1305- General Biology- week 8 (10/12/15)
1305- General Biology- week 8 (10/12/15) General Biology 1305
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This 8 page Class Notes was uploaded by Mercedes Taylor on Friday October 16, 2015. The Class Notes belongs to General Biology 1305 at University of Texas at El Paso taught by Jennifer Apodaca in Summer 2015. Since its upload, it has received 31 views. For similar materials see General Biology in Biology at University of Texas at El Paso.
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Date Created: 10/16/15
1305 General Biology Jennifer Apodaca Week 8 Notes 101215 101415 Inside of Cell Cont 101215 Lysosomes A Materials reach the lysosomes via a Phagocytosis cell eating a specialized cell engulfs a large particle or another cell b Receptormediated Endocytosis brings specific large molecules into a cell via specific receptors This allows cells to control internal processes by controlling locations and abundance of each type of receptor on the cell membrane receptor may be recycled to the cell membrane or degraded in a lysosome c Autophagy is the programmed destruction of cell components Cells break down their own materials and even entire organelles within lysosomes B Primary lysosomes originate from the Golgi Apparatus and may fuse with macromolecules that enter the cell by phagocytosis and a phagosome is formed a Phagosomes the fuse with primary lysosomes to form secondary lysosomes where enzymes hydrolyze the food molecules b Phagocytes are cells specialized to take in materials and break them down C Endocytosis brings macromolecules and particles into eukaryotic cells It is a form of ac ve transports in which a cell engulfs molecules like proteins into the cell endo cytosis in an energy using process and depends on receptors proteins that bind to specific molecules ligands The cell membrane invaginates or folds around the particle form and pinch off vesicle to bring outside material into the cell a In additions to phagocytosis cell eating and endocytosis a third type of endocytosis called pinocytosis cell drinking brings fluids into the cell ll Peroxisomes Oxidative Organelles A Structure a specialized metabolic compartments bound by a single membrane B Function a Center of the Oxidative reaction and performs reactions with many different func ons b Break down long chain of fatty acids through betaoxidation and detoxification of reactive oxygen species c Detoxifies harmful products like alcohol and H202 d Abundant in liver cells Eukarvotic Cells A Events in the origin of the eukaryotic cell a Origin of flexible cell surface b Origin of cytoskeleton c Nuclear Envelope developed d digestive vacuoles appeared e acquisition of certain organelles by endosymbiosis B Flexible Cell Surface a Loss of the cell wall which occurs in some modern prokaryotes opens possibilities i a flexible cell surface allows infolding and increased surface area cells can be larger ii Endocytosis is possible pinching off bits of the environment and bringing them into the cell b Changes in the Oxygen Concentration has changed over time c Organisms that could tolerate 02 evolved IV Semiautonomous Orqanelles Mitochondria Chlor0plmnd Peroxisomes A Chloroplasts and mitochondria have been suggested as descendants of ancient prokaryote cells primary endosymbiosis there is significant evidence for this hypothesis in both a Mitochondria site of energy generation probably evolved from engulfed prokaryotic organisms b Chloroplasts sites of photosynthesis probably evolved from engulfed photosynthetic prokaryotes B The idea that peroxisomes originated from a bacterial origin has been challenged a They can grow and divide to reproduce themselves but they are not completely autonomous because they depend on other parts of the cell for their internal components C Mitochondria and chloroplasts have similarities with bacteria a enveloped by a double membrane b contain free ribosomes and circular DNA molecules c grown and reproduce somewhat independently in cells d These similarities led to the endosymbiont theoryearly ancestor of eukaryotes engulfed an oxygenusing nonphotosynthetic prokaryotic cell i The engulfed cell formed a relationship with the host cell becoming an endosymbiont and evolved into mitochondria ii At least one of these cells may have then taken up a photosynthetic prokaryote which evolved into a chloroplast D Chloroplast development occurred in series of endosymbiosis a Primary endosymbiosis a cyanobacterium was engulfed by a larger eukaryotic cell Remnants of a peptidoglycan cell wall can be found in glaucophytes b Primary endosymbiosis also gave rise to chloroplasts of red algae green algae and land plants The chloroplasts have two membranes c Secondary endosymbiosis the process of engulfing a green or red algal cell retaining its chloroplast and becoming phototrophic i a eukaryote engulfed a green alga cell which became a chloroplast ii Euglenids and chlorarachniophytes green algae iii Alveolates and stramenopiles red algae iv Euglenoid chloroplasts have three membranes and they have the same pigments as land plants and green algae V Mitochondria A Structure a Mitochondria have 2 membranes i the inner one is folded into a series of saclike cristae increase the surface area ii Outer membrane very porous b The solution inside the cristae is called the mitochondrial matrix The fluidfilled matrix contains its own enzymes DNA and ribosomes B Function a In eukaryotes breakdown of energyrich molecules begins in the cytosol ATP production is a mitochondrion s core function b The partially digested molecules enter the mitochondria where chemical energy is converted to energyrich ATP c Cells that require lots of energy often have more mitochondria VI Chloroplasts A Structure a Most plant and algal cells have chloroplasts that like mitochondria have a double membrane and contain their own DNA b Contains chlorophyll site of photosynthesis converts light energy into chemical energy anabolic process c Chloroplasts contain membranebound flattened vesicles called thylakoids which are stacked into piles called grana Outside the thylakoids is the solution called the stroma i Granum is a stack of thylakoids light energy is converted to chemical energy on these membranes ii Stroma aqueous matrix around grana contains ribosomes and DNA carbohydrates are synthesized here B Functions a convert light energy to chemical energy which is Photosynthesis VII Plastids A Semiautonomous organelles found in a variety of forms among plant and algal cells several taxa of marine mollusks and at least one phylum of parasitic protists B Plastid family plays big role a Erequot95th Photosynthesis Amino acid Lipid synthesis Starch amp Oil storage Fruit and flower coloration Gravity sensing Stomatal functioning environmental perception C Plastids arose via an