Module 5 Intro

Module 5—Photosynthesis and Cellular Respiration

Module Introduction

The major concepts developed in this module will lead your exploration of the cellular processes of photosynthesis and cellular respiration. These two processes provide the energy and matter required for the survival of all organisms on Earth. You will relate photosynthesis to the storage of energy in organic compounds. You will also explore the role of cellular respiration in releasing potential energy from organic compounds. You will be drawing on what you have already learned about these processes and the cell structures involved from Science 7, 8, and 10. You will also build upon the concept of energy flow and matter exchange that was developed in Unit A. In this module, instead of looking at an entire ecosystem or biosphere, you will be looking at the starting point of energy and matter exchange at the cellular level.

How does photosynthesis absorb solar energy? Photosynthesis will be broken down into more complex reactions. You will learn how pigments are involved in energy absorption. You will explore how compounds gain and lose electrons in the process of energy transfer to provide energy for photosynthesis and for the production of glucose.

How do organisms harness the energy from photosynthesis? You will investigate different kinds of cellular respiration. You will again explore how compounds gain and lose electrons during this process.

Lessons in this module will guide your discovery of the application of technology to benefit humans. You will also look at how humans may have unintentionally impacted photosynthesis and cellular respiration.

By the end of this module you will have completed activities that are to be marked by your teacher and others that help to build confidence in your ability to understand, interpret, and express key course concepts. Everything should be saved in your course folder so that you are able to review pieces of information for exams, unit assessments, or discussions. For example, once you have completed this module, you will be required to do a three-part unit assessment.  You will answer questions from the textbook, create  some multiple-choice questions, and look at the effects of a herbicide on photosynthesis and cellular respiration. When you are ready to complete the unit assessment you will find the project description and marking rubrics in the Module Summary and Unit Assessment.

Module 5—Photosynthesis and Cellular Respiration

Big Picture

People have a need for energy. Energy is required to run everything from a huge power plant to a single cell. Luckily, people have access to an unlimited energy supply—the Sun. Essentially, all available energy on the planet is derived from the Sun. Earth’s entire biosphere has evolved as an ultra-efficient means to transform solar rays into the chemical energy required for life. Plants have evolved to transform solar energy to potential chemical energy. Animals, such as humans, have evolved to transfer potential chemical energy into many other energy forms.

Science and technology are important in today’s society. This is particularly so with concerns over the rising environmental and economic costs of limited non-renewable energy sources and with the deforestation of large tracts of vegetation.

Technology is produced to enhance or mimic the processes of photosynthesis and cellular respiration. What fundamental principles are the basis for this research and technological advancement?

© Uli Hamacher/iStockphoto

As you discovered in Unit A, massive vegetation equals high plant productivity. Increasing population pressures may create havoc on Earth by reducing the amount of vegetation and, thus, the ability for photosynthesis to support the biosphere. Therefore, it is essential to understand the minute details of the process of photosynthesis and exploit it. What are the opportunities for applying what is known about photosynthesis?

Photosynthesis-based technology could include using the concept of efficient "energy capture" to artificial systems just as plants have been doing. Research is being done in Berkeley, California, on getting green algae to convert water to hydrogen to be harnessed as a

clean-burning fuel. Currently, technology has developed herbicides that inhibit photosynthesis in order to kill weeds.

The value of applying knowledge of cellular respiration has also been utilized in the multi-billion dollar wine industry. Globally, 27 billion litres of wine are made each year. This is an industry where new technologies are being developed to enhance cellular respiration and photosynthesis for the benefit of taste and economics.

Photosynthesis and cellular respiration are the most important biological processes on Earth. Without these two processes, how would the transfer of energy and matter occur?

You will explore the following essential questions in this module:

• What pathways do energy and matter follow in living organisms?
• How does the energy from light flow through living systems?
• Why is oxygen produced during photosynthesis?
• How is carbon dioxide used during the light-independent reactions of photosynthesis?
• How are ATP and NADPH produced by the light-dependent reactions used to make glucose?

As there is only one module in Unit C, there is only a unit assessment for you to consider as you work through Module 5.

As you work through the module, make note of questions or concepts that were particularly challenging or thought-provoking. This list will be helpful when you are ready to complete a unit test as part of your Unit Assessment. You will find the details for this assessment and an evaluation rubric in the Unit Summary section.

Module 5—Photosynthesis and Cellular Respiration

In This Module

Lesson 1—An Introduction to Photosynthesis and Cellular Respiration

If you want to live on Mars, you need to know the basics of photosynthesis and cellular respiration. Understanding these two processes will help you produce the food you will eat and the oxygen you will breathe during your stay on Mars. In this lesson you will review the basics of photosynthesis and cellular respiration. Can you name two organelles that are the sites for photosynthesis and cellular respiration? Lesson 1 will help you review cell structures and functions. You will also review the various mechanisms used for transporting materials in and out of cells, along with the role of ATP. You will be introduced to new vocabulary so that it becomes more familiar to you as you work through this module. As you will find in the following lessons, these topics are very important to help develop a full understanding of photosynthesis and cellular respiration.

• What pathways do energy and matter follow in living organisms?

Lesson 2—Light-Dependent Reactions

Have you ever forgotten to open your window blinds before going on vacation? What happened to your plants? You may have made this mistake despite knowing that your plants need water and sunlight to grow. In this lesson you will explore the specific role of water and sunlight in photosynthesis. This lesson introduces the light-dependent reactions of photosynthesis that release oxygen.

• How does the energy from light flow through living systems?
• How does oxygen become a product of photosynthesis?

Lesson 3—The Light-Independent Reactions of Photosynthesis

Does photosynthesis stop if you turn off the lights? Part of photosynthesis occurs when light is not available. This lesson introduces the light-independent reactions of photosynthesis where carbon dioxide is used to produce glucose.

