Bch 211 - Exam 3

Pyruvate is a product of glycolysis, which is the metabolic pathway that converts glucose into pyruvate. During glycolysis, glucose is broken down into two molecules of pyruvate, along with the production of ATP and NADH. Pyruvate is then further metabolized in various ways depending on the presence or absence of oxygen, leading to the production of either lactate or acetyl CoA. Therefore, pyruvate is the correct answer as it is directly produced during glycolysis.

ATP synthase is responsible for making ATP from ADP and Pi (inorganic phosphate). This enzyme is located in the inner mitochondrial membrane and is involved in the process of oxidative phosphorylation. As protons flow through the enzyme, it causes a rotation of the ATP synthase complex, which then catalyzes the synthesis of ATP from ADP and Pi. This process is crucial for the production of ATP, the main energy currency of the cell.

Most cellular ATP is produced within the mitochondria. Mitochondria are often referred to as the "powerhouses" of the cell because they are responsible for generating most of the cell's energy in the form of ATP through a process called cellular respiration. ATP is the main energy currency of the cell and is essential for various cellular processes. The mitochondria have their own DNA and are thought to have originated from ancient symbiotic bacteria that were engulfed by ancestral eukaryotic cells.

Acetyl coenzyme A is primarily used as a fuel source in the citric acid cycle, also known as the Krebs cycle or tricarboxylic acid cycle. This cycle is a key metabolic pathway that occurs in the mitochondria of cells and is responsible for generating energy in the form of ATP. Acetyl coenzyme A is produced from the breakdown of carbohydrates, fats, and proteins and enters the citric acid cycle to be further oxidized and generate energy-rich molecules such as NADH and FADH2. These molecules then participate in the electron transport chain to produce ATP. Therefore, the chief use of acetyl coenzyme A is to provide fuel for the citric acid cycle.

In the process of electron transport, O2 serves as the final acceptor of electrons. It accepts the electrons and combines with hydrogen ions to form water. This occurs at the end of the electron transport chain, where the electrons have been passed down a series of protein complexes, generating energy in the form of ATP. O2 is essential for this process as it allows for the continuation of electron flow and the production of ATP.

Glucose is the main source of energy for the brain because it is easily transported across the blood-brain barrier and can be readily metabolized by brain cells. The brain relies heavily on glucose as its primary fuel source to support its high energy demands and maintain proper functioning. While fatty acids can also be used as an energy source by the brain, glucose is preferred due to its efficiency and accessibility. Glycogen and glycerol are not direct sources of energy for the brain, as they need to be converted into glucose first.

Glycogen is primarily stored in the muscles. It serves as a source of energy during physical activity, providing fuel for muscle contractions. This storage is essential for maintaining proper muscle function and endurance. The liver also stores glycogen, but its primary role is to regulate blood sugar levels by releasing glucose into the bloodstream when needed. While the heart and pancreas have important roles in the body, they do not store glycogen as significantly as the muscles and liver. Fat deposits, on the other hand, primarily store triglycerides, not glycogen.

The correct answer is the correct order of compounds in the conversion of glucose to pyruvic acid. The process starts with glucose being converted to fructose-6-phosphate, which is then converted to fructose-bisphosphate. Next, 1,3-phosphoglyceric acid is formed, followed by the conversion to 3-phosphoglyceric acid. Finally, phosphoenolpyruvate (PEP) is formed.

During glycolysis, which is the first step of cellular respiration, one molecule of glucose is converted into two molecules of pyruvate. This process generates a net of two molecules of ATP. Therefore, the net ATP yield per glucose during glycolysis is 2.

Complex 4 is the only complex that actually uses molecular oxygen. This is because complex 4, also known as cytochrome c oxidase, is responsible for the final step in the electron transport chain, where it transfers electrons to oxygen to form water. Complex 1, complex 2, and complex 3 are involved in electron transfer processes but do not directly use molecular oxygen.

