BIOL 201 Study Guide 2
BIOL 201 Study Guide 2 BIOL 201-015
Popular in Intro to Cell Biol & Genetics
verified elite notetaker
Popular in Biology
This 21 page Study Guide was uploaded by Kayla Wisotzkey on Friday October 14, 2016. The Study Guide belongs to BIOL 201-015 at Towson University taught by Cheryl D. Warren in Fall 2016. Since its upload, it has received 41 views. For similar materials see Intro to Cell Biol & Genetics in Biology at Towson University.
Reviews for BIOL 201 Study Guide 2
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 10/14/16
Chapter 6 Thermodynamics: the branch of chemistry concerned with energy changes energy: the capacity to do work kinetic energy: the energy of motion… moving objects perform work by causing other matter to move potential energy: stored energy… the capacity to move the sun provides energy to all living things: a) energy absorbed from sunlight is used to combine small molecules into more complex ones b) the sun converts carbon from an inorganic to an organic form c) energy from sunlight is stored as potential energy oxidation: when a molecule or atom loses an electron reduction: when a molecule or atom gains an electron (higher level of energy) The Laws of Thermodynamics st 1 Law of Thermodynamics: energy cannot be created or destroyed; it can only change from one form to another chemical potential energy that is stored in some molecules can be shifted to other molecules and stored in different chemical bonds… some of the energy dissipates into the environment as heat 2 Law of Thermodynamics: some energy is lost as disorder in the universe entropy: all of the disorder in the universe; constantly increasing Free energy: the energy available to do work in any system; the amount of energy available to break and form other chemical bonds the change in free energy allows us to predict whether a chemical reaction is spontaneous or not change in free energy=energy of productsreactants endergonic reaction: the products have more free energy than the reactants… the reaction is not spontaneous because they need an input of energy exergonic reaction: the products have less free energy than the reactants… the reaction is spontaneous an exergonic reaction has an equilibrium favoring the products, and an endergonic reaction has an equilibrium favoring the reactants chemical equilibrium: the forward and reverse reactions proceed at the same rate activation energy: the extra energy needed to destabilize existing chemical bonds and start a chemical reaction to increase the rate of reactions: a. Increase the energy of reacting molecules b. Lower activation energy catalysts: substances that influence chemical bonds to lower the activation needed to start a reaction ATP: the currency that cells use for energy transactions it powers almost every energy requiring process in cells… makes sugars, supplies energy for chemical reactions, transports substances across membranes it is not suitable for long term energy storage structure of ATP: 1. Ribose: 5 carbon sugar that serves as the framework to which the other two subunits are attached 2. Adenine: organic molecule composed of 2 carbonnitrogen rings… weak base 3. Three phosphates How ATP stores energy: the phosphate groups are highly negative charged and repel each other, making the covalent bonds connecting the phosphates unstable when a bond breaks, ATP becomes ADP and a phosphate, and 7.3 kcal/ mole of energy is released cells use ATP to drive endergonic reactions (which don’t proceed spontaneously because their products possess more free energy than their reactants) ATP can provide most of the energy a cell needs: helps generate force in muscles, creates concentration gradients of important ions ATP cycles continuously Enzymes: mostly proteins that act as catalysts to speed up chemical reactions enzymes lower the activation rate of reactions the shape of an enzyme allows it to stabilize an association between substrates (the molecules that will undergo a reaction) by bringing the two substrates together in the correct orientation, which lowers the activation energy required for new bonds to form The enzyme is not changed or consumed in the reaction, so it can be used over and over metabolism: the collection of all chemical reactions By facilitating particular chemical reactions, the enzymes in a cell determine the course of metabolism in that cell active sites: the pockets or clefts on the enzyme that the substrates bind to, forming an enzymesubstrate complex The binding of a substrate makes the enzyme adjust its shape so it fits better with that substrate… this may facilitate the binding of other substrates to the enzyme The steps of catalysis: 1) The substrate (sucrose) consists of glucose and fructose bonded together 2) The substrate binds to the active site of the enzyme, forming an enzymesubstrate complex 3) The binding of the substrate and enzyme places stress on the glucosefructose bond, and the bond breaks 4) Products are released; the enzyme can