 Welcome to A Typical Animal Cell. In this video, you'll explore parts of an animal cell and the function of organelles. The cell is the basis for all life. It's the fundamental building block for all known living organisms. Unlike plant cells, animal cells lack a cell wall, so they come in a variety of shapes and sizes. All animal cells have three main parts, the plasma or cell membrane, the cytoplasm, which contains the organelles, and the nucleus. The plasma membrane encloses the cell. It's made from a bilayer of phospholipids, cholesterol, and proteins, and it acts as a semipermeable barrier. It creates the cell's internal and external environments. The cytoplasm holds all of the organelles, which are specialized subunits within a cell. There are a number of different organelles, and each one performs a specific task. Let's start with the Golgi apparatus, also called the Golgi complex or Golgi body. This is a stack of smooth, membrane sacs and associated vesicles close to the nucleus. It packages, modifies, and segregates proteins for secretion from the cell, for inclusion in lysosomes, and for incorporation into the plasma membrane. Lysosomes are membranous sacs that contain acid hydrolases that break down different types of biomolecules. This is where intracellular digestion takes place. Lysosomes help with other cell processes, including secretion and the repair of plasma membranes. Mitochondria are rod-like, double-membrane structures. This inner membrane is folded into projections called Christe. This is the site of ATP synthesis, and is the powerhouse of the cell. They help with other tasks, like signaling, differentiation, and cell death. The number of mitochondria in a cell varies depending on the cell type. Red blood cells have no mitochondria, and liver cells can have more than 2,000. Paroxysomes are membranous sacs of oxidase enzymes. The enzymes detoxify a number of toxic substances. The most important enzyme, catalase, breaks down hydrogen peroxide. Ribosomes are dense particles that consist of two subunits, each of which is composed of ribosomal RNA and protein. They may be free or attached to the rough endoplasmic reticulum. This is where protein synthesis takes place. The rough endoplasmic reticulum membrane system encloses a cavity, the cisterna, and coils through the cytoplasm. It's externally studded with ribosomes. Sugar groups are attached to proteins within the cisternae. These proteins are bound in vesicles for transport to the Golgi apparatus and other sites. The external face synthesizes phospholipids and cholesterol. The smooth endoplasmic reticulum is a membranous system of sacs and tubules that plays a part in several metabolic processes. It's free of ribosomes and synthesizes steroids, metabolizes lipids, and detoxifies drugs. In addition to organelles, the cytoplasm also contains other cellular structures. These cytoplasm are paired cylindrical bodies. Each one is composed of nine triplets of microtubules. They organize a microtubule network during mitosis to form the spindle, asters, and basis of cilia and flagella. Intermediate filaments are protein fibers whose composition varies. These stable cytoskeletal elements resist mechanical forces acting on the cell. These filaments are fine filaments of the contractile protein actin. They're involved in muscle contraction and other types of intracellular movement. They help form the cell's cytoskeleton, cilia, and if it's present, the flagella. Microtubules are cylindrical structures made of tubulin proteins. They support the cell and give it shape. They're involved in intracellular and cellular movements and form centrioles. Finally, every cell contains a nucleus. It's distinctly different from the plasma membrane and the organelles. The nucleus is the largest organelle. It's surrounded by the nuclear envelope and contains the nucleoplasm, nucleoli, and the chromatin, or DNA. It acts as the control center of the cell and is responsible for the instructions for protein synthesis and for transmitting DNA to the daughter cells. The nuclear envelope is a double membrane structure that is pierced by the pores. The outer membrane is continuous with the endoplasmic reticulum. The nucleolus is a small, dense body within the nucleus. It's composed of ribosomal RNA and proteins, and it's the site of ribosome subunit manufacture. Nucleoli also assemble signal recognition particles and play a role in the cell's response to stress. Chromatin is a granular, thread-like material composed of DNA and histone proteins. Chromatin packages DNA into a smaller volume to fit into the cell, and it controls gene expression and DNA replication. Histones, part of the chromatin, compacts the DNA for transport. Today, we've reviewed the parts of the animal cell and the function of organelles. You've completed a typical animal cell.