2011 Chapter 8 Photosynthesis Class/Homework
Chapter 8 Vocabulary 8.1 Term Definition Adenosine triphosphate (ATP) Autotroph Heterotroph Photosynthesis Compound that cells use to store and release energy A living thing that makes its own food A living thing that gets its food by consuming other living things Process by which autotrophs use sunlight, water, and carbon dioxide to produce carbohydrates and oxygen 8.2 Term Definition Chlorophyll Light-dependent reactions Light-independent reactions NADP + Primary pigment in plants Reactions in photosynthesis that require light and light- absorbing pigments Reactions in photosynthesis in which carbon dioxide and energy-carrying molecules are used to produce highenergy sugars Carrier molecule that transports highenergy electrons
Pigment Stroma Thylakoid Light-absorbing molecule Fluid portion of the chloroplast that surrounds the thylakoid membrane Photosynthetic membrane sac found inside chloroplasts 8.3 Term ATP synthase Calvin cycle Definition Enzyme that converts ADP and a phosphate group to ATP Another name for the light- independent reactions in which carbohydrates are produced Electron transport chain Photosystem Series of electron-carrier proteins that transport high-energy electrons during the process of making ATP Cluster of chlorophyll and proteins in the thylakoids essential to the light-dependent reactions
8.1 Energy and Life Part 1 Lesson Objectives Describe the role of ATP in cellular activities. Explain where plants get the energy they need to produce food. BUILD Vocabulary A. The chart below shows key terms from the lesson with their definitions. Complete the chart by writing a strategy to help you remember the meaning of each term. One has been done for you. Term Definition How I m Going to Remember the Meaning Adenosine triphosphate (ATP) Autotroph Heterotroph Photosynthesis Compound that cells use to store and release energy A living thing that makes its own food A living thing that gets its food by consuming other living things Process by which autotrophs use sunlight, water, and carbon dioxide to produce carbohydrates and oxygen ATP makes a cell able to do work. B. As you work through this lesson, you may find these terms in the activities. When you need to write a key term or a definition, highlight the term or the definition. BUILD Connections ATP as a Charged Battery An analogy takes two things that seem to be different and shows how they can be similar. 1. How is a partially charged battery like ADP? 2. Why do cells contain only a small amount of ATP? A. ATP cannot store large amounts of energy for a long time. B. ATP releases energy too quickly. C. ATP cannot carry out active transport. D. ATP has only two phosphate groups. 110
BUILD Understanding Compare/Contrast Table Use a compare/contrast table when you want to see the similarities and differences between two or more objects or processes. As you read, place an X in the box next to characteristics that are true of an autotroph or a heterotroph. One has been done for you. Autotroph Heterotroph Directly uses sunlight for energy X An oak tree is an example. A mushroom is an example. Makes its own food Consumes other living things to get energy Is capable of photosynthesis Chemical Energy and ATP Chemical Energy Living things use chemical fuels. One of the most important compounds that cells use to store and release energy is ATP. Follow the directions. Then answer the questions. 1. Trace the outlines of the adenosine molecule and the three phosphate groups. 2. Cut out each phosphate group. 3. Arrange the phosphate groups on the adenosine molecule to form a molecule of ATP. 4. When ATP is changed to ADP, it releases energy. Change your ATP molecule so that it forms ADP. What change did you make? 5. ADP can be converted into ATP. Change your ADP molecule into ATP. What change did you make? 6. Fill in the blanks with two or three. The primary difference in the structures of ATP and ADP is that ATP has phosphate groups and ADP has phosphate groups. Name Class Date
Heterotrophs and Autotrophs Look at the feeding relationships in each food chain. Each food chain contains an autotroph and one or more heterotrophs. Follow the directions. 1. Color the autotrophs green. 2. Color the heterotrophs blue. grass worm robin coyote grass mouse hawk grass rabbit cougar tree/shrub deer cougar Answer the questions. 3. Which animal would be most affected if many trees died from disease? A. deer B. mouse C. worm D. None would be affected. 4. The organisms listed in the box belong to a food chain. Use the words in the box to fill in the food chain in the correct order. bear insect salmon grass 5. Explain how top-level consumers such as hawks depend on sunlight for their food. 112
8.1 Energy and Life Part 2 Lesson Objectives Describe the role of ATP in cellular activities. Explain where plants get the energy they need to produce food. Lesson Summary Chemical Energy and ATP Energy is the ability to do work. Organisms need energy to stay alive. Adenosine triphosphate (ATP) is a chemical compound cells use to store and release energy. An ATP molecule consists of adenine, the sugar ribose, and three phosphate groups. Cells store energy by adding a phosphate group to adenosine diphosphate (ADP) molecules. Cells release energy from ATP molecules by subtracting a phosphate group. Energy provided by ATP is used in active transport, to contract muscles, to make proteins, and in many other ways. Cells contain only a small amount of ATP at any one time. They regenerate it from ADP as they need it, using energy stored in food. Heterotrophs and Autotrophs The energy to make ATP from ADP comes from food. Organisms get food in one of two ways. Heterotrophs get food by consuming (eating) other organisms. Autotrophs use the energy in sunlight to make their own food. Photosynthesis is the process that uses light energy to produce food molecules. Chemical Energy and ATP For Questions 1 6, complete each statement by writing the correct word or words. 1. is the ability to do work. 2. The main chemical compound cells use for energy is (ATP). 3. is a 5-carbon sugar molecule that is part of an ATP molecule. 4. The of ATP are the key to its ability to store and supply energy. 5. ATP releases energy when it bonds between its phosphate groups. 6. Most cells only store enough ATP for of activity. 116
7. THINK VISUALLY Label each part of the diagram of an ATP molecule below. For Questions 8 10, refer to the Visual Analogy comparing ATP to a charged battery. 8. VISUAL ANALOGY In the visual analogy, what chemical is represented by the low battery? 9. What are two ways in which the diagram shows an increase in energy? 10. Describe the concepts shown in the diagram. 11. What are two ways in which cells use the energy temporarily stored in ATP? 12. Energy is needed to add a third phosphate group to ADP to make ATP. What is a cell s source of this energy? 117
Heterotrophs and Autotrophs For Questions 13 17, write True if the statement is true. If the statement is false, change the underlined word or words to make the statement true. 13. All heterotrophs must eat food to get energy. 14. Autotrophs do not need to eat food because they make food. 15. The energy in food originally came from ATP. 16. The term photosynthesis means pulling apart with light in Greek. 17. The energy of sunlight is stored in the chemical bonds of carbohydrates. 18. Complete the table comparing two types of organisms. Autotrophs and Heterotrophs Type Description Examples Autotrophs Heterotrophs Apply the Big idea 19. Suppose that you ate a hamburger on a wheat roll with lettuce, tomatoes, and onions for lunch. As you ate, you took in food molecules from plants and animals. Explain why all the energy in the food molecules of this hamburger could be traced back to the sun. 118
8.2 Photosynthesis: An Overview Part 1 Lesson Objectives Describe the role of light and pigments in photosynthesis. Explain the role of electron carrier molecules in photosynthesis. State the overall equation for photosynthesis. BUILD Vocabulary A. The chart below shows key terms from the lesson with their definitions. Complete the chart by writing a strategy to help you remember the meaning of each term. One has been done for you. Term Definition How I m Going to Remember the Meaning Chlorophyll Primary pigment in plants Chlorophyll gives plants their green color. Lightdependent reactions Lightindependent reactions NADP + Pigment Reactions in photosynthesis that require light and lightabsorbing pigments Reactions in photosynthesis in which carbon dioxide and energy-carrying molecules are used to produce high-energy sugars Carrier molecule that transports high-energy electrons Light-absorbing molecule Stroma Thylakoid Fluid portion of the chloroplast that surrounds the thylakoid membrane Photosynthetic membrane sac found inside chloroplasts B. As you work through this lesson, you may find these terms in the activities. When you need to write a key term or a definition, highlight the term or the definition. 113
