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Biology 1201A
Richard Gardiner

Biology: Exploring the Diversity of Life Chapter 2: The cell (PAGES 25 - 47) 2.1. Types of microscopes: 1. Stereoscope: The stereoscope, also called the dissecting microscope and stereo microscope is a light illuminated microscope that allows a three-dimensional view of a specimen. 2. Compound: Like stereoscopes, compound microscopes are illuminated by light. They give a two dimensional view of a specimen under observation 3. Electron Microscopes: An electron microscope (EM) illuminates an object (or specimen) by directing a beam of electrons on it, producing a magnified image of the specimen. Electron microscopes have a greater magnifying power than optical microscopes due to the use of shorter wavelength electrons. Specimens views under this type of microscope may require prior manipulation such as staining and chemical fixation There are various types of electron microscopes, including the reflection electron microscope (REM), scanning electron microscope (SEM), transmission electron microscope (TEM), etc. Cell theory: 1. All organisms are composed of one or more cells 2. The cell is the basic structural and functional unit of all living organisms 3. Cells arise only from the division of pre-existing cells Plasma Membrane - A Bilayer made of lipids with embedded protein molecules - The bilayer acts as a hydrophobic (no affinity to water, “water hating”) barriers to the passage of water-soluble substances - Selected water-soluble substances can penetrate cells through the protein channels DNA - The central region of the cell contains DNA molecules, which store hereditary information. This information is organized in the form of genes – segments of DNA. Cytoplasm - Contains the organelles, the cytosol, and the cytoskeleton o The organelles are small, organized structures each with a specific function o The cytosol is an aqueous solution containing ions and various organic molecules o The cytoskeleton is a protein based framework of filamentous structures:  Maintains cell shape, plays a key role in cell division and chromosome segregation  Dynamic: Dismantles in one part and rebuilds in another, to change cell shape  The cytoskeleton of animal and plant cells contain:  Microtubules (largest in diameter): Assemble from tubulins (types of proteins). Radiate from the centrosome (cell center) and anchor organelles, move chromosomes during cell division (centrioles), maintain shape. Another function is as tracks that guide motor proteins carrying organelles to their destination. In animal cells, the centrosome has a pair of centrioles, each with nine triples of microtubules arranged in a ring  Intermediate filaments: Assembled from intermediate filament proteins. Occur singly, in parallel bundles, and in interlinked networks, either alone in in combination with microtubules, microfilaments, or both. Provide structural support  Microfilaments(smallest): Consist of two polymers of actin subunits wound in a helical spiral. Responsible for cytoplasmic streaming (actively flowing motion of cytoplasm) and dividing the cytoplasm during mitosis - Conducts stimulatory signals (responds to stimuli) Prokaryotes and Eukaryotes (Types of Cells) - Eukaryotic (multicellular) cells contain a nucleus, such as animal, plant, protists and fungi o Has a nucleus – a Nucleoid within a boundary membrane o The cells are about ten times larger than those of prokaryotes o Nucleus is made up of 4 components – Nucleolus (form around the genes coding for rRNA (ribosomal)) > chromatin (combination of DNA and Proteins) > Nuclear Envelope (Separates the nucleus and cytoplasm, connected to the rough ER) > Nuclear pore complex (Protein that exchanges components between and the cytoplasm – A nuclear pore) o Eukaryotic Chromosome – Each DNA molecule and its associated proteins o Endomembrane system consists of:  Endoplasmic Reticulum – An extensive interconnected network of membranous channels and vesicles called cisternae  Rough E.R. – Has ribosomes on the surface. Proteins made on these ribosomes enter the ER lumen (space within the ER) and fold into their final form (quaternary)  Smooth E.R.- Used for the synthesis of lipids that become apart of the cell membrane and modification of by products into more digestible substances  The smooth and rough E.R.s are interconnected  Golgi Complex – Consists of a stack of flattened, independent cisternae. Responsible for packing, “adding postcodes”, and sorting materials for delivery to their final destination (1) Receives proteins within vesicles from the ER to the cis face of the complex (which faces the nucleas) (2) Th
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