Which of the following best describes the primary function of the endoplasmic reticulum in a eukaryotic cell?
Solution
Correct Answer: Option A
The endoplasmic reticulum (ER) is a crucial organelle in eukaryotic cells primarily involved in the synthesis of proteins and lipids. There are two types of ER: rough ER, which is studded with ribosomes and specializes in protein synthesis, and smooth ER, which lacks ribosomes and is primarily responsible for lipid synthesis as well as detoxification processes.
Option 1 is correct because the rough ER facilitates the production of proteins that are either secreted from the cell, incorporated into the plasma membrane, or sent to lysosomes. Meanwhile, the smooth ER synthesizes lipids, including phospholipids and steroids, essential for cell membrane integrity and function.
In contrast:
- Option 2 (ATP production through oxidative phosphorylation) takes place in the mitochondria, not the ER.
- Option 3 (storage and release of calcium ions) is mainly a function of the smooth ER but this role is secondary to its primary role in lipid synthesis.
- Option 4 (degradation of misfolded proteins and cellular debris) is primarily a function of the proteasome and lysosomes, though the ER does participate in quality control via the ER-associated degradation (ERAD) pathway.
Thus, the primary function of the endoplasmic reticulum is the synthesis of proteins and lipids, making Option 1 the best choice.
Reference: Alberts et al., Molecular Biology of the Cell, 6th Edition, Chapter 15, pages 600-620
Option 1 is correct because the rough ER facilitates the production of proteins that are either secreted from the cell, incorporated into the plasma membrane, or sent to lysosomes. Meanwhile, the smooth ER synthesizes lipids, including phospholipids and steroids, essential for cell membrane integrity and function.
In contrast:
- Option 2 (ATP production through oxidative phosphorylation) takes place in the mitochondria, not the ER.
- Option 3 (storage and release of calcium ions) is mainly a function of the smooth ER but this role is secondary to its primary role in lipid synthesis.
- Option 4 (degradation of misfolded proteins and cellular debris) is primarily a function of the proteasome and lysosomes, though the ER does participate in quality control via the ER-associated degradation (ERAD) pathway.
Thus, the primary function of the endoplasmic reticulum is the synthesis of proteins and lipids, making Option 1 the best choice.
Reference: Alberts et al., Molecular Biology of the Cell, 6th Edition, Chapter 15, pages 600-620
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