Cells and Energy Interactive Reader

Preview Key Concepts All cells need chemical energy. The overall process of photosynthesis produces sugars that store chemical energy. Photosynthesis requires a series of chemical reactions. The overall process of cellular respiration converts sugar into ATP using oxygen. Cellular respiration is an aerobic process with two main stages. Fermentation allows the production of a small amount of ATP without oxygen.

Review Academic Vocabulary1. Converts food into usable energy.2. Molecule broken down as a source of energy.3. Decreases activation energy for reactions.

Preview Key Biology Terms1. Aerobic – 2. Anaerobic –

Chemical Energy and ATPKey Concept: All cells need chemical energy.The chemical energy used by most cell processes is carried by ATP.Chemical Energy is used by all organisms and is needed for all life processes. The chemical energy that all cells use is in the form of ATP, which stands for adenosine triphosphate. ATP is a molecule that carries energy that cells can use. This energy from the food is transferred by ATP when ATP gets broken down, the energy is released.

Organisms break down carbon-based molecules to produce ATP – Foods you eat must be digested. Digestion breaks down the food into smaller molecules – such as carbohydrates, lipids, and proteins – that your cells can use to make ATP.The amount of ATP produced depends on the type of molecules that is broken down. A molecule of the simple sugar glucose produces about 36 molecules of ATP. A fat molecule produces about 146 molecules of ATP. A protein molecule

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ATP has three phosphate groups. The bonds that holds the third phosphate molecule is easily broken. When the third phosphate is removed, energy is released. Then, the molecule becomes ADP, which stands for adenosine diphosphate. ADP does NOT carry energy that cells can use. The difference between ATP and ADP is

ATP has three phosphate groups and is high energy. ADP has two phosphate groups and is lower energy.

ADP is a lower energy molecule. If another phosphate is added to ADP, it becomes ATP again, and is high energy. The energy that comes from breaking down food is used to convert ADP into ATP.What is the role of ATP in living things?

produces about 36 molecules of ATP, similar to sugar. However, protein is usually not used for energy. Instead, proteins are broken down into amino acids that are used to build more proteins.Plant cells also need ATP. But plants do NOT eat food the way animals must. Instead, plants make their own food. Through the process of photosynthesis, plants use energy from sunlight to make sugars. Plant cells then break down these sugars to produce ATP, just like animal cells do. What are the three carbon-based molecules that your cells can use to make ATP?

A few types of organisms do not need sunlight and photosynthesis as a source of energy.Some organisms, such as plants, use sunlight and photosynthesis to make their own source of energy. Other organisms, like us, need sunlight and photosynthesis for our source of energy, too, because we eat plants. We also eat other animals – but those animals ate plants that got their energy from sunlight and photosynthesis. Most organisms need sunlight and photosynthesis either directly or indirectly for energy.But some organisms do not need sunlight. In the deep ocean, for example, there are areas too deep for sunlight to reach, but some organisms are able to live there. These organisms live near cracks in the ocean floor that release chemical compounds, such as sulfides. The organisms that live there use these chemicals as their energy source.Chemosynthesis is a process by which some organisms use chemical energy – instead of light energy – as an energy source to make their own food. These organisms still need ATP for energy. The way they make their ATP is very similar to how other organisms make ATP.What is the source of energy for organisms that use Chemosynthesis?Vocabulary Check

1. High-energy molecule with 3 phosphates.2. Lower-energy molecule with 2 phosphates.3. Use of chemicals as an energy source.4. The word beginning chemo- means “chemical”. Synthesis means “making something through chemical

reactions”. How does this meaning or the word parts relate to the meaning of the term chemosynthesis?

Overview of PhotosynthesisKey Concept: The overall process of photosynthesis produces sugars that store chemical energy.Photosynthetic organisms are producers – Some organisms are called producers their own sources of chemical energy. Other organisms also use the chemical energy that producers make. Plants are producers. Plants capture energy from sunlight, and store it as chemical energy in the form of sugars. These sugars are made through Photosynthesis. Remember that chloroplasts are organelles in plant cells where photosynthesis takes place.Chlorophyll is a molecule in chloroplasts that absorbs some of the energy in visible light. Plants use energy in visible light for photosynthesis. Visible light looks white, but it is made up of different wavelengths, or colors of light.Plants have two kinds of chlorophyll, called chlorophyll a and chlorophyll b. These two types of chlorophyll absorb red and blue wavelengths of light. Neither type of chlorophyll absorbs much green light. Plants are green because green wavelengths of light are reflected by the chlorophyll.What is the role of chlorophyll in photosynthesis?

