CHAPTER 4 Cellular Respiration Harvesting Chemical Energy The

CHAPTER 4 Cellular Respiration: Harvesting Chemical Energy

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

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

Cellular Respiration How do we get from THIS To THIS

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

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

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

Three Stages of Aerobic Cellular Respiration C 6 H 1206 + 6 O 2 6 CO 2 +6 H 20 + ENERGY q • q • Glycolysis in cytoplasm Kreb’s cycle in mitochondrial matrix Electron Transport Chain at inner membrane of mitochondria

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 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Collectively, 2 ATP and 6 NADH are made from the 2 pyruvates. NADH will be used in the electron transport chain.

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 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • NAD+ is a coenzyme • It is reduced to NADH when it picks up two electrons and one hydrogen ion

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 1937. • 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 20 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings

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

Structure of the Mitochondria • Organelle with an outer This organelle produces the 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 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings majority of ATP for the cell.

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 Cytosol Mitochondrion Glycolysis Glucose 2 Pyruvic acid 2 Acetyl. Co. A Krebs Cycle Electron Transport Maximum per glucose: by direct synthesis by ATP synthase Figure 6. 14 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 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings