Photosynthesis: Cellular Basis of Life PDF

Photosynthesis Cellular Basis of Life Q: How do plants and other organisms capture energy from the sun? Leaf cells from Canadian pondweed ( Elodea canadensis) (LM 24303) Chapter 8 Chapter Mystery 190 ...

Photosynthesis Cellular Basis of Life Q: How do plants and other organisms capture energy from the sun? Leaf cells from Canadian pondweed ( Elodea canadensis) (LM 24303) Chapter 8 Chapter Mystery 190  Out Of thin Air? inside: When a tiny seed grows into a huge 8.1 Energy and Life tree, where does all the extra mass come from? More than 300 years 8.2 Photosynthesis: An Overview ago, a Flemish doctor named Jan 8.3 The Process of Photosynthesis van Helmont decided to find out. He chose a young willow tree that weighed just 2 kilograms. He planted it in a pot with 90 kilograms of dry soil and placed it in bright sunlight. He watered the plant as needed. Five years later, he took the tree from the pot and weighed it. It weighed about 77 kilograms. Where did the extra 75 kilograms come from? Did it come from the soil, the water—or right out of thin air? read for Mystery Clues As you read this chapter, look for clues to help you discover where the willow tree’s extra mass came from. Then, solve the mystery at the end of the chapter. Plant cells use light energy to make useful chemicals. These reactions take place in special parts of the cell. Before you read the chapter, label index cards with the words water, carbon dioxide, oxygen, sugars, and light. Label one sheet of paper as shown. At the end of the chapter are two activities that use the cards and sheets of paper to help answer the question: How do plants and other organisms capture energy from the sun? THYLAKOID STROMA Sugars Untamed Science Video Flash Cards Photosynthesis 191  Energy and Life Key Questions Chemical Energy Why is ATP useful to cells? Energy is the ability to do work. Nearly everything you do takes What happens during energy. Lights, radios, and computers all use electrical energy to run. photosynthesis? When you toast marshmallows on a campfire, you are using heat energy to warm the food. A car runs on fuel—the chemical energy in gasoline. All these things need energy to work. Living things need energy, too. It takes plenty of energy to play soccer or other sports. Sometimes it is not as easy to tell that something uses energy. Did you know that even when you are sleeping, your cells are Compare/Contrast Table As you busy using energy? They are using energy to build new molecules read, create a table that compares and get rid of wastes. Without the ability to get and use energy, cells autotrophs and heterotrophs. Think would die. about how they get energy. Include in your table a few examples of Energy Changes Form Light, heat, and electricity are just three each type of living thing. forms of energy. Chemical energy is another form of energy. Chemical In Your Workbook Go to energy is the energy stored in chemical bonds. Energy can change your workbook to learn more about from one form to another. When you light a candle, the wax burns. making a compare/contrast table. Complete the compare/contrast Chemical bonds between carbon and hydrogen atoms in the wax are table for Lesson 8.1. broken. New bonds form between these atoms and oxygen from the air. What you get are new molecules of carbon dioxide and water. The bonds in the new molecules store less energy than before. The extra chemical energy that came from the old bonds changes form. The extra energy becomes the heat and light given off by the candle’s flame. ATP Living things use chemical energy. One of the most important chemicals that cells use to store and give off energy is called adenosine triphosphate (uh den uh seen try fahs fayt). It’s known as ATP for short. ATP is made up of adenine, a sugar called ribose, and three phosphate groups. The phosphate groups are the key to why ATP can store and release energy. ATP ATP is the Adenine Ribose 3 phosphate groups basic energy source used by all types of cells. P P P 192 Chapter 8 Lesson 1 Storing Energy Adenosine diphosphate (ADP) is similar to ATP. However, ADP has only two phosphate groups instead of three. This difference is the key to how living things store energy. When a cell has extra energy, it can store small amounts of it by adding a phosphate adenosine triphosphate (ATP) group to ADP molecules, which turns ADP to ATP. one of the principal chemical compounds that living things use to Releasing Energy Cells can give off the energy stored in ATP by store and release energy breaking the chemical bonds between the second and third phosphate groups. A cell can add or subtract these phosphate groups whenever it PREFIXES needs to store or use energy. The prefix di- means “two” and the prefix tri- means “three.” A Key Question Why is ATP useful to cells? molecule of adenosine triphosphate ATP can easily release and store energy by breaking and re-forming (ATP) has three phosphate groups, while adenosine diphosphate (ADP) the bonds between its phosphate groups. has only two. Using Chemical Energy Cells use ATP in many ways. For example, cells use it to power active transport. ATP provides the energy needed to move material into and out of many cells. ATP