Biology: Molecules and Cells week of 2/22
Biology: Molecules and Cells week of 2/22 200001
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This 6 page Class Notes was uploaded by Audrey Notetaker on Friday February 26, 2016. The Class Notes belongs to 200001 at Boston College taught by Danielle Taghian in Spring 2016. Since its upload, it has received 37 views. For similar materials see Molecules and Cells in Biology at Boston College.
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Date Created: 02/26/16
Chapter 7 and 8: Cytoskeleton 2/22/16 Cytoskeleton: complex network of fibers that helps maintain cell shape by providing structural support acts like a transportation highway for the cell It can change to alter cell shape, transport materials into cell or to move the cell so match the function of the cell Three types of cytoskeletal elements: 1. Actin filaments (smallest)/microfilaments: two strands of a polymerized protein that twist around each other to form actin Maintain cell shape by resisting tension (pull), moves cells via muscle contraction or cell crawling, divide animal cells in two, move organelles and cytoplasm in plants, fungi, and animals Motor protein myosin: allows for actin filaments to be involved with movement Main thing that allows for cell movement as it pushes out cytoplasm for it to attached to something then pull itself towards that thing Allows for cytokinesis: cell division/pinching membrane in two 2. Intermediate: defined by size instead of composition; many types depending on type of protein; provides structural support; fiber wound with thicker cables 3. Microtubules: can allow for transport of vesicles (requires ATP and kinesin); large hollow tubes made of tubulin dimers: polar (+ and end), dynamic, usually grow at plus ends. Add tubulin to grow microtubules. Largest of the three Kinesin motor protein: converts chemical energy in ATP into mechanical work (movement); walk along mictrotubule towards + end. Provides stability, involved in movement, structural framework, a track for intracellular transport Originate from microtubule organizing center and grow outward dradiating throughout the cell viscous, gelllike area Animal cells have one mictrotuble organizing center centrosome which have two bundles of mictrotubles centrioles During cell division, mictrobules move chromosomes from original cell to each resulting cell Taxol: mitotic inhibitor used in cancer chemotherapy. Paclitaxel stabilizes microtubules (prevents them from being dynamic/change), interfering with the normal breakdown of microtubules during cell division (prevents the cells from dividing) Polarized cell: everything is oriented towards a certain part of cell Flagella: allows for movment of the cell; long, harlike progjections from the cell surface Baterical: Eukaryotic: Cilia: similar to flagella *Cells typically have one or two flagella but may have many cilia *Cells look the way they do because they have a certain function, cell shape correlates with cell function *Animal cells secrete extracellular matrix (ECM, proteins) which depend on cell. Allow for structural support, cell migration, communication, adhere together, forms proteinprotein attachments that link the ECM to the cytoskeleton Chapter 8: Extracellular Matrix 2/24/16 Extracellular matrix: cells secrete, assemble and remodel an insoluble network of proteins. Provides a pliable but resistant scaffold for the organization of cells in tissues. Decides whether cells will proliferate, or move. Functions: structural support, helps cells stick together, cell migration, cell:cell communication (signaling), proteinprotein attachments linking ECM to cytoskeleton Intestinal epithelium: good model system to study; allows for food absorption and breakdown; undergoes shear forces, compression (squeezing), tension (pulling apart), torsional (twisting) *ECM is a fiber composite, comprised of 5 major groups of proteins with multiple isoform. Like putting steel in concrete so the rebar ca handle tansile forces. Collogens (structural support for cells) Elastin: elasticity to tissues, such as blood vessels so that they don't tear apart Proteoglycans: hydration so that things don't dry out and become brittle and more likely to fall apart or crack Hyaluronan: resist compression Adhesive glycoproteins: resist tensile forces (rebar in concrete) Fibronectin: connects cells to collagen which allows them to move through ECM Basement membrane: semipermeable and physical support 2D netweork for epithelium. Like a rug/sheet that wraps around nerves and blood vessels. Anchors cells of epithelium to the dermis (connective tissue) underneath. Protection: mechanical barrier preventing malignant cells from moving and attaching elsewhere *If an animal lacks any collagen or proteins in basemement membrane will die from defects in basal lamina (BL). Connective tissue ©: supports, connects, or separates different types of tissues and organs in the body. All connective tissue