Pyruvate, a product of glycolysis, can be converted to acetyl-CoA or lactate in humans. The conversion to acetyl-CoA occurs in the mitochondria and is a crucial step in aerobic respiration, where it enters the citric acid cycle to produce ATP. However, under anaerobic conditions or during intense exercise, pyruvate can be converted to lactate in the cytoplasm as a means of regenerating NAD+ for glycolysis to continue. Therefore, the correct answer is that pyruvate can be converted to acetyl-CoA or lactate in humans.

The phosphorylation of glucose to glucose 6-phosphate is an endergonic reaction that takes place because it is coupled to the exergonic hydrolysis of ATP. In this reaction, the transfer of a phosphate group from ATP to glucose requires energy input, making it endergonic. However, this reaction is made favorable by coupling it with the exergonic hydrolysis of ATP, which releases a large amount of energy. The energy released from ATP hydrolysis is used to drive the endergonic phosphorylation of glucose.

The synthesis of glucose from pyruvate during the Cori cycle primarily occurs in the liver. The Cori cycle is a metabolic pathway that allows for the conversion of lactate produced by the muscles during intense exercise back into glucose. This glucose is then released into the bloodstream to be used by other tissues in the body. The liver plays a crucial role in this process as it has the necessary enzymes to convert lactate into glucose through gluconeogenesis. Therefore, the liver is responsible for maintaining blood glucose levels and providing energy to the body during prolonged exercise.

Each turn of the citric acid cycle produces two molecules of CO2. The citric acid cycle, also known as the Krebs cycle, is a series of chemical reactions that occur in the mitochondria of cells. During this cycle, a molecule of acetyl-CoA is oxidized, resulting in the production of three molecules of NADH, one molecule of FADH2, one molecule of ATP, and two molecules of CO2. Therefore, the correct answer is 2.

Marathon runners primarily rely on glycogen as their main source of energy. Glycogen is a stored form of glucose in the muscles and liver, which can be broken down and converted into glucose to fuel the body during prolonged exercise. This is because glycogen is readily available and can be quickly converted into glucose, providing a constant supply of energy for the muscles. While blood glucose also plays a role in providing energy, it is glycogen that is the primary source of fuel for marathon runners. Protein and fatty acids are not typically utilized as the main source of energy during endurance exercise.

In the electron transport chain, electrons are passed along a series of protein complexes, creating a flow of energy. Oxygen serves as the ultimate electron acceptor, as it combines with electrons and protons to form water. This process is crucial for the production of ATP, the main energy currency of cells. NAD+ and FAD are electron carriers that shuttle electrons to the electron transport chain, while ADP is converted to ATP during the process. However, oxygen is the final electron acceptor, allowing the electron transport chain to continue functioning.

Succinate dehydrogenase is a key enzyme in the citric acid cycle and is involved in the electron transport chain. It is located in the inner mitochondrial membrane and is part of complex 2, also known as succinate-ubiquinone oxidoreductase. This complex plays a crucial role in transferring electrons from succinate to ubiquinone, generating FADH2 in the process. Therefore, complex 2 is the correct complex that contains succinate dehydrogenase.

Under aerobic conditions in the body, pyruvate is converted to acetyl CoA. This process occurs in the mitochondria and is known as pyruvate decarboxylation. Pyruvate is first converted to acetyl CoA by the enzyme pyruvate dehydrogenase, which removes a carbon dioxide molecule. Acetyl CoA then enters the citric acid cycle, where it is further oxidized to produce energy in the form of ATP. This conversion of pyruvate to acetyl CoA is an important step in cellular respiration, allowing the body to efficiently extract energy from glucose.

Insulin is a hormone that acts to lower the blood glucose level. It is produced by the pancreas and helps regulate glucose metabolism in the body. Insulin promotes the uptake of glucose by cells, especially in the liver, muscle, and adipose tissue, which reduces the concentration of glucose in the bloodstream. This hormone also stimulates the conversion of glucose into glycogen for storage in the liver and muscles. Overall, insulin plays a crucial role in maintaining blood glucose homeostasis by decreasing its levels.