• How is carbon dioxide used during the light-independent reactions of photosynthesis?
• How are ATP and NADPH produced by the light-dependent reactions used to make glucose?

Lesson 4—Investigating Photosynthesis

In this lesson you will further explore photosynthesis.

• What factors affect photosynthesis?
• What technologies have emerged from photosynthesis-based research?

Lesson 5—Anaerobic Respiration

What, no oxygen? No problem. Cellular respiration can still occur, but much less efficiently. This lesson introduces anaerobic cellular respiration. Not only will you learn about those pesky leg cramps that occur in the middle of a race, but you will also determine how alcohol and bread are made.

• How far can cellular respiration go without the presence of oxygen?
• How does anaerobic respiration release potential energy from organic compounds?

Lesson 6—Aerobic Respiration

Oxygen is the gas that allows you to survive! People actually need oxygen to efficiently obtain energy from sugar molecules. This lesson introduces the aerobic stage of cellular respiration.

• How does the presence of oxygen affect cellular respiration?
• How does aerobic cellular respiration release potential energy from organic compounds?

Lesson 7—Investigating Cellular Respiration

In this lesson you will further explore cellular respiration.

• How can you demonstrate quantitatively that germinating seeds consume oxygen?
• How do metabolic toxins affect cellular respiration?

Module 5—Photosynthesis and Cellular Respiration

Lesson 1—An Introduction to Photosynthesis and Cellular Respiration

Get Focused

In Unit B you learned that photosynthesis and cellular respiration influence the cycling of matter and the transformation of energy in the biosphere. In order to learn more about these processes, you will need to review your understanding of cells and cellular transport. You will also be introduced to ATP, which is involved in photosynthesis and cellular respiration, as well as energy pathways such as electron transport chains. These bits of information will help you understand the concepts in the following lessons.

In this lesson you will explore the following essential question:

• What pathways do energy and matter follow in living organisms?

Module 5: Lesson 1 Assignment

Your teacher-marked Module 5: Lesson 1 Assignment requires you to submit a response to the following:

• TR 2. The Chloroplast and the Mitochondrion
• Reflect and Connect

You can access your Module 5: Lesson 1 Assignment. You can print off the assignment or save the download to your computer. Your answers can be saved on this document to your course folder.

The other questions in this lesson are not marked by the teacher; however, you should still answer these questions. The Self-Check and Try This questions are placed in this lesson to help you review important information and build key concepts that may be applied in future lessons.

After a discussion with your teacher, you must decide what to do with the questions that are not part of your assignment. For example, you may decide to submit to your teacher the responses to Try This questions that are not marked. You may decide to record the answers to all the questions in the lesson and place those answers in your course folder.

Module 5—Photosynthesis and Cellular Respiration

Explore

Read

In Science 10 you studied cell theory, cell structure, and cell function. In this lesson you will build on those basics toward a greater understanding of cellular respiration and photosynthesis.

If you need to review cells, read pages 154 and 155 of the textbook. In particular, review the labelled diagrams of cells so that you have a better idea of where photosynthesis and cellular respiration take place. Once you have reviewed these pages, complete the following Try This.

Try This

TR 1. The Cell

Can you identify the mitochondrion and the chloroplast? Scroll over these two diagrams to see if you can correctly identify these structures. You will be learning more about these structures as you move through this module.

Read

The Chloroplast and the Mitochondrion

Chloroplasts and mitochondria have unique designs that allow them to carry out photosynthesis and cellular respiration. Plant cells have both a chloroplast and a mitochondrion, while animal cells contain only a mitochondrion. 

Try This

TR 2. The Chloroplast and the Mitochondrion

Go to your Module 5: Lesson 1 Assignment. Use the information provided on pages 164 and 165 of the textbook to label the structures of the chloroplast and mitochondrion. On your diagram, add descriptions of the function of the parts you have labelled.

Read

Cells must transport molecules produced during photosynthesis and cellular respiration. Cells must also transport the required compounds for these two processes. Note these types of cellular transport:

• passive transport
• diffusion
• facilitated diffusion
• osmosis
• active transport
• endocytosis
• pinocytosis
• phagocytosis
• exocytosis

These methods of transport move substances across the cell membrane. Membranes exist in every organelle. Transport of materials happens across the membranes of the mitochondrion and the cell. Using information from the glossary definitions and pages 156 to 159 of the textbook, try the following Self-Check.

Self-Check

SC 1. Complete this Self-Check activity.

Self-Check

SC 2. What is the purpose of facilitated diffusion?

SC 3. Where does a cell get energy for active transport?

Read

What is ATP?

Photosythesis produces the energy-rich chemical compound of glucose. The by-products of photosynthesis are oxygen and some ATP. Cellular respiration breaks down energy-rich compounds such as glucose. Breaking down the chemical bonds in glucose generates ATP. Cellular respiration generates more ATP than photosynthesis.

ATP is the energy currency of cells—when cells need energy, they spend ATP. You will learn more about ATP synthesis later on in this module.

Read “ATP and Cellular Activity” on page 163 of the textbook.

Self-Check

SC 4. What is ATP used for?

SC 5. How does ATP supply energy to the cell?

Module 5—Photosynthesis and Cellular Respiration

Read

Metabolic Pathways

© Dept. of Computer Science, University of Helsinki. Used with permission.

Metabolic pathways are interconnected and involve many steps. Plants and animals rely on metabolic pathways to store and provide energy. These pathways can be summarized by the word metabolism.

Photosynthesis and cellular respiration are two important pathways. They can be represented by the following two formulas:

6 CO2(g) + 6 H20(l) + energy → C6H12O6(s) + O2(g)

C6H12O6(s) + O2(g) → 6 CO2(g) + 6 H20(l) + energy

The important thing to keep in mind is that these are summary statements. Both processes are a series of reactions that use initial reactants to produce final products.

