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Chapter 4B: How Cells Obtain Energy 4.2 Glycolysis Where does energy to power endergonic reactions come from? This ____________ can be thought of as the primary ____________ ____________ of cells in the same way that ____________ is the currency that people ____________ for things they need. ____________ is used to ____________ the majority of ____________ -requiring cellular ____________. ATP in Living Systems How many phosphate groups are in ATP? Energy is usually released by ATP when what is removed? Label the ATP molecule Click and drag the triangle to go around ribose Click and drag the square to go around the gamma phosphate group Click and drag the circle to go around adenine Matching _____ ATP A. Transfer of a phosphate group to another molecule _____ ADP B. Used for energy requiring cell functions _____ Phosphorylation C. Functional group containing phosphorous and oxygen _____ Phosphate group D. Lower energy molecule 1 Glycolysis What is glycolysis? Glycolysis begins with the ______________ -carbon, ring-shaped structure of a single ______________ molecule and ______________ with two molecules of a three-carbon sugar called ______________. Glycolysis consists of ______________ distinct ______________. In the ______________ part of the glycolysis pathway, ______________ is used to make ______________ so that the six-carbon sugar molecule can be ______________ evenly into two threecarbon ______________ molecules. In the ______________ part of glycolysis, ______________ and nicotinamideadenine dinucleotide (______________) are produced. Where in the cell does glycolysis take place? Label the diagram by clicking and dragging the labels into the correct places. Glucose 2 ATP 2 ATP 2 ATP 2 ADP 2 ADP 2 ADP Pyruvate 2 Pyruvate NAD+ NAD+ NADH NADH 4.3 The Citric Acid Cycle and Oxidative Phosphorylation The Citric Acid Cycle What end product of glycolysis is transported into the mitochondria? What is required for aerobic respiration to go forward? Pyruvate is transformed into what molecule? What is removed in this reaction? Coenzyme A is a ____________ compound. It is made from ____________. Where in the cell does the citric acid cycle (also called the Kreb’s cycle) take place? How does the citric acid cycle close the loop for its reactions? During the eight steps of the cycles, what is produced? Which two important coenzymes are used to transfer electrons from the citric acid cycle to the next pathway? How many turns of the cycle does it take to process the equivalent of one glucose molecule? Match the following _____ pyruvate A. Occurs in the mitochondria _____ coenzyme A B. The beginning reactant for the second stage of aerobic respiration _____ acetyl-CoA C. Coenzymes carrying electrons and hydrogen released by the reactions of the second stage _____ NADH and FADH2 D. Carries two carbon atoms into the citric acid cycle _____ Citric acid or Krebs cycle E. Binds to pyruvate as a CO2 molecule is released 3 Oxidative Phosphorylation Oxidative phosphorylation is made up of two steps: the electron transport chain and chemiosmosis. All of the NADH and FADH2 that were produced during glycolysis and the citric acid cycle (Kreb’s cycle) are used to make ATP. Protein complexes embedded in the inner mitochondrial membrane are used for this process. Read through the section in the textbook referring to figure 4.15 as the processes are described. Then study the following diagram and answer the questions based on the information in the diagram and text book. Electron Transport Chain NADH and FADH2 carry high energy electrons to the electron transport chain where they are donated and used to make ATP during aerobic respiration. In the diagram, what is used to represent the high energy electrons? When NADH donates electrons, what products are formed (follow the curved arrow from NADH)? As the high energy electrons leave NADH they enter the electron transfer chain. Follow the electrons along the grey arrow to see the route the electrons take. How many molecules/complexes make up the electron transfer chain? The molecules are numbered in the text book figure 4.15. Which molecule accepts electrons from NADH? Which molecule accepts electrons from FADH2? 