Biology 1401 Chapter 7 How Cells Harvest Energy
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Questions and Answers
- 1.
A molecule that stores energy by linking charged phosphate groups each other is called
- A.
ATP.
- B.
NADH.
- C.
FADH.
- D.
Cyclic AMP.
- E.
Pyruvate.
Correct Answer
A. ATP.Explanation
ATP (adenosine triphosphate) is a molecule that stores energy by linking charged phosphate groups to each other. It is commonly referred to as the "energy currency" of the cell because it provides the necessary energy for cellular processes. NADH and FADH are involved in cellular respiration and carry high-energy electrons, but they do not store energy by linking charged phosphate groups. Cyclic AMP is a secondary messenger molecule involved in signal transduction, while pyruvate is a product of glycolysis. Therefore, the correct answer is ATP.Rate this question:
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- 2.
An electron carrier that is used in harvesting energy from glucose molecules in a series of gradual steps in the cytoplasm is
- A.
Pyruvate.
- B.
Cyclic AMP.
- C.
ATP.
- D.
NAD+.
- E.
NADH.
Correct Answer
D. NAD+.Explanation
NAD+ is an electron carrier that is used in harvesting energy from glucose molecules in a series of gradual steps in the cytoplasm. It acts as an oxidizing agent, accepting electrons and becoming reduced to NADH. NADH then carries the electrons to the electron transport chain in the mitochondria, where the energy is ultimately used to produce ATP.Rate this question:
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- 3.
In eukaryotes, the glycolytic reactions take place in the
- A.
Mitochondria of the cell.
- B.
Cytoplasm of the cell.
- C.
Ribosomes of the cell.
- D.
Endoplasmic reticulum of each cell.
- E.
Golgi bodies of the cell.
Correct Answer
B. Cytoplasm of the cell.Explanation
In eukaryotes, the glycolytic reactions take place in the cytoplasm of the cell. Glycolysis is the process by which glucose is converted into pyruvate, producing ATP and NADH in the cytoplasm. This process occurs in the cytoplasm because eukaryotic cells do not have glycolytic enzymes in their mitochondria. The mitochondria is involved in the later stages of cellular respiration, where pyruvate is further metabolized to produce more ATP. Therefore, the correct answer is cytoplasm of the cell.Rate this question:
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- 4.
The first stage of cellular respiration is
- A.
Decarboxylation.
- B.
Deamination.
- C.
Fermentation.
- D.
Chemiosmosis.
- E.
Glycolysis.
Correct Answer
E. Glycolysis.Explanation
Glycolysis is the first stage of cellular respiration. It is a metabolic pathway that occurs in the cytoplasm of cells and involves the breakdown of glucose into two molecules of pyruvate. This process does not require oxygen and is therefore considered anaerobic. Glycolysis is essential for generating energy in the form of ATP and is a common pathway for both aerobic and anaerobic respiration. Decarboxylation, deamination, fermentation, and chemiosmosis are not the first stages of cellular respiration and are not directly involved in the breakdown of glucose.Rate this question:
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- 5.
In the absence of oxygen, hydrogen atoms generated by glycolysis are donated to organic molecules in a process called
- A.
Fermentation.
- B.
Decarboxylation.
- C.
Chemiosmosis.
- D.
Electron transport chain reactions.
- E.
Acetyl-CoA formation.
Correct Answer
A. Fermentation.Explanation
In the absence of oxygen, glycolysis produces hydrogen atoms that need to be donated to organic molecules in order to continue the process. This donation of hydrogen atoms is known as fermentation. Fermentation allows glycolysis to continue producing ATP, even in the absence of oxygen, by regenerating the molecules needed for glycolysis to occur.Rate this question:
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- 6.
Which of the following statements abotu fermentation is false?
- A.
Fermentation takes place only in the absence of oxygen.
- B.
The recipient of hydrogen atoms is an organic molecule.
- C.
Water is not one of the by-products.
- D.
The Krebs cycle and electron transfer system do not occur.
- E.
Cells can only undergo one type of fermentation.
Correct Answer
E. Cells can only undergo one type of fermentation.Explanation
The statement "Cells can only undergo one type of fermentation" is false. Cells can undergo different types of fermentation depending on the organism and the conditions. For example, yeast cells undergo alcoholic fermentation, while muscle cells undergo lactic acid fermentation. Different types of fermentation produce different by-products and have different metabolic pathways. Therefore, cells are not limited to only one type of fermentation.Rate this question:
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- 7.
Chemiosmotic generation of ATP is driven by
- A.
Pi transfer through the plasma membrane.
- B.
The NA+/K+ pump.
- C.
A difference in H+ concentration on the two sides of the mitochondrial membrane.