BUILD Understanding KWL Chart A KWL chart will help you to get the most out of your reading. In the first column, write what you already Know about photosynthesis and the needs of plants. One fact has been added to the chart for you. In the second column, write what you Want to find out. In the last column, write what you ve Learned after reading the lesson. Fill in the chart as you read Lesson 2. K (What I know) W (What I want to know) L (What I learned) Plants make food by using water, carbon dioxide, and energy from the sun. CHAPTER MYSTERY Out of Thin Air? In concluding that the extra mass of his tree came from water, van Helmont had only half the answer. In the space below, draw yourself using the photosynthesis equation to explain to van Helmont why he needs to consider carbon dioxide. 114
Chlorophyll and Chloroplasts In addition to water and carbon dioxide, photosynthesis requires light and chlorophyll. Inside chloroplasts are thylakoids. The region outside the thylakoid is the stroma. A model of a chloroplast is shown below. Follow the directions. 1. Color the stroma blue. Label it. 2. Color each thylakoid green. Label one. 3. Circle the granum in red. Label it. Chloroplast Answer the questions. 4. Where do the light-dependent reactions occur? Circle the correct answer. thylakoids stroma 5. Where do the light-independent reactions occur? Circle the correct answer. thylakoids stroma 6. Is the following statement true or false? In plants, photosynthesis takes place in the chloroplasts. 7. The function of chlorophyll is A. to protect a plant from losing water. B. to help plants absorb oxygen. C. to protect the plant cell. D. to capture energy from the sun. 115
Chlorophyll and Chloroplasts Photosynthesis in plants takes place in organelles called chloroplasts. Within each chloroplast is a fluid-filled area called the stroma. Also inside each chloroplast are many saclike membranes called thylakoids. Thylakoids are connected to each other in stacks. Each stack is a granum. Complete the Venn diagram to compare the stroma and a granum in a chloroplast. Use the phrases below. One has been done for you. contains pigments fluid portion of chloroplast are a part of photosynthesis light-dependent reactions located within a chloroplast stacks of thylakoids Answer the questions. Circle the correct answer(s). 1. Which reactions change the energy of sunlight to energy-rich carriers? light-dependent reactions light-independent reactions 2. Which two reactants are needed for light-dependent reactions? carbon dioxide light oxygen water 3. Which two reactants are needed for light-independent reactions? carbon dioxide energy-rich compounds oxygen stroma 116
8.2 Photosynthesis: An Overview Part 2 Lesson Objectives Explain the role of light and pigments in photosynthesis. Explain the role of electron carrier molecules in photosynthesis. State the overall equation for photosynthesis. Lesson Summary Chlorophyll and Chloroplasts In eukaryotes, photosynthesis occurs in organelles called chloroplasts. Chloroplasts house light-absorbing chemicals. Light is a form of energy. Sunlight is a mixture of all the different colors of visible light. Light-absorbing molecules called pigments capture the sun s energy. Chlorophyll is the principal pigment in photosynthetic organisms. Chlorophyll absorbs blue-violet and red light but reflects green light. Chloroplasts have a complex internal structure that includes: thylakoids: saclike photosynthetic membranes that contain chlorophyll and other pigments and are arranged in stacks called grana. stroma: the fluid portion outside of the thylakoids. High-Energy Electrons The energy in light raises some of the electrons in chlorophyll to higher energy levels. These high-energy electrons are used in photosynthesis. Electron carriers are used to transport the electrons from chlorophyll to other molecules during photosynthesis. NADP + is a compound that can accept and hold 2 high-energy electrons and 1 hydrogen ion. This process converts NADP + into NADPH. An Overview of Photosynthesis Usually summarized by a simple chemical reaction, photosynthesis is a complex process that involves two interdependent sets of reactions. The light-dependent reactions require light, light-absorbing pigments, and water to form NADPH, ATP, and oxygen. The light-independent reactions do not use light energy. They use carbon dioxide from the atmosphere, NADPH, and ATP to make energy-rich carbon compounds. Chlorophyll and Chloroplasts For Questions 1 6, complete each statement by writing the correct word or words. 1. The of light determines its color. 2. Chemicals that absorb light are called. 3. Chlorophyll makes plants look green because it green light. 4. Chloroplasts contain an abundance of saclike photosynthetic membranes called. 119