bond to other substrates Multienzyme complexes: the assemblies of several enzymes catalyzing different steps in a sequence of reactions… speeds the overall process up Advantages of multienzyme complexes: 1) The product of one reaction can be delivered to the next enzyme without releasing it to diffuse away 2) Unwanted side reactions are prevented because the reacting substrate doesn’t leave the complex while it goes through the series of reactions 3) All of the reactions that take place within the multienzyme complex can be controlled as a unit Nonprotein enzymes: enzymes that are not proteins RNA catalysts: “ribosomes,” accelerate the rate of biochemical reactions but aren’t proteins a) Intramolecular catalysis: when the ribosomes have a folded structure and catalyze reactions on themselves b) Intermolecular catalysis: when the ribosomes act on other molecules without being changed themselves Temperature, pH, and the binding of regulatory molecules affect the enzymes ability to catalyze a reaction Temperature: increasing the temp. of an uncatalyzed reaction increases its rate because heat increases molecular movement the rate of an enzymecatalyzed reaction increases with temperature up to the optimum temperature… at extremely high temperatures, the enzyme denatures pH: ionic interactions are sensitive to the H ion concentration of the fluid in which the enzyme is dissolved some enzymes can function in very low pH’s Inhibitors and Activators: enzyme activity is sensitive to the presence of substances that can bind to the enzyme and change its shape inhibitor: a substance that binds to an enzyme and decreases its activity a) competitive inhibitors: compete with the substrate for the same active site, occupying the same site and preventing the substance from binding b) noncompetitive inhibitors: bind to the enzyme in another location, changing the enzymes shape so the substrate can’t bind activator: a substance that binds to an enzyme that increases its activity allosteric site: other sites on an enzyme that inhibitors and activators can bind to cofactors: one or more nonprotein components required by enzymes in order to function, found in the active site of enzymes coenzyme: a nonprotein organic molecule that plays an accessory role in enzyme catalyzed processes by acting as a donor or accepter of electrons Metabolism: the total of all chemical reactions carried out by an organism anabolism: the chemical reactions that expand energy to build up molecules; needs an energy input catabolism: reactions that harvest energy by breaking down molecules; releases energy biochemical pathways: a sequence of chemical reactions in which the product of one reaction becomes the substrate of the next reaction feedback inhibition: control mechanism in which an increase in the concentration of some molecules inhibits the synthesis of the molecule Chapter 4 Part 1 Cells: differ in size and complexity Cells were discovered in 1665 by Robert Hooke Schleiden and Schwann proposed the cell theory Modern cell theory: 1) All organisms are composed of one or more cells, and the life processes of metabolism and heredity occur in these cells 2) Cells are the smallest living things 3) Cells arise only from preexisting cells No additional cells are spontaneously originating at present… life represents a continuous line of descent from early cells Cell size is limited most cells are small because of the necessity of diffusion of substances in and out of them diffusion: movement of molecules or particles from a concentrated region to a less concentrated region Rate of diffusion is affected by: 1) Surface area available for diffusion 2) Temperature 3) Concentration gradient of diffusion substance 4) Distance over which diffusion must occur surfacetovolumeratio: as a cell’s size increases, its volume increases more quickly than its surface area… it’s beneficial for a cell to be small Microscopes other than egg cells, not many cells are visible to the naked eye Resolution: the minimum distance two points can be apart and still be distinguished as two separate points… there is limited resolution in the human eye Lightmicroscopes: operate with visible light, use two magnifying lenses to achieve high clarity and magnification… not powerful enough to resolve many structures within cells, can resolve structures that are 200 nm apart Electron microscope: has 1000 times the resolving power of a light microscope, employs electron beams, resolves structures that are 0.2 nm apart Transmission electron microscope: the electrons used to visualize the specimens are transmitted through the material Scanning electron microscope: beams electrons onto the surface of the specimen (3D image) Chemical stains: stains are absorbed differently by the different structures of the cell, makes it easier to see the different structures Structural features of cells 4 major features all cells have in common: 1) nucleoid or nucleus: where DNA is located 2) Cytoplasm 3) ribosomes: used in protein