also helps proteins in muscles to slide closer together. This motion makes muscles flex. Cells that crawl, twist, and swim depend on ATP as well. Energy from ATP powers many other important events, such as the making of proteins and responses to chemical signals outside of the cell. Short-Term Storage ATP is so useful that you might think cells would be packed with it. In fact, most cells have only a small amount—enough to MoLeCuLAr BATTery last for a few seconds of activity. The reason is that When a phosphate group is added to an ADP ATP is great for giving off a small amount of energy molecule, it makes ATP. ADP has some energy, but very quickly. But, it is not good for storing large not as much as ATP. ADP is like a partially charged battery. It can be fully charged by adding a amounts for a long time. The sugar glucose is much phosphate group. better for energy storage. A single glucose molecule stores more than 90 times the energy of a molecule of ATP. So, it makes sense for cells to store energy ADP in the form of glucose. Cells can then use the stored glucose to make ATP and ADP as needed. ATP Comes From Food Once cells use up their supply of ATP, they must somehow make more of it. So, where do living ATP things get the energy they use to make ATP? The simple answer is that it comes from the chemical compounds that we call food. But, different living things get their food from different sources. In Your Workbook Go to your workbook to learn more about how an ATP molecule stores energy. Lesson 8.1 Visual Analogy 193  Heterotrophs Eat Food Living things that get food by eating other living things are known as heterotrophs. Some heterotrophs get their food by eating plants, such as grasses. Others, such as heterotroph the cheetah shown at right, get food by eating other animals. Still a living thing that gets food by other heterotrophs—mushrooms, for example—get food by consuming, or eating, other living breaking down the tissues of dead things. things autotroph Autotrophs Make Food The energy in nearly all a living thing that can capture food molecules first came from the sun. Plants, algae, energy from sunlight or chemicals and some bacteria can use light energy from the sun to make its own food to make their own food. Living things that make photosynthesis their own food are called autotrophs. All life on the process by which plants and other autotrophs use light energy to Earth depends on autotrophs to get energy from convert water and carbon dioxide sunlight and store it in the molecules that make into oxygen and high-energy up food. The process by which autotrophs use carbohydrates such as sugars and the energy of sunlight to produce high-energy starches carbohydrates—sugars and starches—that can be WORD ROOTS used as food is known as photosynthesis. Photosynthesis comes from the Greek words photo, meaning Key Question What happens during “light,” and synthesis, meaning photosynthesis? “putting together.” Thus, During photosynthesis, plants change the energy of photosynthesis means “using light sunlight into chemical energy stored in the bonds of to put something together.” carbohydrates. Autotrophs and Heterotrophs Grass uses sunlight to make food. Cheetahs, in turn, get their energy by eating organisms who eat the grass. Apply Vocabulary 5. Write to Learn Answer the first clue of Use the highlighted words from the lesson to the mystery. In your answer explain how complete each sentence correctly. autotrophs get food and how that might lead to an increase in mass. 1. An animal that gets its food by eating other animals is a(n) ______. 2. ______ provides a cell with energy when it loses a phosphate group. 3. ______ use photosynthesis to make sugars. Like all plants, the willow tree van Helmont planted Critical Thinking was an autotroph. How might its ability to use 4. Explain Why are decomposers, such as the sun’s energy to make mushrooms, heterotrophs and not autotrophs? food help it gain mass? (Hint: See p. 193.) Lesson 8.1 Lesson Assessment 194 Chapter 8 Lesson 1  Photosynthesis: An Overview Chlorophyll and Chloroplasts Key Questions Our lives, and the lives of nearly every living thing on Earth, depend What role do pigments play in the process of on the sun and photosynthesis. For photosynthesis to take place, photosynthesis? autotrophs must capture light energy from the sun. What are electron carrier Light Energy from the sun travels to Earth in the form of light. molecules? Sunlight, which our eyes see as “white” light, is actually a mixture of What are the reactants and different wavelengths. Many of these wavelengths are visible to our products of photosynthesis? eyes. Our eyes see the different wavelengths of visible light as different colors: shades of red, orange, yellow, green, blue, indigo, and violet. Pigments Plants gather the sun’s energy with light-absorbing molecules called pigments. The most important pigment in plants KWL Chart Make a chart with is chlorophyll (klawr uh fil). Out of all the different colors of light, three columns labeled What I Know, the chlorophyll found in plants absorbs blue-violet light and red light What I Want to Know, and What the best. Chlorophyll does not absorb green light very well. Leaves I Learned. Before you