Chapter 1 - Introduction Cell and Molecular Biology.docx

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Biological Sciences
Rene Harrison

Introduction to the Study of Cell and Molecular Biology o Cell and molecular biology is reductionist; based on the view that knowledge of the parts of the whole can explain the character of the whole. o Cells can only be observed with the aid of a microscope, which is an instrument that provides a magnified image of a tiny object o Robert Hooke, English microscopist, credited for the discovery of cells. One of the many questions he attempted to answer was why stoppers made of cork were so well suited to holding air in a bottle. He examined a cut piece of cork under a microscope and perceived what appeared to be pores which he labeled as cells. Ornate compound (double-lens) microscopes o Anton van Leeuwenhoek, Dutchman, spent spare time grinding lenses and constructing simple microscopes of remarkable quality. He was the first to examine a drop of pond water under a microscope. He was able to observe teeming microscopic animalcules that darted back and forth before his eyes. He was also the first to describe various forms of bacteria, which he obtained from water in which pepper had been soaked and from scrapings of his teeth. o Matthia Schleiden, German lawyer turned botanist, concluded that despite differences in structure of various tissues, plants were made of cells and that plant embryo arose from a single cell. o Theodore Schwann, German zoologist, concluded that the cells of plants and animals are similar in structures and proposed these two tenets of cell theory: a. All organisms are composed of one of more cells. b. The cell is the structural unit of life. o By 1855, Rudolf Virchow, German pathologist, had made a convincing case for the third tenet of the cell theory: c. Cells can arise only by division from a preexisting cell. o Life is the most basic property of cells, and cells are the smallest units to exhibit this property. Unlike parts of cells which simply deteriorate if isolated, whole cells can be removed from a plant or animal and cultured in a laboratory. o Death can also be considered one of the most basic properties of life, because only living entity faces this prospect. Cells within the body generally die by their own hand the victims of an internal program that causes cells that are no longer needed or cells that pose a risk of becoming cancerous to eliminate themselves. o First culture of human cells was begun by George and Martha Gey. The cells were obtained from a malignant tumour and named HeLa cells These cells are so much simpler to study than cells situated within the body, cells grown in vitro (i.e., in culture, outside the body) have become an essential tool of cell and molecular biologists. o Cells are highly complex and organized. The more complex a structure, the greater the number of parts that must be in their proper place, the less tolerance of errors in the nature and interactions of the parts, and the more regulation or control that must be exerted to maintain the system. o Each type of cell has a consistent appearance when viewed under a high-powered electron microscope; its organelles have a particular shape and location, from one individual of a species to another. These organelles have a consistent composition of macromolecules, which are arranged in a predictable pattern. o Many of the most basic processes, such as the synthesis of proteins, the conservation of chemical energy, or the construction of a membrane, are remarkably similar in living organisms. Humans and a cat have very different anatomical features, the cells that make up their tissues, and the organelles that make up their cells are very similar. o Information obtained by studying cells from one type of organism often has direct application to other forms of life. o Cells possess a genetic program and the means it use it Organisms are built according to information encoded in a collection of genes. Genes are more than storage lockers for information: they constitute the blueprints for constructing cellular structures, the directions for running cellular activities, and the program for making more of themselves. Molecular structure of genes allows for changes in genetic information (mutations) that lead to variation among individuals, which forms the basis of biological evolution. o Cells are capable of producing more of themselves Just as individual organisms are generated by reproduction, so too are individual cells. Cells reproduce by division, a process in which the contents of a mother cell are distributed into two daughter cells. The daughter cells receive a complete and equal share of genetic information and both have approximately equal volume. In some cases however, human oocyte undergoes division, this allowing one of the cells to retain nearly all of the cytoplasm, even though it received only half of the genetic material. o Cells acquire and utilize energy Every biological process requires the input of energy. Virtually all of the energy utilized by life on the Earths surface arrives in the form of electromagnetic radiation from the sun. Energy of light is trapped by light-absorbing pigments present in the membranes of photosynthetic cells. This energy is then converted by photosynthesis into chemical energy that is stored in energy-rich carbohydrate, such as sucrose or starch. For most animal cells, energy arrives prepackaged, often in the form of sugar glucose. In humans, glucose is released by the
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