Cellular Respiration—An Overview, Summaries of Biology

Download Cellular Respiration—An Overview and more Summaries Biology in PDF only on Docsity! Cellular Respiration—An Overview 1 Cellular Respiration—An Overview What are the phases of cellular respiration? Why? All cells need energy all the time, and their primary source of energy is ATP. The methods cells use to make ATP vary depending on the availability of oxygen and their biological make-up. In many cases the cells are in an oxygen-rich environment. For example, as you sit and read this sentence, you are breathing in oxygen, which is then carried throughout your body by red blood cells. But, some cells grow in envi- ronments without oxygen (yeast in wine-making or the bacteria that cause botulism in canned food), and occasionally animal cells must function without sufficient oxygen (as in running sprints). In this activity you will begin to look at the aerobic and anaerobic processes that are used by all organisms to produce ATP. Model 1 – Cellular Respiration Glucose 2 Pyruvate Krebs Cycle × 2 Oxidative Phosphorylation 2 Acetyl- CoA Link Glycolysis Cell Membrane Cytoplasm Mitochondrion Inner Membrane Inner Matrix 2 ATP 2 NADH 2 NADH 6 NADH 2 FADH2 2 CO2 2 ATP 4 CO2 34 ATP 6 H2O 6 O2 C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O + Energy 1. According to Model 1, what are the reactants of cellular respiration? 2. According to Model 1, what are the products of cellular respiration? 2 POGIL™ Activities for AP* Biology 3. Cellular respiration occurs in four phases: glycolysis, the link reaction, the Krebs cycle, and oxidative phosphorylation. a. Which phase of cellular respiration occurs in the cytoplasm of the cell? b. Which phases of cellular respiration occur in the mitochondria? c. Which of the four phases of cellular respiration require oxygen? d. Which of the four phases of cellular respiration produce carbon dioxide? e. Which of the four phases of cellular respiration produce water? 4. The goal of cellular respiration is to provide the cell with energy in the form of ATP. a. Which of the four phases of cellular respiration result in the production of ATP? b. How many ATPs (total) are produced for every glucose molecule that undergoes cellular respiration? c. What reactants of ATP must be available in the cell in order to produce ATP? d. Brainstorm several cellular processes for which energy or ATP is necessary. Read This! Glucose, or any carbon-based molecule, can be burned in oxygen (oxidized) to produce carbon dioxide and water. Combustion reactions release large amounts of energy. However, the energy release is uncontrolled. An organism would not be able to handle all that energy at once to do the work of the cell. Cellular respiration is essentially the same reaction as combustion, but the oxidation of glucose occurs in several controlled steps. The same amount of energy is ultimately released, but it is gradually released in small, controlled amounts. High potential energy molecules of ATP are produced while the carbon atoms are used to form various other molecules of lower potential energy. Each of these steps is catalyzed by an enzyme specific to that step. Model 1 illustrates the ideal circumstances for cellular respiration. In some situations, however, one glucose molecule may not result in 38 ATP molecules being produced. 5. Consider Model 1. Besides ATP, what other molecules appear to be high potential energy molecules (free energy carriers) during cellular respiration? Cellular Respiration—An Overview 5 Model 3 – Energy in Anaerobic Environments Glucose 2 Pyruvate 2 Alcohol Glycolysis 2 ATP 2 NADH 2 CO2 Fermentation 2 NAD+ 2 NAD+ Glucose 2 Pyruvate 2 Lactic Acid Glycolysis 2 ATP 2 NADH Fermentation 15. Examine the two anaerobic processes in Model 3. Is oxygen used in either process? 16. What is the definition of anaerobic? 17. Compare the energy output (in the form of ATP) for a single glucose molecule that undergoes glycolysis and fermentation to that of a glucose molecule undergoing cellular respiration. 18. The efficiency of a cell is dependent on the cyclic nature of NAD+ and NADH. Building NAD+ molecules from raw materials each time one was needed would require a huge amount of free energy and resources. Even though the fermentation steps shown in Model 3 do not provide any ATP, they are critical to the energy production of the cell. Predict what would happen to the energy supply in a cell if fermentation did not happen under anaerobic conditions. 6 POGIL™ Activities for AP* Biology Extension Questions 19. The muscle “burn” that you feel when doing strenuous activity (sprints for example) is caused by a buildup of lactic acid in the muscle tissue of your body. Explain this phenomenon in the context of cellular respiration and fermentation. 20. The evolution of photosynthesizing organisms on Earth and the development of an oxygen-rich environment led to a rapid diversification of life. Explain why there is an evolutionary advantage to an organism that requires oxygen to live compared to one that does not require oxygen. 21. Under laboratory conditions muscle cells were broken up and separated into fractions of mito- chondria and cytoplasm in an attempt to learn more about cellular respiration. Each fraction was incubated with glucose or pyruvate. Tests were carried out during incubation for the presence of either carbon dioxide or lactic acid. The results are shown below: Cell Fraction CO 2 Lactic Acid Mitochondria incubated with glucose Absent Absent Mitochondria incubated with pyruvate Present Absent Cytoplasm incubated with glucose Absent Present Cytoplasm incubated with pyruvate Absent Present a. What does the presence of lactic acid in a sample indicate about what process is occurring in each cell fraction? b. Explain why lactic acid was produced by the cytoplasm fraction incubated with glucose, but not the mitochondrial fraction. c. Why was no carbon dioxide produced by either fraction incubated with glucose? Cellular Respiration—An Overview 7 d. Why did the cytoplasm fraction produce lactic acid in the presence of both glucose and pyruvate? e. Why did the mitochondria produce carbon dioxide in the presence of pyruvate but not in the presence of glucose?