The series of reactions becomes a metabolic pathway. Metabolic pathways transfer energy and cycle matter. The products of one reaction become the reactants for the next reaction. You will be learning about the series of reactions in the following lessons.

Self-Check

SC 6.  True or False: Cellular respiration is the same as breathing.

Module 5—Photosynthesis and Cellular Respiration

Read

REDOX

Oxidation and reduction, oxidized and reduced. These are words that you will encounter as you learn more about photosynthesis and cellular respiration. Read page 167 in your textbook.

The words reduction or reduced can sometimes create confusion. Normally one would associate the idea of less with these words; but instead, there is a gain. How does this work?

There is a simple mnemonic device to remember the definition of the terms oxidation and reduction. All you have to do is remember that LEO the lion goes GERRR! (That is a growl.)  Spelled out, it looks like this:

Lose Electrons → Oxidation,     Gain Electrons → Reduction

When electrons transfer in a chemical equation, this is called a redox reaction. Here is a chemical equation to illustrate.

Xe- + Y → X + Ye-

It turns out that the overall reaction of photosynthesis is an oxidation-reduction (redox) reaction. In the first step, the oxygen in water is oxidized by the light energy. This means that the water molecule has lost electrons (LEO). You will learn more about this process when you study light-dependent reactions.

H2O + light energy→1/2 O2 + 2 [H.]+ 2 e-

Here, [H.], or a proton, represents a reducing agent. Next, the [H.] reduces the carbon in CO2. This is not as simple as is shown. However, the idea is that at some point carbon dioxide is reduced (GER). The result is a charboydrate molecule. You will learn about this step during your study of light-independent reactions.

2[H.] + CO2 → (CH2O){carbohydrate molecule}

Note: In order for a glucose molecule to be created, more than one water molecule and one carbon dioxide molecule are involved. This situation is indicated by the balanced chemical equation

6 CO2(g) + 6 H20(l) + energy → C6H12O6(s) + O2(g)

Conversely, in cellular respiration, glucose is oxidized and oxygen is reduced.

Self-Check

SC 7.  A molecule such as NADP+ can be reduced to NADPH. NADPH is said to have reducing power. What does this mean?

SC 8.  Hydrogen ions are also called ______________.

SC 9. True or False: [H+] has one electron.

Watch and Listen

What is an electron transport chain?

Electron transport chains are essential to photosynthesis and cellular respiration. In an electron transport system, energy from electron transfer during oxidation-reduction reactions enables certain carriers to pump protons (H+) across a membrane. As the H+ concentration increases on one side of the membrane, an electrochemical gradient develops and chemiosmosis occurs.

Watch the following animation to get an idea of what chemiosmosis looks like.

Module 5—Photosynthesis and Cellular Respiration

Reflect and Connect

© Jasenka Lukša/shutterstock

As you worked through this lesson, were you able to create a better mental picture of what happens during photosynthesis and cellular respiration?

Go to the Module 5: Lesson 1 Assignment to answer some questions about matter, energy, photosynthesis, and cellular respiration.

Module 5: Lesson 1 Assignment

Remember to submit the Assignment answers to your teacher as part of your Module 5: Lesson 1 Assignment.

Module 5—Photosynthesis and Cellular Respiration

Lesson Summary

In this lesson you explored the following essential question:

• What pathways do energy and matter follow in living organisms?

Energy and matter follow many pathways. Matter is transported in many different ways. Osmosis and active transport are two ways that you explored—both are involved in photosynthesis and cellular respiration.

The most important metabolic pathways for plants are photosynthesis and cellular respiration. Cellular respiration is the most important metabolic pathway for humans. These pathways break down or synthesize carbon dioxide, water, carbohydrates, oxygen, and ATP (energy). The creation or breakdown of these important molecules is reliant on oxidation-reduction reactions. These reactions occur via electron transport systems and chemiosmosis in the mitochondrion and chloroplast.

Lesson Glossary

active transport: a process that requires energy from ATP to move substances against the concentration gradient

ATP (adenosine triphosphate): a high-energy phosphate molecule that provides and stores the energy required for cellular functions

chemiosmosis: the process by which ATP is generated through the movement of protons down a concentration gradient

The protons move across the inner membranes to the mitochondrion and thylakoid membrane of the chloroplast and combine with ADP and phosphate molecules to form ATP.

diffusion: a process in which molecules move from areas of high concentration to low concentration

endocytosis: a process in which cell membranes engulf a substance and pinch off inside the cell

exocytosis: a process in which a vacuole containing substances from inside a cell (cytoplasm) fuses with the cell wall and the contents are released outside of the cell

facilitated diffusion: a process in which larger molecules need the help of proteins in cell walls to move from areas of high concentration to low concentration

metabolism: all of the chemical reactions that occur within a cell to support and sustain its life functions

This can be the synthesis of molecules or the breaking down of molecules for energy.

osmosis: the diffusion of water across a semipermeable membrane

oxidation: a loss of electrons

passive transport: no energy required

phagocytosis: a process in which the cell wall engulfs a large particle, such as bacteria or a blood cell, and pinches off inside of the cell

pinocytosis: the cell wall engulfs liquids and their solutes and pinches off inside the cell

proton: a hydrogen ion containing one electron

redox reaction: a reaction involving the transfer of electrons

reduction: a gain of electrons

Module 5—Photosynthesis and Cellular Respiration

Lesson 2—Light-Dependent Reactions

Get Focused

You may wonder what role plants play in supporting your life on Earth, other than being an obvious supplier of oxygen through photosynthesis. Plants are used for making medicines, perfumes, lotions, clothes, paper, and buildings. People also use plants as a source of amino acids, food energy, and oxygen. In short, plants are a pretty big deal.

A knowledge of photosynthesis may become valuable in the future if Earth experiences food or fuel shortages. By understanding photosynthesis, technologies that could help alleviate these shortages can be explored.

