What are the roles of different organelles in protein synthesis?

The nucleus, ribosomes, endoplasmic reticulum, and Golgi apparatus play key roles in protein synthesis.

The process of protein synthesis involves two main stages: transcription and translation. These stages are facilitated by different organelles within the cell. The nucleus, ribosomes, endoplasmic reticulum, and Golgi apparatus are the primary organelles involved in this process.

The nucleus is the control centre of the cell and houses the cell's DNA. The process of protein synthesis begins here. During transcription, the DNA's genetic information is copied to create messenger RNA (mRNA). This mRNA then leaves the nucleus and travels to the ribosomes.

Ribosomes, which can be found either floating freely in the cytoplasm or attached to the endoplasmic reticulum, are the sites of protein synthesis. They read the mRNA and translate it into a sequence of amino acids, the building blocks of proteins. This process is known as translation. The ribosomes that are attached to the endoplasmic reticulum synthesise proteins that are either secreted from the cell or incorporated into the cell membrane.

The endoplasmic reticulum (ER) plays a crucial role in protein synthesis and folding. The rough ER, which is studded with ribosomes, synthesises and folds proteins. The smooth ER, on the other hand, is involved in lipid synthesis but does not play a direct role in protein synthesis.

Finally, the Golgi apparatus, often considered the 'post office' of the cell, modifies, sorts, and packages the proteins synthesised by the ER. It adds carbohydrates and lipids to the proteins, transforming them into glycoproteins and lipoproteins. These modified proteins are then transported in vesicles to their final destinations, either within the cell or outside it.

In summary, the nucleus, ribosomes, endoplasmic reticulum, and Golgi apparatus work together in a coordinated manner to ensure the successful synthesis, folding, modification, and transport of proteins within the cell. This process is vital for the cell's function and survival.