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BIOL 130 Study Notes Unit I.docx

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University of Waterloo
BIOL 130
Richard Ennis

BIOL 130 Study Notes Unit I THE LIGHT MICROSCOPE: • Invented by Robert Hooke • Hooke used the microscope to look at slices of dried cork, which he named “cellula” o But what he was actually seeing were the cell walls of the dried cork • Antoni Van Leeuwenhoek, who worked with glass, improved the lenses, allowing up to 300X magnification via microscope o Dubbed the “father of microbiology” o Leeuwenhoek observed single-celled animal species (animalcules)  Blood cells  Banded pattern muscle cells  Sperm cells  Protist from pond  Bacteria from his own mouth • Cytology was then stalled for about a century or so o Light microscope had limited resolving power o Emphasis on observations rather than explanation • Then in the 1830s, the compound microscope was created o Improved magnification and resolution drastically o Allowed visualization of things smaller than 1um • General Relative Sizes of Things: AMMVBOC o Atoms < Molecules < Membranes < Viruses < Bacteria < Organelles < Cells THE CELL THEORY: • Robert Brown (1833) – Botanist o Notices that plant cells have a “kernel” nucleus o The nucleus was first discovered in a plant! • Matthias Schleiden (1838) – Botanist o All plants, which are multi-cellular organisms, are composed of cells o Embryonic plants arise initially from a single cell • Theodor Schwann (1839) – Zoologist o Confirmed both observations of Brown and Schleiden in animal cells too o Structural similarities between plants and animal cells seen o Formulated the Cell Theory:  The cell is the basic unit of life  All living things are comprised of cells  All cells come from pre-existing cells FACTS & THE SCIENTIFIC METHOD: • Fact: o Something that is proven or known to be true o Something we believe to be true based on our best current understanding • Fact (scientific): o An attempt to understand something based on our current understanding through experiments and observations o Valid until proven otherwise by empirical testing; then it is discarded or revised • The Scientific Method: o Identifying a phenomenon and making observations on it o Develop a hypothesis that explains why the thing occurs, and predict what will happen o Design and carry out controlled experiments to test for the hypothesis by using empirical testing and observations o Interpret the results to see if it supports the hypothesis o Draw conclusions and discard/refine/confirm the hypothesis HYPOTHESIS vs. THEORY vs. LAW: • A hypothesis is the initial prediction of what and why something happens, to which a controlled experiment is done to test if it is valid. • But a hypothesis that is tested critically under many conditions by many different people and still holds valid is considered a THEORY o A theory is generally accepted to be true by a large community of scientists o E.g. Cell Theory, Germ Theory, Evolution • Then if a theory is further tested and is confirmed over many years by a large number of investigators, and is proven to be undoubtedly true, then it is then considered a LAW o E.g. Law of Gravity, Law of Thermodynamics, etc. MICROSCOPY: • One method to which we can more easily view cells through the microscope is DIC (differential interference contrast) o It is the use of stains to allow cells to be more easily seen, especially within tissue o However, this kills the cells, so you will never view a live specimen • Another method is the use of light to enhance the visualization of the cell o Fluorescent stains/proteins can specifically be designed each to detect different biological molecules o These proteins can bind onto their targeted biological molecule and illuminate them o Allows us to see the filaments that hold a cell together • Finally there is the use of ELECTRON MICROSCOPY, which can be differentiated into two forms o Scanning (SEM – Scanning Electron Microscopy)  Allows us to look at the surface of a cell in 3D o Transmission (TEM – Transmission Electron Microscopy)  Allows us to see a cross-sectional (2D) cut of the cell to see the inner workings of the cell THE CENTRAL DOGMA: • All cells follow the same central dogma o DNA replication  RNA transcription  Protein translation BASIC PROPERTIES OF CELLS: RRMGHHHU • Reproduction – Able to reproduce by themselves (mitosis) • Response – Able to respond to environmental stimuli • Metabolism – Acquire and use energy to carry out metabolic reactions • Growth – Engage in many mechanical activities in its lifespan • Homeostasis – Capable of self-regulation • Highly complex and organized • Have