What is the first thing you think of when you hear the word photosynthesis? Some words that come to mind might be green, plants, and

sun. Plants do require sunlight to perform one part of photosynthesis. You will be studying the light-dependent reactions of plants.

In this lesson you will explore the following essential questions:

• How does the energy from light flow through living systems?
• How does oxygen become a product of photosynthesis?

Module 5: Lesson 2 Assignment

Your teacher-marked Module 5: Lesson 2 Assignment requires you to submit a response to the following:

• LAB: Using Chromatography to Separate Plant Pigments
• Reflect and Connect

You can access your Module 5: Lesson 2 Assignment. You can print off the assignment or save the download to your computer. Your answers can be saved on this document to your course folder.

You must decide what to do with the questions that are not marked by the teacher.

Remember that these questions provide you with the practice and feedback that you need to successfully complete this course. You should respond to all the questions and place those answers in your course folder.

Module 5—Photosynthesis and Cellular Respiration

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Where does photosynthesis occur?

In Lesson 1 you studied the chloroplast and learned to identify its structures and functions. As you begin to explore the light-dependent reactions of photosynthesis, you will be focusing on the reactions that happen in the thylakoid membrane.

Chlorophyll is the light-capturing pigment that absorbs all wavelengths of light except for green and some yellow. Read “The Light-Dependent Reactions of Photosynthesis” on page 170 of the textbook. Make note of the graphs and diagrams on page 171. You may also want to revisit the Module 1: Lesson 1 Assignment, where you completed a virtual experiment discussing factors that affect photosynthesis. One factor discussed was light wavelengths.

A Closer Look at Chloroplasts

The flattened thylakoids in the chloroplasts of plant cells are stacked into columns called grana. Surrounding the thylakoids and filling the interior of the chloroplast is the fluid stroma, which is where the chemical reactions that synthesize carbohydrates take place.

Light-reflecting and Light-absorbing Characteristics of Pigments

When you look at an object, you see the colours that were not absorbed by the object.

This absorbance spectrum for three photosynthetic pigments shows that each pigment absorbs a different combination of colours of light.

This action spectrum for photosynthesis shows the rate at which oxygen is produced during photosynthesis. Notice that the shape of the graph line generally mirrors the shape of the graph lines in the absorbance spectra above.

© YAKOBCHUK VASYL/shutterstock

Self-Check

SC 1.  Why do plants appear green?

SC 2. What is the difference between chlorophyll a, chlorophyll b, and beta carotene?

SC 3.  Why would it be an advantage for a plant to have several pigments in a chloroplast?

SC 4.  At what wavelength of light is oxygen production the lowest? Highest?

Module 5—Photosynthesis and Cellular Respiration

LAB. Using Chromatography to Separate Plant Pigments

To identify the different pigments present in the leaves of a green plant, a separation process called chromatography is used. Your textbook gives a procedure for “Investigation 5.B: Using Chromatography to Separate Plant Pigments” on pages 172 and 173. If you have access to a lab, you may be instructed to complete this lab as indicated in the textbook. You should not attempt this investigation outside of a lab, since the solvent used is volatile, poisonous, and flammable.

If you do not have access to a lab, you will be given a diagram of pigments separated by chromatography in your assignment.

In this experiment, liquid from crushed leaves is painted onto special paper. The paper is then placed in a test tube containing a solvent. The solvent is absorbed up through the paper and, as the solvent rises, it separates the different pigments. Generally, the pigments with the smallest molecules will move through the paper the fastest, but results may differ when some solvents—or combinations of solvents—are used.

Before you go to your Module 5: Lesson 2 Assignment to complete this Lab, complete the following Self-Check on reference flow.

Self-Check: Reference Flow

(Rf) is a measure of how far a substance is transported in chromatography relative to the movement of the solvent used. It is calculated by dividing the distance a substance (pigment) moves by the distance the solvent moves.

SC 5. Using the measurements shown on the diagram, what is the Rf for carotene?

Module 5—Photosynthesis and Cellular Respiration

Read

The Path of Electrons in Light-Dependent Reactions

You may choose to read the following description or read pages 172 to 174 of the textbook before you watch the animation “Oxygenic Photosynthesi” in the next Watch and Listen. This animation clearly shows the path of electrons in the light-dependent reactions of photosynthesis.

The electron transport chain that exists in the thylakoid membrane involves photosystem I and II. Photosystem II (PSII) absorbs all wavelengths of light allowed by its pigments. When light is absorbed, energy is transferred to a designated reaction-centre molecule. The reaction centre becomes “excited.” This means that an electron will want to move to a higher energy level, so the electron leaves to catch the electron-transport chain. PSII oxidizes water molecules to provide hydrogen ions for chemiosmosis and electrons to replace the electrons leaving the “reaction centre.” Oxygen is produced at this step.

The electron from photosystem II travels down the electron-transport chain. Every encounter with an electron-carrying molecule releases energy. This energy pushes H+ from the stroma into the thylakoid space. A hydrogen ion concentration gradient is formed. This gradient will be used to produce ATP from ADP (adenosine diphosphate) and free phosphate groups.

The e- (electron) from photosystem II reaches photosystem I (PSI). Light has also been absorbed by PSI. The energy has been passed on to the reaction centre. A highly energized electron leaves photosystem I to be replaced by the e- from PSII at the end of its electron-transport chain. The highly energized electron from PSI moves down an electron-transport chain. The electron is used to reduce NADP+ to form NADPH. NADP+ gains electrons from PSI and hydrogen ions.

Lastly, remember that hydrogen ions are building up in the thylakoid space. Once a hydrogen ion is in the thylakoid space, it cannot diffuse back to the stroma. However, ATP synthase embedded in the thylakoid membrane will move H+ down the concentration gradient (high [H+] in the thylakoid space to low [H+] in the stroma). The energy from this concentration gradient is chemiosmosis. ATP is created.