consists of three main components: fibers (elastic and collagenic), ground substance (viscous fluid), and cells *Bioengineeringspatial placement of cells is dependent on underling geometry of basement membrane like the foundation that supports a building. Basement membrane determines 3D shape of cells *ECM is strengthened by connections to transmembrane proteins. *Actin protein filaments in the cytoskeleton bind to transmembrane proteins which bind to ECM. This helps keep individual cells in place and helps adjacent cells stick together Integrin: bound to actin filament of cytoskeleton through plasma membrane; physical attaching ECM to the cell Collagen: like a cable stay and suspension bridges; many cables twisted together. Three proteins twisted around one another to give it strength, strongest tissue in the body (can hold more than 10 kg) mostly foundn in fibrous tissues such as tendon, ligament and skin and also in cornea, cartilage, bone, blood vessels, and the gut and intervertebral disc; elastic and bendable. Its about 2535% of bodyprotein content. Each polypeptide has a helical conformation that Is more open than an alpha helix to form a superhelical cable Side chains of lysine form a covalent bond so the three strands are covalently bonded Fibronection: comes from fibroglass; extracellular matrix glycoprotein that binds to membrane spanning receptor proteins called integrins; can bind collagen; durable, tough, insoluble; cell adhesion, growth, migration and differentiation like most extracellular matrix proteins; forms blood clots (forms a net like structure that forms a barrier so blood can't leave body, also helps prevent infection) Tumor cells look similar to primary tumor even if they are in the blood stream or other tissues. How do cells find their way into the blood? If you can stop them from moving from primary tissue into blood stream then you can stop cancer from metastisizing (moving into the rest of the body) you can cure it more likely Tumor cell degrades collagen of cell by releasing proteinases which chews through ECM Tissues: groups of cells that serve a similar function Tight junctions: prevent material from flowing between; physical barrier between cells; maintain cell polarity; form specialized proteins in the plasma membrane of adjacent animal cells helps adhesion of cells Proteins line up and bind to each other F14 tomcat: wings don't rip off because it is attached to airframe via rivets Adherens junctions: physical interaction between two cells that hold the two together tightly; resist shearing forces; can appear as bands encircling the cell (zonula adherens) or as spos of attachement to the axtracellular matrix (adhesion plaques); has hundreds of cadherins Desmosomes: made of proteins that link the cytoskeletons of adjacent cells "adhering sports" Domain maps of cadherins: generally interact with each other; similar to a zipper Cell communication via cellcell gaps: direct connections between cells in tissues allowing cells to communicate; membrane proteins (connexins) connect the membranes hat can open and close; forms channels that allow the flow of small molecules between cells (allows the heart cells to beat as one) Metastasis: integrin receptors turn on and stimulate endocytosis of cadherins meaning that their taken off of cell surface and they fall apart and prevent other cadherins from being added on to membrane Chapter 8 2/26/16 Desmosomes: connects cytoskeletons Gap junctions: acts as channels between cells Long distance cells: coordinates the activities of cells, tissues, and organs in different parts of a multicellular organism Hormone: information carrying molecule secreted from cell that circulates in the body and acts on target cells far from the signaling cell Small molecules emitted by one cell and picked up by another Parocrine signaling SIGNAL TRANSDUCTION WILL BE ON TEST Long distance messengers: different hormones have different hydrophilicity/lipophilicity Steroid hormones: small hydrophobic steroids can pass through membrane easily Signaling molecule Ligand: chemical message that gets received on receptor of another cell Non steroid hormone Receptors: found in cell membrane or cytosol (on the inside so that if it passes through membrane, it can bind to inside receptor to get in) Hormones and other cellcell signals bind to receptors Different cells have different receptors for specific signals (some cells don't have specific receptors because they don't need it) Receptors that bind to steroid hormones are located inside the cell, but most are in the ECM Binding of hormone/signal > receptor changes shape (activated) > information is relayed Types of receptors: (be able to draw them) Hormone Gprotein Slide Slide Lipidsoluble steroid hormone: can pass through the membrane and then bind to receptor to go into nucleus *activated: changed shape and then something can bind to it or it can serve another function
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