Monday, July 15, 2013

Eukaryotic Cell

Eukaryotic animal cell

There are three basic components to the cell.  There is a nucleus, or nucleus-like area, that contains the information that governs the cell.  There is a protective barrier encapsulating the cell, made of a membrane and maybe a cell wall.  The interior of the cell contains a gelatinous substance called the cytoplasm in which various components exist, performing the cell’s metabolism – providing for the cell’s energy needs and synthesizing its structures.  This is the basic make-up of a generic cell most familiar to people’s conception.  It is called a Eukaryotic cell and it makes up all the cells of the plants and animals surrounding us, including ourselves.  There are other forms of life, such as bacteria, whose cells have fewer components and they are called prokaryotic cells.  There exists also an even simpler living form that is categorized as the virus.  Its minimal nature challenges the cell model for all living things.

Possibly the most important fact to consider is that all life’s functions fit within a single, microscopic cell.

The nucleus has a double membrane separating it from the metabolizing portion of the cell.  Contained within this area are nucleic acids.  The most important of these is DNA – the repository of the entire cell’s genetic information.  This long molecular structure is best known for its role in inheritance during reproduction but it also provides all the necessary instructions to maintain the life of the cell.  This macromolecule is made up of a long sequence of units composed of nitrogenous bases.  There are four different bases represented in varying order.  A triplet of these bases provides the code for a specific amino acid.  There are twenty amino acids used in various combinations to make the many proteins important to life.  The sequence of the many amino acids contained within each protein determines the molecule’s characteristics.  Enzymes that catalyze the cell’s many chemical reactions are made of proteins as are much of the cell’s structure.

Suspended within the cytoplasm that surrounds the nucleus are various structures with specific functions.  A tubular structure arises from the nuclear membrane and creates a maze within the cell.  This endoplasmic reticulum is the site for the synthesis of proteins and of fats, called lipids, which are important to membrane construction.  The structure most important for making chemical energy available to the cell is the mitochondria.  This is the sight for the creation of the energy transfer molecule, ATP, and for respiration – utilizing the conversion of oxygen to carbon dioxide in order to provide the cell’s energy.  Mitochondria are self-replicating.  They have their own DNA, leading to the speculation that at some point in biological history they were a separate living entity that joined in a mutually beneficial relationship with the ancestor to the Eukaryotic cell, much as fungus and algae have joined in a symbiotic relationship to form lichen.  Another of these self-contained cell structures, call organelles, is the Golgi apparatus – a complex of stacked vesicles that provides for digestion and storage.  A fundamental organelle in plant cells is the chloroplast, the location for photosynthesis, making the cell an autotroph – capable of sustaining itself on nonliving, inorganic matter.

The cell depends on lipids to give its membrane flexibility.  Cholesterol is a water insoluble molecule embedded in the membrane to toughen the protective barrier.  Proteins are used in a similar manner as well as enabling the selective transport of material into the cell and in expelling waste from the cell’s interior.  The cell also utilizes reactions of various proteins to specific stimulus as a means of detecting the nature of the external environment. 

The depiction of the cell in a generalized diagram is a simple abstraction giving no appreciation for the cell’s extraordinary complex role in providing the basis for life.  This word depiction is likewise only a vague overview that, at best, should stimulate questions as the starting point for further inquiry.  Each statement of fact poses new questions that, when answered, in turn provide more questions.  At this point we are located at the very top of a rapidly widening pyramid that can never find its ultimate base.  When following the path of any science the final conclusion remains always over the horizon.

Biology Topics:


Opportunistic Bacteria

Molecular Basis of Life 

Limited Male

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