- D.
Osmosis of macromolecules.
- E.
Large quantities of ADP.
Correct Answer
C. A difference in H+ concentration on the two sides of the mitochondrial membrane.Explanation
The chemiosmotic generation of ATP is driven by a difference in H+ concentration on the two sides of the mitochondrial membrane. This process involves the movement of protons across the membrane, creating an electrochemical gradient. The energy from this gradient is then used by ATP synthase to produce ATP. This mechanism is essential for cellular respiration and is a key step in the production of ATP in mitochondria.Rate this question:
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- 8.
The reaction, C(6)H(12)O(6) + 6O(2) = 6 CO(2) + 6 H(2)O, when it occurs in living cells is known as
- A.
Aerobic fermentation.
- B.
Anaerobic fermentation.
- C.
Aerobic respiration.
- D.
Glycolysis.
- E.
Oxidative phosphorylation.
Correct Answer
C. Aerobic respiration.Explanation
The given reaction involves the breakdown of glucose (C6H12O6) in the presence of oxygen (O2) to produce carbon dioxide (CO2) and water (H2O). This process is known as aerobic respiration, as it occurs in the presence of oxygen. Aerobic respiration is the main energy-producing process in living cells, where glucose is oxidized to release energy in the form of ATP.Rate this question:
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- 9.
In oxidative respiration, energy is harvested from glucose molecules in a sequence of four major pathways. Which of the following is not one of these four pathways?
- A.
Krebs cycle
- B.
Glycolysis
- C.
Electron transfer through the transport chain
- D.
Beta oxidation
- E.
Pyruvate oxidation
Correct Answer
D. Beta oxidationExplanation
Beta oxidation is not one of the four major pathways in oxidative respiration. Beta oxidation is the process by which fatty acids are broken down into acetyl-CoA, which can then enter the Krebs cycle. The four major pathways in oxidative respiration are glycolysis, Krebs cycle, electron transfer through the transport chain, and pyruvate oxidation.Rate this question:
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- 10.
A process common to all living organisms, aerobic and anaerobic, is
- A.
Glycolysis.
- B.
Fermentation.
- C.
The Krebs cycle.
- D.
Electron transport chain reactions.
- E.
Pyruvate oxidation.
Correct Answer
A. Glycolysis.Explanation
Glycolysis is a metabolic process that occurs in all living organisms, both aerobic and anaerobic. It is the initial step in cellular respiration, where glucose is broken down into pyruvate. This process is essential for generating energy in the form of ATP. While the other options mentioned (fermentation, the Krebs cycle, electron transport chain reactions, and pyruvate oxidation) are also involved in cellular respiration, they are not universal to all organisms. Therefore, glycolysis is the correct answer as it is the only process common to all living organisms.Rate this question:
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- 11.
All of the following are the end products of glycolysis except
- A.
Pyruvate.
- B.
ATP.
- C.
NADH.
- D.
NAD+.
- E.
Energy.
Correct Answer
D. NAD+.Explanation
Glycolysis is the metabolic pathway that converts glucose into pyruvate, producing ATP and NADH in the process. Pyruvate, ATP, NADH, and energy are all end products of glycolysis. However, NAD+ is not an end product but rather a coenzyme that is reduced to NADH during glycolysis. Therefore, NAD+ is not an end product of glycolysis.Rate this question:
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- 12.
The end-product of glycolysis is
- A.
ATP.
- B.
NAD+.
- C.
Alcohol.
- D.
ADP.
- E.
Pyruvate.
Correct Answer
E. Pyruvate.Explanation
The end-product of glycolysis is pyruvate. Glycolysis is the metabolic pathway that converts glucose into pyruvate, producing a small amount of ATP and NADH in the process. Pyruvate can then be further metabolized in the presence of oxygen to produce more ATP through the citric acid cycle and oxidative phosphorylation, or it can undergo fermentation in the absence of oxygen to produce lactate or alcohol. However, in the context of glycolysis, the immediate end-product is pyruvate.Rate this question:
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- 13.
The enzymes catalyzing the reactions of glycolysis are found in the
- A.
Mitochondria.
- B.
Cytoplasm.
- C.
Chloroplasts.
- D.
Nucleus.
- E.
Golgi apparatus.
Correct Answer
B. Cytoplasm.Explanation
The correct answer is cytoplasm because glycolysis is the process of breaking down glucose into pyruvate, and it takes place in the cytoplasm of the cell. The enzymes responsible for catalyzing the reactions of glycolysis are also found in the cytoplasm.Rate this question:
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- 14.
The decarboxylation step of oxidation of pyruvate takes place in the
- A.
Cytoplasm.
- B.
Golgi body.
- C.
Ribosome.
- D.
