BIOL 1020, Fall 2016, Zanzot Chapter 6 Notes
BIOL 1020, Fall 2016, Zanzot Chapter 6 Notes BIOL 1020-001
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This 6 page Class Notes was uploaded by Tamia Kettles on Saturday September 17, 2016. The Class Notes belongs to BIOL 1020-001 at Auburn University taught by James Zanzot in Fall 2016. Since its upload, it has received 110 views.
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Date Created: 09/17/16
Tamia Kettles BIOL 1020 Fall2016 Zanzot Chapter 6: A Tour of the Cell This is a cover of chapter 6 in the Campbell Biology book. These notes are strictly from the book and not from any lecture Dr. Zanzot may have given, so there may be material that he has covered that is not here, and vice versa. I am not allowed to use the images from the book in these notes since they are all copyrighted, but they are in the book. There may have been points others may feel are important that I left out, mistakes I have made, or questions that need to be asked, so feel free to email me at email@example.com . 6.1 Microscopes were invented in 1590 and further refined in the 1600s The microscopes first used by scientist were light microscopes (LM), where visible light is passed through specimen and then through glass lenses Three important parameters in microscopy are magnification, resolution, and contrast Magnification is the ratio of an objects projected size to its real size Resolution is a measure of the clarity of an image Contrast is the difference in brightness between the light and dark areas of an image. Contrast can be improved by staining or labeling the cell components Scanning electron microscopes (SEM) focuses an electron beam on the surface of a specimen to produce a 3D image Transmission electron microscopes (TEM) focuses a beam of electrons through a very thin section of the specimen Cell fractionation takes cells apart and separates organelles and other subcellular structures from one another using a centrifuge 6.2 Organisms of the domains Bacteria and Archaea are made of prokaryotic cells Protist, fungi, animals, and plants are made of eukaryotic cells All cells are bounded by a plasma membrane, contain cytosol, contain chromosomes, and have ribosomes Most of the DNA in eukaryotic cells is contained in the nucleus, while in a prokaryotic cell, the DNA is in a region called the nucleoid The interior of either type of cell is called the cytoplasm In the cytoplasm of eukaryotic cells are membrane bound organelles, which are absent in prokaryotic cells The plasma membrane functions as a selective barrier that allows the passage of enough oxygen, nutrients, and waste to service the cell according to its size 6.3 Tamia Kettles BIOL 1020 Fall2016 Zanzot The nucleus contains most of the genes in eukaryotic cells, and is enclosed by the nuclear envelope (a double membrane), which separates the contents of the nucleus from the cytoplasm The nuclear side of the nuclear envelope is lined by the nuclear lamina, an array of protein filaments that maintain the shape of the nucleus Chromosomes are structures that carry the genetic information within the nucleus Chromatin is the DNA and proteins that make up chromosomes When cell division is not occurring, the chromatin is a diffused mass The nucleolus appears through the EM as a mass of densely stained granules and fibers adjoining part of the chromatin In the nucleolus, ribosomal RNA (rRNA) is synthesized from instructions in the DNA and proteins imported from the cytoplasm are assembled with rRNA into large and small subunits of ribosomes Ribosomes carry out protein synthesis Free ribosomes are suspended in cytosol and bound ribosomes are attached to the outside of the ER or nuclear envelope. 6.4 Endomembrane system includes the nuclear envelope, the endoplasmic reticulum, the Golgi apparatus, lysosomes, various kinds of vesicles and vacuoles, and the plasma membrane Membranes of this system are related either through direct continuity or the transfer of vesicles (sacs made of membrane) Endoplasmic Reticulum (ER): o Accounts for more than half the total membranes in many eukaryotic cells o Consists of a network of membranous tubules and sacs called cisternae o Is continuous with the nuclear envelope o Smooth ER Outer surface lacks ribosomes Synthesis of lipids, metabolism of carbs, detoxification of drugs and poisons, and storage of calcium ions o Rough ER Has ribosomes attached that secrete proteins As a polypeptide chain grows from a bound ribosome, the chain is threaded into the ER lumen through a pore formed by a protein complex in the ER membrane Glycoproteins are proteins with carbs covalently bonded to them Vesicles in transit from one part of the cell to another are called transport vesicles o Golgi apparatus: Warehouse for receiving, sorting, shipping, and some manufacturing Tamia Kettles BIOL 1020 Fall2016 Zanzot Products of ER are stored and sent to other destinations Consists of cisternae The cis face of Golgi stack is for receiving, and the trans for shipping The cis face is usually located near the ER, the trans face gives rise to vesicles that pinch off and travel to other sites Products of the ER are usually modified in the Golgi The Golgi also manufactures some macromolecules o Lysosomes Membranous sac of hydrolytic enzymes that eukaryotic cells use to digest macromolecules Work best in acidic environments within lysosomes Hydrolytic enzymes and lysosomal membrane are made by the rougher then transferred to the Golgi apparatus for further processing Some lysosomes bud on the trans face of the Golgi apparatus Many unicellular eukaryotes carry out digestion through phagocytosis, after which the lysosomal enzymes breakdown the food Lysosome use a process called autophagy to recycle the cells own organic material o Vacuoles Large vesicles derived from the ER and Golgi apparatus Food vacuoles are formed phagocytosis Unicellular eukaryotes living in freshwater have contractile vacuoles that pump excess water out of cells Can act as storage and contain pigments Mature plant cells contain a large central vacuole 6.5 Mitochondria are the sites of