4.4. Overview of Cellular Respiration. Teacher Notes and Answers

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1 section 4.4 Overview of Cellular Respiration Teacher Notes and Answers SECTION 4 Instant Replay 1. It means that it needs oxygen to happen. 2. 6CO 2 molecules and 6H 2 O molecules should be circled. Vocabulary Check 1. aerobic and anaerobic 2. glycolysis 3. Krebs cycle 4. cellular respiration The Big Picture 5. mitochondria 6. reactants: C 6 H 12 O 6 and 6O 2, products: 6CO 2 and 6H 2 O 7. the electron transport chain Interactive Reader 1

2 section 4.4 Overview of Cellular Respiration Key Concept The overall process of cellular respiration converts sugar into ATP using oxygen. Cellular respiration makes ATP by breaking down sugars. You probably know that you need to breathe oxygen to survive. But how does your body use that oxygen? That oxygen helps your body to release chemical that is stored in sugars and other carbonbased molecules. The is released to produce ATP. This process of using oxygen to produce ATP by breaking down carbon-based molecules is called cellular respiration. Cellular respiration makes most of the ATP that a cell needs. Cellular respiration is an aerobic process. Aerobic (air-oh-bihk) means that it needs oxygen to happen. Cellular respiration takes place in mitochondria. These organelles are sometimes called the cell s powerhouses because this is where most of the cell s ATP is made. Mitochondria do not make ATP directly from food. ATP is made through many chemical reactions. Before cellular respiration can happen, food has to be broken down into smaller molecules. Food gets broken down into smaller molecules like glucose. Then, glucose gets broken down. Remember that glucose is a six-carbon sugar. Glycolysis (gly-kahl-uh-sihs) breaks glucose into two molecules that each have three carbons. 2 ADP 2 ATP Mitochondria (middle) are found in both animal (top) and plant (bottom) cells. They make ATP through cellular respiration. C C C C C C glucose C C C C C C 2 three-carbon molecules Glycolysis breaks glucose into 2 three-carbon molecules. Glycolysis is an anaerobic process. Anaerobic means that it does not need oxygen to happen. Glycolysis happens in the cell s cytoplasm. The three-carbon molecules from glycolysis then enter the mitochondria. The products of glycolysis the three-carbon molecules enter the mitochondria and are used in cellular respiration. Why is cellular respiration called an aerobic process? 2 McDougal Littell Biology

3 Cellular respiration is like a mirror image of photosynthesis. A mirror image is like an opposite the same thing, but in reverse. Cellular respiration and photosynthesis are not really opposites, but it can be helpful to think about them in that way. Photosynthesis makes sugars and cellular respiration breaks down sugars. The chemical equations of the two processes are basically opposites. The structures of mitochondria and chloroplasts are very similar. Remember that part of photosynthesis happens inside the stroma the fluid in the chloroplast and part of photosynthesis happens inside the membrane of the thylakoid. Similarly, part of cellular respiration happens in the fluid inside the mitochondria, called the matrix. The other part of cellular respiration happens in the inner membrane of the mitochondria. After glycolysis, the three-carbon molecules enter the mitochondria and begin the process of cellular respiration. There are two main parts of cellular respiration: COMPARING Processes Photosynthesis REACTANTS light Cellular Respiration PRODUCTS ATP, heat The products of photosynthesis sugars and O 2 are the reactants in cellular respiration. Stage 1: Krebs cycle The molecules from glycolysis enter a series of reactions called the Krebs cycle. The Krebs cycle produces a small amount of ATP and other molecules that carry to the next part of cellular respiration. It also makes carbon dioxide as a waste product. Stage 2: Electron Transport Energy is moved through a chain of proteins and a large number of ATP molecules are made. Oxygen enters the process here. The oxygen is used to make water molecules, which are waste products. CO 2 H 2 O CO 2 H 2 O PRODUCTS Sugars (C 6 H 12 O 6 ) O 2 REACTANTS Sugars (C 6 H 12 O 6 ) O 2 Interactive Reader 3

4 overview of cellular respiration STAGE 1: Krebs Cycle 1 Three-carbon molecules from glycolysis enter cellular respiration in mitochondria. matrix (area enclosed by inner membrane) mitochondrion ATP 6CO 2 2 Energy-carrying molecules transfer to Stage 2. STAGE 2: Electron Transport 3 Energy-carrying molecules from glycolysis and the Krebs cycle enter Stage 2 of cellular respiration. inner membrane from glycolysis ATP 6O 2 6H 2 O 4 ATP molecules are produced. Heat and water are released as waste products. Up to 38 ATP molecules are made from the breakdown of one glucose molecule. The equation for cellular respiration is shown below. You can see that there are many arrows between the reactants C 6 H 12 O 6 and 6O 2 and the products 6CO 2 and 6H 2 O. These arrows are there to tell you that there are many steps in the process. For example, the equation for cellular respiration includes glycolysis. Many enzymes also play important roles in the production of ATP. C 6 H 12 O 6 1 6O 2 6CO 2 1 6H 2 O a sugar oxygen carbon dioxide water 4 McDougal Littell Biology

5 Follow the steps of cellular respiration shown on in the figure on the previous page. Circle the products of cellular respiration in the figure on the previous page. 4.4 Vocabulary Check cellular respiration anaerobic aerobic Krebs cycle glycolysis Mark It Up Go back and highlight each sentence that has a vocabulary word in bold. 1. Which two terms are opposites? 2. Which term is a process that must happen in the cell s cytoplasm before cellular respiration? 3. Which term is a process that happens within the mitochondria as part of cellular respiration? 4. Which term is the name for this chemical equation: C 6 H 12 O 6 1 6O 2 6CO 2 1 6H 2 O a sugar oxygen carbon dioxide water 4.4 The Big Picture 5. In which organelle does cellular respiration take place? 6. What are the products and the reactants for cellular respiration? 7. Where is most of the ATP made during cellular respiration? Interactive Reader 5