Biology 1305 Exam 2 Study Guide
Biology 1305 Exam 2 Study Guide BIOL 1305 - 010
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This 12 page Study Guide was uploaded by Sofia Romero on Saturday October 3, 2015. The Study Guide belongs to BIOL 1305 - 010 at University of Texas at El Paso taught by Hsin-i Lin in Fall 2015. Since its upload, it has received 297 views. For similar materials see General Biology - 15965 in Biological Sciences at University of Texas at El Paso.
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Date Created: 10/03/15
Biology 1305 Study Guide Chapters 4 amp 5 KEY RED is vocabulary The bullet points are usually titles are details and is subcategories beneath Chapter 4 0 Cell Theory Cells are the fundamental units of life All living organisms are composed of cells All cells come from preexisting cells 0 2 important implications of cell theory Studying cell biology is similar to studying life the fundamental biology is the same All life is continuous everything can be traced back to the rst living cell 0 Cell diameters range from 1100 micrometers Small cell size is necessary in order to maximize surface areatovolume ratio The volume of a cell determines the amount of metabolic activity it carries out the larger the volume the more metabolic activity The surface area of a cell determines the amount of substances that can enter and exit the cell the larger the surface area the more substances can enter or exit But since volume increases faster than surface area the need for resources for increased metabolic activity would increase faster than the surface area therefore leaving the cell at a de cit The cell membrane encloses all biological functions within the cell o It consists of a phospholipid bilayer with protein 0 Cell membranes act as a selectively permeable barrier it lets some substances to enter and leave the cell while others can39t to maintain a stable internal environment Because it is the boundary with the outside environment it is important for communicating and receiving signals from cells and the environment has proteins protruding from it that need to bind and adhere to adjacent cellssurfaces This means that they are important for structure and cell shape 0 All cells are prokaryotic or eukaryotic Prokaryotic cells do not have a membrane enclosed compartment or a nucleus Eukaryotic cells have organelles membrane enclosed compartments and a nucleus where the DNA is locatedgene expression starts Prokaryotes have the same basic structure have a cell membrane have a nucleoid a region similar to the nucleus where DNA is located has cytoplasm which is made up of cytosol a liquid component and insoluble laments and particles especially ribosomes It is in constant motion Ribosomes are complexes of RNA and proteins They are the sites of protein synthesis where the info encoded by nucleic acids directs the linking of amino acids to form proteins Some specialized features in prokaryotes are cell walls a rigid wall that determines the shape of the cell and supports it Most cell walls contain peptidoglycan a molecule that can link to others to form a cell wall Some have another layer called the outer membrane which encloses the cell wall Many bacteria also have capsules a slimy layer that can protect from attack keep cells from drying out and occasionally help bacteria attach to other cells 0 Internal Membranes can carry required molecules needed for photosynthesis or have internal membrane folds that are attached to the cell membrane these can function in cell division or energyreleasing reactions Fagela look like tiny corkscrews The lament of the agellum is made of a protein called agellan The motor protein inside the cell spins like a propeller in order to drive the cell It is anchored to the cell membrane and occasionally to the outer membrane of the cell wall Cytoskeleton It39s the collective name for laments made up of polymers of monomer subunits that are used for cell division or in maintaining cell shape Eukaryotic cells also have a cell membrane cytoplasm and ribosomes but also have organelles within the cytoplasm Ribosomes are factories for protein synthesis They translate the nucleotide sequence of messenger RNA molecules into polypeptide chains they have one larger and one smaller subunit each subunit has 13 large RNA molecules called ribosomal RNA and many smaller protein molecules that are bonded noncovalently Ribosomes either oat freely or are attached to surface of the endoplasmic reticulum mitochondria and chloroplasts The nucleus contains most of the cell39s DNA in eukaryotic cells most of the DNA is in the nucleus it is usually the largest organelle it is the location of DNA site of DNA replication where DNA is transcribed into RNA and contains the nucleolus where ribosomes begin to assemble from RNAproteins The nucleus is contained by two membranestwo lipid bilayers that form the nuclear envelope this envelope has pores which regulate traffic Each DNA molecule is combined with proteins to form chromosomes long thin threads in the nucleus Groups of chromosomes are called chromatin Endomembrane System An interconnected system which includes the nuclear envelope endoplasmic reticulum Golgi apparatus and lysosomes which are derived from the Golgi apparatus Vesicles tiny membrane surrounded droplets shuttle substance between various components of the endomembrane systemcell membrane Endoplasmic reticulum a network of interconnected membranes throughout the cytoplasm These are called