4 How many molecules span the entire membrane (referred to as “embedded protein channels” in the diagram)? High potential energy electrons provide the energy necessary to pump hydrogen ions across the inner mitochondrial membrane. H+ moves from which region to which region on the diagram (see the labels on the right side for the names of the regions) What is the name of the region where the highest concentration of hydrogen ion (H+) is located? Energy is required to move the hydrogen ions across the membrane in the direction indicated in the diagram. Why is energy required? (Remember membrane transport and concentration gradients from chapter 3) What molecule is the final electron acceptor after the electron has moved through the electron transport chain? What compound is formed as a final product of the electron transport chain? Is any ATP produced in the electron transport chain? Is any ATP used in the electron transport chain? 5 Chemiosmosis Once a concentration gradient of hydrogen ions has formed, the process of chemiosmosis occurs. How do the hydrogen ions move through the membrane? Would energy be required for the hydrogen ions to move in the direction shown in the figure? Explain your reasoning. What is the name of the embedded protein that provides a channel for the hydrogen ions to pass through the membrane? (It is labeled in the diagram) The flow of hydrogen ions through the protein channel provides free energy to do work. Besides allowing hydrogen ions to pass through the membrane what other function does ATP Synthase have? Which direction is the reaction going: ATP ADP + Pi ADP + Pi ATP or Which molecule is higher energy ATP or ADP? Does it require energy for this reaction? What provides the free energy to do the work required? In the electron _________________ chain, the free _________________ from the series of _________________ just described is used to _________________ hydrogen ions across the _________________. The uneven distribution of H+ ions across the membrane _________________ an electrochemical _________________, owing to the H+ ions’ positive charge and their higher _________________ on one side of the membrane. Hydrogen ions _________________ through the inner membrane through an integral membrane _________________ called ATP Synthase. This complex protein acts as a tiny _________________, turned by the force of the _________________ ions diffusing through it, down their _________________ gradient from the _________________ space, where there are _________________ mutually repelling hydrogen ions to the matrix, where there are _________________. The turning of the parts of this molecular machine _________________ ATP from ADP. This flow of _________________ ions across the _________________ through ATP synthase is called _________________. 6 ATP Yield Fill in the table. Some of the information has been filled in as an example. How many ATP formed How many NADH/FADH2 reduced Glycolysis Krebs cycle List other end products (besides ATP and NADH) Pyruvate 1 per cycle 2 per one molecule of glucose zero Electron transfer phosphorylation 4.4 Fermentation In the absence of O2 aerobic respiration cannot occur. If _______________ respiration does not occur, _____________ must be reoxidized to NAD+ for reuse as an _______________ carrier for _______________ to continue. How is this done? Some living systems use and _______________ molecules as the _______________ _______________ _______________. Processes that use an organic molecule to _______________ NAD+ from NADH are collectively referred to as _______________. In contrast, some living systems use an _______________ molecule as a _______________ electron acceptor; both methods are a type of _______________ cellular respiration. Anaerobic respiration _______________ organisms to convert _______________ for their use in the _______________ of oxygen. Choose from the following A. Alcohol fermentation B. Lactic Acid fermentation C. Both types of fermentation ______ Glycolysis is the first stage ______ Yeasts are famous for their use of this pathway ______ Animals use this for a quick fix of energy for their muscles ______ Pyruvate and NADH form, and the net energy yield is two ATP ______ The final steps regenerate NAD+, the coenzyme that assists the breakdown reactions ______ Each pyruvate molecule that formed in glycolysis is converted to the intermediate acetaldehyde ______ These reactions do not completely degrade glucose to CO2 and H2O ______ Saccharomyces cerevisiae (bread yeast) makes bread dough rise ______ Drunken birds such as tipsy wild turkeys and robins consume fermented fruit or grain ______ Lactobacillus of yogurt and some other bacteria use this anaerobic pathway 7 4.5 Connections to Other Metabolic Pathways Briefly describe how other sugars are connected to glucose metabolism Briefly describe how proteins are connected to glucose metabolism. Briefly describe how lipids are connected to glucose metabolism. 8