Setion I: Introduction to Cell Biology 

  What is Cell Biology?

   The science of biology is built upon three indispensable theories:   1) the theory of evolution,   2) the cell theory, and 3) equilibrium thermodynamics, the science of energy transformations that occur between cells, the tiny building blocks upon which all of life is built, and their external surroundings.

     Just as an atom is the smallest particle of a chemical element (see the periodic table), which can exist either alone or in combination and still possess the chemical and physical properties of that element, so then, a cell is the smallest entity which can exhibit the characteristic of life.

     Cell Biology is the scientific discipline that studies the cell as an individual unit and as a contributing part of a larger organism. A single cell is often considered a complete organism in itself, such as a bacterium or yeast. An individual cell is capable of digesting its own nutrients and transforming simple nutritional substances into cellular protoplasm, producing some of its own useable energy, and eventually replicating itself. A cell may be viewed as an enclosed vessel composed of smaller subcell parts, organelles, each of which has specific metabolic functions.  Within the cell, countless chemical reactions take place simultaneously, all of them controlled, so that they contribute to the processes we call life and the eventual procreation of the cell.

    In a multi-cellular organism individual cells, by differentiating in order to acquire particular functions, can become the building blocks of a larger multi-cellular organisms. In order to do this each cell keeps in continuous communication with its neighboring cells. Cooperative assemblies of like cells make up tissues, and a collaboration between tissues helps forms organs, the functional units of a whole organism as complex as a human being. 

    The smallest known cells are a group of tiny bacteria called mycoplasms. Some of these single-celled organisms are spheres about 0.3 micrometer in diameter with a total mass of 10-14 gram (a gram is a metric system unit of weight).  Human cells are about 400,000 times larger, but even then, they are only about 20 micrometers across. Guesstimates' are that a human being may be composed of more than 75,000,000,000,000 cells  (7.5 x 1013 cells). 

    A Cell Biologist is a scientist who studies the properties of cells: the functional structures within them, including organelles as mitochondria, chloroplasts, the Golgi apparatus, microsomes, and many others, the interactions and communication among cells, and the biochemical phenomena, which are shared by all cells.

    The cell may be defined by its metabolism, as well as by its structure. Molecular Biology has become the underpinning of contemporary Cell Biology.  It has established, not only that basic processes, such as the genetic code and protein synthesis are similar in all living systems, but also, that these processes are made possible by the same cell structures, which are found in all cells, structures such as microtubules, chromosomes, ribosomes, and membranes. Although biochemistry and molecular biology, as disciplines, might have made substantial development without the advent of the cell theory, each science has strongly influenced the other almost from the start.

   Contemporary cell biology, often referred to as Cell and Molecular Biology, is then a compilation of four separation disciplines: 
    1) cell physiology, which takes a comparative approach looking at how cells answer
             universal problems, from  water conservation to cell communication, 
    2) systemic physiology, which is the science of organ systems and whole organism
             physiology, such as insect, plant or fish physiology,  
   
3) biochemistry, which looks at the chemical and physical commonality of the mechanisms
             of cellular reactions, and 
    4) molecular biology, which studies the properties of organisms through their
             constituent molecules.

    The goals of cell and molecular biology lie in understanding the Cell Theory, which by itself cannot explain the development and unity of the multi-cellular organism. A cell is not necessarily an independently functioning unit, and a plant or an animal is not merely an assembly of individual cells.

    Cell and molecular biology is not so self-inclusive as to eliminate the concept of the organism as more than the sum of its parts. But the study of a particular organism does require the investigation of cells, as both individuals and groups. The problem of cancer may provide an analogy: a plant or animal governs the division of its own cells; the correct cells must divide, become differentiated, and then be integrated into the appropriate organ system at the right time and place. Breakdown of this process results in a variety of abnormalities, one of which may be cancer. When a cell biologist studies the problem of the regulation of cell division, the ultimate objective is to understand the effect of the individual cell on the whole organism.

    The intent of modern cell and molecular biology is to interpret the properties of the whole organism through the structure of its own cell's component molecules. Cell and molecular biology is the study of the life processes, which occur within the makeup of a cell and its molecules. 

  Charles Mallery, CASUM,  Last Update - 04/02/2007