Light-dependent reactions produce oxygen, which is released from chloroplasts to the atmosphere. Light-dependent reactions produce intermediate products of NADPH and ATP. These molecules are required in light-independent reactions for the production of glucose.

The following diagram is a summary.

Watch and Listen

The Path of Electrons in Light-Dependent Reactions

Watch the animation “Oxygenic Photosynthesis” or watch the animation “Photosynthetic Electron Transport and ATP Synthesis.” Note that these animations label molecules in the electron-transport chain that you are not required to know. You just need to realize these molecules are electron-carrying molecules. However, the molecules clearly show the path of electrons in the light-dependent reactions of photosynthesis. You may want to refer to a copy of the summary diagram as you watch the animation.

If you prefer to be in control of the animation speed, select “Oxygenic Photosythesis.” If you prefer to have audio with an animation, watch “Photosynthetic Electron Transport and ATP Synthesis.”

Now watch this Cyclic and Noncyclic Photophosphorylation animation. Which animation helped you better understand the light-dependent reactions of photosynthesis? Did the reading and/or diagram help you as well?

Self-Check

SC 6. Complete this Self-Check activity to check your understanding of light-dependent reactions.

Module 5—Photosynthesis and Cellular Respiration

Reflect and Connect

Go to your Lesson 2 Assignment to answer two questions about photosynthesis.

Reflect on the Big Picture

Brainstorm a list of potential technologies based on photosynthesis that could be explored. Maybe these technologies are being explored already. Perform a web search to see what you can find.  Save your list to your course folder to be revisited later in this module.

Summarize in point form, by illustration, by podcast, or by poem the events that take place in the light-dependent reactions of photosynthesis.

Module 5: Lesson 2 Assignment

Remember to submit the Assignment answers to your teacher as part of your Module 5: Lesson 2 Assignment.

Module 5—Photosynthesis and Cellular Respiration

Lesson Summary

In this lesson you explored the following essential questions:

• How does the energy from light flow through living systems?

• Why is oxygen produced during photosynthesis?

In order for photosynthesis to occur, there has to be light energy. There also has to be a way to harness light, because light travels at many different wavelengths. To account for this, plants contain many different pigments in their chloroplasts. To show this, you worked through a chromatography investigation.

Plants contain pigments, such as chlorophyll, that absorb all wavelengths of light except for greens, yellows, and some oranges (carotene). Once this light energy is absorbed, it is transferred to electrons that become highly excited and enter an electron-transport chain.

The production of oxygen happens when photosystem II oxidizes water molecules. Oxidized water molecules provide electrons for the electron-transport chain and hydrogen ions for chemiosmosis, or ATP Synthesis. Oxygen is a by-product that diffuses to the atmosphere. Photosystem I also transports highly-energized electrons and reduces NADP+ to NADPH.

In summary, the light-dependent reactions rely on the reactants of water and light energy. These reactions produce the end product of oxygen and the intermediate products of ATP and NADPH, which are used in light-independent reactions to produce glucose. You will discover the final step of photosynthesis in Lesson 3. As you can see, photosynthesis is a series of reactions more complex than the simple statement of 

6 CO2(g) + 6 H20(l) + energy → C6H12O6(s) + O2(g)

Lesson Glossary

ATP synthase: an enzyme that bonds free phosphates to ADP to form ATP

NADP+: nicotinamide adenine dinucleotide phosphate in its oxidized state

NADPH: nicotinamide adenine dinucleotide phosphate in its reduced state; used in light-independent reactions to form glucose

photosystem: a cluster of light-absorbing pigment molecules in the thylakoid membrane of chloroplasts

reference flow: a measure of how far a substance is transported in chromatography

thylakoid membrane: flattened stacks within the stroma that contain chlorophyll

Module 5—Photosynthesis and Cellular Respiration

Lesson 3—The Light-Independent Reactions of Photosynthesis

Get Focused

What if humans decide to colonize space? How could they apply information about photosynthesis to make colonization sustainable? In Lesson 2 you investigated how energy was converted during photosynthesis. You also know that plants absorb carbon dioxide and use it to make sugar.

In Lesson 3 you will study how plants are able to produce biomass.

Knowing how much plant matter is needed to produce enough oxygen to support life is valuable information. The values for oxygen production and carbon dioxide use stated in the previous quotation could be very helpful for scientists trying to design efficient crops or gardens able to sustain life in a space colony. Since the light-independent reactions of photosynthesis require carbon dioxide and produce biomass, this information is of great interest to researchers.

You may have noticed from the name of this process that light does not appear to be necessary. Does this mean that this series of reactions could happen without sunlight? As you work through this lesson, consider the necessary reactants for this step to occur and determine if they will be available to plants in space.

In this lesson the following essential questions will be examined:

• How is carbon dioxide used during the light-independent reactions of photosynthesis?
• How are ATP and NADPH produced by the light-dependent reactions used to make glucose?

Module 5: Lesson 3 Assignment

Your teacher-marked Module 5: Lesson 3 Assignment requires you to submit a response to the following:

• TR 1. You Be the Critic
• Reflect and Connect

You can access your Module 5: Lesson 3 Assignment. You can print off the assignment or save the download to your computer. Your answers can be saved on this document to your course folder.

You must decide what to do with the questions that are not marked by the teacher.

Remember that these questions provide you with the practice and feedback that you need to successfully complete this course. You should respond to all the questions and place those answers in your course folder.

Biology 20 © 2008 Alberta Education

Module 5—Photosynthesis and Cellular Respiration

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The Calvin-Benson Cycle

As photosynthesis progresses to the light-independent reactions, these reactions move from the thylakoid space to the stroma of the chloroplast. It is not necessarily dark outside either.

Simply put, light-independent reactions do not directly depend on light energy in order to proceed. They do, however, depend on the products of the light-dependent reactions of NADPH and ATP. The energy contained in these two molecules is used in glucose synthesis.

