Lectures 1-4 (midterm notes)

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University of Toronto Scarborough
Biological Sciences
Tanya Da Sylva

Cells: Rayana Alawie 1.1 The Discovery of Cells: Robert Hooke: Discovered cells by looking through a microscope at cork cells Leeuwenhoek: the first to examine a drop of pond water under the microscope and observe the teeming microscopic animalcules = bacteria. Matthias Schleiden: (1839) a German lawyer turned botanist concluded that plants were made of cells and that the plant embryo arose from a single cell. Schwann concluded that the cells of plants and animals are similar structures and proposed these two tenets of the cell theory: All organisms are composed of one or more cells. The cell is the structural unit of life. Rudolf Virchow, a German pathologist, had made a convincing case for the third tenet of the cell theory: Cells can arise only by division from a preexisting cell. 1.2 Basic Properties of cells: Cells are the smallest units of life. Death is most basic property of life. Cells obtained from a tumor called HeLa cells (by George and Martha Gey): became the first human cells to be kept in culture for a long time. (grown in vitro = outside the body ina cultural medium) Cells are Highly complex and Organized: o More complex= less tolerance of errors. o Complex structure matches the function of the cells o Ex epithelial cells lining the intestine have microvilli on the apical ends of the cells that facilitate the absorption of nutrients. Apical ends have protein actin to help project the microvilli outward. Basal end = a lot of mitochondria Cells Possess a Genetic Program and the means to use it: o Information is packaged into a set of chromosomes that occupies the space ofa cell nucleus o Gene store and contain info. For constructing cellular structures. o Mutations lead to biological evolutions Cells are capable of producing more of themselves: o Most cells reproduce via mitosis into daughter cells. www.notesolution.com Cells: Rayana Alawie o Some cells (oocytes) undergo division were only half genetic material is distributed. Cells Acquire and utilize energy: o Light energy is converted by photosynthesis into chemical energy that is stored in energy-rich carbohydrates, such as sucrose or starch. o Cells expend an enormous amount of energy simply breaking down and rebuilding the macromolecules and organelles of which they are made. (turnover in order to maintain integrity of cell components.) Cells Carry out a variety of chemical reactions: o Via enzymes. o Sum of chemical reactions in a cell = Metabolism. Cells engage in mechanical Activities: o Materials are transported, assembled and disassembled and in many cases the cells actually move. Motor Proteins. Cells are able to respond to stimuli: o Receptors help cells interact with other cells and the environment. Cells are capable of self regulation: o Most evident when cells break down. o EXP: Hans Driesch, a German embryologist, found that he could completely separate the first two or four cells of a sea urchin embryo and each of the isolated cells would proceed to develop into a normal embryo. Cells Evolve: o Thought that cells evolved from a pre-cellular life form which evolved from nonliving organic materials. 1.3 Two Fundamentally Different Classes of Cells: 1) Prokaryotic: (pro-before; karyon-nucleus) - Ex: Bacteria, Cyanobacteria - Structurally simpler. 2) Eukaryotic: (Eu- true) - Ex: Protists, Fungi, Animals, Plants - Structurally more complex www.notesolution.com Cells: Rayana Alawie Similarities between Eukaryotes & Prokaryotes: o Both types of cells share common structural features -cell membrane, cell walls (same function, different chemical composition): Ribosomes: Non membrane bound that help make protiens. o Both types of cells share an identical genetic language o Both types of cells share a common set of metabolic pathways (photosynthesis and protein synthesis, glycolysis, TCA cycle) o ATP located in the plasma membrane of prokaryotes and the mitochondrial membrane of eukaryotes) o Proteasomes (protein digesting structures) of similar construction (between archaebacteria and eukaryotes) Characteristics That Distinguish Eukaryotes From Prokaryotes o Eukaryotic cells are internally much more complex (structurally and functionally) - Ex: ER= cells protein and lipids are manufactured. , Golgi= materials are sorted modified and transported., Lysosomes, Endosomes, Peroxisomes, glyoxisomes, mitochondria, chloroplast, flagella, cilia - Prokaryotes have nucleoid (poorly demarcated cell region) o Eukaryotes have complex cytoskeletal system - Contains microfilaments, microtubules and motor proteins, Endo and phagocytosis. o Most eukaryotes have significantly more DNA : - Prokaryotes have a single circular chromosome. - Eukaryotes DNA is tightly compressed into chromatin. o No mitosis or meiosis in prokaryotes: In eukaryotes: - Presence of 2 copies of genes per cell (diploid) - Uses micro tubules - Prokaryotes can reproduce non sexually except conjugation (forms bridge pilus and exchange genes) Types of Prokaryotic Cells: 1) Archaebacteria: a. Extremophiles: live in inhospitable environemnts b. Methanogens: Convert CO2 and H2 into methane c. Halophiles: Love salty environments d. Acidophiles: Love acidic environments e. Thermophiles: Love high temp. environments f. Hyperthermalophiles: live in hydrothermal vents of the ocean floor 2) Bacteria (Eubacteria): a. Mycoplasma: smallest known cells www.notesolution.com Cells: Rayana Alawie b. Cyanobacteria: most complex contain membranes similar to those of the membranes of a chloroplast therefore they can photosynthesize by splitting the water. Also Nitrogen fixation chloroplasts evolved from symbiotic cyanobacteria Types of Eukaryotic cells: Cell Specialization: Eukaryotic cells are believed to be descended from prokaryotic cells Endosymbionts (via phagocytosis) 1) Unicellular Organisms: 2) Multicellular Organisms: a. Differentiation: process of specializing cells i. Pathway of differentiation followed by each embryonic cell depends on the signals it receives from the surrounding environment. ii. Result: Different cells structure = Specialized functions. iii. Ex: red Blood cell = disc shaped + haemoglobin to transport oxygen iv. The #, appearance and location of the various organelles can be correlated with the activities of the particular cell type. v. Cells will have the same house-keeping Proteins for metabolism Aerobic Prokaryote (+mitochondrion) Aerobic heterotrophic prokaryote (+membrane invagination) Pro-eukaryotic cell (+ER) Protist Fungal animal cells (+Photosynthetic cyanobacterium) Algal and plant cells The Sizes of Cells and Their Components - Micrometers/ Micron (m; = 10-3mm): Ex Mmitochondion, bacteria, epithelial cell -6 - Nanometer (nm; = 10 mm): Ex Ribosome, Myoglobin, DNA - Angstrom ( ; 10 mm): Ex Water molecule 1.4 Viruses: Dimitri Ivanovsky: forced sap from a diseased plant through filter paper. The filter paper was still infective which led him to conclude that there are pathogens smaller than the smallest bacteria known as viruses: obligatory intracellular parasites. Properties of a virus: - Cannot reproduce, metabolize outside of host cell. www.notesolution.com
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