Biology 1401 Chapter 7 How Cells Harvest Energy

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.

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.

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.

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.