Mitochondrion.
- E.
Nucleus.
Correct Answer
D. Mitochondrion.Explanation
The decarboxylation step of oxidation of pyruvate takes place in the mitochondrion. This is because the mitochondria are the powerhouse of the cell and are responsible for cellular respiration, where pyruvate is further broken down to generate energy in the form of ATP. The mitochondria have specialized enzymes that carry out the decarboxylation reactions, converting pyruvate into acetyl-CoA, which then enters the citric acid cycle to produce more ATP. Therefore, the mitochondrion is the correct organelle where this step occurs.Rate this question:
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- 15.
The decarboxylation of pyruvate produces all of the following except
- A.
NADH.
- B.
Acetyl-CoA.
- C.
CO(2).
- D.
ATP.
Correct Answer
C. CO(2).Explanation
During the decarboxylation of pyruvate, one molecule of CO2 is released, resulting in the formation of acetyl-CoA. This process also generates one molecule of NADH, which is an electron carrier, and does not directly produce ATP. Therefore, the correct answer is CO2, as it is the only option that is not produced during the decarboxylation of pyruvate.Rate this question:
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- 16.
In the cyclic reaction sequence called the Krebs cycle, the following chemical events take place except
- A.
The acetyl group is joined with a four carbon molecule, oxaloacetate.
- B.
The resulting six carbon molecule is oxidized.
- C.
Electrons generated are used to produce NADH.
- D.
Two carbons per cycle are made into CO(2) molecules.
- E.
Pyruvate molecules are restored to the cycle.
Correct Answer
E. Pyruvate molecules are restored to the cycle.Explanation
In the Krebs cycle, pyruvate molecules are not restored to the cycle. Instead, they are converted into acetyl-CoA before entering the cycle. The other options are all correct statements about the Krebs cycle. The acetyl group is indeed joined with oxaloacetate to form a six carbon molecule, which is then oxidized. Electrons generated in the cycle are used to produce NADH, and two carbons per cycle are released as CO2 molecules.Rate this question:
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- 17.
A single glucose molecule can drive the Krebs cycle
- A.
One turn.
- B.
Two turns.
- C.
Three turns.
- D.
Four turns.
- E.
Six turns.
Correct Answer
B. Two turns.Explanation
The Krebs cycle, also known as the citric acid cycle, is a series of chemical reactions that occur in the mitochondria of cells. It is an important part of cellular respiration, where glucose is broken down to produce energy. In each turn of the Krebs cycle, one molecule of glucose is oxidized, resulting in the production of two molecules of ATP. Therefore, a single glucose molecule can drive the Krebs cycle for two turns, leading to the production of four molecules of ATP.Rate this question:
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- 18.
The coenzyme electron carriers produced in the Krebs cycle are
- A.
ATP and ADP.
- B.
Pyruvate and acetyl-CoA.
- C.
FADH(2) and NADH.
- D.
NAD and NADH.
- E.
NADH and ATP.
Correct Answer
C. FADH(2) and NADH.Explanation
The correct answer is FADH(2) and NADH. During the Krebs cycle, FADH(2) and NADH are produced as coenzyme electron carriers. These molecules play a crucial role in transferring high-energy electrons to the electron transport chain, where ATP is generated through oxidative phosphorylation. ATP and ADP are not produced directly in the Krebs cycle, but rather in the subsequent electron transport chain. Pyruvate and acetyl-CoA are not electron carriers, but rather substrates involved in the initial steps of the Krebs cycle. NAD and NADH are also involved in the Krebs cycle, but FADH(2) and NADH are the main coenzyme electron carriers produced.Rate this question:
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- 19.
The oxygen utilized in cellular respiration finally shows up as
- A.
CO(2).
- B.
ATP.
- C.
New O(2).
- D.
H(2)O.
- E.
Part of a sugar.
Correct Answer
D. H(2)O.Explanation
During cellular respiration, oxygen is used to break down glucose molecules and release energy. This process produces carbon dioxide (CO2) as a waste product, which is expelled from the body through exhalation. Additionally, water (H2O) is formed as a byproduct of cellular respiration when oxygen combines with hydrogen ions. Therefore, the oxygen utilized in cellular respiration finally shows up as water (H2O).Rate this question:
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- 20.
The enzymes of the Krebs cycle are located in the
- A.
Cytoplasm.
- B.
Inter-membrane space of mitochondria.
- C.
Vesicles of the ER.
- D.
Outer membrane of the mitochondria.
- E.
Matrix of the mitochondria.
