Unit 5 Test Rebate
Questions and Answers
- 1.
The three-carbon molecule formed by glycolysis is ___.
- A.
Pyruvate
- B.
NADH
- C.
Citric acid
- D.
Carbon dioxide
Correct Answer
A. PyruvateExplanation
Glycolysis is the metabolic pathway that breaks down glucose into pyruvate. It is the first step in cellular respiration and occurs in the cytoplasm of cells. During glycolysis, glucose is converted into two molecules of pyruvate, along with the production of ATP and NADH. Therefore, the correct answer is pyruvate.Rate this question:
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- 2.
In the diagram to the right, what is structure A?
- A.
Folded inner membrane
- B.
Mitochondrial matrix
- C.
Stroma
- D.
Thylakoid membrane
Correct Answer
A. Folded inner membrane -
- 3.
In the diagram to the right, what is structure B?
- A.
Folded inner membrane
- B.
Mitochondrial matrix
- C.
Stroma
- D.
Thylakoid membrane
Correct Answer
B. Mitochondrial matrixExplanation
Structure B in the diagram to the right is the mitochondrial matrix. The mitochondrial matrix is the fluid-filled space inside the inner membrane of the mitochondria. It contains enzymes that are involved in various metabolic reactions, including the citric acid cycle and fatty acid oxidation. The matrix also contains mitochondrial DNA and ribosomes, which are necessary for the production of proteins within the mitochondria.Rate this question:
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- 4.
Which of the following stages occurs in the mitochondrial matrix?
- A.
Krebs cycle
- B.
The Calvin cycle
- C.
Glycolysis
- D.
Oxidative phosphorylation
Correct Answer
A. Krebs cycleExplanation
The Krebs cycle, also known as the citric acid cycle, occurs in the mitochondrial matrix. This stage of cellular respiration takes place in the innermost compartment of the mitochondria, where it completes the oxidation of glucose and generates energy-rich molecules such as NADH and FADH2. The Krebs cycle involves a series of chemical reactions that produce ATP and carbon dioxide as byproducts, ultimately providing the necessary energy for the cell's functions.Rate this question:
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- 5.
Which organelle converts molecules from the food you eat into usable energy?
- A.
Golgi apparatus
- B.
Chloroplast
- C.
Mitochondrion
- D.
Lysosome
Correct Answer
C. MitochondrionExplanation
The mitochondrion is the organelle responsible for converting molecules from the food we eat into usable energy. It is often referred to as the "powerhouse" of the cell because it produces adenosine triphosphate (ATP), which is the main source of energy for cellular activities. The mitochondrion carries out cellular respiration, a process that breaks down glucose and other molecules to release energy. This energy is then stored in ATP molecules and can be used by the cell to perform various functions.Rate this question:
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- 6.
In the electron transport chain, hydrogen ions are pumped across the mitochondrial membrane. What provides the energy to operate the protein pumps?
- A.
Electrons
- B.
ATP
- C.
Oxygen
- D.
Carbon dioxide
Correct Answer
A. ElectronsExplanation
Electrons provide the energy to operate the protein pumps in the electron transport chain. As electrons move through the chain, they transfer energy to protein complexes, which use this energy to pump hydrogen ions across the mitochondrial membrane. This creates an electrochemical gradient, which is later used to generate ATP, the energy currency of the cell. Oxygen is the final electron acceptor in the chain, but it does not directly provide the energy for the protein pumps. Carbon dioxide is not involved in this process.Rate this question:
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- 7.
What enzyme is located at the end of the electron transport chain?
- A.
ATP synthase
- B.
Dehydrogenase
- C.
NADPH
- D.
Glycolase
Correct Answer
A. ATP synthaseExplanation
ATP synthase is located at the end of the electron transport chain. This enzyme is responsible for the synthesis of ATP, the main energy currency of the cell. It uses the energy from the flow of protons down their electrochemical gradient to convert ADP and inorganic phosphate into ATP. This process is known as oxidative phosphorylation and occurs in the inner mitochondrial membrane in eukaryotes or the plasma membrane in prokaryotes. ATP synthase plays a crucial role in generating ATP, which is essential for various cellular processes.Rate this question:
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- 8.
The electron transport chain produces water and ATP. Where do the hydrogen atoms come from that are used to form water?
- A.
Carbon dioxide
- B.
NADH and FADH2
- C.
The Calvin Cycle
- D.