synthesis 4) plasma membrane: phospholipid bilayer, proteins embedded in it In prokaryotes, most of the genetic material lies in a single circular molecule of DNA located in the nucleoid In eukaryotes, the DNA is stored in the nucleus, which is surrounded by the double membrane nuclear envelope Cytoplasm: the semifluid matrix that fills the interior of the cell; aqueous medium Organelles: any macromolecular structure in the cytoplasm that has a job Cytosol: the fluid portion of the cytoplasm; contains dissolved organic molecules and ions Plasma membrane: encloses a cell, separates its contents from its surroundings; phospholipid bilayer Prokaryotes consist of cytoplasm surrounded by a plasma membrane singlecelled, encased within a rigid cell wall: the whole prokaryote operates as one unit chromosomes are circular some harvest light by photosynthesis, and some break down organisms and recycle their components contain organelles like ribosomes that carry out protein synthesis, but lack membrane bound organelles… so DNA, enzymes, and other cytoplasmic constituents have access to the whole cell Two main domains: Archaea and Bacteria Bacteria: encased by a cell wall that is composed of peptidoglycan (carbohydrate matrix crosslinked by polypeptide units) Bacterial cell walls protect the cell, maintain its shape, and prevents excessive uptake or loss of water Archaea: their cell walls are composed of various compounds including polysaccharides and proteins, but lack peptidoglycan Archaea can’t adapt to changing temperatures because they aren’t able to alter the degree of saturation of their hydrocarbons Prokaryotic flagellum: protein fibers that extend out from the cell. Their rotary motor, which is powered by a protein gradient, powers the flagellum Eukaryotes central vacuole: a large membranebound sac that is inside a plant cell stores proteins, pigments, and waste materials involved in plant cell growth tonoplast: the membrane surrounding the central vacuole contains channels for water that are used to maintain the cell’s osmotic balance vesicles: small sacs found in both plants and animals that store and transport a variety of materials the DNA is found in the nucleus and is wound around proteins and packaged into chromosomes cytoskeleton: a network a protein microfilaments and microtubules in the cytoplasm that maintains the shape of the cell and anchors the organelles nucleus: the largest organelle that is usually found in the center of the cell membrane bound, stores DNA and enables the synthesis of all proteins nucleolus: dark middle of the nucleus, intensive synthesis of rRNA happens here nuclear envelope: the bounding structure of the nucleus made of two phospholipid bilayers with the outer one connected to the endoplasmic reticulum nuclear pores: shallow openings in the nuclear envelope that allow some proteins and nucleic acids in and out of the nucleus nuclear lamina: network of fibers on the inner surface of the nucleus made of nuclear lamins, gives nucleus shape chromatin: the complex of DNA and proteins of which chromosomes are composed can cause changes in gene expression ribosomes: make proteins; there are to forms: bound: attached to the Endoplasmic Reticulum, synthesizing a protein free: floating in the cytoplasm, synthesize proteins in cytoplasm, nucleus, mitochondria, and other organelles The Endomembrane System endoplasmic reticulum: largest of the internal membranes, composed of a phospholipid bilayer embedded with proteins, forms channels in the cytoplasm. Two types of endoplasmic reticulum: 1. Rough E.R.: has a pebbly surface because there are proteins synthesized on the surface. glycoprotein: newly synthesized proteins attached to carbohydrates cells that synthesize proteins have more R.E.R. (antibodies) 2. Smooth E.R.: contains a variety of structures ranging from a network of tubules to flattened sacs and tubular arrays; more tubular than R.E.R. enzymes anchored within the S.E.R. are involved in the synthesis of carbohydrates and lipids S.E.R. stores intracellular Ca to keep the cytoplasmic level low so Ca can be used as a signaling molecule S.E.R. modifies foreign substances to make them less toxic cells that carry out lipid synthesis have more S.E.R. (brain, testes, intestine) Golgi bodies: collections of flattened stacks of membranes in the cytoplasm functions in collection, packing, and distribution proteins and lipids manufactured in the E.R. are transported and modified in the Golgi apparatus (the Golgi bodies add and modify sugar chains) Polysaccharides secreted by plants are synthesized by the Golgi bodies lysosome: membranebound enzyme that is produced by the Golgi bodies help catalyze macromolecules microbodies: membraneenclosed vesicles that contain enzymes peroxisome: a microbody that contains enzymes involved in the oxidation of fatty acids; contains the enzyme catalase which breaks down hydrogen peroxide into water and oxygen Chapter 4 Part 2 Mitochondria and chloroplasts They are both surrounded by