Organelles

Organelles are specialized subcellular structures that perform distinct functions essential to the life of the cell. In eukaryotic cells, most organelles are bounded by membranes, creating discrete environments for specific biochemical processes; some structures, such as ribosomes and proteasomes, lack membranes.

Key organelles include the nucleus, which houses genetic material and coordinates gene expression; mitochondria, which generate ATP through respiration; and chloroplasts (in plants and algae), which perform photosynthesis and contain their own DNA. The endoplasmic reticulum comes in two forms—rough, studded with ribosomes, and smooth—synthesizing proteins and lipids. The Golgi apparatus modifies, sorts, and ships proteins and lipids to their destinations. Lysosomes and peroxisomes carry out degradation and detoxification, while vacuoles store substances and help maintain turgor pressure in plant cells. Vesicles and endosomes mediate transport between compartments, and the cytoskeleton provides structural support and facilitates movement within the cell.

Non-membrane-bound components also play essential roles. Ribosomes synthesize proteins, proteasomes degrade damaged or unneeded proteins, and the cytoskeleton organizes cellular architecture and traffic. Some organelles, such as mitochondria and chloroplasts, contain their own DNA and ribosomes, reflecting an endosymbiotic origin.

Prokaryotic cells generally lack membrane-bound organelles, though they possess simple compartments and protein complexes that perform specialized tasks. Organelles continually interact through vesicular trafficking and membrane contact sites, coordinating metabolism and signaling. Dysfunction of organelles is linked to a range of diseases and disorders, underscoring their importance to cellular health.