Once again, there are a series of reactions that take place to synthesize carbohydrates (glucose). This series of reactions takes place in the Calvin-Benson cycle. The purpose of the cycle is for carbon-dioxide fixation. When studying the Calvin-Benson cycle, you will be introduced to the following familiar and unfamiliar molecules.

Ribulose biphosphate (RuBP) is a 5-carbon molecule in the stroma that initially bonds to carbon dioxide. After RuBP is bonded to carbon, it becomes unstable and breaks down into two 3-carbon molecules:

RuBP + C02 (g) → unstable C6 → 2 C3

The two low energy, 3-carbon molecules are activated by ATP and reduced by NADPH (gain electrons) to become high-energy phosphoglyceraldehyde (PGAL). Some molecules leave the cycle to create glucose, while other molecules remain in the cycle to replace RuBP.

The following diagram shows where these chemicals are needed in the Calvin-Benson cycle.

If you want to further explore the Calvin-Benson cycle, refer to “The Light-Independent Reactions of Photosynthesis” on pages 176 and 177 of the textbook. If you feel confident that you understand what is happening in the Calvin-Benson cycle, try answering the following Self-Check questions.

Self-Check

SC 1. Complete this Self-Check activity to test your understanding of the Calvin-Benson cycle.

Try This

TR 1. You Be the Critic

In the last two lessons you have learned a great deal about photosynthesis. View the following animation of photosynthesis.

You may think that some aspects of the animation seem overly simple and don’t explain the complexity of the process well enough. Why? What would you change or add?

Create a modified storyboard (PowerPoint) or a script that could be given to a multimedia developer to make this animation more suitable for you and your classmates. View the following template for ideas about how to create a storyboard.

Storyboard Template

Space will be provided in the Module 5: Lesson 2 Assignment to place your ideas. A rubric will be provided in the assignment as well.

Self-Check

SC 2. Complete this Self-Check activity.

Biology 20 © 2008 Alberta Education

Module 5—Photosynthesis and Cellular Respiration

Reflect and Connect

This lesson describes how the light-independent reactions of photosynthesis are responsible for the conversion of carbon dioxide into glucose. Although there are other processes that could be used to remove carbon dioxide from the air inside a space colony, not many other processes would be able to produce food at the same time.

Imagine that you are in charge of a greenhouse on a space station. The greenhouse has three purposes:

• to produce food
• to control air quality
• to provide fresh water

Prepare a large, detailed diagram to describe the greenhouse organization. How would each of the three listed purposes be performed? You may wish to consider what types of plants would be best to have in your greenhouse, as well as the light conditions and the atmospheric composition. Save this diagram in your course folder. This would be great to share with your classmates. Post your diagram and view the diagrams of other students. Review your response and make necessary edits.

Discuss

Global warming is an issue that emerges from many areas of biological study. You can describe the complex process of photosynthesis thanks to discoveries made by scientists.

If you were a scientist trying to stop global warming, what part of photosynthesis would you study? Why? Post your response in the discussion area. Your response should contain specific details and logical reasoning, instead of one general statement. Read other postings and save your response to your course folder. Did you learn anything new? Your teacher may use this as an Assessment item.

Reflect on the Big Picture

Photosynthesis is an evolved process that has happened over millions of years. Scientists are working on ways to manipulate the evolution of photosynthesis in order to reduce global warming.

Going Beyond

How does biomass energy relate to photosynthesis? You discussed biomass in Unit A when you talked about biomass pyramids. You now know six carbon dioxide molecules are absorbed (assimilated) by photosynthetic organisms to produce one glucose molecule. These molecules become biomass. If you go to the CBC website, you can do a web search for a “Quirks and Quarks” radio episode on biomass. Use the following words in your search: “quirks quarks biomass September 16.” You are looking for the September 16, 2006, episode. Once you are on the page, scroll down until you find the title “Biomass.” The future of biomass fuels is discussed.

OR

What is RuBisCO? RuBisCO is the most abundant enzyme on Earth, but it is one of the most inefficient enzymes. Do a web search to find out what role RuBisCO plays in photosynthesis.

Module 5: Lesson 3 Assignment

Remember to submit the Assignment answers to your teacher as part of your Module 5: Lesson 3 Assignment.

Biology 20 © 2008 Alberta Education

Module 5—Photosynthesis and Cellular Respiration

Lesson Summary

In this lesson the following essential questions were explored:

• How is carbon dioxide used during the light-independent reactions of photosynthesis?

• How are ATP and NADPH produced by the light-dependent reactions used to make glucose?

The Calvin-Benson cycle is the last step in photosynthesis. The purpose of the Calvin-Benson cycle is to take the energy from photosystem I and fix carbon. Carbon-dioxide fixation occurs when atmospheric CO2 (g) binds with a 5-carbon RuBP molecule to form two, 3-carbon PGAL molecules. ATP and NADPH, which are products from light-dependent reactions, provide energy and reducing power to form PGAL. Two PGAL molecules leave the Calvin-Benson cycle to form glucose, while the other molecules continue on to be broken down.

With the help of ATP, PGAL bonds are broken and RuBP is remade. This part of photosynthesis is responsible for removing carbon dioxide (a greenhouse gas) from the atmosphere—it is also responsible for the creation of biomass.

Applications of light-independent reactions may lead to the colonization of space, the reduction of global warming, or increased crop production.

