Introduction to Cell Biology 2023 PDF

Introduction to Cell Biology R. Craig Gillam, DC, MS Logan University  deci- (d) = 10-1 (tenth) centi- (c) = 10-2 (hundredth) Review milli- (m) = 10-3 of Metric (thousandth) micro- (μ) = 10-6 Prefixes (millionth)...

Introduction to Cell Biology R. Craig Gillam, DC, MS Logan University  deci- (d) = 10-1 (tenth) centi- (c) = 10-2 (hundredth) Review milli- (m) = 10-3 of Metric (thousandth) micro- (μ) = 10-6 Prefixes (millionth) nano- (n) = 10-9 (billionth) pico- (p) = 10-12 (trillionth) Levels of Structural Organizati on  Three historical strands of science weave together into modern cell biology, each with The important contributions to understanding cells. Emergen  Cytology (cytopathology) ce of  Focuses mainly on cellular structure, and emphasizes optical techniques (e.g., microscopes) Modern  Biochemistry Cell  Focuses on cellular function Biology  Genetics  Focuses on information flow and heredity The Emergence of Modern Cell Biology  In 1839, Schwann postulated the cell theory  1. All organisms consist of one or more cells. Cell  2. The cell is the basic unit of structure Theory for all organisms. Later, Virchow (pronounced Vir-k-o)(1855) added  3. All cells arise only from pre-existing cells. A Brief History of Cell Theory Robert Hooke (1665) observed compartments in cork, under a microscope, and first named cells (the basic unit of biology). Cytology The study of the microscopic appearance of cells, especially for the diagnosis of disease. This study is accomplished using microscopes. Microscopes There are 2 types of microscopes used in cell biology:  Light microscope  Uses a beam of light that travels through a specimen. The beam is then magnified by a lens or lenses before reaching your eye.  Electron microscopes  Uses a beam of electrons that can be either deflected off a specimen, or travel through a specimen before reaching a sensor that creates an image.  Magnification – the process of enlarging the apparent size of an object. Abilities Resolving power – the distance by which of a two objects must be separated to appear as two objects. Microsco The resolving power of the unaided human eye is 2 mm. pe Limitations of Early Microscopy Early light microscopes had only 1 lens, so magnification and resolution were limited. Hooke’s microscope had a magnification power of 30X, and resolution was limited to 8.3 μm. Modern Microscopes By the 1830s, compound light microscopes with two lenses increased magnification and resolution dramatically. Modern Microscopes Modern light microscopes can magnify objects by 1000-1400X and they have a 200 nm limit of resolution.  Modern Microscopes Electron microscopes can magnify objects up to 100,000X and they have a resolving power of 0.1 - 0.2 nm. The Light Microscope The light microscope was the earliest tool of cytologists. It allowed scientists to identify organelles within a cell.  Organelles are membrane-bound structures, such as nuclei, mitochondria, endoplasmic reticula, etc. Different Types of Light Microscop y Sample Micrographs Filamentous fungal cells Treponema bacteria Human blood cells and a platelet Sample Micrograph Trichomonas vaginalis (a protozoan parasite) Sample Micrograph Human ovum and sperm cells Electron Microscope s The electron microscope was a breakthrough for cell biology. The magnification is much higher than light microscopes (up to 100,000X). The limit of resolution is around 0.1-0.2 nm. Electron microscopes allow us to observe smaller structures. Types of Electron Microscopy In transmission electron microscopy (TEM), electrons are transmitted through a specimen which gives us an image of the inside of a cell. In scanning electron microscopy (SEM), electrons are deflected off the outer surface of a specimen which gives us an image of the cell’s outer surface. Specialized approaches in electron microscopy allow for visualization of specimens in three dimensions. Electron Micrographs Biochemistry Biochemists study the chemistry of biological structure and function. Much of biochemistry dates from the work of Fredrich Wöhler (1828), who showed that a compound (urea) made in a living organism could be synthesized in the lab. Developments in Early Biochemistry Louis Pasteur (1860s) showed that yeasts could ferment sugar into alcohol. This eventually led to the discovery of enzymes, which are biological catalysts. Developments in Early Biochemistry Gustav Embden and Otto Meyerhof described the steps of glycolysis (the Embden- Meyerhof pathway) in the early 1930s. Hans Krebs described the Kreb’s (TCA) cycle soon after. Both pathways are important in the energy metabolism of cells.  Important Advances in Biochemistry Chromatography - techniques to separate molecules in a solution based on size, charge, or chemical affinity. Electrophoresis - uses an electrical field to move proteins, DNA or RNA molecules through a medium based on size/charge. Mass spectrometry - determines the mass-to- charge ratio of ions. Advances in Biochemistry Gas Chromatography Electrophoresis Mass Spectrometry Clinical Application of Simple Chromatogra phy Clinical Application of GC/MS Genetics Gregor Mendel’s experiments with peas (1866) laid the foundation for understanding the passage of “hereditary factors” from parents to offspring. The hereditary factors are now known to be genes. Genetics Walther Flemming (1880) saw threadlike bodies in the nucleus called chromosomes. Wilhelm Roux (1883) and August Weisman (shortly after) suggested that chromosomes carried the genetic material. Genetics Morgan, Bridges, and Sturtevant (1920s) were able to connect specific traits to specific chromosomes in the model organism, Drosophila melanogaster (the common fruit fly). Progress in Understandi ng DNA Friedrich Miescher (1869) first isolated DNA, which he called nuclein. DNA was known to be a component of chromosomes by 1914. DNA was known to be composed of only 4 different nucleotides by the 1930s. Progress in Understanding DNA Experiments with bacteria and viruses in Many advances were the 1940s began to made toward implicate DNA as the understanding DNA genetic material carried replication, synthesis, by chromosomes. and the genetic code. 1940s 1953 1960s Watson and Crick, assisted by Rosalind Franklin, proposed the double helix model for DNA structure. Rosalind Franklin Important Techniques in Genetics Electrophoresis is used for separating DNA and RNA molecules.  An electrical current is used to separate these molecules based on their electrical charge and size. Advances in DNA Technology Recombinant DNA technology  Uses enzymes to cut DNA at specific locations.  This allows scientists to create new recombinant DNA molecules by inserting DNA from different sources into the cut strand. The Science is based on fact, not ill- Scientific considered opinions, political or religious beliefs. Method  The scientific method is used to assess new information.  Observation is the first step. The  Questions are asked about these observations. Scientific  A hypothesis (tentative explanation or model Method that can be tested) is formulated around these questions. Hypotheses are typically made with respect to what is already known.  Data are collected, analyzed statistically, and the results are interpreted. The hypothesis is then either accepted or rejected. Levels of Scientific Certainty Hypothesis – a statement consistent with most of the data; may take the form of a model (an explanation that appears to account for the data); must be testable. Theory - a hypothesis that has been extensively tested by many investigators, using different approaches, and is widely accepted. Law - a theory that has been tested and confirmed over a long period of time with virtually no doubt of its validity. Occam’s Razor The simplest explanation consistent with an observation is most likely to be true.