Question
3. Describe the overall process of aerobic respiration. Use the following key terms in your explanation: mitochondria, pyruvic acid, acetyl-CoA, citric acid cycle, electron transport chain, carbon dioxide, hydrogen, NAD+, NADH, ATP, oxygen. Specify where in the process is oxygen, from the air we breathe, utilized.
Answers
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GPT-4o mini
Aerobic respiration is a crucial metabolic process that takes place in cells to produce energy in the form of ATP (adenosine triphosphate), using oxygen. Here’s an overview of the entire process, including the key terms mentioned:
1. **Glycolysis**: This process occurs in the cytoplasm, where one molecule of glucose (a six-carbon sugar) is broken down into two molecules of pyruvic acid (a three-carbon compound). During glycolysis, a small amount of ATP is generated, and NAD+ is reduced to NADH as it picks up electrons and hydrogen ions.
2. **Pyruvic Acid to Acetyl-CoA**: Once glycolysis is complete, the pyruvic acid molecules enter the mitochondria. Here, each pyruvic acid undergoes a transformation into acetyl-CoA (a two-carbon molecule) through a process called oxidative decarboxylation. During this step, carbon dioxide is released, and NAD+ is reduced to NADH again as electrons and hydrogen are transferred from pyruvic acid.
3. **Citric Acid Cycle (Krebs Cycle)**: Acetyl-CoA then enters the citric acid cycle within the mitochondria. In each turn of this cycle, acetyl-CoA combines with a four-carbon molecule to form citric acid (a six-carbon molecule). The citric acid undergoes a series of transformations, resulting in the release of two molecules of carbon dioxide for each acetyl-CoA that enters the cycle. Additionally, more NADH is produced along with FADH2 (another electron carrier) and a small amount of ATP.
4. **Electron Transport Chain**: The NADH and FADH2 generated in the previous steps carry high-energy electrons to the electron transport chain, located in the inner mitochondrial membrane. As the electrons pass through a series of protein complexes in the chain, they release energy. This energy is used to pump hydrogen ions (H+) from the mitochondrial matrix into the intermembrane space, creating a concentration gradient.
5. **Chemiosmosis and ATP Synthesis**: The hydrogen ions flow back into the mitochondrial matrix through ATP synthase, a protein that synthesizes ATP from ADP and inorganic phosphate, using the energy from the flow of hydrogen ions. This process is known as chemiosmosis.
6. **Utilization of Oxygen**: Oxygen, which we breathe in from the air, is the final electron acceptor in the electron transport chain. At the end of the chain, oxygen combines with the low-energy electrons and hydrogen ions to form water (H2O). This step is critical because it allows the electron transport chain to continue functioning; without oxygen, the entire system would back up, and ATP production would cease.
Overall, the aerobic respiration process efficiently converts the energy stored in glucose into ATP while producing carbon dioxide and water as byproducts. The overall equation for aerobic respiration can be summarized as:
\[ \text{Glucose} + \text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O} + \text{ATP} \]
1. **Glycolysis**: This process occurs in the cytoplasm, where one molecule of glucose (a six-carbon sugar) is broken down into two molecules of pyruvic acid (a three-carbon compound). During glycolysis, a small amount of ATP is generated, and NAD+ is reduced to NADH as it picks up electrons and hydrogen ions.
2. **Pyruvic Acid to Acetyl-CoA**: Once glycolysis is complete, the pyruvic acid molecules enter the mitochondria. Here, each pyruvic acid undergoes a transformation into acetyl-CoA (a two-carbon molecule) through a process called oxidative decarboxylation. During this step, carbon dioxide is released, and NAD+ is reduced to NADH again as electrons and hydrogen are transferred from pyruvic acid.
3. **Citric Acid Cycle (Krebs Cycle)**: Acetyl-CoA then enters the citric acid cycle within the mitochondria. In each turn of this cycle, acetyl-CoA combines with a four-carbon molecule to form citric acid (a six-carbon molecule). The citric acid undergoes a series of transformations, resulting in the release of two molecules of carbon dioxide for each acetyl-CoA that enters the cycle. Additionally, more NADH is produced along with FADH2 (another electron carrier) and a small amount of ATP.
4. **Electron Transport Chain**: The NADH and FADH2 generated in the previous steps carry high-energy electrons to the electron transport chain, located in the inner mitochondrial membrane. As the electrons pass through a series of protein complexes in the chain, they release energy. This energy is used to pump hydrogen ions (H+) from the mitochondrial matrix into the intermembrane space, creating a concentration gradient.
5. **Chemiosmosis and ATP Synthesis**: The hydrogen ions flow back into the mitochondrial matrix through ATP synthase, a protein that synthesizes ATP from ADP and inorganic phosphate, using the energy from the flow of hydrogen ions. This process is known as chemiosmosis.
6. **Utilization of Oxygen**: Oxygen, which we breathe in from the air, is the final electron acceptor in the electron transport chain. At the end of the chain, oxygen combines with the low-energy electrons and hydrogen ions to form water (H2O). This step is critical because it allows the electron transport chain to continue functioning; without oxygen, the entire system would back up, and ATP production would cease.
Overall, the aerobic respiration process efficiently converts the energy stored in glucose into ATP while producing carbon dioxide and water as byproducts. The overall equation for aerobic respiration can be summarized as:
\[ \text{Glucose} + \text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O} + \text{ATP} \]