a double membrane, and both have their own protein synthesis machinery (DNA) both involved in energy metabolism 1. Mitochondria: tubular organelles that are found in all eukaryotic cells bounded by two membranes smooth outer membrane and inner folded membrane containing cristae cristae: the contiguous layers and folds in the inner membrane matrix: the solution in the interior space surrounded by cristae; contains enzymes and proteins that carry out oxidative metabolism oxidative metabolism: energy in macromolecules is used to produce ATP; requires oxygen intermembrane space: the space that lies between the two membranes when a cell divides, the mitochondria divides into 2 2. Chloroplasts: celllike organelles in plants that carry out photosynthesis contain chlorophyll (pigment) that makes plants green more large and complex than mitochondria grana: stacked columns of flat, interconnected disks that are in the chloroplasts’ inner membrane; stacks of thylakoids thylakoid: a complex, organized, internal membrane composed of flattened discs, which contain lightcapturing photosynthetic pigments stroma: the fluid matrix surrounding the thylakoid, contains enzymes used to synthesize glucose during photosynthesis leucoplasts: DNA containing organelle in plants that serve as starch storage sites amyloplast: stores amylose (starch) plastids: chloroplasts, leucoplasts and amyloplasts Endosymbiosis: theory that proposes that eukaryotic cells evolved from a symbiosis between different species of prokaryotes (one prokaryote was engulfed by another and they joined together) Cytoskeleton: network of protein fibers that supports the shape of the cell and anchors organelles to fixed locations; dynamic system, always assembling and disassembling Three types of cytoskeletal fibers: 1) Actin filaments (microfilaments): made up of 2 strands of actin twisted together, usually concentrated below the plasma membrane responsible for cell contraction, crawling, “pinching” during division, and formation of cellular extensions 2) Microtubules: composed of and tubulin protein subunits that are arranged side by side to form a tube; very stiff functions in intracellular transport and the separation of chromosomes during mitosis 3) Intermediate filaments: composed of overlapping staggered tetramers of protein, which are bundled into ropelike cables gives strength to the cell Centrioles: barrel shaped organelles that occur in pairs; found in the cells of animals and most protists, divides and organizes spindle fibers during mitosis and meiosis, organizes microtubules centrosome: the region surrounding the pair of centrioles pericentriolar material: surrounds the centrosome, contains ringshaped structures that nucleate the assembly of microtubules in animal cells 4 components required to move material along microtubules: a. A vesicle or organelle that needs to be transported b. A motor protein that provides the energydriven motor c. A connecter molecule that connects the vesicle to the motor molecule d. microtubules that the vesicle will ride Extracellular structures and cell movement The arrangement of actin filament within the cell’s cytoplasm allows cells to crawl myosin: a protein that plays a big role in muscle contraction myosin motors along the actin filaments contract, pulling the contents of the cell towards the front edge 9+2 structure: the flagellum of a eukarotic cell that consists of a circle of 9 microtubule pairs and 2 central microtubules the flagellum in eukaryotic cells moves up and down rather than rotating basal body: a selfreproducing, cylindrical, cytoplasmic organelle composed of microtubules; where the flagella and cilia arise cilia: short cellular projections from the surface of a eukaryotic cell that has a 9+2 arrangement, organized in rows that beat to propel things along cell wall: composed of fibers of cellulose; protects and supports cells primary wall: the wall layer deposited during the period of cell expansion middle lamella: cements the primary walls of adjacent plant cells secondary wall: innermost layer that has a highly organized structure extracellular matrix: a mixture of glycoproteins that animal cells secrete around them this is a protective layer integrins: proteins that are in the plasma membrane and extend into the cytoplasm; they link the extracellular matrix to the cytoskeleton they can alter gene expression and cell migration patterns by mechanical and chemical signaling pathways Cell to cell interactions surface proteins: give cells identity; cells of the same tissue type recognize each other and form connections between their surfaces to coordinate functions glycolipids: lipids with carbohydrate heads; most tissuespecific cell surface markers MHC proteins: help tell cells in the immune system apart Anchoring junctions: a. Adhesive junctions: mechanically attach the cytoskeleton of a cell to the cytoskeletons of other cells or to the extracellular matrix b. Adherins junction: an anchoring junction that connects the actin