The binding of glucose to hexokinase is an example of induced-fit binding of a substrate to the active site of an enzyme. This means that the active site of the enzyme undergoes a conformational change upon binding with the substrate. In this case, the active site of hexokinase undergoes a shape change to accommodate the glucose molecule and form a stable enzyme-substrate complex. This induced-fit binding allows for a more precise and efficient catalysis of the reaction. It differs from lock-and-key binding, where the active site has a rigid shape that perfectly matches the substrate. The binding of glucose to hexokinase has been well characterized.

The citric acid cycle is amphibolic because it is involved in both anabolism and catabolism. In anabolism, the cycle provides precursors for the synthesis of molecules such as amino acids, nucleotides, and lipids. In catabolism, the cycle breaks down acetyl-CoA, derived from carbohydrates, fats, and proteins, to produce energy in the form of ATP. This dual role allows the citric acid cycle to contribute to both the breakdown and synthesis of molecules, making it an important metabolic pathway in cells.

Riboflavin serves as part of the coenzyme FAD. Coenzymes are molecules that assist enzymes in carrying out their functions. FAD (flavin adenine dinucleotide) is a coenzyme that plays a crucial role in various metabolic reactions, particularly in energy production. Riboflavin, also known as vitamin B2, is converted into its active form, FAD, within the body. FAD is involved in processes such as the breakdown of carbohydrates, fats, and proteins to produce energy. Therefore, riboflavin is the correct answer as it serves as part of the coenzyme FAD.

Glycolysis is a metabolic pathway that occurs in the cytoplasm of cells and is the first step in the breakdown of glucose to generate energy. It is an anaerobic process, meaning it does not require oxygen to generate energy. Instead, glycolysis converts glucose into pyruvate, producing a small amount of ATP in the process. This makes glycolysis an important energy-producing pathway in cells, especially in situations where oxygen is limited or unavailable, such as during intense exercise or in anaerobic microorganisms.

Gluconeogenesis is the process by which glucose is synthesized from non-carbohydrate precursors. This is an important metabolic pathway that occurs primarily in the liver and kidneys. During times of fasting or low carbohydrate intake, the body needs to maintain blood glucose levels for energy production. Gluconeogenesis allows the body to produce glucose from molecules such as amino acids, lactate, and glycerol, which are derived from non-carbohydrate sources. This process ensures a constant supply of glucose for the brain and other glucose-dependent tissues.

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In each turn of the citric acid cycle, three molecules of NADH coenzyme are produced. This is because during the cycle, three molecules of NAD+ are reduced to NADH. NADH is an important molecule in cellular respiration as it carries high-energy electrons to the electron transport chain, where ATP is produced. Therefore, the correct answer is 3.

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Complex 4, also known as cytochrome c oxidase, is the complex that contains cytochrome oxidase. Cytochrome c oxidase is an enzyme that plays a crucial role in the electron transport chain, where it transfers electrons to oxygen, resulting in the formation of water. This complex is responsible for the final step in aerobic respiration, making it an essential component in the production of ATP.

Based on the given information, the change in Gibbs free energy (deltaG) is negative, indicating that the reaction is exergonic and releases energy. The production of ATP is coupled to the conversion of phosphoenolpyruvate to pyruvate, which is an exergonic reaction. Each molecule of ATP is produced by the transfer of a phosphate group from a high-energy compound to ADP. Since the reaction is exergonic, it can potentially produce enough energy to form two molecules of ATP. Therefore, the correct answer is 2.

During active aerobic respiration, the mitochondria produce ATP by utilizing oxygen. This process involves the electron transport chain, which pumps protons (H+) from the matrix to the intermembrane space. As a result, the concentration of protons is higher in the intermembrane space compared to the matrix, leading to a lower pH in the intermembrane space. Therefore, the pH of the matrix is greater than the pH of the intermembrane space.

Complex III of the electron transport chain oxidizes coenzyme Q, reduces cytochrome c, and pumps protons in the process.

In the electron transport chain, electrons are passed along a series of protein complexes and coenzymes. These electrons ultimately combine with molecular oxygen (O2) and hydrogen ions (H+) to form water (H2O) as the final reduced species. This process occurs in the last step of the electron transport chain, where oxygen acts as the final electron acceptor. Therefore, the correct answer is H2O.

