Fundamentals of Molecular Biology. Part 1: Molecular Cell Biology - A. N. Ogurtsov 2011

Molecular Biology. Subject Matter and Core Sections of the Course
Study of Cells and Cellular Structures

The world of biology spans a scale of sizes exceeding a billion-fold (Figure 12). Ecology and ecogeography border this size scale of biological objects on the "macro" end, while chemistry and physics approach it from the "micro" side. To observe objects smaller than 0.1 mm, special magnification instruments are required. Direct observation of Cells only became possible with the invention of the microscope in the 17th century.

Cell/15.html">Microscopy is most effective when special stains and fluorophores are used to provide contrast for different Tissues or various cellular components (most of which are inherently colorless).

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Figure 12 – Range of sizes of biological objects: a – DNA; b – human embryo on the third day after Fertilization (eight cells); c – spider, 15 mm in size; d – emperor penguins, about one meter tall

For instance, The Use of fluorescent tags attached to the tubulin protein—whose polymerization forms microtubules—has made it possible to observe mitosis. During this process, these microtubules, attached at one end to centrioles and at the other to Chromosomes, pull the chromosomes from the equatorial plate of the dividing cell toward its poles.

Figure 13 shows a micrograph of a dividing cell, revealing the microtubule system (gray filaments; in the color micrograph, they are stained red) forming "meridians," along with chromosomes (black) near the "poles."

Figure 13 – Micrograph of a late-stage mitosis

The use of the Electron microscope has enabled researchers to study The Structure of most cellular Organelles and large Protein Complexes.

To study individual protein molecules, it is necessary to employ Physical and Chemical purification Methods and enrichment techniques involving fractionation and various types of Chromatography.

The three-dimensional structure of macromolecules (their conformation) is determined using X-ray crystallography. Computer Analysis of the resulting X-Ray Diffraction patterns allows researchers to determine the spatial arrangement of every atom within the macromolecule.

Thus, our current understanding of the molecular functioning of cells has been achieved through the collective efforts of many generations of researchers studying all types of biological organisms, from Viruses and Bacteria to birds, animals, and humans. Historically, experiments on certain organisms proved more convenient because the Answers to the questions posed by investigators were clearer, more unequivocal, and more consistent when working with those specific organisms. Moreover, due to the high evolutionary conservation of genes, Proteins, organelles, and cell types across species, data and insights regarding biological structures and Functions obtained from experiments on one Organism can generally be applied to others.

Figure 14 illustrates typical biological organisms whose study has made the greatest contributions to cell and molecular biology.

Figure 14 – Model organisms used in cell biology: a – viruses; b – bacteria; c – Yeast; d – nematodes; e – fruit fly (Drosophila); f – zebrafish; g – mice; h – plants

Listed below are the specific research problems addressed using these model organisms.

Viruses. Proteins involved in DNA, RNA, and Protein Synthesis. Introduction/30.html">Regulation of Gene Expression. Cancer and the control of cell proliferation. Protein and organelle transport within The Cell. Infection and Immunity. Gene Therapy.

Bacteria. Proteins involved in DNA, RNA, and protein synthesis. METABOLISM. Regulation of Gene Expression. Targets for novel Antibiotics. Cell Cycle. Signaling systems.

Yeast (Saccharomyces cerevisiae). Control of the CELL CYCLE AND Cell Division. Protein secretion and membrane biogenesis. Cytoskeletal functions. Cell Differentiation. Aging. Gene regulation and Chromosome structure.

Roundworms (nematodes). (The Caenorhabditis elegans nematode consists of only 959 cells). Organismal development. Cell lineages. Formation and function of The Nervous system. Programmed cell death. Cell proliferation and cancer genes. Aging. Behavior. Gene regulation and chromosome structure.

Fruit fly (Drosophila melanogaster). Organismal development. Generation of differentiated cell lineages. Formation of the nervous system, Heart, and musculature. Programmed cell death. Genetic control of behavior. Cancer genes and the control of cell proliferation. Control of cell polarity. Effects of drugs, alcohol, and pesticides.

Zebrafish (Danio rerio, frequently referred to in English-language literature simply as zebrafish). A popular aquarium fish whose embryos are transparent and develop from a single-celled egg to a larva within three days. Vertebrate body tissue development. Brain and nervous system formation and function. Birth defects. Cancer.

Mice (fast-breeding mammals). Body tissue development. Functioning of the mammalian immune system. Brain and nervous system formation and function. Models of cancer and other human diseases. Gene regulation and heredity. Infectious diseases.

Plants (Arabidopsis thaliana). Tissue development and morphogenesis. Genetics of cell biology. Agricultural Applications. Physiology. Gene regulation. Immunity. Infectious diseases.