filaments of one cell with those of adjacent cells or the extracellular matrix Desmosomes: a cadherinbased junction only found in vertebrates; join adjacent cells, and these connections support tissues against mechanical stress contain democollin and demoglein Separate junctions: form a barrier that can seal off a sheet of cells; found in both invertebrates and vertebrates Tight junctions: act as a wall within the tissue, keeping molecules on one side or the other; contain Claudin proteins that block substances from passing between cells only found in vertebrates Communicating junctions: allow communication between cells by diffusion through small openings… 2 types: 1) Gap junction: found in animals, allows the passage of materials between cells forms when the connexons and pannexins of two cells align perfectly allows simple sugars and amino acids to pass from cell to cell, but block proteins and large molecules When a cell gets damaged, highly concentrated groups of atoms will flow into the cell and close the gap junction so the damage doesn’t spread 2) Plasmodesmata: found in plants, cytoplasmic connections from one cell to another lined with plasma membrane and contain a central tubule that connects the E.R. of the two cells Chapter 5 Structure of membranes Fluid mosaic model: a. Integral membrane proteins: embedded in the membrane b. Peripheral proteins: associated with the surface of the membrane Cellular membranes are composed of 4 components: 1) Phospholipid bilayer: provides a flexible matrix, is selectively permeable (only lets certain molecules pass through) 2) Transmembrane proteins: a collection of proteins that float in the lipid bilayer. They function in transport and communication across the membrane… many integral proteins are not fixed in the membrane Carriers: transport molecules across the membrane Channels: passively transport molecules across the membrane Receptors: transmit information into the cell 3) Interior protein network: intracellular proteins that support the membrane and reinforce its shape. They control the lateral movement of key membrane proteins, anchoring them to sites Spectrins: determine the shape of the cell Clathrins: anchor proteins to certain sites 4) Cell surface markers: glycoproteins (aid in tissue recognition) and glycolipids (aid in selfrecognition) Electron microscopy: allows biologists to closely study the cell membrane Ways to prepare a specimen for viewing: 1) Embed the tissue in a matrix and cut it into “epoxy shavings” which are put into a grid. Beams of electrons are directed through the grid 2) Freezefracturing: the tissue is embedded in a medium and quick frozen with liquid nitrogen. The frozen tissue is tapped with a knife and a crack is formed, visibly revealing the membrane Phospholipids Three classes of lipids: glycerol phospholipids, sphingolipids, and sterols Glycerol phospholipids: most diverse, vary in length and composition of their fatty acid tail Sphingolipids: contain saturated hydrogen chains sterols: groups of naturally occurring unsaturated steroid alcohols Phospholipids spontaneously form bilayers because they are amphipathic (polar heads, nonpolar tails) The nonpolar interior of a lipid bilayer stops the passage of watersoluble substances through the bilayer The phospholipid bilayer is fluid and stable because water’s affinity for hydrogen bonding never stops The hydrogen bonding of water holds the membrane together Proteins 6 key classes of membrane proteins: 1) Transport: only certain solutes can enter the cell through channels or carriers composed of proteins 2) Enzymes: cells use enzymes attached to the membrane to carry out chemical reactions on the interior surface 3) Cellsurface receptors: surface receptor proteins detect important chemical messages 4) Cellsurface identity markers: identify the cell to other cells; different proteins in each cell 5) Celltocell adhesion proteins: act by forming temporary or permanent interactions to another cell 6) Attachments to the cytoskeleton: surface proteins that interact with other cells are anchored to the cytoskeleton by linking proteins Anchoring molecules: modified lipids that have nonpolar regions that insert into the internal portion of the lipid bilayer and chemical bonding domains that link directly to proteins; attach some membrane proteins to the membrane Transmembrane domain: a hydrophobic region of a transmembrane protein that anchors it in the protein composed of hydrophobic amino acids usually arranged into helices pores: nonpolar regions of the membrane with pleated sheets that form a polar environment on the inside of the sheet. This allows molecules to pass through. integral proteins: amphipathic, hydrophilic, regions span the protein peripheral proteins: found only on one membrane’s side, attached to integral proteins or lipids Passive transport: the movement of substances across a cell’s membrane without expending energy concentration gradient: a difference between the concentrations on the