Correct Answer
E. Matrix of the mitochondria.Explanation
The Krebs cycle, also known as the citric acid cycle, is a series of enzymatic reactions that occur in the mitochondria. The enzymes involved in this cycle are located in the matrix of the mitochondria, which is the innermost compartment of the organelle. This is where the majority of the metabolic reactions take place, including the breakdown of glucose and the production of ATP. Therefore, the correct answer is the matrix of the mitochondria.Rate this question:
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- 21.
Since membranes are relatively impermeable to ions, most of the protons re-enter the matrix of mitochondria by passing through special channels in the inner mitochondrial membrane. Because of the inward flow of protons these channels allow the synthesis of
- A.
ADP from ATP and Pi.
- B.
ATP from ADP and Pi.
- C.
Glucose from pyruvate.
- D.
Acetyl-CoA from pyruvate.
- E.
Citrate from oxaloacetate and acetyl-CoA.
Correct Answer
B. ATP from ADP and Pi.Explanation
The passage states that most of the protons re-enter the matrix of mitochondria by passing through special channels in the inner mitochondrial membrane. This inward flow of protons allows for the synthesis of ATP from ADP and Pi. Therefore, the correct answer is ATP from ADP and Pi.Rate this question:
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- 22.
Regardless of the electron or hydrogen acceptor used, one of the products of fermentation is always
- A.
ADP.
- B.
ATP.
- C.
NAD+.
- D.
Pyruvate.
- E.
Alcohol.
Correct Answer
D. Pyruvate.Explanation
During fermentation, glucose is broken down into pyruvate through a process called glycolysis. Pyruvate is a three-carbon molecule that is produced regardless of the electron or hydrogen acceptor used in fermentation. This molecule can then be further metabolized into various end products such as alcohol, lactate, or other organic compounds, depending on the type of fermentation and the organism involved. Therefore, pyruvate is always one of the products of fermentation.Rate this question:
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- 23.
Yeast cells under anaerobic conditions
- A.
Die.
- B.
Produce ethyl alcohol (ethanol).
- C.
Produce oxygen.
- D.
Switch to oxidative respiration.
- E.
Push the glycolytic pathway backward.
Correct Answer
B. Produce ethyl alcohol (ethanol).Explanation
Yeast cells under anaerobic conditions produce ethyl alcohol (ethanol). This is because in the absence of oxygen, yeast cells undergo fermentation, a process in which glucose is converted into ethanol and carbon dioxide. This allows the yeast cells to generate energy without the need for oxygen.Rate this question:
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- 24.
In muscle cells, fermentation produces not alcohol but
- A.
ATP.
- B.
NADH.
- C.
Pyruvate.
- D.
Kinetic energy.
- E.
Lactic acid.
Correct Answer
E. Lactic acid.Explanation
In muscle cells, during intense exercise or in the absence of oxygen, fermentation occurs. This process helps to generate energy in the form of ATP. However, instead of producing alcohol like in some other organisms, muscle cells produce lactic acid as a byproduct of fermentation. Lactic acid is then transported to the liver where it can be converted back into glucose or used as an energy source.Rate this question:
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- 25.
During respiration the final acceptor of the hydrogen atoms is
- A.
Oxygen.
- B.
Carbon dioxide.
- C.
Water.
- D.
Glucose.
- E.
Pyruvate.
Correct Answer
A. Oxygen.Explanation
During respiration, the final acceptor of the hydrogen atoms is oxygen. This is because oxygen acts as the terminal electron acceptor in the electron transport chain, which is the final step in cellular respiration. In this process, hydrogen atoms are passed along a series of protein complexes, releasing energy that is used to generate ATP. Ultimately, oxygen accepts these hydrogen atoms and combines with them to form water, completing the process of respiration.Rate this question:
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- 26.
Select the correct sequence concerning glucose catabolism.
- A.
Glycolysis --> Pyruvate --> Acetyl CoA --> Electron Transport Chain --> Krebs Cycle
- B.
Glycolysis --> Pyruvate --> Acetyl CoA --> Krebs Cycle --> Electron Transport Chain
- C.
Glycolysis --> Acetyl CoA --> Pyruvate --> Electron Transport Chain --> Krebs Cycle
- D.
Glycolysis --> Acetyl CoA --> Pyruvate --> Krebs Cycle --> Electron Transport Chain
Correct Answer
B. Glycolysis --> Pyruvate --> Acetyl CoA --> Krebs Cycle --> Electron Transport ChainExplanation
The correct sequence for glucose catabolism starts with glycolysis, which breaks down glucose into pyruvate. Pyruvate then enters the mitochondria and is converted into acetyl CoA. Acetyl CoA then enters the Krebs Cycle, also known as the citric acid cycle, where it undergoes further oxidation. The final step is the electron transport chain, where electrons from the Krebs Cycle are used to generate ATP through oxidative phosphorylation.Rate this question:
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