Photosynthesis in plants occurs in chloroplasts

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Chloroplasts are plant cell organelles. Two main parts of chloroplasts are needed for photosynthesis:

The Grana are stacks of compartments called thylakoids. Thylakoids are shaped like coins, flat and circular. The thylakoids compartments are enclosed by membranes. These membranes contain chlorophyll.

The Stroma is fluid that is all around the grana inside the chloroplast.

There are two stages of photosynthesis, which are called the light-dependent reaction and the light-independent reactions.The Light –dependent reactions capture energy from sunlight. These reactions happen in the thylakoids and their membranes. Chlorophyll absorbs energy from sunlight. The energy moves along the thylakoids membrane and is transferred to molecules that carry energy, such as ATP. During this process, water (H2O) molecules are broken down, and oxygen (O2) molecules are released.The Light-independent reactions use the energy from the light-dependent reactions to make sugars. These reactions happen in the stroma. During this process, carbon dioxide (CO2) and energy from the light-dependent reaction are used to build sugars, usually glucose (C6H12O6).The equation for the whole process of photosynthesis is shown below. You can see that there are many arrows between the reactants – 6CO2 and 6H2O – and the products – C6H12O6 and 6O2. Although there is only one arrow, there are many steps in the process.6CO2 + 6H2O C6H12O6 + 6O2

Carbon Dioxide Water light, enzymes Glucose OxygenSimple sugars, such as glucose, are not the only carbohydrates that come from photosynthesis. Plants use simple sugars to build starch and cellulose molecules. Another important product of photosynthesis is oxygen. Vocabulary Check

1. Which two terms are things found in the chloroplasts?2. Which term is a process that is made up of two other terms?3. Which term is part of photosynthesis when light energy is captured and transferred to a molecule, such as ATP?4. Which term is the part of photosynthesis when energy is used to make sugars like glucose?5. Where in the plant cell does photosynthesis take place?6. What molecule absorbs sunlight for photosynthesis?7. Why are plants called producers?8. Complete the chart below:

Reaction Where does it happen? What is needed in the reaction?

What is produced in the reaction?

Light-dependent reactionLight –independent reaction

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Photosynthesis in DetailKey Concept: Photosynthesis requires a series of chemical reactions.The first stage of photosynthesis captures and transfers energy – During the light-dependent reactions, energy is captured from sunlight and moved along the thylakoids membrane. This process involves two groups of molecules called Photosystems. The two photosystems are called photosystem I and photosystem II. Both photosystems absorb energy from sunlight.Photosystem II and Electron Transport – In photosystem II, several things happen.

Chlorophyll and other light-absorbing molecules absorb energy from sunlight. The energy is transferred to electrons (e-) that leave the chlorophyll. These high-energy electrons enter the electron transport chain, which is made of proteins in the thylakoids membrane.

Water molecules are split apart into oxygen, hydrogen ions, and electrons. The oxygen is released – the same oxygen you breathe. The electrons from water take the place of the electrons that left the chlorophyll.

Electrons in the electron transport chain move from protein to protein. Their energy pumps hydrogen ions (H+) across the thylakoids membrane, from outside the thylakoids to the inside. The transport of H+ ions across the membrane makes the inside of the thylakoids have a higher concentration of H+ ions than on the outside of the thylakoid membrane. When there is a difference in the concentration of a substance – like there is here with H+ ions – it is called a concentration gradient.

Photosystem I and Energy-Carrying Molecules – In photosystem I, several things happen.

