the electron transport chain.

Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Electron Transport Chain The loss of electrons from NADH result in the addition of energy to protein pumps in the membrane H + is moved from the inside to the outside of the inner membrane A gradient of H + is created

Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings What Carries the Electrons ? NAD + (nicotinadenine di-nucleotide) acts as the energy carrier NAD + (nicotinadenine di-nucleotide) acts as the energy carrier NAD + is a coenzyme NAD + is a coenzyme It is reduced to NADH when it picks up two electrons and one hydrogen ion It is reduced to NADH when it picks up two electrons and one hydrogen ion

Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Electron Transport Chain ATP is made as H + ions diffuse back into the matrix of the mitochondria by a different protein (ATP synthase). The energy released by the “rush” of H + is used by this enzyme to make ATP (kind of like a rush of water in a stream being used to turn a water wheel).

Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings A Little Krebs Cycle History Discovered by Hans Krebs in He received the Nobel Prize in physiology medicine in 1953 for his discovery. Forced to leave Germany prior to WWII because he was Jewish.

Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Why do we need Oxygen? Oxygen is required by any organism that has mitochondria because it is used to keep the Electron Transport Chain running Oxygen pulls electrons from the chain and combines with 2 H + to form H 2 0

Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Electron Transport Chain Animation Electron Transport Chain Animation

Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Structure of the Mitochondria Organelle with an outer and inner membrane The Krebs cycle takes place in the matrix of the mitochondria – space bordered by the inner membrane Electron Transport Chain takes place across the inner membrane – between the matrix and intermembrane space This organelle produces the majority of ATP for the cell.

Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Ultimately, aerobic respiration produces about 36 ATP molecules from each glucose molecule.

Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Adding Up the ATP from Cellular Respiration Figure 6.14 Cytosol Mitochondrion Glycolysis Glucose 2 Pyruvic acid 2 Acetyl- CoA Krebs Cycle Electron Transport by direct synthesis by direct synthesis by ATP synthase Maximum per glucose:

Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Energy yield from complete oxidation of glucose by aerobic respiration

Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings THE END