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Chapter 6 The cell: Bound by a selective barrier - Plasma membrane …

- - - - Centrosome: function as compression-resisting girders of the cytooskeleton
        Centrioles: composed of nine sets of triplet microtubules arranged in a ring, there is a pair in each cell
      - Extracellular Matrix (ECM):
        the main ingredients are glycoproteins and other carbohydrate-containing molecules secreted by the cells.
        Collagen - Most abundant glycoprotein in animal cells, forms strong fibers outside the cells (COVALENTLY Bonded Carbs)
        Proteoglycans: consists of a small core protein with many carbohydrate chains covalently attached, so that it maybe up to 95% carb
        Fibronectin: Large, multifunctional glyoprotein found in the blood and tissues that acts as a key component of the extracellular matrix (ECM), playing cruicial roles in cell adhesion, migration, wound healing, and embryonic development.
        Integrins: any of a class of animal transmembrane proteins involved in the adhesion of cells to each other and to their substrate
        
        *Three Main Types of Cell Junctions:
        all types are common in epithelial tissue, which lines the external and internal surfaces of the body
        
        1. Tight Junctions: the plasma membranes of neighboring cells are very tightly pressed against each other, bound together by specific proteins. they provide seals around cells that establish a barrier that prevents leakage of extracellular fluid across a layer of epitheliel cells
        2. Desmosomes: anchoring junction, functions like rivets, fastening cells together into strong sheets
        
        3. Gap Junctions: are communicating junctions in animals cells; most like the plasmodesmata of plants, although gap junction pores are not lined with membrane, they consist of proteins extending from each cell's membrane that form a connecting pore
    - - Mitochondria: sites of cellular respiration, the metabolic process that uses oxygen to drive
        Peroxisome: specialized metabolic compartment bounded by a single membrane; membrane-bound metabolic compartments that specialize in the production of hydrogen peroxide (H2O2) and its conversion to water.
        Chloroplasts: sites of photosynthesis, converts solar energy to chemical energy by absorbing sunlight and using it to drive the synthesis of organic compounds such as sugars from carbon dioxide and water
        EX: Family (Plastid, Chromoplasts, Chloroplasts, Amyloplasts)
        cristae: the convoluted inner membrane of the mitochondria phospholipid bilayer with infoldings, which divides the mitochondrion into two internal compartments.
        
        the first compartment: intermembrane space, the narrow region between the inner and outer membranes
        -- the second compartment: is the mitochondrial matrix, contains enzymes that catalyze cellular respiration, mitochondrial DNA, ribosomes and proteins built into the inner membrane.
        
        thylakoids: inside the chloroplast is a membranous system, flattened and interconnected sacs
        Granum: thylakoids stacked up like poker chips, each stack
        Stroma: The fluid outside the thylakoids
        
        Evidence that supports the prokaryotic origins are:
        
        multiple copies of circular DNA molecules associated with their membranes
        
        can grow and reproduce within a cell
        
        ancestral prokaryote had two outer membranes, which became the double membranes
      - Cell Walls: an extracellular structure of plant cells
        
        protects the plant cell, maintains its shape, and prevents excessive uptake of water
        
        Primary cell wall: a relatively thin and flexible wall
        
        Middle lamella: - a thin layer rich in sticky polysaccharides called pectins
        
        Secondary cell wall: located between plasma membrance and the primary wall, usually deposited in several laminated layers, strong and durable matrix that affords the cell protection and support.
        
        Plasmodesmata: channels that connect cells
- - - - Scanning Electron Microscopy (SEM):
        Show a 3-D image of the surface of a specimen, will kill specimen
        
        Cryo-Electron Microscopy (cryo-EM):**
        Specimens of tissues or proteins are frozen rapidlyy at temps less than -160 degrees Celsius , locking the molecules into a rigid state. A beam of electrons is passed through the sample to visualize the molecules by electron microscopy