the ER for short the lumen interior compartment of the ER is separate from the cytoplasm There are two types of ER rough endoplasmic reticulum and smooth endoplasmic reticulum RER is called rough because of the ribosomes that attach to the outer surface of the membrane making it look rough These ribosomes are not permanently attached to the ER A protein can only enter the RER if it is a unique amino acid that signals for attachment to the RER After the protein synthesizes they are quottaggedquot for delivery They then pass through the RER and are pinched off into vesicles Once in the cell many proteins link to carbs becoming glycoprotein Smooth Endoplasmic Reticulum can be connected to the RER but lacks ribosomes and is more tubular It is responsible for chemical modi cation of small potentially toxic molecules is the site for glycogen degradation in animal cells where lipids and steroids are synthesized and store calcium ions Golgi Apparatus It has 2 components the attened membranous sacs called cisternae and small membrane enclosed vesicles lt concentrates packages and stores proteins it adds carbs to proteins It is where some polysaccharides for the plant cell wall are synthesized The Golgi apparatus have 3 distinct regions the cis region lies closest to the nucleusRER it fuses with protein containing vesicles the trans region lies closest to the cell membraneit creates vesicles and carries their contents away from the apparatus the medial region lies in between Lysosomes originate from the Golgi apparatus contain digestive enzymes hydrolases are where macromolecules proteins polysaccharides nucleic acids and lipids are hydrolyzed into monomers it is surrounded by a single membrane and a featureless interior some macromolecules that are hydrolyzed into lysosomes enter from outside the cell through a process called phagocytosis n phagocytosis small vesicles called phagosomes break free of the cellular membrane to move to the cytoplasm The phagosome then fuses with a primary lysosome to form a secondary lysosome where hydrolysis occurs Phagocytes are cells who primarily take in and break down materials what they do is called autophagy the programmed destruction of the cell components Mitochondria The breakdown of molecules happens in the cytosol and then goes to the mitochondria The molecules then are converted to ATP adenosine triphosphate Cels that need more energy have more mitochondria They have 2 membranesthe outer porous membrane and the inner membrane with extensive folds called cristae The inner membrane is lled with a liquid matrix which contains enzymes DNA and ribosomes Plastids Are exclusively in plant and algae cells They can differentiate into organelles some are used to store carbs lipids proteins or pigments Choroplast contains chlorophyll and is the site of photosynthesis photosynthesis converts light energy into chemical energy Choroplast has 2 membranes and has a series of internal membranes called thylakoids Each stack of thylakoids is called a granum this is where light energy is converted Carb synthesis happens in the stroma the aqueous uid surrounding the thylakoids Peroxisomes are small organelles that collect and break down toxic peroxides A peroxisome has a single membrane and a granular interior Glyoxysomes are found only in plants and are where lipids are converted into carbs for transportation Vacuoles occur in many cells but mostly in plants fungi and are used for Storage of waste products and toxic compounds Structure for plant cells water enters the vacuole by osmosis which makes the vacuole swell and create turgor pressure pressure from the vacuole pressing up against the cell wall Reproduction the pigments of owering plants are contained in vacuoles which help attract animals for pollination Catabolism Digestive enzymes hydrolyze stored food into monomers Contractile vacuoles get rid of excess water in a cell by enlarging then quickly contracting Cytoskeleton it supports and maintains the cells shape it holds organelles and other particles in position it moves organelles and other particles around it39s involved with movements of the cytoplasm called cytoplasmic streaming it interacts with extracellular structures and helps hold the cell in place It has 3 components micro laments intermediate laments and microtubules Micro laments are usually in bundles heps the cellsparts of the cell to move determinestabilize cell shape are assembled from actin monomers that attach at the quotplusquot end and detach at the quotminusquot end aments can be made shorter or longer through detachment or assembly dynamic instability means that the cytoskeleton can be broken down or reassembled quickly through actinrelated proteins in muscle cells actin is related to the motor protein myosin which means the actions of the two result in muscle contradiction in nonmuscle cells micro laments are involved in cytoplasmic streaming and the formation of cellular extensions Intermediate Filaments There are min 50 different kinds They are tough rope proteins that are 812 nm in diameter are more permanent than the other 2 types of laments do not have dynamic instability they anchor cell structures in place they resist tension and maintain rigidity by extending through the cytoplasm and attaching to desmosomes Microtubules are long hollow unbranched cylinders approx 25 nm in diameter they form a rigid internal skeleton act as a framework so that motor proteins can move structures inside the cell are assembled from the protein