inside and outside of the membrane diffusion: the net movement of dissolved molecules from a region where they are more concentrated to where they are less concentrated this will continue until the concentration is the same in all regions… after that, movement in both directions still occurs, but no net change occurs facilitated diffusion: the diffusion of molecules or ions through carrier proteins or ion channels… no energy needed, but a concentration gradient is needed channel proteins: have hydrophilic interiors that provide an aqueous channel through which polar molecules can pass carrier proteins: bind to a specific molecule that cannot cross the membrane and help it cross the membrane… change shape during the transport process The cell membrane is selectively permeable… only some substances can pass through Ion channel: has a hydrated interior that spans the membrane; allows ions to pass through 3 conditions determine the movement of the ions: 1) The concentrations on both sides of the ions 2) The voltage difference across the membrane and for the gated channels 3) If the gate is open or closed osmosis: the net diffusion of water across a membrane towards a higher concentration osmotic concentration: the concentration of all solutes in the solution hypertonic: a solution with a higher concentration of solutes than the cell; the water will rush out of the cell and it will shrink isotonic: a solution with the same concentration of solutes as the cell; the cell is healthy and normal hypotonic: a solution with a lower concentration of solutes than the cell; the water will rush into the cell and it will swell and possibly burst aquaporin: a membrane channel that allows water to cross the membrane more easily than by diffusion osmotic pressure: the force needed to stop osmotic flow Maintaining osmotic balance: a. Extrusion: some singlecelled eukaryotes use a vacuole to rhythmically contract and pump out water b. Osmotic regulation: many terrestrial animals will circulate a fluid through their body that bathes the cells in an isotonic solution c. Turgor pressure: the internal pressure in plant cells that presses its cell membrane against the cell wall, carrying rigidity Active transport: moving substances up a concentration gradient; requires the expenditure of energy… enables a cell to move substances out of the cytoplasm and into the extracellular fluid protein carriers: 1) uniporters: transports a single type of molecule/ion 2) symporters: transports 2 molecules/ions in the same direction 3) antiporters: transports 2 molecules/ions in different directions sodiumpotassium pump: ▯ 1) Three Na+ bind to the cytoplasmic side of the protein, causing the protein to change its shape. ▯ 2) In its new shape, the protein binds a molecule of ATP and cleaves it into ADP and phosphate. ADP is released, but the phosphate group is covalently linked to the protein. The protein is now phosphorylated. ▯ 3) The phosphorylation of the protein induces a second shape change in the protein. This change translocates the three Na+ across the membrane, so they now face the outside. In this new shape, the protein has a low affinity for Na+, and the three bound Na+ break away from the protein and diffuse into the extracellular fluid. ▯ 4) The new shape has a high affinity for K+, 2 bind to the extracellular side of the protein as soon as it is free of the Na+. ▯ 5) The binding of the K+ causes another shape change in the protein, this time resulting in the hydrolysis of the bound phosphate group. 6) Freed of the phosphate group, the protein reverts to its original shape, exposing the two K+ to the cytoplasm. This shape has a low affinity for K+, so the two bound K+ dissociate from the protein and diffuse into the interior of the cell. The original shape has a high affinity for Na+. When these ions bind, they initiate another cycle. coupled transport: molecules are moved against their concentration gradient using the energy stored in the gradient of a different molecule Bulk transport Endocytosis: the uptake of material into cells 1) Phagocytosis: endocytosis of a solid molecule; the plasma membrane folds inwards around the particle and engulfs it to form a vacuole 2) Pinocytosis: the process of fluid uptake in a cell receptormediated endocytosis: process by which specific macromolecules are transported into eukaryotic cells at clathrincoated pits Exocytosis: the discharge of material from vesicles at the cell surface Chapter 10 Bacterial cell division Bacteria divide to reproduce, and each cell produced by cell division is an exact copy of the original cell binary fission: asexual reproduction by division of one cell or body into 2 equal parts during binary fission, the chromosome is replicated and the 2 products are partitioned to each end of the cell before the actual division of the cell Process of binary fission: 1) Prior to cell division, the bacterial DNA replicates. This occurs in the origin of replication 2) The replication enzymes move out in both directions from that site and make copies of each strand in the DNA duplex. They continue until the meet at the terminus of replication. 