endosymbiotic event D Other plastids a b Chromoplasts make and store red yellow and orange pigments especially in flowers and fruits Leucoplast store macromolecules such as starch Vlll vacuoles mainlv in plants and fungi A Structure a b fluidfilled vesicle that may occupy more than 30 of cell volume related to lysosomes and contain a variety of hydrolytic enzymes but have functionally diverse roles B Function a b Storage of waste products and toxic compounds some may deter herbivores Structure for plant cells water enters the vacuole by osmosis creating turgor pressure Reproduction vacuoles in flowers and fruits contain pigments whose colors attract pollinators and aid seed dispersal Catabolism digestive enzymes in seed vacuoles hydrolyze stored food for early growth Contractile vacuoles in freshwater protists get rid of excess water entering the cell due to solute imbalance Food vacuoles formed by phagocytosis Central vacuoles found in many mature plant cells hold organic compounds and water 1305 General Biology Jennifer Apodaca Week 8 Notes 101415 Cell Signaling Chapter 5 l The Cell Surface A Cell Communication is the process of cell detecting and responding to signals in the extracellular environment B Needed to coordinate cellular activities in a multicellular organism C Important to promote cell division D Cell communication or cell signaling involves incoming and outgoing signals a Signals are agents that influence the properties of cells b Signals affect the conformation of a receptor leading to a response in the cell E Why Do Cells need to respond to signals a Need to respond to a changing environment i Adaptation or a cellular response is critical for survival ii Glucose acts as a signal to yeast cells to increase number of glucose transporters and enzymes allowing efficient uptake and use of glucose iii Light acts as a signal in plants phototrophism to grow toward it II General Steps of CellCell Siqnalinq A Cellcell signaling occurs in 4 steps a Signal reception ligand binding several different types of signals can be received b 2 Signal processingtransduction c 3 Signal response d 4 Signal deactivation B The membrane plays a key role in a cell s response to environmental signals a In cell signaling cells can process information from their environment b Signals include physical stimuli like heat or light and chemicals ligands The cell must have receptors for the signal in order to respond Iquot Step 1 Signal Reception a Hormones and other cellcell signal bond to signal receptors i The presence of an appropriate receptor protein dictates which cells will be able to respond to a particular hormone ii identical receptors in diverse cells and tissues allow long distance signals to coordinate the activities of cells throughout a multicellular organism b The binding between a signal molecule ligand and receptor is highly specific c A shape change in a receptor is often the initial transduction of the signal d Signal receptors are proteins that change their shape or activity after binding to a signaling molecule i Receptors are dynamic and may change in their sensitivity to particular hormones ii Receptors can be blocked iii Signal receptors that bind to lipid soluble hormones are located inside the cell but most signal receptors are located in the plasma membrane e Receptors can be classified by their locations i Intracellular receptors are located inside a cell Their ligands are small or nonpolar and can diffuse across the membrane ii Membrane receptors located on the cell surface have large or polar Hgands that cannot diffuse through the membrane Most signal receptors are plasma membrane proteins a A chemical ligand fits into a 3D site on the receptor protein b The receptor may have a catalytic domain on the cytoplasmic side The ligand is an allosteric regulator it exposes the active site on the catalytic domain c Reversible binding is important because cells need to stop responding to a signal after the appropriate response has occurred d Inhibitors or antagonists can bind in place of the normal ligand f Ion Channel receptors are ligandgated ion channels they change shape when a ligand binds i Acetylcholine receptors on skeletal muscle cells bind acetylcholine to open the channel and allow Na to diffuse into the cell g Protein Kinase receptor also change shape when a ligand binds The new shape exposes or activates a cytoplasmic domain that has protein kinase activity it modifies proteins by adding phosphate groups i Not all protein kinases are receptors IV Step 3 Signal Resnonse A The ultimate response to a cellcell signal varies from signal to signal and from cell to cell but fall into two general categories a A change in which genes are being expressed in the target cell b Activate or deactivate a particular target protein that already exists in the cell V Step 4 Signal Deactivation A Turning off cell signals is just as important as turning them on B Cells have automatic and rapid mechanisms for signal deactivation a These mechanisms allow the cell to remain sensitive to small changes in the concentration of hormones or in the number and activity of signal receptors VI CrossTalk Interaction between signal pathways A Crosstalk integrates the diverse signals that a cell receives a Elements or products from one pathway may affect another pathway ultimately affecting the overall cell response i Cell response can be reduced when one pathway inhibits another ii Cell response can be increased when one pathway stimulates another There are multiple points where the cell can regulate the flow of information allowing the cell to respond appropriately to many simultaneous signals The activities of cells tissues and organs in different parts of a multicellular organism are coordinated by longdistance signals Hormones are long distance messengers i A hormone is an informationcarrying molecule that is secreted from a cell circulates in the body and acts on target cells far from the signaling cell ii Although hormones are usually small molecules and are typically present in minute concentrations they have a large impact on the condition of the organism as a whole iii The function and chemical structure of plant and animal hormones vary widely VII SiqnaL relaved between cells A Direct intercellular signaling a Cell junctions allow signaling molecules to pass from one cell to another B Contactdependent signaling a Some molecules are bound to the surface of cells and serve as signals to cell coming in contact with them C Autocrine signaling a Cells secrete signaling molecules that bind to their own cell surface or neighboring cells of the same type D Paracrine signaling a Signal does not affect cell secreting the signal but does influence cells in close proximity synaptic signaling E Endocrine signaling a Signals hormones travel long distances and are usually longer lasting