Correct Option: C. Mitochondrion
Detailed Explanation:
- Understanding Cellular Respiration:
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Cellular respiration is the process by which cells convert glucose and oxygen into energy in the form of ATP (adenosine triphosphate). This process occurs in several stages: glycolysis, the Krebs cycle (also known as the citric acid cycle), and oxidative phosphorylation (electron transport chain and chemiosmosis).
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Role of Mitochondria:
- Mitochondria are often referred to as the "powerhouses" of the cell because they are the primary site of ATP production. They have a double membrane structure: an outer membrane and a highly folded inner membrane (forming structures called cristae). The folds increase the surface area for chemical reactions to occur.
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The Krebs cycle takes place in the mitochondrial matrix, where acetyl-CoA (derived from glucose) is oxidized to produce electron carriers (NADH and FADH2). These carriers then enter the electron transport chain located in the inner mitochondrial membrane.
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ATP Production:
- In the electron transport chain, electrons from NADH and FADH2 are transferred through a series of proteins, releasing energy that pumps protons (H⁺ ions) from the mitochondrial matrix into the intermembrane space. This creates a proton gradient.
- The protons then flow back into the matrix through ATP synthase, a protein that uses the energy from this flow to convert ADP (adenosine diphosphate) and inorganic phosphate into ATP. This process is known as oxidative phosphorylation.
Why Other Options Are Incorrect:
- A. Ribosome:
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Ribosomes are the cellular structures responsible for protein synthesis, not ATP production. They translate messenger RNA (mRNA) into polypeptide chains (proteins) but do not play a role in energy production.
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B. Golgi apparatus:
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The Golgi apparatus is involved in modifying, sorting, and packaging proteins and lipids for secretion or delivery to other organelles. While it plays a crucial role in the cell's overall function, it does not produce ATP.
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D. Endoplasmic reticulum (ER):
- The endoplasmic reticulum (both rough and smooth) is involved in the synthesis of proteins (rough ER) and lipids (smooth ER), as well as detoxification processes. Like the Golgi apparatus and ribosomes, it does not directly produce ATP.
Summary of Key Points:
- Mitochondria are the primary organelles responsible for ATP production through cellular respiration.
- The process involves the Krebs cycle and the electron transport chain, both of which occur in the mitochondria.
- Other organelles like ribosomes, Golgi apparatus, and endoplasmic reticulum have different functions related to protein and lipid synthesis, not ATP production.
Revision Summary:
- Mitochondria are the "powerhouses" of the cell, producing ATP through cellular respiration.
- ATP production occurs mainly in the Krebs cycle and the electron transport chain within mitochondria.
- Ribosomes, Golgi apparatus, and endoplasmic reticulum do not produce ATP; they are involved in protein and lipid synthesis.
- Understanding the specific functions of each organelle is crucial for grasping cellular processes.