The document summarizes the cellular level of organization, describing the key components of eukaryotic cells including the plasma membrane, cytoplasm, cytoskeleton, organelles, and their functions. Specifically, it outlines the structure and selective permeability of the plasma membrane, transport mechanisms across membranes, components and roles of the cytoplasm and cytoskeleton, and functions of important organelles such as the endoplasmic reticulum, Golgi complex, lysosomes, peroxisomes, mitochondria, and ribosomes.