read the look green because they reflect green light. lesson, fill in the first two columns. Complete the last column as you Key Question What role do pigments play in the process read the lesson. of photosynthesis? In Your Workbook Go to Living things that carry out photosynthesis use pigments to get your workbook to learn more about making a KWL chart. Complete the energy from sunlight. KWL chart for Lesson 8.2. Chloroplasts Photosynthesis takes place inside organelles called chloroplasts. These organelles hold many flat, bag-shaped membranes called thylakoids (thy luh koydz). Thylakoids are connected to one another and arranged in stacks. These stacks are called grana. Chlorophyll and other pigments are found in these thylakoid membranes. The liquid-filled space around the thylakoids is known as the stroma. You can see what makes up a chloroplast in the picture below. PLANT CELL The Chloroplast In plants, Chloroplast Outer membrane photosynthesis takes place Inner membrane inside chloroplasts. Stroma Thylakoid Granum Thylakoid membrane Thylakoid space Lesson 8.2 Visual Analogy 195  NADPH NADP+ NADP+ H+ H+ 2e- 2e- High-Energy Electrons Carrying ElECtrons Light is a form of energy. Anything that absorbs light takes in energy. + NADP is a carrier molecule that When chlorophyll takes in light, much of that energy is moved transports pairs of high-energy directly to electrons in the chlorophyll. The energy levels of the electrons (and an H+ ion). Compare electrons go up. A stream of these high-energy electrons is what its role to that of an oven mitt used to transport a hot baked potato. makes photosynthesis work. These high-energy electrons cannot keep their energy for long on their own. They need a special carrier. Plant cells use molecules to carry high-energy electrons from chlorophyll to other places. One of these carrier molecules is NADP+ (nicotinamide adenine dinucleotide phosphate). It accepts and holds two high-energy electrons, along with a hydrogen ion (H+). This process changes NADP+ into NADPH. The NADPH carries the electrons to other parts of the cell. There, the electrons and their energy can be used to thylakoid a baglike photosynthetic membrane help build useful molecules, such as sugars. found in chloroplasts Key Question What are electron carrier molecules? stroma Electron carrier molecules are compounds that can transfer a the liquid-filled space surrounding the thylakoids in chloroplasts pair of high-energy electrons, along with most of their energy, to NADP + another molecule. one of the molecules that accepts high-energy electrons from chlorophyll and carries A Summary of Photosynthesis them to other molecules during Photosynthesis has many steps. It usually has 6-carbon sugars photosynthesis (C6H12O6) as the final product. All of the steps of photosynthesis can light-dependent reaction be summed up in the following equation: a reaction of photosynthesis that uses atP, naDPH, and carbon In Symbols: light dioxide to make high-energy 6CO2 + 6H2O C6H12O6 + 6O2 sugars light-independent reaction In Words: light a reaction of photosynthesis that Carbon dioxide + Water Sugars + Oxygen uses light energy to make atP and naDPH Plants use the sugars from photosynthesis to make other carbohydrates, such as starches. The sugars are also used to make CHEMICAL NAMES other compounds, such as proteins and lipids. When a plus sign appears in a chemical name, it means the Key Question What are the reactants and products of chemical has a positive charge photosynthesis? and can accept electrons. Photosynthesis uses light energy to change water and carbon dioxide (reactants) into sugars and oxygen (products). 196 Lesson 8.2 InterActive Art Tutor Tube  The Stages of Photosynthesis Light-Dependent Light-Independent There are two stages of Reactions Reactions photosynthesis: light-dependent H2O CO2 reactions and light-independent Light reactions. NADPH ATP THYLAKOID ADP STROMA NADP + O2 Sugars Light-Dependent Reactions The equation for photosynthesis looks simple, but that is because it does not show all of the smaller steps. In fact, there are two sets of reactions. The first set is the light-dependent reactions. They take place in the thylakoids. These reactions need light and light-absorbing pigments to take place. They use energy from sunlight and electrons and hydrogen ions from water to make high-energy ATP and NADPH. Oxygen gas, the oxygen we breathe every day, is also released. Light-Independent Reactions The second set of reactions in photosynthesis is called the light-independent reactions. In this set, plants use the ATP and NADPH made in the light-dependent reactions. They make high-energy sugars out of carbon dioxide from the air. Light-independent reactions do not need light. They take place in the stroma. Apply Vocabulary 4. Write to Learn Answer the second clue of the Use the highlighted words from the lesson to mystery. Think about the things that plants complete each sentence correctly. need for photosynthesis. Which of these things might cause the plant to gain mass? 1. The set of reactions that takes place in the stroma are called the ______. 