Oxygen
Correct Answer
B. NADH and FADH2Explanation
NADH and FADH2 are molecules that carry high-energy electrons produced during cellular respiration. These electrons are transferred to the electron transport chain, where they are passed along a series of protein complexes. As the electrons move through the chain, they release energy that is used to pump hydrogen ions across the inner mitochondrial membrane. These hydrogen ions are then used to form water when they combine with oxygen at the end of the electron transport chain. Therefore, the hydrogen atoms used to form water come from NADH and FADH2.Rate this question:
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- 9.
Two products of the Krebs cycle are
- A.
Water and carbon dioxide.
- B.
ATP and carbon dioxide.
- C.
ATP and oxygen.
- D.
ADP and water.
Correct Answer
B. ATP and carbon dioxide.Explanation
In the Krebs cycle, also known as the citric acid cycle, ATP and carbon dioxide are produced. ATP is a high-energy molecule that serves as the main source of energy for cellular processes. Carbon dioxide is a waste product that is released as a result of the breakdown of glucose during cellular respiration. Therefore, the correct answer is ATP and carbon dioxide.Rate this question:
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- 10.
The part of cellular respiration in which glucose is broken down is called
- A.
Photosynthesis.
- B.
Aerobic respiration.
- C.
Electron transport.
- D.
Glycolysis.
Correct Answer
D. Glycolysis.Explanation
Glycolysis is the correct answer because it is the initial step of cellular respiration where glucose is broken down into pyruvate. This process occurs in the cytoplasm and does not require oxygen. Photosynthesis is the process by which plants convert sunlight into energy, while aerobic respiration and electron transport are later stages of cellular respiration that require oxygen and occur in the mitochondria.Rate this question:
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- 11.
What is the main function of the Krebs cycle?
- A.
Breaking down pyruvate molecules to form molecules of NADH and oxygen
- B.
Forming citric acid to make NADH, water, and carbon dioxide
- C.
Producing molecules that carry high-energy electrons to the electron transport chain
- D.
Bonding coenzyme A to pyruvate
Correct Answer
C. Producing molecules that carry high-energy electrons to the electron transport chainExplanation
The main function of the Krebs cycle is to produce molecules that carry high-energy electrons to the electron transport chain. The Krebs cycle, also known as the citric acid cycle, is a series of chemical reactions that occur in the mitochondria of cells. During this cycle, acetyl-CoA is oxidized, resulting in the production of energy-rich molecules such as NADH and FADH2. These molecules then carry high-energy electrons to the electron transport chain, where they are used to generate ATP, the cell's main source of energy.Rate this question:
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- 12.
In the electron transport chain, energy from the Krebs cycle is used to pump hydrogen ions
- A.
Across the inner mitochondrial membrane.
- B.
Through the ATP synthase enzyme in the mitochondrial matrix.
- C.
Along a concentration gradient in the thylakoid.
- D.
Along the thylakoid membrane.
Correct Answer
A. Across the inner mitochondrial membrane.Explanation
In the electron transport chain, energy from the Krebs cycle is used to pump hydrogen ions across the inner mitochondrial membrane. This is because the electron transport chain is located in the inner mitochondrial membrane, and as electrons pass through the chain, they create a proton gradient across the membrane. This gradient is used to drive the synthesis of ATP, the cell's main energy source. Therefore, the correct answer is that the hydrogen ions are pumped across the inner mitochondrial membrane.Rate this question:
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- 13.
Which process breaks down sugars to make ATP when oxygen is present?
- A.
Anaerobic respiration
- B.
Cellular respiration
- C.
Glycolysis
- D.
Photosynthesis
Correct Answer
B. Cellular respirationExplanation
Cellular respiration is the correct answer because it is the process by which cells break down sugars, such as glucose, to produce ATP (adenosine triphosphate) in the presence of oxygen. This process occurs in the mitochondria of cells and involves several stages, including glycolysis, the Krebs cycle, and the electron transport chain. Cellular respiration is an aerobic process, meaning it requires oxygen to efficiently produce ATP. Anaerobic respiration, on the other hand, occurs in the absence of oxygen, while glycolysis is the initial step of cellular respiration. Photosynthesis, on the other hand, is the process by which plants convert sunlight into energy and produce glucose, which is then used in cellular respiration.Rate this question:
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- 14.
Where does glycolysis take place?
- A.
Cytoplasm
- B.
Mitochondrial matrix
- C.
Mitochondrial inner membrane
- D.
Chloroplast
Correct Answer
A. CytoplasmExplanation
Glycolysis is the process of breaking down glucose into pyruvate molecules. It is the first step in cellular respiration and occurs in the cytoplasm of the cell. This process does not require oxygen and is therefore considered an anaerobic process. The cytoplasm is the fluid-filled region of the cell where many metabolic reactions take place, including glycolysis.Rate this question:
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- 15.