The Second Stage of Photosynthesis uses energy from the first stage to make sugars – The second stage of photosynthesis is the light-independent reactions. This stage also happens in the chloroplast – but in the stroma, NOT in the thylakoids. This stage is light-independent because it does NOT need light. These reactions use energy from ATP and NADPH to run the chemical reactions that make up the Calvin Cycle. The chemical reactions of the Calvin Cycle use carbon dioxide (CO2) and energy from ATP and NADPH to make sugar.

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The electrons from photosytem II move on to photosystem I. In addition, chlorophyll absorbs energy from sunlight, which results in even more high-energy electrons.

The electrons are added to NADP+, a molecule that is similar to ADP. This makes NADPH, a molecule that acts a lot like ATP.

The concentration gradient in the thylakoid provides the energy to make ATP. The H+ ions will diffuse, or flow, back out of the thylakoids through a channel in the membrane. This channel is part of an enzyme called ATP Synthase. As the H+ ions flow through ATP synthase, phosphate groups are added to ADP to make ATP. The energy form both ATP and NADPH is used later to make sugars.

Vocabulary Check:1. Which part of photosynthesis produces sugars?2. What molecule adds a phosphate group to ADP to make ATP?3. What group of molecules are involved in photosynthesis?4. What is the name for the set of proteins in the thylakoids membrane that electrons move through?5. In which stage of photosynthesis does electron transport begin? In which stage is sunlight needed?6. What is the main product of the Calvin Cycle?7. What are the reactants of photosynthesis? What are the products?

Overview of Cellular RespirationKey Concept: The overall process of cellular respiration coverts sugar into ATP using oxygen.Cellular Respiration makes ATP by breaking down sugars.You probably don’t know that you need to breathe oxygen to survive. But how does your body use that oxygen? That oxygen helps your body to release chemical energy that is stored in sugars and other carbon-based molecules. The energy is released to produce ATP. This process of using oxygen to produce ATP by breaking down carbon-based molecules is called cellular respiration. Cellular Respiration makes most of the ATP that a cell needs. Cellular respiration is an aerobic process. Aerobic means that is needs oxygen to happen.Cellular Respiration takes place in mitochondria. These organelles are sometimes called the cell’s “powerhouses” because this is where most of the cell’s ATP is made. Mitochondria do NOT make ATP directly from food. ATP is made through many chemical reactions.

Glycolysis is an anaerobic process. Anaerobic means that it does not need oxygen to happen. Glycolysis happens in the cell’s cytoplasm. The three-carbon molecules from glycolysis then enter the mitochondria. The products of glycolysis – the three-carbon molecules – enter the mitochondria and are used in cellular respiration.Why is cellular respiration called an aerobic process?

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Photosynthesis is important for many reasons. Plants produce food for themselves and for other organisms. They use the sugars from photosynthesis to build carbohydrates necessary for plant growth and development. Photosynthesis also removes carbon dioxide from Earth’s atmosphere and produces the oxygen that you breathe.What is the product of the Calvin Cycle?

Before cellular respiration can take place, food has to be broken down into smaller molecules like glucose. Then, glucose gets broken down. Remember that glucose is a six-carbon sugar. Glycolysis breaks glucose into two molecules that each have three carbons.

Cellular Respiration is like a mirror image of photosynthesis –A mirror image is like an opposite – the same things, but in reverse. Cellular respiration and photosynthesis are not really opposites, but it can be helpful to think about them in that way. Photosynthesis makes sugars and cellular respiration breaks down sugars. The chemical equations of the two processes are basically opposites.

The structure of mitochondria and chloroplasts are very similar. Remember that part of photosynthesis happens inside the stroma – the fluid in the chloroplast – and part of photosynthesis happens inside the membrane of the thylakoids. Similarly, part of cellular respiration happens in the fluid inside the mitochondria, called the Matrix. The other part of cellular respiration happens in the inner membrane of the mitochondria.After glycolysis, the three-carbon molecules enter the mitochondria and begin the process of cellular respiration.