2. The light-dependent reactions need ______, a carrier molecule that is able to accept high-energy electrons and a hydrogen ion. Van Helmont concluded that water must have supplied the extra mass Critical Thinking gained by the tree. In fact, he had 3. Describe the overall process of photosynthesis. only half of the answer. What photosynthesis reactant was he missing Include the reactants and the products. in his conclusion? (Hint: See p. 196.) Lesson 8.2 Lesson Assessment Photosynthesis 197  What Waste Product Is Produced During Photosynthesis? Analyze and Conclude What is a waste product? It is like garbage 1. Observe What did you see on the plant’s in your kitchen. You may eat the food that leaves? comes out of a jar, but your body cannot use 2. Infer Think about the products of the jar. The empty jar is a waste product. But photosynthesis. What do you think formed on you might be able to use the jar for something the leaves of the plant? How do you know? else, like storing leftover soup. During many reactions, cells make waste products as well 3. Draw Conclusions Do you think that the as needed products. Sometimes these waste product that formed on the leaves is a waste products cannot be used by the cell at all. product? Explain. At other times, the waste product is used in 4. Infer Think about the reactants of another part of the cell or by other cells. In photosynthesis. What do you think happened this activity, you will study photosynthesis in to the carbon dioxide in the sodium a water plant called Elodea. You will see one bicarbonate solution? product of photosynthesis. You will decide if it 5. Apply Concepts Which plant organelle is a waste product for this plant. carries out photosynthesis? How can you tell 1 Fill a clear, plastic cup halfway with that this plant’s cells have that organelle? sodium bicarbonate solution. This In Your Workbook Get more help for this solution has carbon dioxide in it. activity in your workbook. 2 a. Place a piece of plant in a test tube. Make sure that the cut part of the plant is at the bottom. b. Add sodum bicarbonate solution. CAUTION: Be careful with glass. 3 a. Hold your finger over the open end of the test tube. Elodea b. Turn the test tube over. Lower it to the Sodium bottom of the cup. Make sure no air is bicarbonate inside the test tube. solution 4 Place the cup in bright light. 5 Wait 20 minutes. 6 Look closely at the leaves. Write down what you see. 198 Chapter 8 Lesson 2  The Process of Photosynthesis The Light-Dependent Reactions: Key Questions Making ATP and NADPH What happens during the light-dependent reactions? Remember that the steps of photosynthesis are divided into two sets. What happens during the They are the light-dependent reactions and the light-independent light-independent reactions? reactions. The light-dependent reactions cannot take place in the What factors affect dark. They are the reason that plants need light. photosynthesis? The light-dependent reactions take place in the thylakoids of chloroplasts. These baglike membranes hold groups of chlorophyll and proteins known as photosystems. Photosystems take in sunlight and use it to add energy to electrons. These electrons are passed to a set of carriers in the thylakoid membrane. There are two photosystems, and they are named in order of their discovery—not in the order that they do their work. Flowchart As you read, create a flowchart that clearly shows the steps of the light-dependent Photosystem II The pigments of photosystem II absorb light energy reactions. and release high-energy electrons. These electrons then get passed In Your Workbook Go to down the electron transport chain. This chain is a group of carrier your workbook to learn more about proteins. They use energy from the electrons to pump H+ ions inside making a flowchart. Complete the the thylakoid. flowchart for Lesson 8.3. As light shines on chlorophyll, more and more electrons enter the electron transport chain. Chlorophyll gets new electrons when enzymes break up water molecules (H2O). As plants take electrons from water, oxygen and hydrogen are left behind. The oxygen goes into the air that we breathe. The hydrogen becomes ions that are left inside the thylakoid. ATP Formation In photosystem II, hydrogen ions build up inside the thylakoid. Some of these ions come from water breaking up. Others come from the electron transport chain. The building up of H+ ions inside the thylakoid makes the outside of the thylakoid more negatively charged than the inside. This difference in charge and number of H+ ions on either side of the membrane is what powers the making of ATP. H+ ions cannot cross the membrane directly. Instead, they pass through a protein called ATP synthase that is like a revolving door in the membrane. The buildup of H+ ions on one side causes them to pass through ATP synthase and force it to turn. As it turns, it adds a phosphate group to ADP to make ATP. Photosynthesis 199  Photosystem I The electrons from photosystem II lost energy when they pumped ions across the membrane. In photosystem I, light gives them energy again. Then, they go through another electron transport chain. Here, they are used to make NADP+ into NADPH, which goes on to the next set of reactions. Summary of Light-Dependent Reactions The light-dependent reactions give off oxygen gas. They also make ATP and