tubulin they show dynamic instability Poymerization of tubulin means rigid structure while depolymerization leads to collapse ine movable appendages cilia and agella Cilia are short and usually have many present that move stif y to move a cell or to move uidly over a cell Flagella are much longer and cells usually have only 1 or 2 that push or pull the cell Usually come in 92 arrangement of doublets where nine fused pairs of microtubules form a cylinder with an unfused pair in the center Three different proteins facilitate cilia and agella Dynein a motor protein which can change its 3D shape to facilitate the sliding of doublets Nexin which can crosslink the doublets to prevent sliding so instead the cilia bends Kinesin which carries protein lled vesicles from 1 part of the cell to the other 2 methods to show the speci c relationship between a structuremolecule A and function B lnhibition where you use a drug to inhibit A see if B still occurs If B occurs the 2 are not related Mutation Examine a cell that lacks the gene for A and then see if B still occurs If B occurs the 2 are not related Extracellular Structures are attached to the outside of the membrane and are made up of 2 components A brous macromolecule A gellike medium where bers are embedded The plant cell wall is an example of an extracellular structure it39s a semirigid structure outside the cell membrane the brous component is polysaccharide cellulose The gellike matrix contains crosslinked polysaccharides proteins It has 3 major cell roles provides support and limits volume by remaining rigid it acts as a barrier for infections that could cause diseases it contributes to plant form by controlling the direction of cell expansion They are attached to each other through cellmembrane lined channels called plasmodesmata which allows the movement of water ions small molecules hormones and some RNA and protein molecules to move between connected cells Extracellular matrix The brous component is a protein called collagen The gellike medium consists of proteoglycans glycoproteins with ling carb side chains Their roles are hoding cells together in tissues contributing to physical properties of cartilage skin and other tissues hep lter materials passing between different tissues hep orient cell movement between embryonic development and tissue repair proteins like integrin connect the cell membrane to the extracellular matrix and connect to micro laments and collagen these binding sites are noncovalent and reversible CeHjunc ons are specialized protruding structures that connect adjacent cells 3 different types of cell junctions Tight junctions prevent substances from moving in the spaces between cells Desmosomes hold cells together with stable protein connection but materials can still move between cells It provides mechanical stability for tissues that receive physical stress skin Gap junctions are channels that run between membrane pores in adjacent cells that allow substances to move through gaps between cells Chapter 5 Cell Membranes and Signaling A membrane39s structures and functions are determined by the chemical properties of its constituents lipids proteins and carbs The general structure of membranes are known as the uid mosaic model where the phospholipid bilayer serves as a quotlakequot where proteins quot oatquot Membranes contain a wide array of proteins most of which are noncovalently embedded in the phospholipid bilayer They are held within the membrane by their hydrophobic regions or domains Membrane proteins have 3 functions move materials through the membrane they are involved in intercellular recognition and adhesion receive chemical signals from the cells outside environment The carbs associated with membranes are attached to lipids or protein molecules and are located on the outside of the cell Lipids Lipids in biological membranes are usually phospholipids with 2 regions the hydrophilic regions the quotheadquot of the phospholipid is electrically charged and can associate with H20 The hydrophobic region the long nonpolar fatty acid quottailsquot that only associate with other nonpolar materials A bilayer forms when fatty acid tails associate with each other and the heads face out into the environment A bilayer organization helps membranes fuse during vesicle formation and phagocytosis A phospholipid can vary from cell to cell The ways that it can differ includes fatty acid chain length of carbon atoms degree of saturation of double bonds kinds of polar groups present phosphate containing between 1618 carbon atoms and 02 double bonds There are 2 important factors in membrane uidity Lipid Composition the type of fatty acid can increase or decrease uidity choestero helps retain membrane integrity nonpolar anesthetics which can decrease uidity Temperature uidity can decrease underneath colder conditions saturated fatty acids get replaced with unsaturated fatty acids with shorter chains Biological Proteins Cel membranes have 1 protein molecules for every 25 phospholipid molecules This can vary depending on function ex In the mitochondrion there is 1 protein for every 5 lipids There are 2 types of membrane proteins Peripheral membrane proteins which don39t have hydrophobic group and aren39t embedded in the bilayer They have polarcharged regions that interact with exposed parts of integral membrane proteins or with polar heads of phospholipid molecules lntegral membrane proteins are partially embedded in the phospholipid bilayer that have both hydrophilic and