3) As the DNA is replicated, the cell elongates… the DNA is partitioned in that the origins are at the ¼ and ¾ positions in the cell and the termini are oriented towards the middle 4) Separation begins; new membrane and cell wall material begin to grow and form a septum at the midpoint of the cell. A protein molecule called Fts7 facilitates this process 5) When the septum is complete, the cell pinches in two, and two daughter cells are formed, each containing a bacterial DNA molecule Septum: a wall between two cavities Septation: the formation of a septum where new cell membrane and cell wall is formed to separate the two daughter cells Eukaryotic chromosomes monosomy: human embryos missing one chromosome; usually fatal trisomy: human embryos that have an extra copy of one chromosome; usually fatal chromatin: makes up chromosomes composed of 40% DNA and 60% proteins each chromosome contains a single DNA molecule heterochromatin: the portion of a chromosome that is not expressed (not transcribed into RNA) euchcromatin: portion of a chromosome that is expressed (transcribed into RNA) Chromosome structure: every 200 nucleotides, the DNA duplex is coiled around a core of 8 histone proteins histone proteins: positively charged because of an abundance of the amino acids arginine and lysine; attracted to phosphate group of nucleotides nucleosome: the complex of DNA and histone proteins During mitosis, proteins are assembled into a scaffold (Xshaped) karyotype: the particular array of chromosomes an individual organism possesses; viewed with a light microscope haploid (n): having only one set of chromosomes diploid (2n): having two sets of chromosomes homologue: one pair of chromosomes of the same kind located in a diploid cell Chromosome replication: cohesins: protein complexes that hold sister chromatids together during cell division sister chromatids: one of two identical copies of each chromosome still linked at the centromere Overview of the Eukaryotic cell cycle cell cycle: the repeating sequence of growth and division through which cells pass each generation Requires the duplication of the genome, its accurate segregation, and the division of cellular contents 5 phases of the cell cycle: 1) G1: gap phase 1, primary growth phase of the cell; usually the longest phase 2) Synthesis (S): the cell synthesizes a replica of the genome 3) G2: gap phase 2, the second growth phase of the cell; prepares for separation of the newly replicated genome… during this phase, microtubules begin to form a spindle 4) Mitosis: the spindle apparatus fully assembles, binds to the chromosomes, and moves the sister chromatids apart 5 stages: prophase, prometaphase, metaphase, anaphase, telophase 5) Cytokinesis: the cytoplasm divides, creating 2 daughter cells G0 phase: the stage of the cell cycle occupied by cells that are not actively dividing; cells sometimes pause here before DNA replication Interphase centromere: a point of constriction on a chromosome that contains repeated DNA sequences that bind specific proteins kinetochore: diskshaped protein structure within the centromere to which spindle fibers attach functions as an attachment site for microtubules necessary to separate the chromosomes during cell division G1 and G2 segments of interphase are periods of active growth S phase: chromosomes replicate G2 phase: chromosomes condense and coil motor proteins: involved in the final condensation of the chromosomes that occurs early in mitosis cells begin to assemble the machinery needed to later move the chromosomes to opposite poles of the cell (spindle) tubulin: the protein that forms microtubules Mitosis PROPHASE: the first stage of mitosis in which the condensed chromosomes become visible and appear bulky, and it ends when the nuclear envelope breaks down spindle apparatus: the assembly that carries out the separation of chromosomes; composed of spindle fibers (microtubules) and formed during prophase in animal cells, the 2 centriole pairs formed during the G2 phase begin to move apart (early in prophase) in plant cells, there are no centrioles, but a similar bridge of microtubular fibers still forms aster: an array of microtubules extending from the centrioles towards the plasma membrane in animal cells; serves to brace the centrioles for retraction of the spindle the nuclear envelope breaks down and the endoplasmic reticulum reabsorbs its components. At this point, the microtubular spindle fibers extend across the whole cell PROMETAPHASE: the second stage in which the spindle attaches to the kinetochores of sister chromatids follows the disassembly of the nuclear envelope a second group of microtubules grow from the poles of the cells towards the centromeres those microtubules are captured by kinetochores on each pair of sister chromatids… results in the kinetochores of each sister chromatid being connected to opposite