Chapter 7 Oxidation and Reduction Introduction to Respiration Day 2

© 2014 Pearson Education, Inc. Cellular respiration can best be described as A.using energy released from breaking high-energy covalent bonds in organic molecules to make ATP. B.taking electrons from food and giving them to oxygen to make water and using the energy released to make ATP. C.converting higher-energy organic molecules to lower-energy organic molecules and using the energy released to make ATP.

The Principle of Redox transfer electrons Chemical reactions that transfer electrons between reactants are called oxidation-reduction reactions, or redox reactions. © 2014 Pearson Education, Inc.

Oxidation In oxidation, a substance loses electrons, or is oxidized.

Redox In reduction, a substance gains electrons, or is reduced (the amount of positive charge is reduced). © 2014 Pearson Education, Inc.

The electron donor is called the reducing agent. (Na) The electron acceptor is called the oxidizing agent. (Cl) becomes oxidized (loses electron) becomes reduced (gains electron)

Figure 7.UN02 becomes oxidized becomes reduced The electron donor is called the reducing agent. (X) The electron acceptor is called the oxidizing agent. (Y)

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Figure 7.3 Reactants Products Methane (reducing agent) Oxygen (oxidizing agent) Carbon dioxide Water becomes reduced becomes oxidized

© 2014 Pearson Education, Inc. Figure 7.UN03 becomes oxidized becomes reduced

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Stepwise Energy Harvest via NAD + and the Electron Transport Chain  In cellular respiration, glucose and other organic molecules are broken down in a series of steps.  Electrons from organic compounds are usually first transferred to NAD , a coenzyme.  As an electron acceptor, NAD  functions as an oxidizing agent during cellular respiration.  Each NADH (the reduced form of NAD  ) represents stored energy that is tapped to synthesize ATP. © 2014 Pearson Education, Inc.

Figure 7.4 NAD  Nicotinamide (oxidized form) Nicotinamide (reduced form) Oxidation of NADH Reduction of NAD  Dehydrogenase NADH  2[H] (from food) 2 e −  2 H  2 e −  H  HH HH 

Figure 7.UN04

 NADH passes the electrons to the electron transport chain.  Unlike an uncontrolled reaction, the electron transport chain passes electrons in a series of steps instead of one explosive reaction.  O 2 pulls electrons down the chain in an energy- yielding tumble.  The energy yielded is used to regenerate ATP. © 2014 Pearson Education, Inc.

Figure 7.5 Explosive release (a) Uncontrolled reaction (b) Cellular respiration H2OH2O Free energy, G Electron transport chain Controlled release of energy H2OH2O 2 H  2 e − 2 H   2 e − ATP ½ ½ ½ H 2  O2O2 O2O2 O2O2 2 H 

Zombie Ladybug When a female Dinocampus coccinellae wasp stings a ladybug, it leaves behind a single egg. After the egg hatches, the larva begins to eat its host form the inside out. When ready, the parasite emerges and spins a cocoon between the ladybug’s legs. Though the body is now free of the tormentor, the bug remains enslaved, standing over the cocoon and protecting it form predators.