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BIO206H5 (60)
Chapter 1

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University of Toronto Mississauga
George S Espie

Pages: 1-38 Chapter 1: Introduction to cells Pages: 1-38 Cells:small, membrane in closed units filled with a concentrated aqueous solution of chemicals and endowed with the ability to create copy of them. Cells: fundamental units of life Main question: what life is and how it works? Unity and diversity of cells  Cells vary in appearance and function.  Size: in micrometers.  Examples  Paramecium: single celled, moves by beating cilia.  Branched nerve cell, receives thousands of signals  Human white blood cells: approach and engulf red blood cells  Small bacterium  Living cells have a similar basic chemistry  Cells are living things in the sense that they can grow reproduce and convert energy from one form to another.  In all living things, genetic instructions-genes- are stored in DNA molecules.  Written in same chemical code  Constructed out of same chemical building blocks  Interpreted by same chemical machinery  Duplicated in the same way  DNA polymer chain is made out of 4 monomers (nucleotides)  DNA instructions are transcribed into set of polymers called RNA.  Serves as mRNA: messages carried by this polymer chain are translated into protein.  Protein: structural support, catalysts and molecular motors.  Made from same set of 20 amino acids but different sequences giving diff 3-D shape or conformation. Pages: 1-38  Viruses  Contain genetic info in the form of DNA or RNA  Have no ability to reproduce on its own  Copied by parasitizing the reproductive machinery of the host cell.  Inert and inactive outside their host cells  All cells evolved from the same ancestor  DNA replication  2 daughter cells  Copying is not always perfect, may cause mutations  Mutations can create offspring that are changed for worse, better or neutral  Survivor genes : genes of next generations  Sexual reproduction: 2 cells fuse, DNA mixed and then new combination is presented in next generation Evolution: the process by which, living species become gradually modified and adapted to their environment in more and more sophisticated ways.  Genes provide the instruction for cellular form, function and complex behavior.  Cell’s genome: the entire set of genetic info in its DNA.  It’s a genetic program that instructs cell how to function.  Diff types of cells: fat, skin, bone  ^ All contain identical copies of DNA.  They vary in terms of their use of the genetic instruction.  Diff cells express diff genes Cells under microscope  Light microscope (17 century) vs electron microscope(1930s)  Electron microscope transmits beam of electron instead of light  The invention on light microscope led to the discovery of cells  Cell theory 1. The cell is the smallest unit of life 2. All living things are made up of cells 3. New cells arise only from pre-existing cells  Cells, organelles and even molecules can be seen under light microscope  Cells separated by extracellular matrix: dense material made of protein fibers embedded in polysaccharide gel.  Cell components differ in terms of refractive index.  General cell anatomy  5 nm thick enclosing membrane surrounding cell  Internal membranes : membrane surrounding organelles  Plasma membrane: external membrane Pages: 1-38  Types of microscopes 1. Light microscope: magnifies up to 1000 times and resolves as small as 0.2micrometers. 2. Transmission electron microscope: electron microscope used to look at thin section of tissue. 3. Scanning electron microscope: scatters electrons off the surface of the sample and used to look at surface details of sample and other structures The prokaryotic cell  Presence or absence of nucleus used as a fundamental classification of living things.  Prokaryotes: organism whose cells don’t have a nucleus.  The terms Bacterium and prokaryotes are interchangeable  Archaea are related to bacteria  Diff shapes and sizes of bacteria   Prokaryotes are the most diverse of cells  Most are single celled  Diverse in terms of chemistry  Aerobic (using oxygen) vs anaerobic prokaryotes species that live Bacteria in soil or make us ill Prokaryotes archaea live in harsh conditions The eukaryotic cell  Organisms whose cells have nucleus.  Plants, animals and fungi are formed from eukaryotic cells. Table: structure and function Pages: 1-38 Structure Diagram Function and description Nucleus  Stores info of cell  Most prominent organelle  Contains most of the DNA of eukaryotes  Enclosed within 2 membrane that form nuclear envelope  In light microscope giant DNA molecules become visible as chromosomes  RNA synthesized in nucleus  Ribosome synthesis Mitochondria  Generate energy to power the cell  Present in all eukaryotic cells  Contain their own DNA  Reproduce by dividing into 2  Thought to evolve from engulfed bacteria in ancestral eukaryotic cell.(symbiotic relationship)  Intestinal parasite giardia lack mitochondria. Chloroplast  Found in plant and algae cells, capture energy from sunlight.  Contain internal sacks which contain chlorophyll.  Photosynthesis  sugar + oxygen  Chloroplast contain their own DNA  The sugar is then used by mitochondria to produce energy  Thought to evolve from
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