Which type of structure is NOT considered an organelle?

The heart is classified as an organ rather than an organelle. Organs are larger structures composed of various tissues that work together to perform specific functions within an organism. In contrast, organelles are specialized subunits within a cell that have distinct functions, such as the endoplasmic reticulum, ribosomes, and lysosomes. Each of these organelles plays a critical role in cellular processes: the endoplasmic reticulum is involved in the synthesis and processing of proteins and lipids, ribosomes are the sites of protein synthesis, and lysosomes contain enzymes for digestion and waste management within the cell. Understanding the distinction between organelles and organs is essential for grasping the organization and functionality of biological systems.