phobic regions Membrane proteinslipids interact only covalently unless they are anchored membrane proteins which have fatty acids or other lipid groups that are covalently attached and then the hydrophobic lipid components that anchor them in the bilayer Proteins are asymmetrically distributed in the bilayer A protein that equally extends on both sides of the bilayer is called a transmembrane protein and may have different functions on either side of the bilayer A peripheral membrane proteins are located on one or the other side of the membrane Some proteins moves freely through the bilayer while others stay in speci c regions other proteins or the cytoskeleton can restrict this movement Cell Membrane Carbohydrates they are located on the outer surface and can be covalently bonded a glycolipid consists of a carb covalently bonded to a protein a glycoprotein has 1 short carb chains covalently bonded to a protein usually oligosaccharides a proteoglycan is a protein with even more carb molecules attached to it and the chains are usually much longer than glycoproteins these structures can play roles in cell communication and branched structures Passive Transport across Membranes Membranes utilize a process called selective permeability where the membrane allows some substances to pass but not others Substances can pass through the membrane by either passive transport simple or facilitated diffusion which requires no energy or active transport which requires ATP Diffusion is a process of random movement toward equilibrium It moves from high concentration to low concentration The speed of diffusion depends on 3 factors Diameter smaller molecules diffuse faster Temperaturehigher temps lead to faster diffusion because the heat provides more energy for movement Concentration gradient the greater the concentration gradient the faster the diffusion A higher concentration of substance inside the cell will cause the cell to diffuse out and vice versa Simple diffusion allows small molecules to pass through the bilayer A molecule that is hydrophobic and soluble in lipids can pass through while a polar hydrophilic molecule can39t Osmosis is the diffusion of water across membranes It depends on the concentrations of water molecules water passes through membrane channels aquaporin osmotic pressure is the pressure that needs to be applied to the solution to prevent the ow of water across the membrane by osmosis Water will move towards the solution with the higher solute concentration and lower water There are 3 types of solute concentration hypertonic solution has a higher solute concentration than the other solution isotonic solution has equal solute concentrations hypotonic solution will have a lower solute concentration than the other side Turgor pressure is the internal pressure against the cell wall as it builds up it prevents more water from entering Diffusion as aided by channel proteins channe proteins are integral membrane proteins that form channels across the membrane so that certain substances can pass Carrier Proteins can speed up diffusion through the bilayer Both these processes are facilitated diffusion Ion Channels are a type of gated channel protein Gated channels open when a stimulus causes a change in the 3D shape a stimulus can be a ligand or the binding of a chemical signal water diffuses at a faster rate if it quothitchhikesquot on ions such as Na which pass through ion channels Aquaporins are speci c channels that allow water to move against the concentration gradient Carrier Proteins involves the binding of the transported substance to a carrier protein a transported substance ex Glucose binds to the carrier protein causing it to change shape and allow it to be released on the other side to the cell much faster than simple diffusion both are driven by the concentration gradient the facilitated diffusion system can become saturated when all carrier molecules are bound Active Transport requires energy to move substances against the protein gradient is used to overcome concentration imbalances the energy source is often ATP which is made in the mitochondria and plastids it moves in the direction of the substances needs 2 types of active transport primary active transport involves the direct hydrolysis of ATP secondary active transport doesn39t use ATP directly and its energy is supplied by an ion concentration or electrical gradient ln primary active transport energy is released by the hydrolysis of ATP drives the movement of speci c ions across the concentration gradients Ex A sodium potassium pump is an integral membrane glycoprotein For every molecule of ATP it brings in 2K ions and 3Na ions In secondary active transport the movement is accomplished by using energy across the membrane along the concentration gradients Secondary active transport may begin with diffusion or a carrier protein Large molecules cross the membranes through vesicles Macromolecules that are too largecharged enter the membrane through vesicles To take in or release molecules cells must use endocytosis or exocytosis Exocytosis is how materials are secreted from the cell The vesicle membrane fuses with the plasma membrane and the contents are released into the environment Endocytosis is how materials are brought into the cell The cell invaginates folds inward forming a small pocket of materials it then brings it into the cell39s interior Endocytosis is often based on receptors that set off speci c cellular responses There are 3 types of endocytosis