There are two main parts of cellular respiration:Stage 1: Krebs cycle – The molecules from glycolysis enter a series of reactions called the Krebs cycle. The Krebs cycle produces a small amount of ATP and other molecules that carry energy to the next part of cellular respiration. It also makes carbon dioxide as a waste product.Stage 2: Electron Transport – Energy is moved through a chain of proteins and a large number of ATP molecules are made. Oxygen enters the process here. The oxygen is used to make water molecules, which are waste products

Cellular Respiration in DetailKey Concept: Cellular respiration is an aerobic process with two main stages.Glycolysis is needed for cellular respiration – The process of glycolysis happens in all cells, including yours. It does NOT require oxygen. If oxygen is available, the products of glycolysis are used in cellular respiration. Glycolysis alone produces a small amount of ATP. But other products of glycolysis are used later in cellular respiration to make lots of ATP. These other products are NADH, which carries energy, and pyruvate. NADH is an energy-carrying molecule similar to NADPH in photosynthesis. In cellular respiration, NADH carries energy to an electron transport chain. Pyruvate is the three-carbon molecule that is broken down in the mitochondria during cellular respiration.

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Up to 38 ATP molecules are made from the breakdown of one glucose molecule. The equation for cellular respiration is shown below. You can see that there are many arrows between the reactants – C6H12O6 and 6O2 – and the products – 6CO2 and 6H2O. These arrows are there to tell you that there are many steps in the process. For example, the equation for cellular respiration include glycolysis. Many enzymes also play important roles in the production of ATP.C6H12O6 + 6O2 6CO2 + 6H2O

Vocabulary Check:1. Which two terms in cellular respiration are opposites?2. Which term is a process that must happen in the cell’s

cytoplasm before cellular respiration?3. Which term is a process that happens within the

mitochondria as part of cellular respiration?4. Write the equation for cellular respiration.5. In which organelle does cellular respiration take place?6. What are the products and reactants of cellular respiration?7. Where is most of the ATP made during cellular respiration?

Notice that two ATP are used in the process of glycolysis. Four ATP are made. The net gain is 4 ATP made – 2 ATP used = 2 ATP molecules. In summary, for each molecule of glucose that is broken down, the products of glycolysis are:

2 ATP 2 NADH 2 pyruvate

The ATP is energy for the cell. The NADH and pyruvate are needed for cellular respiration.The Krebs Cycle is the first main part of cellular respiration.Cellular respiration makes many more ATP molecules than does glycolysis. The process begins with pyruvate entering the mitochondria. Pyruvate then gets broken down. Next, the process continues with the Krebs cycle. There are many steps in the Krebs cycle, highlighted below.

What are NADH and FADH2 use for in the cell?

The electron transport chain is the second main part of cellular respiration – The electron transport chain in cellular respiration is similar to the electron transport chain in photosynthesis. Some of the similarities include:

Both are made of proteins that are in a membrane. In cellular respiration, the electron transport chain takes place in and across the inner membrane of the mitochondrion.

Both move energy along the electron transport chain. In cellular respiration, energized electrons are provided by NADH and FADH2.

Both use that energy to pump hydrogen ions (H+) across a membrane, so that there are more H+ ions on one side of the membrane than on the other.

In both processes, the H+ ions then flow back through ATP synthase in the membrane to produce ATP.

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The main function of the Krebs cycle is to produce energy-carrying molecules such as NADH. Another energy-carrying molecule that the Krebs cycle produces is called FADH2. These molecules transfer energy to the electron transport chain, the next main part of cellular respiration.For each pyruvate, the products of the Krebs cycle are:

3 CO2 1 ATP 4 NADH 1 FADH2

Carbon Dioxide is given off as a waste product. The ATP is energy for the cell. NADH and FADH2 are energy-carrying molecules that are used in the next part of respiration.

Comparing Cellular Respiration and PhotosynthesisAgain, think about how photosynthesis and cellular respiration are almost opposites of each other. Photosynthesis stores energy from sunlight as chemical energy. Cellular respiration releases chemical energy to make ATP, the energy molecule that cells can use. Look at the table below, and think about other similarities and differences between processes.

Photosynthesis Cellular RespirationOrganelle for this process Chloroplast MitochondrionReactants CO2 and H2O Sugars and OxygenElectron transport chain Proteins within the thylakoid

membraneProteins within inner mitochondrial membrane

Cycle of chemical reactions Calvin cycle in the stroma of chloroplasts builds sugar molecules.