many processes that are conserved at the molecular level • Use of the Central Dogma o DNA replication  RNA transcription  Protein Translation THE TWO CLASSES OF CELLS: I: THE PROKARYOTE: • General characteristics: o No membrane-bound nucleus; DNA stored in a region of the cytoplasm called nucleoid o No membrane-bound organelles internally o Naked DNA not associated with proteins and is therefore a singular circular strand o Most have a cell-wall as well as a plasma membrane o Most diverse cell group • Two domains of prokaryotes: o (Eu)bacteria:  All have cell walls except for mycoplasma  Scale of size: mycoplasma (smallest) --------------> Cyanobacteria (most complex) • Cyanobacteria are capable of carbon and nitrogen fixation o Archaebacteria (archae):  All have cell walls  Possess genes and several metabolic pathways that are more closely related to those of eukaryotes  Best known are extremophiles, but other prominent species are: • Halophiles (Great Salt Lake, Dead Sea) • Acidophiles • Themophiles (source of Taq polymerase) II: THE EUKARYOTE: • Generic Animal Cell: • Parts and Functions of the Animal Cell: o The Nucleus – Stores and protects genetic information which control cell functions  Nucleolus – transcribes rRNA and combines it with proteins to form almost-complete ribosomes  Chromosomes – stores the genetic information of the cell o Endoplasmic reticulum  Produces membrane proteins and proteins for secretion (it is rough when there are bound ribosomes, and smooth when there are not) o Ribosome  synthesize proteins by translating mRNA o Golgi Apparatus  modifies and sorts proteins, and places them into vesicles to be secreted o Lysosome  digests/hydrolyzes structures that are not needed in the cell o Peroxisome  Small membrane-enclosed vesicles that provide a contained environment where reactions using hydrogen peroxide are generated or degraded. o Mitochondrion  produce cellular energy in the form of ATP by aerobic respiration o Cytoskeletal element  The system of crisscrossed filaments of protein  Gives the cell: • Mechanical strength • Shape  Guides movement of cell  Transports molecules from one location to another in the cytoplasm  Determines the position of organelles inside cell • Generic Plant Cell: • Parts and Functions of the Plant Cell: for overlapping parts see animal cell o Vacuole – functions as storage, where enclosed compartments are filled with water containing inorganic and organic molecules including enzymes in solution; also maintains turgor pressure against the cell wall o Chloroplast – have chlorophyll within them that allows plants to perform photosynthesis o Cell Wall – made of cellulose (or in some cases chitin) and provides protection and support for the plant cell and also makes it harder for the cell to burst under high pressure. • Four Groups of Eukaryotes: Remember “FAPP” o Fungi  Can be single celled (e.g. yeast) or multi-celled (mushrooms)  Have cell walls  Are heterotrophs (i.e. dependent on external source of organic compounds (food)) o Animal  Multi-cellular  No cell wall  Are heterotrophs o Plants  Multi-cellar  Have cell walls  Are autotrophs (i.e. capable of producing its own form of food) o Protists  Mostly single celled, but some live as colonies  Includes algae, water molds, slime molds, and protozoa • Compartmentalization in Eukaryotic Cells: o Cytoplasm  Includes everything between the plasma membrane and the nuclear membrane (i.e. all membrane-bound organelles excluding the nucleus) o Cytosol  Refers to only the fluid component and no organelles o Endomembrane system – internal membranes that are either in direct contact or connected via transfer of sac structures of the membrane (vesicles)  This system comprises of: the nuclear envelop, plasma membrane, the Golgi apparatus, the endoplasmic reticulum, lysosomes, and vacuoles (in plants only). • Compartments within Eukaryotic Cells: o Nucleus – stores genetic information, and also the site of RNA transcription o Endomembrane System – creates inner compartments with different functions inside of the cell o Mitochondria – generates energy to power the cell through ATP o Chloroplasts – capture energy from the sun and converts into carbohydrates o Cytoskeleton – regulates cell shape, guides movement of the cell, and guides movement of organelles or other materials within the cell – especially important to chromosome movements during mitosis • Transcription and Translation o Occurs in separate compartments in eukaryotes  Synthesis of mRNA occurs in the nucleus  The mRNA then moves into cytoplasm by going through a nuclear pore  It will then be translated by a r
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