Which of the following are end products of glycolysis?
- A.
Two three-carbon molecules, ATP, and NAD+
- B.
Carbon dioxide, water, and ATP
- C.
NAD+, oxygen, and two ATP molecules
- D.
Pyruvate, NADH, and ATP
Correct Answer
D. Pyruvate, NADH, and ATPExplanation
The end products of glycolysis are pyruvate, NADH, and ATP. Glycolysis is the first step in cellular respiration, where glucose is broken down into two molecules of pyruvate. During this process, NAD+ is reduced to NADH, and ATP is produced through substrate-level phosphorylation. Therefore, the correct answer is pyruvate, NADH, and ATP.Rate this question:
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- 16.
In the diagram to the right, the structure labeled E is the ___.
- A.
Stroma
- B.
Chlorophyll
- C.
Granum
- D.
Thylakoid membranes
Correct Answer
D. Thylakoid membranesExplanation
In the given diagram, the structure labeled E represents the thylakoid membranes. Thylakoid membranes are found in chloroplasts and are responsible for the light-dependent reactions of photosynthesis. They contain pigments such as chlorophyll, which capture sunlight and convert it into chemical energy. The thylakoid membranes are stacked together to form structures called grana, which are not labeled in the diagram. Therefore, the correct answer is thylakoid membranes.Rate this question:
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- 17.
In the diagram to the right, the structure labeled C is the ___.
- A.
Stroma
- B.
Chlorophyll
- C.
Granum
- D.
Thylakoid membranes
Correct Answer
A. StromaExplanation
The diagram to the right is showing a cellular structure labeled as C. Based on the options provided, the correct answer is stroma. The stroma is the fluid-filled space inside the chloroplasts, where various metabolic reactions take place. It surrounds the thylakoid membranes, which are responsible for carrying out the light-dependent reactions of photosynthesis. The stroma also contains enzymes necessary for the light-independent reactions (Calvin cycle) of photosynthesis. Therefore, stroma is the most appropriate choice for the structure labeled C in the diagram.Rate this question:
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- 18.
In the diagram to the right, the structure labeled D is the ___.
- A.
Stroma
- B.
Chlorophyll
- C.
Granum
- D.
Thylakoid membranes
Correct Answer
C. GranumExplanation
In the diagram, the structure labeled D appears to be a stack of flattened sacs. This is characteristic of a granum, which is a structure found in chloroplasts. Granum is responsible for housing the thylakoid membranes, where the chlorophyll molecules are located. Therefore, the correct answer is granum.Rate this question:
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- 19.
The purpose of the light reactions is to___.
- A.
Make ATP and NADPH for use in the Calvin cycle
- B.
To make oxygen
- C.
To split water
- D.
To make glucose
Correct Answer
A. Make ATP and NADPH for use in the Calvin cycleExplanation
The purpose of the light reactions is to produce ATP and NADPH, which are both essential molecules for the Calvin cycle. ATP provides the energy necessary for the Calvin cycle to convert carbon dioxide into glucose, while NADPH acts as a reducing agent to transfer high-energy electrons to the Calvin cycle. Therefore, the light reactions play a crucial role in providing the energy and reducing power needed for the synthesis of glucose.Rate this question:
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- 20.
What are the products of photosynthesis?
- A.
Carbon dioxide and water
- B.
Glucose and oxygen
- C.
Water and glucose
- D.
Carbon dioxide and oxygen
Correct Answer
B. Glucose and oxygenExplanation
Photosynthesis is the process by which plants convert sunlight, carbon dioxide, and water into glucose and oxygen. Glucose is a type of sugar that serves as a source of energy for the plant, while oxygen is released as a byproduct. Therefore, the correct answer is "glucose and oxygen."Rate this question:
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- 21.
Which of the following statements best describes the process of photosynthesis?
- A.
Plants use oxygen to make simple sugars.
- B.
Chlorophyll builds sugars in the thylakoid membrane.
- C.
Light breaks down water molecules and releases carbon dioxide.
- D.
Chloroplasts absorb sunlight and store chemical energy.
Correct Answer
D. Chloroplasts absorb sunlight and store chemical energy.Explanation
Chloroplasts are organelles found in plant cells that contain the pigment chlorophyll. Chlorophyll absorbs sunlight and converts it into chemical energy through a process called photosynthesis. During photosynthesis, carbon dioxide and water are converted into glucose (simple sugars) and oxygen. The glucose is then stored in the plant cells for energy. Therefore, the statement "Chloroplasts absorb sunlight and store chemical energy" best describes the process of photosynthesis.Rate this question:
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- 22.