NADPH. These compounds are important for the cell. They provide the energy needed to build sugars in the light-independent reactions. Key Question What happens during the light-dependent reactions? The light-dependent reactions use water and energy from sunlight to make oxygen and change ADP and NADP+ into the energy carriers ATP and NADPH. Light-Dependent Reactions The light-dependent reactions of photosynthesis take place in the thylakoids of the chloroplast. They use Light-Dependent Light-Independent energy from sunlight to produce ATP, Reactions Reactions NADPH, and oxygen. H2O CO2 O2 Sugars C YTOP L ASM 2H+ + 2 NADP + + 4e- 2 NADPH To Light- H+ Independent Reactions S TRO MA Light ATP To Light- H+ Independent Light Thylakoid ADP + P Reactions Electron membrane carriers ATP Photosystem I synthase Photosystem II ATP Formation Excess H+ ions spill 4e– out through ATP synthase. The protein rotates as each ion + passes through, which Photosystem II H+ 2 H2O 4H+ O2 Photosystem I changes ADP to ATP. Light shining on T H YL A KO ID pigments energizes Electrons are electrons that come Electron Transport reenergized with Electron Transport from water. High-energy electrons more light. The reenergized move down the chain, electrons are which pumps H+ ions to transferred to NADP+, inside of the thylakoid. to make NADPH. 200 Lesson 8.3 Art in Motion  Seeing Green The color green of most plants is caused by the reflection of green light by the pigment chlorophyll. Light-Independent Reactions: Making Sugars The ATP and NADPH made by the light-dependent reactions store a lot of chemical energy. However, they are not very stable. They last only a few minutes. During the light-independent reactions—also called the Calvin cycle—plants build high-energy sugars. These sugars are stable, so they can store energy for a long time. The Calvin cycle is photosystem the light-collecting units of the named after the American scientist Melvin Calvin. chloroplast Carbon Dioxide Enters the Cycle One of the reactants of the electron transport chain Calvin cycle is carbon dioxide. It comes from the air around a plant. a series of proteins in which high-energy electrons are used to An enzyme joins carbon dioxide molecules with molecules that are change ADP to ATP already in the cell. Then, one chemical step at a time, the cycle produces energy-rich carbohydrates. These steps use energy from ATP and NADPH. WORD ROOTS The Greek word photo means Sugar Production With each turn of the cycle, a few energy-rich “light.” A photosystem is a system carbohydrate molecules leave the cycle. This is the step that makes the of pigment molecules that collects energy from light. Calvin cycle important. These molecules become the building blocks that the plant cell uses to make sugars, lipids, amino acids, and other compounds. The plant will use these compounds as the food and building materials it needs to grow. The rest of the higher-energy molecules stay in the cycle. Enzymes use ATP to change them to molecules that will join with new carbon dioxide molecules. Then, the cycle begins again. Summary of Light-Independent Reactions The Calvin cycle uses compounds made in the light-dependent reactions and carbon dioxide from the air to make sugars. The plant uses the sugars to meet its energy needs and to build molecules needed for growth. When other living things eat plants, they, too, get the energy they need. Key Question What happens during the light-independent reactions? During the light-independent reactions, ATP and NADPH are used to make high-energy sugars. Photosynthesis 201  The End Results The two parts of photosynthesis work together. The light-dependent reactions change the energy of sunlight into chemical energy. The light-independent reactions use that energy to make sugars from carbon dioxide and water. Both plants and animals use the sugars and oxygen from photosynthesis to live and grow. Factors Affecting Photosynthesis Temperature, Light, and Water Photosynthesis can speed up or slow down depending on several factors. Temperature is one factor that can affect the rate of photosynthesis. Photosynthesis enzymes work best between 0°C and 35°C. Light intensity is another factor. Very bright light speeds up photosynthesis. Water levels also affect the rate of photosynthesis. Light-Independent Reactions The Key Question What factors affect photosynthesis? light-independent reactions of Three important factors that affect photosynthesis are photosynthesis take place in the stroma. They use ATP and NADPH temperature, light intensity, and the availability of water. from the light-dependent reactions to make high-energy sugars. Light-Dependent Light-Independent Reactions Reactions H2O CO2 CO2 O2 Sugars 1 Carbon dioxide combines with molecules CYT O PLASM from the cycle that have five carbon atoms. Molecules with three carbon atoms result. 