poles of the spindle each chromosome is attached to the spindle by microtubules running from opposite poles to the kinetochores of sister chromatids the chromosomes are pulled towards each pole… leads to a jerky motion that pulls all of the chromosomes to the cell’s equator the chromosomes are arranged at the equator, with the sister chromatids under tension and oriented towards opposite poles by their kinetochore microtubules two basic mechanisms to explain the force behind chromosome movement: 1) assembly and disassembly of microtubules provides the force to move chromosomes 2) motor proteins located at the kinetochore and poles of the cell pull on microtubules to provide force METAPHASE: the 3 stage of mitosis; the alignment of the chromosomes in the center of the cell metaphase plate: an imaginary plane perpendicular to the axis of the spindle that passes through the circle of chromosomes along the inner circumference of the cell all of the chromosomes line up on the metaphase plate… at this point, their centromeres are arrayed in a circle, equidistant from the two poles of the cell, with microtubules extending back towards the opposite poles of the cell ANAPHASE: the 4 stage of mitosis; the stage contains the separation of the sister chromatids begins when the cohesion proteins holding together sister chromatids at the centromere are removed the sister chromatids are pulled towards the poles to which their kinetochores are attached Anaphase A: the kinetochores are pulled towards the poles as the microtubules that connect them to the poles shorten… causes the chromatids to be pulled closer to the poles of the cell Anaphase B: the poles move apart as microtubular spindle fibers anchored to opposite poles slide past each other, away from the center of the cell… the chromosomes move apart TELOPHASE: the last phase of mitosis when the spindle apparatus disassembles as the microtubules are broken down into tubulin monomers that can be used to construct the cytoskeletons of the daughter cells A nuclear envelope forms around each set of sister chromatids, which can now be called chromosomes because they are no longer attached at the centromere the chromosomes uncoil into the more extended form that permits gene expression rRNA genes are reexpressed, resulting in the appearance of the nucleolus Animal cells: a belt of actin pinches off the daughter cells cleavage furrow: the constriction that forms during cytokinesis that is responsible for dividing the cell into two daughter cells Plant cells: a cell plate divides the daughter cells cell plate: the structure that forms at the equator of the spindle that grows outward until it reaches the interior surface of the plasma membrane and fuses with it, dividing the cell in 2 cellulose is then laid down on the new membranes, creating two new cell walls Fungi and some protists: daughter nuclei are separated during cytokinesis Control of the cell cycle 2 irreversible points of the cell cycle: 1) replication of genetic material 2) separation of sister chromatids 3 check points of the cell cycle: 1) G1/S checkpoint: cell decides to divide, primary point for external cell influence 2) G2/M checkpoint: cells make a commitment to mitosis; assesses success of DNA replication 3) Late metaphase (spindle) checkpoint: cell ensures that all chromosomes are attached to the spindle Cyclindependent kinases (Cdk’s): enzymes that phosphorylate proteins; primary mechanism of cell cycle control Cdk partners with different cyclins at different points in the cell cycle for many years, a common view was that the cyclins drove the cell cycle… the periodic synthesis and destruction of cyclins acted as a clock Now we know that the Cdk itself is also controlled by phosphorylation Kinase Phosphorylate: add a phosphate Phosphatase: take out a phosphate Anaphasepromoting complex: also called APC/C at the spindle checkpoint, presence of all chromosomes at the metaphase plate and the tension on the microtubules between opposite poles are both important the function of the APC/C is to trigger anaphase marks securing for destruction; no inhibition of separase destroys cohesin Cancer: unrestrained, uncontrolled growth of cells failure of cell cycle control 2 kinds of genes can disturb the cell cycle when they are mutated 1) Tumorsuppressor genes both copies of a tumorsuppressor gene must lose function for the cancerous phenotype to develop Retinoblastoma susceptibility gene (Rb): predisposes individuals to a rare form of cancer that affects the retina of the eye Rb protein: integrates signals from growth factors; role is to bind regulatory proteins and prevent stimulation of cyclin or Cdk production 2) Protooncogenes: normal cellular genes that become oncogenes when mutated can cause cancer some encode receptors for growth factors, and some encode signal transduction proteins Only one copy of protooncogene needs to undergo this mutation for uncontrolled division to happen
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'