phagocytosis which is cellular eating where part of the membrane engulfs a large particlecell A food vacuole then forms and then fuses with a lysosome pinocytosis which is cellular drinking where the vesicle brings in uidsdissolved substances including proteins in the cell Receptor mediated endocytosis involves receptors in order to bind to speci c molecules They are located in regions called coated pits The cytoplasmic protein is coated by another protein clathrin When receptors bind to the ligands the coated pit invaginates and forms a coated vesicle The clathrin stabilizes the vesicle as it moves the macromolecules into the cytoplasm Then the vesicle loses its clathrin coat and the substance is digested It also plays an important role in cell signaling Cell signaling it s the ability to process information from the environment a chemical signal can be referred to as a ligand once the cell activates its receptors it sets off a signal transduction pathway a sequence of molecular events and chemical reactions within a cell that leads to the response of the signal Cells can respond to many different signals Autocrine signals affect the same cell that release them Paracrine signals diffuse to and affect nearby cells Luxacrine signals requires direct contact between the signaling and responding cells and usually involves interaction Hormones travel to distant cells through circulatory systems Only the cells with the necessary receptors can respond to a signal A signal transduction pathway involves a signal receptor and a response a common signal transduction method is allosteric regulation this involves the alteration of a 3D shape of a protein as a result of the binding to another molecule A signal transduction pathway may end in a long or short term response Receptors can be classi ed be locationfunction lntraceluar receptors are inside the cell Smallnonpolar ligands can diffuse across the bilayer and enter the cell They are regulator of gene reception Membrane receptors are located on the cell surface This is for large or polar ligands They must bind to a transmembrane receptor Membrane receptors are found outside of the cells and respond to signals from outside of the cells If the external signal is a chemical ligand it ts the 3D site on the receptor protein Binding of the ligand can change the 3D shape and initiate a cellular response Ligands are usually not metabolized further and they can reveal an active site The binding in noncovalent and reversible An inhibitor can bind instead preventing the binding of the ligand Receptors can be identi ed by their location lon Channel Receptors Also called gated ion channels Ex The acetylcholine receptor a ligandgated sodium channel binds with acetylcholine to open the ion channel and allow Na to diffuse into the cell Protein Kinase Receptors lT modi es speci c target proteins in the cell by adding phosphate groups to them lt catalyzed this reaction ATP Protein gt ADP phosphorylated protein Each protein kinase has a speci c target protein whose activity changes when phosphorylated G ProteinLinked Receptors A ligand binding on the extracellular domain of the receptor exposes a site on the cytoplasmic side that can bind to a mobile membrane protein called a G protein lt is partially inserted into the lipid bilayer and partially exposed on the cytoplasmic surface of the membrane G proteins can bind to 3 molecules The G protein linked receptor the GDP and GTP for energy transfer An effector protein to cause an effect in the cell the active Gprotein linked receptor exchanges a GDP for a higher energy GTP The activated Gprotein activates the effector protein leading to signal ampli cation Cellular Response Signa activation of a speci c receptor leads to a cellular response which is then mediated by a signal transduction pathway Signaling can lead to a series of protein interactions whose signal can then be ampli ed and distributed A secondary messenger is an intermediary between the receptor and the responses Ex In the fightor ight response epinephrine adrenaline activates the liver enzyme glycogen phosphorylase The enzyme catalyzes the breakdown of glycogen to provide quick energy The secondary messenger is known as cAMP or cyclic AMP Secondary messengers do not have enzymatic activity but instead distribute and amplify the cell signal Signal Transduction Pathways involve multiple steps enzymes can either be activated or inhibited Ex Taken from PowerPoint quotIn liver cells a signal cascade begins when epinephrine stimulates a G protein mediated protein kinase pathway Epinephrine binds to its receptor and activates a G protein cAMP is produced and activates protein kinase A it phosphorylates two other enzymes with opposite effects Inhibit glycogen synthase activity Activate phosphorylase kinase activityquot Signal transduction is temporary and turns off after the cell responds The balance between regulating and signal enzymes determines the cells response to a signal Cells can alter this balance in several ways including synthesis or breakdown of the enzymes involved and by the activation or inhibition of the enzymes by other molecules Ce functions can also change in response to environmental signals The opening of ion channels which changes the electrical potential across the membrane The upregulation or downregulation in gene expression Alteration of enzyme activities the activation of phosphorylase kinase or the inhibition of gycose synthase
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