Krebs cycle in matrix of mitochondria breaks down carbon-based molecules

Products Sugar and Oxygen CO2 and WaterVocabulary Check

1. What products of glycolysis are used in cellular respiration?2. What products of the Krebs cycle are used in the electron transport chain?3. What are the products of the whole process of cellular respiration, including glycolysis?4. How does the concentration gradient of H+ ions help to make ATP?

FermentationKey Concept: Fermentation allows the production of a small amount of ATP without oxygen.

Fermentation allows glycolysis to continue.The amount of oxygen that you breathe in is enough for your cells during most activities. But if you are doing high levels of activity, you body cannot bring in enough oxygen for your cells. Even though you breathe faster, there is still not enough oxygen for cellular respiration.Glycolysis happens all the time, even when there is NO oxygen. If there is oxygen, the products of glycolysis are used in cellular respiration. If there is NO oxygen, your cells can keep producing small amount of ATP through the anaerobic processes of glycolysis and fermentation.

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At the end of cellular respiration, oxygen picks up electrons that have gone through the chain, forming water. In summary, the products of the whole process of cellular respiration – including glycolysis are:

Carbon dioxide (CO2), as a waste product. Water (H2O), as a waste product. Up to 38 ATP

Suppose that a molecule of glucose was just split by glycolysis in one of your muscle cells. If there is no oxygen available, lactic acid fermentation will happen. Lactic Acid fermentation happens in your muscle cells, in the cells of other vertebrates, and in some microorganisms. Lactic acid is what makes your muscles burn during hard exercise. Here is what happens in your muscle cells without oxygen:

1. Pyruvate and NADH from glycolysis enter fermentation. Pyruvate is turned into lactic acid. NADH is turned into NAD+.

2. The NAD+ molecules are recycled back to glycolysis. This allows glycolysis to continue.When your muscles are burning during exercise, it is because your cells are using fermentation. By itself, fermentation does NOT make ATP. But it allows glycolysis to keep going, and glycolysis does make some ATP. After the hard exercise is over, and oxygen is available, cellular respiration will start again.What molecule does fermentation provide to glycolysis?

Fermentation and its products are important in several ways – Fermentation also helps produce food. Cheese, bread, and yogurt are just a few of the foods that are made by fermentation. There are other types of fermentation, too, in addition to lactic acid fermentation. Alcoholic fermentation is used by many yeasts and some plants. Yeast makes bread rise by breaking down sugar through glycolysis and alcoholic fermentation. The carbon dioxide gas released causes the dough to rise.Bacteria that use fermentation are important in the digestive systems of animals. These microorganisms make their ATP without oxygen – because they are in an animal’s digestive system. Without these organisms, neither you nor other animals would be able to fully digest foods.List three foods made through fermentation processes.Vocabulary Review:

1. Fermentation alone does not make ATP. How does fermentation help a cell make ATP?2. What is lactic acid?

Unit Review:1. What cellular process makes most of a cell’s ATP?2. Do humans need photosynthesis to survive? Explain your answer.3. What are the three major steps in cellular respiration?4. Which of the descriptions below best describes cellular respiration?

a. Chemical energy is released when glucose is broken down into carbon dioxide.b. Sunlight energy is stored in carbon-based molecules like glucose.c. 6CO2 + 6H2O C6H12O6 + 6H2Od. When oxygen is available, fermentation occurs

5. Which of the descriptions below best describes photosynthesis?9

Fermentation does NOT make ATP, but it allows glycolysis to continue. Remember that the products of glycolysis are pyruvate, ATP and NADH. In the process of glycolysis, NAD+ is turned into NADH. In order for glycolysis to keep going, there need to be molecules of NAD+ that can be turned into NADH. This is what fermentation does. It provides a supply of NAD+ that allows glycolysis to continue.

a. C6H12O6 + 6O2 6CO2 + 6H2Ob. Sunlight energy is stored in carbon-based molecules like glucosec. An ATP-making process that occurs in mitochondriad. Chemical energy is released when glucose is broken down into carbon dioxide.

6. Where in the cell does cellular respiration take place?7. Where does photosynthesis take place?

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