KEY CONCEPT Cellular respiration is an aerobic process with two main stages.

1. KEY CONCEPT Cellular respiration is an aerobic process with two main stages.

2. Objectives • Describe the process of glycolysis. • Describe the details of the Krebs cycle and the electron transport chain.

3. Glycolysis is needed for cellular respiration. • The products of glycolysis enter cellular respiration when oxygen is available. • two ATP molecules are used to split glucose • four ATP molecules are produced • two molecules of NADH produced • two molecules of pyruvate produced

4. The Krebs cycle is the first main part of cellular respiration. • Pyruvate is broken down before the Krebs cycle. • carbon dioxide released • NADH produced • coenzyme A (CoA) bonds to two-carbon molecule

5. The Krebs cycle produces energy-carrying molecules.

6. The Krebs cycle produces energy-carrying molecules. • NADH and FADH2 are made • intermediate molecule withCoA enters Krebs cycle • citric acid(six-carbon molecule)is formed • citric acid is broken down,carbon dioxide is released,and NADH is made • five-carbon molecule is broken down, carbon dioxide is released, NADH and ATP are made • four-carbon molecule is rearranged

7. The electron transport chain is the second main part of cellular respiration. • The electron transport chain uses NADH and FADH2 to make ATP. • high-energy electrons enter electron transport chain • energy is used to transport hydrogen ions across the inner membrane • hydrogen ionsflow through achannel in themembrane

8. The electron transport chain is the second main part of cellular respiration. • The breakdown of one glucose molecule produces up to38 molecules of ATP. • The electron transport chain uses NADH and FADH2 to make ATP. • ATP synthase produces ATP • oxygen picks up electrons and hydrogen ions • water is released as a waste product

9. Question/Answer • How does glycolysis result in a net gain of two ATP molecules? • Glycolysis makes four ATP molecules but two ATP are used to split the glucose molecule, yielding a net gain of two ATP. • Does glycolysis directly produce as much ATP as the Krebs cycle? Indirectly? Explain. • Glycolysis and the Krebs cycle directly produce equal amounts of ATP. Indirectly, the Krebs cycle is responsible for more ATP production through the transfer of energy to the electron transport chain. • In what two ways is the Krebs cycle important for making ATP? • The Krebs cycle produces two ATP and energy-carrying molecules that are used to produce more ATP in the electron transport chain.

10. Question/Answer • What event starts the Krebs cycle? • Pyruvate (from glycolysis) is broken down and a two-carbon molecule bonded to Coenzyme A (acetyl-CoA) enters the Krebs cycle. • Where does the Krebs cycle take place? • Mitochondrion matrix • How many membranes does a pyruvate molecule cross? Two: outer and inner membranes of mitochondrion. • How does the electron transport chain depend on the Krebs cycle? • Energy from the Krebs cycle is necessary for the electron transport chain to function.

11. Question/Answer • How are hydrogen ions involved in the electron transport chain? • Hydrogen ions are transported across the inner membrane and then flow through ATP synthase to produce ATP. • Where do hydrogen ions accumulate? • On the inside of the inner mitochondrial membrane. • Where does the energy come from that pumps H+ against their gradient? • From electrons removed from NADH and FADH2.