5 The 5-carbon-atom molecules can go through the cycle again. ST RO MA ATP ADP From ADP Light-Dependent Reactions ATP NADPH 2 Energy from ATP and From NADPH energizes the Light-Dependent NADP + 3-carbon-atom molecules. Reactions 4 Eneregy from ATP changes the rest of the 3-carbon-atom molecules 3 Some of these back into 5-carbon-atom molecules leave the cycle molecules. to make sugars and other compounds. Sugars and Other Compounds 202 Lesson 8.3 Art Review Photosynthesis in Extreme Conditions Plants lose water through the tiny openings in their leaves that let in carbon dioxide. When it is hot, most plants close these openings to keep from drying out. But, doing so means less carbon dioxide enters, which slows photosynthesis. Some plants that live in dry, sunny areas have special ways to save water and still carry out photosynthesis. C4 Plants C4 plants have a special chemical pathway that gets carbon into the Calvin cycle even when there is not much carbon dioxide available. The pathway uses extra ATP but lets the plants carry out photosynthesis when it is hot. Corn and sugar cane are examples of C4 plants. CAM Plants CAM plants save water by taking air into their leaves only at night. In the dark, carbon dioxide is used to make acids. During the day, these acids are turned back into carbon dioxide for photosynthesis. Some examples of CAM plants are pineapple trees, many desert cacti, and ice plants. CAM Plants Plants like this ice plant can survive in dry places. The leaves let in carbon dioxide only at night, minimizing water loss. Apply Vocabulary 5. Write to Learn Answer the third clue of the Use the highlighted words from the lesson to mystery. How would labeling carbon atoms complete each sentence correctly. in carbon dioxide tell apart the products of photosynthesis? 1. Energy produced by the _______ is used to pump hydrogen ions from the stroma to the inside of the thylakoid. 2. A _____ is a cluster of pigments and proteins that allows plants to absorb light energy and transfer it to electrons. Melvin Calvin was able to label carbon atoms Critical Thinking in carbon dioxide. 3. Sequence Put the following events of the He used these labeled atoms to light-dependent reactions in the order in which show what happens they occur: photosystem I, photosystem II, to the carbon that is making NADPH, and pumping hydrogen ions used during the into the inside of the thylakoid. light-independent reactions. Where does 4. Compare and Contrast List at least three this carbon end up? differences between the light-dependent and (Hint: See p. 201.) light-independent reactions of photosynthesis. Lesson 8.3 Lesson Assessment Photosynthesis 203  guided iNQuiRY Pre-Lab: Plant Pigments and Photosynthesis Problem Do red leaves have the same pigments as 3. Design an Experiment Why must you place a leaf green leaves? about 2 cm from the bottom of the paper before rubbing the leaf with the coin? Materials paper clips, one-hole rubber stoppers, 4. Predict Will red leaves contain the same amount of chromatography paper strips, metric ruler, green and chlorophyll as green leaves? Why or why not? red leaves, coin, sheet of paper, large test tubes, test tube rack, glass-marking pencil, 10-mL graduated cylinder, isopropyl alcohol, colored pencils Chapter 8 Lab Manual Chapter 8 Lab Visit Chapter 8 online to test yourself on chapter content and to find activities to help you learn. Skills Focus Predict, Analyze Data, Draw Conclusions Untamed Science Video Journey to Panama with the untamed Science crew to discover how CO2 affects Connect to the Almost all life on plant growth. Earth depends, directly or indirectly, on energy from sunlight. Photosynthesis is the process in which light Data Analysis Look at pigment color data in the ocean to find out how marine algae photosynthesize in energy is captured and converted to chemical energy. the blue light available underwater. Many reactions are required for this conversion, which takes place in the chloroplasts of plant cells. Some of Tutor Tube Learn how to sort out the products the reactions depend on light and some do not. Plant and reactants in both the light-dependent and pigments play a major role in the light-dependent light-independent reactions. reactions. In this lab, you will use chromatography to compare the pigments in red leaves with those in Art Review Focus on the thylakoid membrane to review green leaves. your knowledge of the light-dependent reactions. Background Questions InterActive Art Bring the components of a. Compare and Contrast What do all plant pigments photosynthesis together to run an animation. have in common? How are they different? b. Review Why do most leaves appear green? Art in Motion Watch the steps of the light-dependent reactions in motion at the molecular level. c. Review What property makes chlorophyll so important for photosynthesis? Visual Analogies Compare ATP production to a charged battery. See how the electron transport chain Pre-Lab Questions is like passing a hot potato. Preview the procedure in the lab manual. 