Questions: La synthèse des phospholipides et du cholestérol est principalement effectuée par : le réticulum endoplasmique les riboson?s le complexe golgien les mitochondries le noyau

The answer is the first one: le réticulum endoplasmique.

Explanation for each option:

1. Le réticulum endoplasmique: This is correct. The endoplasmic reticulum (ER), specifically the smooth endoplasmic reticulum (SER), is primarily responsible for the synthesis of phospholipids and cholesterol. These lipids are essential components of cellular membranes.

2. Les ribosomes: This is incorrect. Ribosomes are responsible for protein synthesis, not lipid synthesis.

3. Le complexe golgien: This is incorrect. The Golgi apparatus is involved in modifying, sorting, and packaging proteins and lipids for secretion or delivery to other organelles, but it is not the primary site of lipid synthesis.

4. Les mitochondries: This is incorrect. Mitochondria are primarily involved in energy production through the process of oxidative phosphorylation and the citric acid cycle, not in the synthesis of phospholipids and cholesterol.

5. Le noyau: This is incorrect. The nucleus contains the cell's genetic material and is involved in processes such as DNA replication and transcription, but it does not synthesize lipids.

Summary: The synthesis of phospholipids and cholesterol is primarily carried out by the smooth endoplasmic reticulum (SER).