cellular respiration Chloroplast are the sites of photosynthesis Endosymbiont theory early ancestor of eukaryotic cells engulfed nonphotosynthetic prokaryotes, which eventually became eukaryotic cells with mitochondria, and the same occurred for plant cells, except with photosynthetic prokaryotes Mitochondria and typical chloroplast have two membranes, contain ribosomes and circular DNA molecules associated with their inner membranes, and they are somewhat autonomous and grow and reproduce within the cell Usually, cells have hundreds, even thousands, of mitochondria The outer membrane of a mitochondrion is smooth, but the inner membrane is convoluted, with infoldings called cristae The mitochondrial matrix is enclosed by the inner membrane, and contains many different enzymes as well as mitochondrial DNA and ribosomes Chloroplast contain the green pigment chlorophyll Tamia Kettles BIOL 1020 Fall2016 Zanzot Thylakoids are interconnected sacs within chloroplast, and stack to form a granum The fluid outside the thylakoids is called stroma, and contains the chloroplast DNA and ribosomes Chloroplast space is divided into three compartments: intermembrane space, the stroma, and thylakoid space Chloroplasts and mitochondria are mobile Chloroplast is a specialized member of a family of closely related plant organelles called plastids Peroxisome a specialized metabolic compartment bounded by single membrane Peroxisomes contain enzymes that remove hydrogen atoms from various substrates and transfer them to oxygen, producing hydrogen peroxide 6.6 Cytoskeleton is a network of fibers throughout the cytoplasm The functions of the cytoskeleton are to give mechanical support, maintain the cell shape, and motility (change in cell location and movement of cell parts) Cell motility generally requires interaction of the cytoskeleton with motor proteins The three main types of fibers that make up the cytoskeleton are: microtubules, microfilaments (actin filaments), and intermediate filaments Microtubules: o Are the thickest of the three types and are hollow rods constructed from tubulin o They grow in length by adding tubulin dimers and can be disassembled to be built elsewhere o Shape and support the cell and can also serve as tracks which organelles equipped with motor proteins can move, and also involved with the separation of chromosomes during cell division In animal cells, microtubules grow out from centrosomes (often located near the nucleus) Within each centrosome is a pair of centrioles, each with nine sets of triplet microtubules arranged in a ring A specialized arrangement of microtubules is responsible for the beating of flagella and cilia, which are microtubulecontaining extensions that project from some cells Cilia and flagella act as locomotor appendages or to move fluid over the surface of tissue Cilia are in large numbers over the cell and are short, while flagella are usually limited to one or a few per cell and are longer Flagella move like the tail of a fish. Cilia move like oars A primary cilium may act like as a signalreceiving antennae, and there is only one per cell Each motile cilium or flagellum has a group of microtubules arranged in the “9+2” pattern, nine doublets of microtubules in a ring, with two single microtubules in the center A basal body anchors the microtubule assembly of cilia or flagella Tamia Kettles BIOL 1020 Fall2016 Zanzot In many animals, the basal body of the sperm’s flagellum enters the egg and becomes and centriole Bending in the flagella or cilia involves large motor proteins called dyneins Microfilaments (actin filaments): o The smallest of the three, solid rod, and are twisted double chains of actin subunits o Role is to bear tension Cortex outer cytoplasmic layer of cell Myosin is a protein that makes filaments that interact to cause contraction of muscle cells Cells crawl along a surface by extending cellular extensions called pseudopodia and moving toward them Cytoplasmic streaming a circular flow of cytoplasm within cells Intermediate: o In between in size of the three o Not found in all eukaryotic cells, only in some animals o Specialize in bearing tension o More permanent fixtures in cell than microtubules or microfilaments 6.7 The cell wall is an extracellular structure of plant cells that distinguishes them from animal cells. It protects the cell, maintains its shape, prevents excessive uptake of water, and hold the plant up against gravity Prokaryotes, fungi, and some unicellular eukaryotes also have cell walls Young plant cells secrete primary cell walls, which are thin and flexible In between the cell walls of other cells is the middle lamella, which glues cell walls together When a cell stops growing, it strengthens its walls by adding a hardening substance to its primary walls or adding a secondary cell wall Animal cells do not have cell walls, but an extracellular matrix (ECM) The most abundant glycoprotein in the ECM of most animal cells is collagen, which forms strong fibers outside the cell Collagen accounts for about 40% of the proteins in the human body The collagens are embedded into a network woven out of proteoglycans, which consist of a small core protein with many covalently attached carbohydrate chains Some cells attach to the ECM by ECM glycoproteins such as fibronectin, which bind to cellsurface receptor proteins called integrins that are built into the plasma membrane Neighboring cells often adhere, interact, and communicate via sites of direct contact Cell walls are perforated with plasmodesmata, which are channels that connect cells. These connections unify most of the plant into one living continuum The three main types of cell junctions in animal cells are: Tamia Kettles BIOL 1020 Fall2016 Zanzot o Tight junctions plasma membranes of neighboring cells are very tightly pressed against each other, bound together by specific proteins o Desmosomes function like rivets, fastening cells together in strong sheets o Gap junctions provide cytoplasmic channels from one cell to an adjacent cell and are similar in function to the plasmodesmata in plants
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