Animal Eukaryotic Cell Components: Structure and Function

I posted a picture of the eukaryotic animal cell earlier, but it was simply a labeled diagram. Here we will go into each of the major parts of the cell, as well as each organelle's function, not to mention the overall structure of the cell. As the name suggests, this type of cell can be found in all animals including fish, amphibians, reptiles, and mammals.

STRUCTURE OF THE CELL:

In the case of this cell, the eurkaryotic animal cell is encased by what is known as a plasma membrane, which keeps the cytoskeleton and various organelles inside. The inside of the cell has a gel-like matrix called the cytoplasm (the cytoplasm does not include organelles). 

COMPONENTS OF THE CELL: 

Nuclear Components

1. Nucleus: Spherical in shape and typically located in the middle of the cell (exceptions do occur), the nucleus is the source of all genetic information (before it is transcribed and translated), that leads to formation of nearly all the proteins that are in the eukaryotic cell. This organelle also has a double membrane around it. 
2. Nucleolus: A region surrounding the nucleus whose main function is in the synthesis of ribosomal RNA (also known as rRNA).
3. Nuclear envelope: Surface of the nucleus that contains two phospholipid bilayers, that are interspersed with holes, called nuclear pores. The outer most membrane of the nuclear envelope is continuous with the endoplasmic reticulum (ER).
4. Nuclear pores: Located where both of the phospholipid bilayers touch, these pores function in allowing small molecules to diffuse between the cytoplasm and nucleoplasm, while regulating the passage of proteins or RNA/RNA-protein complexes. 

Cytoplasmic Components

1. Actin filament: Long filaments that are about 7 nm in diameter and are made up of two globular alpha helices that wrap around each other. The main functions of these filaments in the cell concern with movement and range from contraction, pinching (during division), as well as, the formation of cellular extensions of the cell. These filaments can add or remove length through a process known as polymeration and depolymeration.
2. Microtubules: Hollow tubes ranging around 25 nm in diameter and composed of 13 protein protofilaments (each protofilament has subunits that alternate as alpha and beta tubulin subunits). Along with providing cellular movement, like the actin filaments, microtubules also help structure where the organelles are in the cell itself. 
3. Intermediate filament: These filaments are the most durable of all filaments, in terms of tensile strength and clock in at a diameter of 8-10 nm (intermediate in size between actin filaments and microtubules -- easy way to remember). The main function of these fibers is to provide structural stability to cells.

Remaining Organelles

1. Centriole: An organelle identical in structure to a basal body. It functions in dividing and organizing spindle fibers during the processes of mitosis and meiosis.
2. Lysosome: A membrane-bound vesicle that contains enzymes that break down worthless organelles and cell debris. These digestive enzymes are produced by the Golgi apparatus.
3. Plasma membrane: This membrane is composed of a phospholipid bilayer that surrounds the cytoplasm of the cell and can contain embedded proteins. The main functions of plasma membrane (PM) are to regulate what comes in and out of the cell, cell-to-cell recognition, adhesion and connection, and cell communication.
4. Ribosome: Small organelles found in the cytoplasm, as well as, the rough endoplasmic reticulum (rough ER) and are made up of RNA and proteins. They function as the site for protein and/or lipid synthesis. 
5. Endoplasmic reticulum (ER): This particular organelle is a network of internal membranes that function  in forming transport vesicles, lipid synthesis, and synthesis of membrane proteins. 
6. Golgi apparatus: A sack of flattened vesicles that receives transport vesicles from the ER and packages/modifies them for export of the cell. From that point, the Golgi apparatus secretes them into the cytoplasm. 
7. Mitochondria: Bacteria-like organelles that have a double membrane and are known as the 'power plants' because they provided energy to the cell via ATP and also are the sites of oxidative metabolism.

This is simply just a run through of the main components of an animal eukaryotic cell. If you have any question concerning details on any of these organelles/features, please don't hesitate to let me know by emailing me at holtzj@email.sc.edu. Thank you.