1. Design an Experiment What is the purpose of this lab? 2. Control Variables What is the control in this lab? 204 Chapter 8 Pre-Lab  8.1 Energy and Life 8.2 Photosynthesis: An Overview ATP can easily release and store energy by Living things that carry out photosynthesis use breaking and re-forming the bonds between its pigments to get energy from sunlight. phosphate groups. An electron carrier is a compound that can This ability makes ATP very useful as a basic transfer a pair of high-energy electrons, along with energy source for all cells. most of their energy, to another molecule. During photosynthesis, plants change the energy Photosynthesis uses light energy to change water of sunlight into chemical energy stored in the and carbon dioxide (reactants) into sugars and bonds of carbohydrates. oxygen (products). adenosine triphosphate (ATP) (p. 192) thylakoid (p. 195) light-dependent heterotroph (p. 194) stroma (p. 195) reactions (p. 197) autotroph (p. 194) NADP+ (p. 196) light-independent photosynthesis (p. 194) reactions (p. 197) H2O CO2 O2 Sugars 8.3 The Process of Photosynthesis The light-dependent reactions use energy from sunlight to make oxygen and change ADP and NADP+ into the energy carriers ATP and NADPH. During the light-independent reactions, ATP and NADPH are used to make high-energy sugars. Three important factors that affect photosynthesis are temperature, light intensity, and the availability of water. photosystem (p. 199) electron transport chain (p. 199) Chapter 8 Crossword Chapter Assessment 205  Cellular Basis of Life Foundations for Learning Wrap-Up Write an answer to the question below. Use the index cards and notebook page you prepared Q: How do plants and other organisms capture when you started the chapter as a tool to help you energy from the sun? organize your thoughts about photosynthesis. Constructed Response Activity 1 Working with a partner, use the index cards and notebook page to create a diagram to show Write an answer to each of the questions below. the two stages of photosynthesis. Then, use the index The answer to each question should be one or two cards to create a chemical equation that summarizes paragraphs. To help you begin, read the Hints below photosynthesis. the questions. 1. Yeast are single-celled fungi that feed off of Light sugars in their environment. How do yeast depend on other living things for survival? Hint Many yeast get their food from plants that THYLAKOID STROMA produce sugars in fruits and saps. Hint Yeast are heterotrophs because they rely on other living things to make sugars for them. 2. How is the function of chlorophyll related to Sugars its very specific location within the cell? Hint Chlorophyll absorbs sunlight and transfers its energy to electrons. Hint Chlorophyll is found in the thylakoid, Activity 2 With your partner, label four more where many steps of photosynthesis take place. index cards with NADPH, ATP, ADP, and NADP+. 3. The light-independent reactions are sometimes Using your diagram from Activity 1, add the called the “dark reactions” to tell them apart cards to the diagram in the correct positions from the light-dependent reactions. Do the to complete the stages of photosynthesis. Draw steps of the light-independent reactions ever arrows to show the movement of the molecules depend on light? Explain. between the stages. Hint The photosystems need light to energize electrons. These electrons are used to make ATP and NADPH. Light Hint NADPH and ATP are needed to carry out the light-independent reactions. THYLAKOID STROMA ATP Sugars 206 Check Understanding  8.1 Energy and Life 6. What W at iss the t e function u ct o of a. It absorbs light. o NADP N ? b. It is an electron carrier. Understand Key Concepts c. It is a light-reflecting pigment. 1. Which of the following are autotrophs? a. deer c. leopards d. It acts as long-term energy storage. b. grasses d. mushrooms 7. Some plants hav a e leav a es that are bright red. How do red leav a es diff ffer fr f om green leav a es in Test-Taking Tip the typ y es of light they absorb and refl f ect? Eliminate Incorrect Answers Read all of the answer Think Critically choices carefully. Even if you are not sure of the correct answer, you may be able to cross out one 8. Predict Why would a plant grow better in white or two of the answer choices that are incorrect. In light than in green light? Explain your answer. question 1, answers a and c are incorrect because they are animals, and animals are heterotrophs. So, you can eliminate these answer choices. 8.3 The Process of Photosynthesis Understand Key Concepts 2. Where do plants get the energy they need to 9. What drives the formation of ATP by ATP carry out photosynthesis? synthase? a. air c. sunlight a. buildup of H+ ions b. soil d. water b. burning oxygen 3. How does a molecule of ATP compare to a c. light absorption molecule of glucose in terms of the amount of d. splitting carbon dioxide energy stored? 10. Which substance from the light-dependent Think Critically reactions of photosynthesis is a source of 4. Relate Cause and Effect How might the energy for the light-independent reactions? disappearance of all autotrophs on Earth affect a. ADP c. NADPH other living things? Explain. b. H2O d. pyruvic acid 8.2 Photosynthesis: An Overview 11. The light-independent reactions of photosynthesis are also known as the a. ATP cycle. c. carbon cycle. Understand Key Concepts b. Calvin cycle. d. sugar cycle. 