Human body contains approximately 37.2 trillion cells. Cells are basic functional units in all living things
The endomembrane system consists of ER, Golgi apparatus, and vesicles. Rough ER synthesizes proteins and modifies them for export. Smooth ER synthesizes lipids and regulates cellular calcium. Golgi apparatus sorts, modifies, and packages cellular products. Lysosomes contain enzymes for cellular digestion and self-destruction
Endocytosis actively transports molecules into cells through membrane engulfing. Equal flow of molecules in and out maintains cell homeostasis. Essential components include early, late endosomes, and lysosomes
Endomembrane system spans from nuclear to plasma membranes in eukaryotic cells. System modifies, packages, and transports lipids and proteins. Components communicate through direct contact or vesicular transport
GERL is a cell system consisting of Golgi apparatus, endoplasmic reticulum, and lysosomes. Golgi apparatus forms stacks of cisternae connected by microtubules. Endoplasmic reticulum exists as rough (RER) and smooth (SER) types. Lysosome contains digestive enzymes with optimal pH 4.5-5.0
Lysosomes are membrane-bound organelles containing digestive enzymes. They are spherical bodies about 50-70 nm in diameter. Found in most eukaryotic cells except red blood cells. Can be observed only under electron or fluorescence microscope