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Chapter Four Student Presentations The Nucleus Section 4.4 Nucleolus • • • The nucleolus is where protein and RNA molecules are being constructed Protein and RNA are subunits from which ribosomes are built and pass through the pores of the nuclear envelopes and reach the cytoplasm. Ribosomes form at times of protein synthesis in the cytoplasm. QuickTime™ and a decompressor are needed to see this picture. Nuclear Envelope • • • • Two outer membranes surrounding the nucleus are called the nuclear envelope DNA is anchored to envelope which keeps it organized Lipid bilayers (the envelope) keeps out and control the flow of water soluble substances in and out of nucleus Pores let in small molecules QuickTime™ and a decompressor are needed to see this picture. Chromosomes • Chromosomes, which are defined as DNA molecules and their associated proteins, are found in the nucleus. Chromatin is known as the cells collection of DNA. • They have two forms; when the cell is not dividing, chromosomes appear as thin strands inside the nucleus. When the cell is dividing, the chromosome condenses into a double helix structure. QuickTime™ and a decompressor are needed to see this picture. Section 4.5: The Cytomembrane System By Andrew Lindquist, Nobska Goodhue, Anna Bortnick, and Danny Flannigan (Spell checker) The Cytomembrane System is a series of organelles in which lipids are assembled and new polypeptide chains are modified into final proteins. These products are shortened and shipped to their final destinations. Endoplasmic Reticulum • • • • • • Functions of the Cytomembrane begin in the endoplasmic reticulum (ER) In animal cells, the ER is continuous with the nuclear envelope, and extends through the cytoplasm. Rough ER are typically observed as being arranged into flattened sacs with many ribosomes attached. These ribosomes synthesize all new polypeptide chains. Once these chains are in the rough ER, enzymes may attach oligosaccharides and other side chains to them, and these final proteins are secreted by many cells. The smooth ER is free of ribosomes and curves through the cytoplasm, where most lipids are assembled. Golgi Bodies • • • • • Located in the cytoplasm, in eukaryotic animal cells Golgi bodies are where enzymes put finishing touches on proteins and lipids for usage in the body Finished proteins and lipids are packaged inside vesicles to ship to specific locations Golgi bodies are composed of a series of flat, membrane-bound sacs Vesicles form as sections of the membrane of the top sac break away into the cytoplasm QuickTime™ and a decompressor are needed to see this picture. QuickTime™ and a decompressor are needed to see this picture. Variety of Vesicles • Vesicles are tiny, membrane sacs that move through the cytoplasm • Lysosome are organelles of intracellular digestion and buds from the Golgo membranes of animal cells and certain fungal cells they contain diverse enzymes that speed the breakdown of proteins, complex carbohydrates, nucleic acids, and some lipids • Peroxisomes- tiny sac of enzymes that break down fatty acids and amino acids • Hydrogen peroxide, a potentially harmful product, forms during the reactions, helps break down alcohol QuickTime™ and a decompressor are needed to see this picture. Mitochondria •The barista of Eukaryotic cells •Creates ATP molecules (coffee), which are energy carrying nucleotides •Mitochondria are located in the cytoplasm of a eukaryotic cell Structure • 2 compartments: 1. outer membrane-->holds Hydrogen Ions and controls the flow of energy 2. inner membrane-->folds on itself, creating the cristae -->energy releasing reactions happen here Function • Mitochondria break down organic compounds into carbon dioxide, water • They also form ATP molecules-->these are energy carrying nucleotides • Energy demanding cells have more mitochondria • Power houses of eukaryotic cells • Mitochondria require oxygen Chloroplasts and other Plastids •Plastids are organelles that specialize in photosynthesis or function in storage. Including: chloroplasts, chromoplasts, amyloplasts. •Of all eukaryotic cells only photosynthetic cells have chloroplasts. Chloroplasts are generally oval or disk shaped. •These organelles convert sunlight into ATP energy which is used to make sugars and other organic compounds. •Chloroplasts: Primarily contain chlorophylls (photosynthetic pigments which reflect green light) •Chromoplasts: lacks chlorophylls but have an abundance of carotenoids (source of red or yellow colors in plants). •Amyloplasts: lack pigments. •Chloroplasts are apart of the innermost membrane. Plant Cell Structure • • • • • • • • • • Plastids- category of organelles that specialize in photosynthesis Three types: chloroplasts (oval or disc shape), chromoplasts, and amyloplasts Only photosynthetic have plastids Stroma (semi-liquid interior) Stroma surrounded by two outer membrane layers In stroma is a third membrane layer-thylakoid membrane: folded disc shape compartments Compartments stack. Each stack is a granum light-trapping pigment enzymes (chlorophylls, carotenoids) inside stroma, ATP energy is used Central vacuole- fluid filled. stores amino acids,sugars, ions, and toxic wastes Photosynthesis • Photosynthesis is the process of converting sunlight to energy • Of all eukaryotic cells, only photosynthetic ones have chloroplasts, which are used to convert sunlight into energy. • The first stages of photosynthesis starts at a thylakoid membrane, where pigments, enzymes and other proteins trap light, and convert it and store it in the form of ATP. • The most abundant photosynthetic pigments are chlorophylls, which reflect or transmit green light. • Inside the stroma, ATP energy is used to make sugar, starch and other organic compounds. • The abundances of certain photosynthetic pigments determine what color a plant is. An example would be carotenoids which, in abundance can make a plant appear red, yellow, or green. Cytoskeleton • • • • Interconnected system of fibers, threads and lattices between nucleus and plasma membrane of eukaryotic cells Gives cells internal organization, shape and capacity to move Two classes of cytoskeletal elements: microtubules and microfilaments Animal cells also have intermediate filament—imparts mechanical strength to cells and tissues Microtubules and Microfilaments • • MICROTUBULES Long, hollow, cylinder—25 nanometers wide Made of tubulin monomers – • • Largest cytoskeletal element Tubulin: protein of 2 chemically distinct polypeptides folded into a globular shape Function: – Govern the division of cells and some aspects of their shape as well as many cell movements • MICROFILAMENTS Thinnest cytoskeletal element – • • 5-7 nanometers wide Made of two polypeptide chains helically twisted together Function: – – Take part in movements, especially those that affect the cell surface Contribute to development and maintenance of animal cell shape Myosin and Intermediate Filaments • MYOSIN Monomers of other proteins can be attached to the tubulin and actin that make up the microtubules and microfilaments – Ex: Monomers of myosin, dynein, or other motor protein attach to surface of microtubules and microfilaments in ways that cause cell movement • • • • • INTERMEDIATE FILAMENTS Most stable part of the cytoskeleton 8-12nm wide 6 known groups: desmins, vimentins, lamins, cytokeratins are 5 Mechanically strengthen cells Present in only certain animal tissue – Can be used to identify cells The Structural Basis of Cell Motility Chapter 4.9 By Diva, Olivia, and Timmy Mechanisms of Cell Movements • Microfilaments, microtubules, or both take part in most aspects of mobility through three mechanisms • 1. Length of a microtubule or microfilament can grow or diminish by the controlled assemble or disassembly of its subunits • 2. Parallel rows of microfilaments or microtubules actively slide in specific directions • 3. Microtubules or microfilaments shunt organelles or parts of the cytoplasm from one location to another • Pseudopods: temporary lobe-like protrusions from the body inside each lobe, microfilaments Flagella and Cilia • Flagellum and Cilia: structures for cell mobility • Have a ring of nine pairs or microtubules and a central pair • System of spokes and links stabilize the array • Centriole: barrel shaped structure that is one type of microtubule producing center • Basal body: refers to the location of the centriole • Flagella - longer and less profuse, sperm use the flagella as a tail to move • Cilia - stir air and fluids Flagella, Cilia and the Basal Body Centriole Eukaryotic Cell Walls -The cell wall is a structural component, which wraps entirely around the plasma membrane. -Not only does it offer support physically to the cell owner, but it also protects it. -The wall is porous so that water and solutes can move to and from the membrane easily. -The primary wall consists glue-like secretions (polysaccharides, glycoproteins, and cellulose) which combine together to form the wall. This wall is thin and plyable. -Deposits on the primary wall’s inner surface combine to form a rigid, secondary wall, which reinforces cell shape. Matrixes Between Animal Cells • • • • Animal cells don’t have cell walls. Therefore… Matrixes are composed of cell secretions and materials from surroundings. These are the ‘walls’ Cartilage is made up of scattered cells, this forms collagen fibers in a ‘ground substance’ of modified polysaccharides An extensive matrix yields a wide separation of cells QuickTime™ and a decompressor are needed to see this picture. Cell-to-Cell Junctions • • • The only contact a cell has with the outside world is through its plasma membrane In plant cells tiny channels connect adjacent cell’s cytoplasm In animal cells there are three junctions; Tight junctions, adhering junctions, and gap junctions QuickTime™ and a decompressor are needed to see this picture. – Tight junctions link cells in the epithelial tissue, they prevent water soluble substances from leaking through – Adhering junctions join cells in organs subjected to stretching – Gap junctions link the cytoplasm of neighboring cells allowing for a quick transfer of signals and substances