The main light-absorbing molecules found in plant leaves are called
- A.
Chloroplasts
- B.
Thylakoids
- C.
Chlorophyll
- D.
Grana
Correct Answer
C. ChlorophyllExplanation
Chlorophyll is the correct answer because it is the main light-absorbing molecule found in plant leaves. It is responsible for capturing light energy during photosynthesis and converting it into chemical energy. Chlorophyll is located within the chloroplasts, specifically in the thylakoid membranes. The grana are stacks of thylakoids where chlorophyll is concentrated. Therefore, while chloroplasts, thylakoids, and grana are all related to chlorophyll and photosynthesis, chlorophyll itself is the specific molecule that absorbs light.Rate this question:
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- 23.
Which phrase best describes the electron transport chain in photosynthesis?
- A.
A chain of photosynthetic proteins located in the stroma
- B.
A collection of enzymes used to make ADP
- C.
A series of proteins located in the thylakoid membrane
- D.
A group of enzymes that carries energy to the Calvin cycle
Correct Answer
C. A series of proteins located in the thylakoid membraneExplanation
The electron transport chain in photosynthesis is a series of proteins located in the thylakoid membrane. This chain is responsible for transferring electrons from photosystem II to photosystem I, generating ATP and NADPH in the process. The thylakoid membrane is where the photosystems and electron carriers are located, allowing for the efficient transfer of electrons and the production of energy-rich molecules.Rate this question:
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- 24.
Which of the following takes place in the light-dependent reactions of photosynthesis?
- A.
Sugars are made.
- B.
Energy is captured.
- C.
Chlorophyll is pumped.
- D.
Carbon dioxide is formed.
Correct Answer
B. Energy is captured.Explanation
In the light-dependent reactions of photosynthesis, energy from sunlight is captured by chlorophyll molecules in the chloroplasts of plant cells. This energy is used to convert water molecules into oxygen and high-energy molecules, such as ATP and NADPH. These high-energy molecules are then used in the light-independent reactions to produce sugars, such as glucose, through a process called carbon fixation. Therefore, the correct answer is "Energy is captured."Rate this question:
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- 25.
Which process breaks down sugars to make ATP when oxygen is NOT present?
- A.
Anaerobic respiration (a.k.a. Fermentation)
- B.
Cellular respiration
- C.
Glycolysis
- D.
Photosynthesis
Correct Answer
A. Anaerobic respiration (a.k.a. Fermentation)Explanation
Anaerobic respiration, also known as fermentation, is the process that breaks down sugars to produce ATP when oxygen is not available. This process occurs in the absence of oxygen and is an alternative to cellular respiration. During anaerobic respiration, glucose is partially broken down through glycolysis, producing a small amount of ATP and converting it into either lactic acid or ethanol, depending on the organism. This process allows cells to continue producing ATP for energy even in the absence of oxygen.Rate this question:
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- 26.
Which of the following statements is true for all cells?
- A.
They use solar energy.
- B.
They use photosynthesis.
- C.
They use chemical energy.
- D.
They use chemosynthesis.
Correct Answer
C. They use chemical energy.Explanation
All cells use chemical energy because chemical reactions within the cells convert molecules into usable energy in the form of ATP. This energy is used for various cellular processes such as metabolism, movement, and synthesis of molecules. While some cells, like plant cells, can also use solar energy through photosynthesis, not all cells have the ability to do so. Similarly, chemosynthesis is a process used by certain bacteria to obtain energy, but it is not true for all cells. Therefore, the statement "They use chemical energy" is the only one that applies universally to all cells.Rate this question:
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- 27.
Where does the chemical energy to produce ATP come from?
- A.
The conversion of ATP to ADP.
- B.
The use of chemicals from the environment to build sugars.
- C.
The addition of a phosphate group to ATP.
- D.
The breakdown of carbon-based molecules into smaller molecules.
Correct Answer
D. The breakdown of carbon-based molecules into smaller molecules.Explanation
The chemical energy to produce ATP comes from the breakdown of carbon-based molecules into smaller molecules. During cellular respiration, these molecules such as glucose are broken down through a series of metabolic reactions, releasing energy that is used to synthesize ATP. This process occurs in the mitochondria of cells and is essential for providing energy for various cellular activities. The other options mentioned, including the conversion of ATP to ADP, the use of chemicals from the environment to build sugars, and the addition of a phosphate group to ATP, are not directly involved in generating chemical energy for ATP production.Rate this question:
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- 28.