5. The is the fluid portion of the chloroplast located outside the thylakoids. 6. The visible light absorbed by chlorophyll the energy level of the chlorophyll s electrons. 7. THINK VISUALLY Label the internal parts of the chloroplast below. High-Energy Electrons For Questions 8 9, refer to the Visual Analogy comparing electron carriers to oven mitts. 8. VISUAL ANALOG In the visual analogy of carrying electrons, what represents the highenergy electrons? 9. Write another analogy that describes the process of electron carriers. 10. Where do the high-energy electrons carried by NADPH come from? 120
An Overview of Photosynthesis For Questions 11 13, write the letter of the correct answer on the line at the left. 11. What are the reactants of the photosynthesis reaction? A. chlorophyll and light C. carbohydrates and oxygen B. carbon dioxide and water D. high-energy electrons and air 12. What are the products of the light-dependent reactions? A. chloroplasts and light C. oxygen and ATP B. proteins and lipids D. water and sugars 13. Where do the light-independent reactions occur? A. stroma C. chlorophyll B. thylakoids D. mitochondria 14. Complete the illustration by writing the reactants and products of the light-dependent and light-independent reactions. Also, fill in the energy source that excites the electrons. Apply the Big idea 15. Solar power uses cells or panels to absorb the sun s energy. That energy is then used to create electricity. How does this compare to the light dependent reactions of photosynthesis? 121
8.3 The Process of Photosynthesis Part 1 Lesson Objectives Describe what happens during the light-dependent reactions. Explain what happens during the light-independent reactions. Identify factors that affect the rate at which photosynthesis occurs. BUILD Vocabulary A. The chart below shows key terms from the lesson with their definitions. Complete the chart by writing a strategy to help you remember the meaning of each term. One has been done for you. Term Definition How I m Going to Remember the Meaning ATP synthase Calvin cycle Enzyme that converts ADP and a phosphate group to ATP Another name for the lightindependent reactions in which carbohydrates are produced Many enzymes end in the suffix ase, and ATP synthase is an enzyme that produces ATP. Electron transport chain Photosystem Series of electron-carrier proteins that transport highenergy electrons during the process of making ATP Cluster of chlorophyll and proteins in the thylakoids essential to the light-dependent reactions B. As you work through this lesson, you may find these terms in the activities. When you write a key term or a definition, highlight the term or the definition. 118
BUILD Understanding Flowchart A flowchart is a way to show the steps in a process. As you read, complete the flowchart to show the steps involved in the light-dependent reactions of photosynthesis. light-dependent reactions Light-Dependent and Light-Independent Reactions Photosynthesis involves two sets of reactions. The light-dependent reactions need sunlight. They use energy from this sunlight to produce energy-rich compounds, like ATP. The lightindependent reactions use these energy-rich compounds to produce sugars from carbon dioxide. Complete the T-chart. Write the phrases in the box that belong in each side of the chart. Use energy from the sun Use carbon dioxide Produce oxygen Produce sugars Convert ADP into ATP Take place in the stroma Take place in thylakoids Require water Also called Calvin cycle Light-dependent Reactions Light-independent Reactions 119
The Light-Independent Reactions: Producing Sugars Both ATP and NADPH are produced by the light-dependent reactions of photosynthesis. The Calvin cycle uses the energy in ATP and NADPH to produce high-energy sugars. A model of the Calvin cycle is shown below. Follow the directions. 1. Circle the places where ATP and NADPH are used. 2. Draw an X over the two 3-carbon molecules that are removed from the cycle to produce sugars, lipids, and other compounds. Calvin Cycle Answer the questions. Sugars and other compounds 3. Circle the letter of each statement that is true about the Calvin cycle. A. The main products of the Calvin cycle are six carbon dioxide molecules. B. Carbon dioxide molecules enter the Calvin cycle from the atmosphere. C. Energy from ATP and high-energy electrons from NADPH are used to convert 3-carbon molecules into higher-energy forms. D. The Calvin cycle uses 6 molecules of carbon dioxide to produce a single 6-carbon sugar molecule. 4. Why are the reactions of the Calvin cycle also called the light-independent reactions? 120
