Question

Proteins of the extracellular matrix, soluble lysosomal enzymes, peripheral proteins of the inner surface of the plasma membrane, nuclear DNA binding transcription factor:

"Only the nuclear DNA binding transcription factor is made by the cytosolic ribosomes, all others are synthesized by the ribosomes of the rough ER."
True
False?

Answer 1

Proteins of the extracellular matrix, soluble lysosomal enzymes, peripheral proteins of the inner surface of the plasma membrane, and nuclear DNA binding transcription factors can all be synthesized by the ribosomes of the rough endoplasmic reticulum (ER), not just the nuclear DNA binding transcription factor.

False

Step-by-step explanation:

The statement is incorrect, as all the mentioned proteins—proteins of the extracellular matrix, soluble lysosomal enzymes, peripheral proteins of the inner surface of the plasma membrane, and nuclear DNA binding transcription factors—can be synthesized by ribosomes associated with the rough endoplasmic reticulum (ER). The rough ER is involved in the synthesis of proteins that are either secreted from the cell, incorporated into the cell membrane, or transported to an organelle like lysosomes.

The ribosomes associated with the rough ER facilitate the synthesis of proteins that are either translocated into the endoplasmic reticulum for processing or released into the cytoplasm. Proteins destined for the extracellular matrix, lysosomes, or the inner surface of the plasma membrane often undergo post-translational modifications in the rough ER before reaching their final destinations. This includes the addition of signal sequences and modifications like glycosylation.

While it's true that some proteins, like the nuclear DNA binding transcription factors, may be synthesized by free cytosolic ribosomes, it's important to recognize that the rough ER plays a significant role in the synthesis and processing of a diverse range of proteins that are critical for various cellular functions.

Answer 2

The nuclear DNA binding transcription factor is synthesized by cytosolic ribosomes, while the other mentioned proteins are produced by the ribosomes of the rough endoplasmic reticulum. Hense, the statement is "False".

Step-by-step explanation:

Proteins destined for various cellular locations are synthesized by different ribosomes within the cell. The nuclear DNA binding transcription factor, involved in regulating gene expression, is produced by cytosolic ribosomes. In contrast, proteins of the extracellular matrix, soluble lysosomal enzymes, and peripheral proteins of the inner surface of the plasma membrane are synthesized by ribosomes associated with the rough endoplasmic reticulum (ER).

The rough ER plays a crucial role in the synthesis and modification of proteins that are either secreted from the cell, incorporated into the cell membrane, or targeted to lysosomes. The ribosomes associated with the rough ER facilitate the synthesis of these proteins, ensuring proper folding and post-translational modifications.

On the other hand, cytosolic ribosomes synthesize proteins that function within the cytoplasm or nucleus of the cell. The nuclear DNA binding transcription factor, being involved in gene regulation within the nucleus, is synthesized by these ribosomes.

In summary, the cellular location and function of proteins determine the type of ribosomes involved in their synthesis. While the nuclear DNA binding transcription factor is produced by cytosolic ribosomes, proteins associated with the extracellular matrix, lysosomes, and inner surface of the plasma membrane are synthesized by ribosomes associated with the rough ER.