Complex 4, also known as cytochrome c oxidase, is the final complex in the electron transport chain. It is responsible for transferring electrons from cytochrome c to oxygen, resulting in the production of water. Unlike the other complexes in the electron transport chain, complex 4 does not contain an iron-sulfur cluster. Instead, it contains copper ions that help facilitate the transfer of electrons to oxygen.

The hydrolysis of ATP is an exergonic reaction, meaning it releases energy. The given value of -7.3 kcal/mol for ΔG indicates that 7.3 kcal of energy is released per mole of ATP hydrolyzed. Since 3.00 moles of product are produced, the total energy released would be 7.3 kcal/mol * 3.00 moles = 22 kcal. Therefore, the correct answer is 22 kcal released.

During the catabolism of glucose, the majority of ATP is produced during oxidative phosphorylation. This process occurs in the mitochondria and involves the transfer of electrons from NADH and FADH2 to the electron transport chain. As the electrons pass through the chain, they create a proton gradient across the inner mitochondrial membrane. This gradient is then used by ATP synthase to generate ATP from ADP and inorganic phosphate. Therefore, oxidative phosphorylation is the main process responsible for the production of ATP during glucose catabolism.

Oxidative phosphorylation is the process in which ATP is synthesized using energy from electron transport. Complexes 1, 3, and 4 are involved in the electron transport chain, which is a series of protein complexes that transfer electrons and generate a proton gradient. This proton gradient is then used by ATP synthase (complex 5) to produce ATP. Therefore, oxidative phosphorylation is coupled to electron transport in complexes 1, 3, and 4.

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 cells. The cytoplasm is the fluid-filled region outside the nucleus but within the cell membrane. This is where most of the cellular activities take place. Glycolysis does not occur in the mitochondria, nucleus, or vacuoles, as these organelles have different functions in the cell.

The reaction shown involves the conversion of NAD+ to NADH and the addition of a phosphate group (Pi). This is consistent with the answer choice NAD+ NADH Pi, as it correctly represents the molecules involved in the reaction.

The correct answer is 1-glycogenolysis, 2-glycogenesis, 3-gluconeogenesis, and 4-glycolysis. Glycogenolysis is the breakdown of glycogen into glucose, glycogenesis is the synthesis of glycogen from glucose, gluconeogenesis is the production of glucose from non-carbohydrate sources, and glycolysis is the breakdown of glucose into pyruvate.

The conversion of -CH2-CH2 to -CH=CH- involves the removal of two hydrogen atoms. This type of reaction is typically carried out by enzymes called dehydrogenases, which require a coenzyme to accept the hydrogen atoms. FAD (Flavin adenine dinucleotide) is a common coenzyme for dehydrogenase enzymes. Therefore, an enzyme catalyzing this conversion is most likely accompanied by FAD.

FADH2 delivers hydrogen ions and electrons to coenzyme Q in the electron transport chain. Coenzyme Q acts as a carrier molecule, accepting electrons and hydrogen ions from FADH2 and transferring them to the next molecule in the chain, which is cytochrome b. This transfer of electrons and hydrogen ions is crucial for the production of ATP, the energy currency of the cell. NAD+ and flavoprotein (FP) are also involved in the electron transport chain, but they do not directly receive electrons and hydrogen ions from FADH2.

Glycogenolysis refers to the breakdown of glycogen into glucose. This process occurs when the body needs glucose for energy. Therefore, the correct representation of glycogenolysis is "glycogen -> glucose", as it shows the conversion of glycogen into glucose.

The Cori cycle is a metabolic pathway that occurs in the liver and muscle cells. During intense exercise, muscles produce lactic acid as a byproduct of glycolysis. This lactic acid is then transported from the muscles to the liver through the bloodstream. In the liver, gluconeogenesis takes place, which is the process of converting lactic acid back into glucose. The glucose is then released into the bloodstream and transported back to the muscles, where it can be used as a source of energy. Therefore, the correct answer is that glycolysis takes place in muscle and gluconeogenesis occurs in the liver.

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