8.3 The Process of Photosynthesis Part 2 Lesson Objectives Describe what happens during the light-dependent reactions. Describe what happens during the light-independent reactions. Identify factors that affect the rate at which photosynthesis occurs. Lesson Summary The Light-Dependent Reactions: Generating ATP and NADPH Photosynthesis begins with these reactions, which occur in thylakoid membranes. Photosystems are clusters of proteins and chlorophyll in thylakoid membranes. High-energy electrons form when pigments in photosystem II absorb light. The electrons pass through electron transport chains, a series of electron carrier proteins. The movement of electrons through an electron transport chain causes a thylakoid to fill up with hydrogen ions and generates ATP and NADPH. ATP synthase is a membrane protein through which excess hydrogen ions escape a thylakoid in a process that makes ATP. The Light-Independent Reactions: Producing Sugars They occur in the stroma of thylakoids and are commonly called the Calvin cycle. Six carbon dioxide molecules from the atmosphere enter the Calvin cycle and combine with 5-carbon compounds already present. They produce twelve 3-carbon molecules. Two 3-carbon molecules are removed from the cycle. They are used by the plant to build sugars, lipids, amino acids, and other compounds. The remaining ten 3-carbon molecules are converted back to 5-carbon molecules and begin a new cycle. Factors Affecting Photosynthesis Many factors influence the rate of photosynthesis. Temperature, light intensity, and availability of water affect photosynthesis. C4 and CAM plants have a modified type of photosynthesis that enables the plants to conserve water in dry climates. The Light-Dependent Reactions: Generating ATP and NADPH For Questions 1 5, write True if the statement is true. If the statement is false, change the underlined word or words to make the statement true. 1. Photosystems are clusters of chlorophyll and proteins. 2. The light-dependent reactions begin when photosystem I absorbs light. 3. Electrons from water molecules replace the ones lost by photosystem II. 4. ATP is the product of photosystem I. 5. ATP and NADPH are two types of protein carriers. 122
6. How does ATP synthase produce ATP? 7. When sunlight excites electrons in chlorophyll, how do the electrons change? 8. Where do the light-dependent reactions take place? 9. Complete the table by summarizing what happens in each phase of the light-dependent reactions of photosynthesis. Light-Dependent Reactions Summary Photosystem II Electron Transport Chain Photosystem I Hydrogen Ion Movement and ATP Formation 123
The Light-Independent Reactions: Producing Sugars 10. What does the Calvin cycle use to produce high-energy sugars? 11. Why are the reactions of the Calvin cycle called light-independent reactions? 12. What makes the Calvin cycle a cycle? 13. Complete the diagram of the Calvin cycle by filling in the missing labels. 124
Factors Affecting Photosynthesis 14. What are three factors that affect the rate at which photosynthesis occurs? 15. Would a plant placed in an atmosphere of pure oxygen be able to conduct photosynthesis? Explain your answer. 16. Complete the table about variations of photosynthesis. Type Description Examples Occurs in plants that have a specialized chemical pathway that allows them to capture even very low levels of carbon dioxide and pass it to the Calvin cycle. pineapple trees, many desert cacti, and ice plants Apply the Big idea 17. Photosynthesis plays an important role in supplying energy to living things. Considering what the products of photosynthesis are, what is another way in which photosynthesis is vital to life? 125
Chapter Review Use the clues and words to help you write the vocabulary terms from the chapter in the blanks. You may use a word once or not at all. ATP synthase NADP + photosynthesis pigment 1. molecule that carries high-energy electrons 2. light-absorbing molecule 3. enzyme that converts ADP into ATP Answer the following questions. 4. What is the source of energy for plants? 5. What compound is broken down during photosynthesis to produce oxygen? A. ATP B. carbon dioxide C. glucose D. water 6. Which term is used for the series of electron carrier proteins that move high-energy electrons during ATP-generating reactions? Circle the correct answer. electron transport chain food chain hydrogen ion movement 7. What causes the gradient across the thylakoid membrane? A. charge B. H + ion concentration C. charge and H + ion concentration D. None of the above. Use the diagrams of the ADP and ATP molecules to answer question 8. 8. Circle the compound that shows a cell s stored energy. 9. The chart below compares ADP and ATP to a battery. Place check marks under the category that best describes each molecule. Partially Charged Battery Fully Charged Battery ADP ATP 121