Lesson Glossary

ATP: a reduced high-energy adenosine triphosphate molecule

Calvin-Benson cycle: the process in which photosynthetic organisms fix carbon from atmospheric carbon dioxide to produce carbohydrates

carbon-dioxide fixation: a carbon atom in carbon dioxide is chemically bonded to a pre-existing 5-carbon compound in the stroma of the chloroplast

glucose: a saccharide or sugar; can be linked to many other saccharides to form different types of sugars or carbohydrates

NADPH: a reduced nicotinamide adenine dinucleotide molecule

phosphoglyceraldehyde (PGAL): a high-energy compound used to make glucose

ribulose biphosphate (RuBP): a 5-carbon molecule in the stroma that initially bonds to carbon dioxide

Biology 20 © 2008 Alberta Education

Biology 20 © 2008 Alberta Education

Biology 20 © 2008 Alberta Education

Biology 20 © 2008 Alberta Education

Biology 20 © 2008 Alberta Education

Biology 20 © 2008 Alberta Education

Biology 20 © 2008 Alberta Education

Biology 20 © 2008 Alberta Education

Biology 20 © 2008 Alberta Education

Biology 20 © 2008 Alberta Education

Biology 20 © 2008 Alberta Education

Biology 20 © 2008 Alberta Education

Biology 20 © 2008 Alberta Education

Biology 20 © 2008 Alberta Education

Biology 20 © 2008 Alberta Education

Biology 20 © 2008 Alberta Education

Module 5—Photosynthesis and Cellular Respiration

Lesson 7—Investigating Cellular Respiration

Get Focused

Cellular respiration—everything’s doing it! If you think about it, cellular respiration is the most-performed function by living organisms. All domains of organisms depend on cellular respiration to fuel life processes. Scientists know that understanding this important process is key to the advancement of many types of technology. Included technologies are in the food and agricultural industry and in medical research.

As you do some research, can you see how understanding cellular respiration is important to science, society, and technology?

In this lesson the following essential questions will be explored:

• How can you demonstrate quantitatively that germinating seeds consume oxygen?
• How do metabolic toxins affect cellular respiration?

Module 5: Lesson 7 Assignment

Your teacher-marked Module 5: Lesson 7 Assignment requires you to submit a response to the following:

• LAB: Oxygen Consumption and Heat Production in Germinating Seeds
• TR 1. The Effects of Metabolic Toxins on Cellular Respiration

You can access your Module 5: Lesson 7 Assignment. You can print off the assignment or save the download to your computer. Your answers can be saved on this document to your course folder.

You must decide what to do with the questions that are not marked by the teacher.

Remember that these questions provide you with the practice and feedback that you need to successfully complete this course. You should respond to all the questions and place those answers in your course folder.

Biology 20 © 2008 Alberta Education

Module 5—Photosynthesis and Cellular Respiration

Explore

Read

The germination of seeds is an example of a plant process that requires energy and oxygen. When you think of plants, you generally think about photosynthesis. But plants need energy to grow as well. When a seed germinates, it uses stored energy present within the seed to support the growth of the seedling.

During germination, cellular respiration converts energy from the carbohydrate within the seed into a form usable by the seedling cells. The chemical potential energy available from the starch and other sugars within most seeds is converted into glucose and then into ATP by the process of cellular respiration.

While cellular respiration breaks chemical bonds to release energy to produce ATP, the process also releases 64% of its energy as heat. In the following lab you will be asked to interpret collected data as evidence of oxygen consumption and heat production in germinating seeds. Research such as this opens avenues of further research which can benefit humans.

Biology 20 © 2008 Alberta Education

Module 5—Photosynthesis and Cellular Respiration

LAB: Oxygen Consumption and Heat Production in Germinating Seeds

Investigate the energy required during the germination of seeds by completing the lab “Oxygen Consumption and Heat Production in Germinating Seeds.” You will be completing this lab as outlined in your textbook on pages 184 and 185. You may choose to do “Part 1: Oxygen In Cellular Respiration” by using the virtual lab.

“Part 2: Heat Production in Cellular Respiration” will be completed as described in the textbook. You may decide to work in a group to complete Part 2. In this part of your investigation you will create an experimental plan that demonstrates that heat is a product of germinating seeds. If you are unable to carry out your experimental design, data will be provided for your interpretation in your Assignment.

You will also be asked to provide hypotheses for Part 1 and Part 2. Click on the tab below to give you a clear idea of how to prepare your hypotheses.

To complete this lab you will need to read pages 184 and 185 of the textbook. You will also need to access your Assignment.

Biology 20 © 2008 Alberta Education

Module 5—Photosynthesis and Cellular Respiration

Read

Metabolic Toxins

What are metabolic toxins? They are chemicals that impair or disrupt metabolic pathways. As you have studied in Module 5, both photosynthesis and cellular respiration are metabolic pathways. A metabolic toxin will target the function of chloroplasts or mitochondria.

Science has moved technology toward creating pesticides and herbicides that interfere with the metabolic processes of organisms and ultimately cause death. Scientists must use the scientific process to determine harmful effects on humans and desired effects on pests and weeds. Metabolic toxin research may also help scientists discover ways to inhibit cancer cell growth by creating toxins that specifically inhibit cellular respiration in cancer cell mitochondrion that cause the cancer cells to die.

Try This

TR 1. The Effects of Metabolic Toxins on Cellular Respiration

In this investigation you will be choosing one of the following metabolic toxins to investigate:

• antimycin
• cyanide
• hydrogen sulfide
• malonate
• oligomycin
• rotenone
• arsenic

You may have heard of arsenic or cyanide, and you may know that they are poisonous to humans as well.

You will be completing “Thought Lab 5.3” on page 189 of the textbook. You will be asked to research a metabolic toxin and create a Metabolic Toxin Profile based on the information you have collected. You can present the profile in a variety of formats such as slide show, poster, report, or podcast. You must, however, include an introductory paragraph that summarizes the results of your research. Post your profile in the discussion area so that other students can view your research results. You will be constructing a comparison chart between the toxin you chose to research and two toxins that other students have researched and posted in the discussion area. You will also be asked to complete analysis questions as well.

This activity and how you will be marked on it is outlined in your Assignment.

