An Introduction to the Cell Structure

This article is intended to provide a brief synopsis over the cellular structure and history, in addition to the present-day perception of it.

Cell Wall: The cell wall is the outermost layer of the cell, and its main function is to act as a protective barrier to prevent any damage to the cell's interior. The cell wall is made up ofcellulose fibrils that provide for strength re-enforcement of the layers.

Cell Membrane: The cell membrane is composed of both proteins and lipids, and it serves three main functions: it provides for a boundary around the cytoplasm; it binds the cells together; and it filters different chemicals to determine which penetrate the cell.

Facilitated Diffusion: Facilitated Diffusion is the process in which tiny uncharged molecules can diffuse the cell membrane.

Fluid Mosaic Model: This is a model that outlines the structure of the cell membrane. A flexible layer consisting of lipid molecules is interfused with larger protein molecules that functions as channels in which other molecules can enter and exit the cell.

Chloroplast: The chloroplast contains a double layer of modified membrane that is composed of protein, chlorophyll, and lipid. There is also an inner membrane that forms a layer known as "grana", where there is a high chlorophyll concentration. Chloroplasts are the central site of the photosynthesis process that takes place in plants.

Vacuole: The vacuole is composed of one layer of unit membrane, with fluid that is enclosed in a sack. The vacuole applies pressure against the cell wall for support, and also is used for storage of water and chemicals, including some insoluble wastes.

Lysosome: The lysosome is structurally composed of a membrane bag that contains hydrolytic enzymes. A hydrolytic enzyme is a "water split, biological catalyst".

Ribosome: The ribosome is composed of RNA (ribonucleic acid) and protein enzymes, and the chemical composition is approximately: 60% RNA and 40% protein. They are accountable for the majority portion of the RNA of a cell. It is also the site of the protein synthesis process.

Endoplasmic Reticulum: The ER is a system of membranes within the cytoplasm of the eukaryotic cell, and it makes up more than 1/2 of the membrane of a cell. Consists of sheets with ribosomes on the outside. The ER transports chemicals from cell to cell, and it contains a large surface area suitable for chemical reactions and the synthesis process.

Golgi Bodies: Golgi Bodies consist of flattened sacs of unit membrane, and they allow for chemicals to fulfill their functions. It allows acts as a chemical storage area, and is able to produce Endoplasmic Reticulum.

Osmosis: Osmosis is the process of the diffusion of solvents through a semi-permeable membrane that doesn't allow liquids to pass. It is not to be confused with dialysis, as osmosis is the transfer of a solvent only, whereas dialysis is the transfer of a solute. It influences the distribution of vital nutrients throughout the body, and the discharge of the metabolic wastes.

Cytoskeleton: A system within the cytoplasm of the cells that is primarily responsible for the maintenance/changes in cell features (cell shape, cell locomotion, movement, integration, division, and organization). It is composed of three filament types: microfilaments (six nanometers in diameter), microtubules (twenty-five nanometers in diameter), and intermediate filaments (ten nanometers in diameter).

Symbiosis: The close association between two or more organisms from different species, and it is mutually beneficial to both parties. True symbiosis can be found in the relationship between herbivores and bacteria.

Tissue: A collection of cells that are similar in function and structure. These cells can be observed through high-powered lenses, and thus, there is more accuracy in a medical diagnosis. There are four fundamental tissue types in animals: epithelial, nerve, connective, and muscle tissue.

Prokaryotes: These are cells that lack a nucleus, nor do they contain organelles (cellular parts that perform specific functions). It is believed that these were the first cells on Earth, and they are approximately four billion years old. Prokaryotes are capable of inhabiting most places in the world.

Eukaryotes: An organism whose cell contains a nucleus and organelles. Other than bacteria (which is a prokaryote), all organisms are eukaryotes. Eukaryotes are approximately two billion years old. They evolved from a prokaryote "swallowing" another prokaryote. Eukaryotes are ten times the size of prokaryotes and up to one-thousand times more volume.

Chromosomes: Carriers of genetic material, and they are composed of NA and proteins. There are 150 million DNA bases in chromosomes. Humans typically have 46 chromosomes: 44 autosomes (non-sex defined); females have XX chromosomes, whereas males have XY chromosomes. Chromosomal "defects" can sometimes be detected by dying and then examining them, most DNA changes, however, are too subtle to see visually.

Organism: A living body that has the ability to function independently. It is made up of cells, some contain a single cell (unicellular) and some include multiple cells (multi-cellular). A complex organism is one with more than one cell. All organisms are (theorized) to have atleast one cell.

Organ: A part of an organism that serves a specific purpose. It is made up of tissues and are grouped into systems (i.e. the digestive system). There is main tissue and sporadic tissues within them. Some organs include: kidneys, heart, lungs, brain, eyes, stomach, spleen, pancreas, liver, skin, bladder, and more.

Flagella: An extension of certain cells/unicellular organisms that are used for locomotion. Often, its function is to cause water currents that are necessary for not only respiratory functions, but circulation as well.

Cilia: A microscopic strand that is an extension of the plasma membrane. It has a rhythmical motion and reacts with other parts of the cell to cause movement. It is an organelle whose foundation is the eukaryotic cell. It is also structurally identical to the flagella.

Lipid Bi-layer: A critical component of membranes, thus it is absolutely vital for all life on earth. It also functions as a barrier and is composed of two regions: hydrophilic and hydrophobic.

Chromatin: A combination of DNA and other proteins (histones particularly). It is located in the cell nucleus of eukaryotic cells and its job is to stain with its dyes, and assist in condensing in the formation of chromosomes during the process of cell division. There are two types of chromatin: euchromatin and heterochromatin.