5. In addition to light and chlorophyll, photosynthesis requires 12. Identify the chloroplast parts labeled A, B, and a. carbon dioxide and sugars. C. In which part(s) do the light-dependent reactions take place? In which part(s) do the b. carbon dioxide and water. light-independent reactions take place? c. oxygen and sugars. d. oxygen and water. A C " Check Understanding 207 13. Discuss three factors that affect the rate at Out Of thin Air? which photosynthesis takes place. Which steps of photosynthesis are affected by these factors? Most plants grow out of the soil, so you might think that think Critically soil adds to plant mass. But, at the end of Jan van Helmont’s 14. Predict Suppose you water a potted plant and experiment with the willow tree, he place it by a window in a clear, airtight jar. discovered that the mass of the soil Predict how the rate of photosynthesis might was about the same—even though be affected over the next few days. What might the tree had gained nearly 75 kilograms. Van happen if the plant were left there for several Helmont decided that the mass must have come weeks? from water, because water was the only thing he 15. form a hypothesis Many of the sun’s rays may had added. The tree grew parts that did contain be blocked by dust or clouds formed by volcanic atoms like those found in water, but what van eruptions or pollution. What are some possible Helmont didn’t know was that the new parts short-term and long-term effects of this on also contained carbon. We now know that most plants in an area? On other forms of life? of that carbon comes from carbon dioxide in air. Thus, mass comes from two sources: carbon Connecting Concepts dioxide and water. What form does the added mass take? Think about the origin of the word carbohydrate, from carbo-, meaning “carbon,” use Science Graphics and hydrate, meaning “to combine with water,” A water plant placed under bright light gives off and you have your answer. bubbles of oxygen. The table below contains the results of an experiment in which the distance from the light 1. infer Although soil does not add much to to the plant was varied. Use the data table to answer plant mass, how might it help plants grow? questions 16–18. 2. infer Imagine that a scientist measures the Oxygen Production exact mass of carbon dioxide and water that Distance From Bubbles Produced entered a plant and the exact mass of the Light (cm) per Minute sugars produced. Would these masses be 10 39 identical? Why or why not? 20 22 30 8 3. Apply Concepts What do plants do 40 5 with all of the sugars they make through photosynthesis? (Hint: Plant cells have 16. Graph Use the data in the table to make a line mitochondria in addition to chloroplasts. graph. What do mitochondria do?) 17. interpret Graphics Describe the trend in the data. How many bubbles would you predict if Finding the solution the light was moved to 50 cm away? Explain. to the mystery is only 18. Draw Conclusions What relationship exists the beginning. Take a video field trip with the between the plant’s distance from the light ecogeeks of Untamed Science to see where the and the number of bubbles produced? What is mystery leads. taking place to cause this relationship? Explain your answer. 208 Chapter 8 Untamed Science Video Chapter Mystery Standardized Test Prep Multiple Choice Questions 8–10 1. Autotrophs differ from heterotrophs because they A scientist mashes up spinach leaves to make a liquid, or A use oxygen to burn food. extract, that has lots of pigment in it. She places a drop of B do not require oxygen to live. the liquid at one end of a strip of paper towel. After the C make carbon dioxide as a product of using food. liquid dries, she hangs the paper in a test tube containing D make their own food from carbon dioxide and alcohol so that only the tip of the paper is in the alcohol. water. As the alcohol is absorbed and moves up the paper, the different pigments separate as shown below. 2. The principal pigment in plants is A chlorophyll. C ATP. B oxygen. D NADPH. Distance solvent 3. Which of the following is NOT produced in the Yellow-orange traveled light-dependent reactions of photosynthesis? A NADPH B sugars Yellow C hydrogen ions D ATP 4. Which of the following correctly summarizes Blue-green Original photosynthesis? Yellow-green spot of A H2O  CO2 light sugars  O2 extract B sugars  O2 light H2O  CO2 C H2O  O2 light sugars  CO2 D sugars  CO2 light H2O  O2 8. Which pigment traveled the shortest distance? A yellow-orange C blue-green 5. The color of light that is LEAST useful to a plant B yellow D yellow-green during photosynthesis is A red. 9. Which of the following is a valid conclusion that B blue. can be drawn from this information? C green. A Spinach leaves use only chlorophyll during D violet. photosynthesis. B Spinach leaves contain several pigments. 6. The first step in photosynthesis is the C Spinach leaves contain more orange pigment A synthesis of water. than yellow pigment. B production of sugars. D Spinach leaves are yellow-orange rather than green. C breakdown of carbon dioxide. D absorption of light energy. 10. In which organelle would MOST of these pigments be found? 7. In a typical plant, all of the following factors are A vacuoles C mitochondria necessary for photosynthesis EXCEPT B centrioles D chloroplasts A chlorophyll. C oxygen. B light. D water. Open-Ended Response 11. Describe how high-energy electrons are ultimately responsible for driving the reactions of photosynthesis. If You Have Trouble With... Question 1 2 3 4 5 6 7 8 9 10 11 See Lesson 8.1 8.2 8.2 8.2 8.2 8.3 8.3 8.2 8.2 8.2 8.3 Photosynthesis 209