Discuss

Don’t forget to post your Metabolic Toxin Profile to the discussion area. Also be sure to read other postings so that you can complete your comparison chart.

Biology 20 © 2008 Alberta Education

Module 5—Photosynthesis and Cellular Respiration

Reflect and Connect

After taking part in the scientific process and doing some research, are you able to make a list of how respiration research affects science, technology, and society? Create a list that can be posted in the discussion area and shared with other students.

Reflect on the Big Picture

Investigating cellular respiration and photosynthesis allows you to explore ways in which technology has benefited humans. Both processes are complex and involve many steps. You can now describe how energy and matter flow through photosynthesis and cellular respiration.

Self-Check

SC 1. Complete this Self-Check activity.

SC 2. The human body contains about 50 grams of ATP at any one time, and yet about 8 kilograms of ATP per hour are being produced. Explain the apparent discrepancy in this data.

Module 5: Lesson 7 Assignment

Remember to submit the Assignment answers to your teacher as part of your Module 5: Lesson 7 Assignment.

Biology 20 © 2008 Alberta Education

Module 5—Photosynthesis and Cellular Respiration

Lesson Summary

In this lesson you explored the following essential questions:

• How can you demonstrate quantitatively that germinating seeds consume oxygen?
• How do metabolic toxins affect cellular respiration?

Working through both investigations allowed you to take a more in-depth look at cellular respiration. By investigating oxygen consumption and heat production in germinating seeds, you took part in the scientific process that is used by scientists hoping to make great discoveries.

As you researched metabolic toxins, you saw how a knowledge of cellular respiration is essential when determining what may inhibit the functioning of a cell. This knowledge has applications in the industries of agriculture, food, and medicine.

Now that you have completed this module and unit, you will finish the Unit Assessment. The Unit Assessment can be found on the Unit Summary and Assessment file. It is a three-part assignment. You will be answering questions from the textbook, creating some multiple-choice questions, and looking at the effects of a herbicide on photosynthesis and cellular respiration. There will not be a module assessment because the module and unit assessments for this module have been combined.

Biology 20 © 2008 Alberta Education

Module 5—Photosynthesis and Cellular Respiration

Module Glossary

acetyl CoA: an oxidized form of glucose

active transport: a process that requires energy from ATP to move substances against the concentration gradient

ATP (adensosine triphosphate): a high-energy phosphate molecule that provides and stores the energy required for cellular functions

ATP synthase: an enzyme that bonds free phosphates to ADP to form ATP

biofuel: ethanol produced during the fermentation of biomass

biogas: methane captured from animal waste that is used as fuel

Calvin-Benson cycle: the process in which photosynthetic organisms fix carbon from atmospheric carbon dioxide to produce carbohydrates

CAM: crassulacean acid metabolism (CAM photosynthesis); an elaborate carbon fixation pathway in some plants

carbon-dioxide fixation: a carbon atom in carbon dioxide is chemically bonded to a pre-existing 5-carbon compound in the stroma of the chloroplast

chemiosmosis: the process by which ATP is generated through the movement of protons down a concentration gradient

The protons move across the inner membranes to the mitochondrion and thylakoid membrane of the chloroplast and combine with ADP and phosphate molecules to form ATP.

diffusion: a process in which molecules move from areas of high concentration to low concentration

endocytosis: a process in which cell membranes engulf a substance and pinch off inside the cell

exocytosis: a process in which a vacuole containing substances from inside a cell (cytoplasm) fuses with the cell wall and the contents are released outside of the cell

facilitated diffusion: a process in which larger molecules need the help of proteins in cell walls to move from areas of high concentration to low concentration

FADH2: an important coenzyme produced during Krebs cycle

It acts as an electron donor to the electron transport system involved in the production of ATP.

glucose: a saccharide or sugar; can be linked to many other saccharides to form different types of sugars or carbohydrates

glycolysis: a metabolic pathway in which one glucose molecule is broken down to form two, 3-carbon molecules and a small amount of ATP

Glycolysis is the first step in both anaerobic and aerobic respiration.

Krebs cycle: a metabolic pathway consisting of a series of reactions that break down the end products of glycolysis, producing carbon dioxide and generating a large amount of ATP; also know as the citric acid cycle; named after the 1953 Nobel Prize winning scientist who made the discovery

metabolism: all of the chemical reactions that occur within a cell to support and sustain its life functions

This can be the synthesis of molecules or the breaking down of molecules for energy.

NADH: a high-energy electron carrier

It acts as an electron donor to the electron transport system involved in the production of ATP.

NADP+: nicotinamide adenine dinucleotide phosphate in its oxidized state

NADPH: nicotinamide adenine dinucleotide phosphate in its reduced state; used in light-independent reactions to form glucose

osmosis: the diffusion of water across a semipermeable membrane

oxidation: a loss of electrons

passive transport: no energy required

phagocytosis: a process in which the cell wall engulfs a large particle, such as bacteria or a blood cell, and pinches off inside of the cell

phosphoglyceraldehyde (PGAL): a high-energy compound used to make glucose

phosphorylation: the process of adding a phosphate to a molecule; occurs in cellular respiration and photosynthesis

photosystem: a cluster of light-absorbing pigment molecules in the thylakoid membrane of chloroplasts

pinocytosis: a process in whichthe cell wall engulfs liquids and their solutes and pinches off inside the cell

proton: a hydrogen ion containing one electron

pyruvate: three carbon molecules produced by glycolysis

redox reaction: a reaction involving the transfer of electrons

reduction: a gain of electrons

reference flow: a measure of how far a substance is transported in chromatography

ribulose biphosphate (RuBP): a 5-carbon molecule in the stroma that initially bonds to carbon dioxide

thylakoid membrane: flattened stacks within the stroma that contain chlorophyll

VO2 max: used to measure how well an athlete is able to use oxygen during an activity: units are mL/kg/min