Energy is released from ATP molecules for cellular processes when it ...
- A.
Has a phosphate group removed.
- B.
Stores an extra phosphate group.
- C.
Converts a phosphate group to ADP.
- D.
Produces a sugar molecule.
Correct Answer
A. Has a phosphate group removed.Explanation
When ATP molecules have a phosphate group removed, energy is released. This is because ATP (adenosine triphosphate) is a high-energy molecule that stores energy in the phosphate bonds. When a phosphate group is removed, it becomes ADP (adenosine diphosphate) and releases energy that can be used for cellular processes.Rate this question:
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- 29.
A molecule of ATP is made of ...
- A.
Adenosine, ribose, and three phosphate groups.
- B.
Adenine, ribose, and two phosphate groups.
- C.
Adenosine, deoxyribose, and three phosphate groups.
- D.
Adenosine, ribose, and two phosphate groups.
Correct Answer
A. Adenosine, ribose, and three phosphate groups.Explanation
A molecule of ATP is made of adenosine, ribose, and three phosphate groups. Adenosine is a nucleoside consisting of adenine and ribose. Ribose is a five-carbon sugar molecule that forms the backbone of RNA. ATP, or adenosine triphosphate, is a high-energy molecule used by cells to store and transfer energy. It consists of adenosine, which is adenosine combined with ribose, and three phosphate groups. The phosphate groups are responsible for storing and releasing energy when the bonds between them are broken.Rate this question:
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- 30.
What is the part labeled C in this diagram?
- A.
Adenosine
- B.
Ribose
- C.
Phosphate
- D.
ATP
Correct Answer
C. PhosphateExplanation
In the given diagram, the part labeled C is phosphate. Phosphate is an essential component of ATP (adenosine triphosphate), which is the primary energy source in cells. It consists of a ribose sugar molecule, an adenine base, and three phosphate groups. The phosphate group plays a crucial role in storing and releasing energy during cellular processes. Therefore, labeling C as phosphate is accurate based on the information provided.Rate this question:
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- 31.
What molecule is pictured in this diagram?
- A.
Adenosine
- B.
Ribose
- C.
Phosphate
- D.
ATP
Correct Answer
D. ATPExplanation
The molecule pictured in the diagram is ATP (adenosine triphosphate). ATP is a molecule that stores and releases energy for cellular processes. It consists of an adenosine molecule bonded to three phosphate groups. The high-energy bonds between the phosphate groups can be broken to release energy, which is used by cells for various activities such as muscle contraction, active transport, and synthesis of molecules.Rate this question:
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- 32.
Which phrase about fermentation is correct?
- A.
Takes place without oxygen
- B.
Uses the electron transport chain
- C.
Only occurs in bacteria
- D.
Is an aerobic process
Correct Answer
A. Takes place without oxygenExplanation
Fermentation is a metabolic process that occurs in the absence of oxygen. It is a way for cells to produce energy when oxygen is not available. During fermentation, glucose is broken down into simpler compounds, such as lactic acid or ethanol, and this process does not require the use of the electron transport chain. While fermentation can occur in bacteria, it is not limited to them and can also occur in other organisms, including yeast and muscle cells. Therefore, the correct phrase about fermentation is that it takes place without oxygen.Rate this question:
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- 33.
Which endproduct of fermentation causes the burning feeling in muscles that are working hard?
- A.
Alcohol
- B.
Lactic acid
- C.
Carbon dioxide
- D.
Pyruvic acid
Correct Answer
B. Lactic acidExplanation
During intense exercise, the body may not be able to supply enough oxygen to the muscles for energy production. As a result, the muscles switch to anaerobic respiration, which produces lactic acid as a byproduct. The accumulation of lactic acid in the muscles leads to a burning sensation, commonly known as muscle fatigue or soreness. Therefore, lactic acid is the end product of fermentation that causes the burning feeling in working muscles.Rate this question:
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- 34.
Which end product of alcoholic fermentation is important in the baking industry?
- A.
Lactic acid
- B.
Carbon dioxide
- C.
ATP molecules
- D.
Alcohol
Correct Answer
B. Carbon dioxideExplanation
Carbon dioxide is the correct answer because it is the end product of alcoholic fermentation. In the baking industry, carbon dioxide is important because it helps dough rise. During fermentation, yeast converts sugars into alcohol and carbon dioxide. The carbon dioxide gas gets trapped in the dough, causing it to expand and create air pockets. This gives the bread a light and fluffy texture. Without carbon dioxide, bread would be dense and flat. Therefore, carbon dioxide plays a crucial role in the baking industry.Rate this question:
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