BIOL 1305, Lecture Notes, Weeks 4 and 5
BIOL 1305, Lecture Notes, Weeks 4 and 5 BIOL 1305
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This 12 page Class Notes was uploaded by Rachel Pankuch on Saturday October 3, 2015. The Class Notes belongs to BIOL 1305 at University of Texas at El Paso taught by Horacia O Gonzalez in Summer 2015. Since its upload, it has received 34 views. For similar materials see General Biology in Biology at University of Texas at El Paso.
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Date Created: 10/03/15
BIOL 1305 General Biology Professor Horacio Gonzalez Email Monzalez utenedu Week 4 and 5 Notes from Lecture Chapter 4 Cells Cell theory the first unifying theory of biology Cells are fundamental units of life Everything responsible for life is contained Within the cell All organisms are comprised of cells All cells come from preexisting cells Studying biology is the same as studying life Life is continuous Surface areatovolume ratio Cells are tiny to maintain their areatovolume ratio The volume determines metabolic activity The surface area determines how many substances can leave or enter cell As volume increases surface area decreases Looking for cells To find or look at different cells microscopes are used Light microscopes use glass lenses and a light source Resolution 02 pm Electron microscopes electromagnets focus an electron beam Resolution 20 nm Can only observe dead cells Chemical analysis of cells Involves breaking cells with chemicals The composition and chemical reactions of the extract can be examined Plasma membrane All cells have it Complex Very exible Controls materials Composed of a phospholipid bilayer Is a selectively permeable barrier that allows cells to maintain a constant internal environment Is important in communication and receiving signals Often has proteins for binding and adhering to adjacent cells Types of cells Prokaryotic Have no membraneenclosed components Do not have a nucleus B acteria Good for research Its DNA is a long circular chromosome located in nucleoid and ows freely Rest of the cell is made out of cytoplasm Cytosol water and dissolved materials Ribosomes sites of protein synthesis Are complex organelles Where translation occurs Has a rigid cell wall to protect itself Called peptidoglycans in bacteria cells Some have an additional slimy membrane called a capsule Some swim by agella Eukaryotic plant and animal cells and human cells Have membraneenclosed components called organelles such as the nucleus ribosomes cytoplasm and a plasma membrane Evolved from prokaryotes 10X larger than prokaryotes DNA located in nucleus Two types ofEukaryotes Animal cells Nucleus has the largest volume Comprised of chromatin Enclosed to protect DNA Cytoplasm very reactive Mitochondria the power plant of the cell Involves energy Beanshaped and looks like bacteria Inner membrane composed of proteins Travel around the cell giving offaway energy Important in cell differentiation Important in research Cytoskeleton each animal cell has a skeleton Three di erent parts of the cytoskeleton Microtubules Helps a cell or parts of a cell to move Determine cell shape Are made from the protein actin which attaches to the plus end and detaches at the minus end of the lament The filaments can be made shorter or longer Cilia short usually many present move with stiff power stroke and exible recovery stroke Flagella longer usually one or two present movement is snakelike Cilia and agella appear in a 9 2 arrangement Intermediate laments At least 50 different kinds in six molecular classes Have tough ropelike protein assemblages more permanent than other filaments and do not show dynamic instability Anchor cell structures in place Resist tension maintain rigidity And microfilaments The largest diameter components with two roles Form rigid internal skeleton for some cells or regions Act as a framework for motor proteins to move structures in the cell Supports cells Involved in cell and organelle movement Provides movement Rough endoplasmic reticulum Site of much protein synthesis Some ribosomes attached to surface making it rough More linear elongated Usually next to nucleus Where most proteins are produced Golgi apparatus the post office of the cell More circular Independent oating Smooth endoplasmic reticulum No ribosomes attached to surface making it smooth Important in detoxification and metabolism More tubular Abundant in cells With metabolism Plasma membrane Very exible Ribosomes Attached to the rough endoplasmic reticulum The only organelle not enclosed in an organelle membrane some are called organi Translate the nucleotide sequence of messenger RNA into a polypeptide chain Centrioles Associated With nuclear and cell diVision Control movement of chromosomes Extracellular matrix Many animal cells are surrounded by it The fibrous component is the protein collagen The gellike matrix consists of proteoglycans A third group of proteins links the collagen and the matrix together Hold cells together in tissues Contribute to physical properties of cartilage skin and other tissues Filters materials Orient cell movement during growth and repair Plant cells Ribosomes Float freely in cytoplasm of prokaryotes Site of protein synthesis Have a larger and smaller subunit Each subunit consists of ribosomal RNA rRNA bound to smaller protein molecules Translate the nucleotide sequence of messenger RNA into a polypeptide chain Nucleus Largest organelle Site of DNA and DNA replication Where DNA is transcribed to RNA Contains the nucleolus Surrounded by two membranes that form the nuclear envelope Nuclear pores in the envelope control movement of molecules between nucleus and cytoplasm DNA combines with proteins to form chromatin in long thin threads called chromosomes Nucleolus Where ribosomes begin to be assembled from RNA into proteins Golgi apparatus Processes and packages proteins Composed of attened sacs cisternae and small membraneenclosed vesicles C is region receives vesicles containing protein from the ER Trans region vesicles bud off from the Golgi apparatus and travel to the plasma membrane or to lysosomes Medial region lies in between the trans and cis regions Mitochondria Chemical energy is converted to energyrich ATP Has two membranes Outer membrane quite porous Inner membrane extensive folds called cristae to increase surface area The uidfilled matrix inside the inner membrane contains enzymes DNA and ribosomes Cell wall Supports the cell Semirigid structure outside the plasma membrane The brous component is the polysaccharide cellulose The gellike matrix contains crosslinked polysaccharides and proteins Cytoskeleton Supports and maintains cell shape Holds organelles in position Moves organelles Is involved in cytoplasmic streaming Interacts with extracellular structures to anchor cell in place Dynamic instability allows quick assembly or breakdown of the cytoskeleton Peroxisome Break down toxic peroxides Plasmodesmata Plasma membranelined channels connecting adjacent plant cells Allow movement of water ions small molecules hormones and some RNA and proteins Glyoxysomes Found only in plants are where lipids are converted to carbohydrates for growth Chloroplasts Harvest energy of sunlight to produce sugar Are organelles Contain chlorophyll and is the site of photosynthesis Enclosed within two membranes with a series of internal membranes called thylakoids Smooth endoplasmic reticulum Chemically modifies small molecules such as drugs and pesticides Is the site of glycogen degradation in animal cells Is the site of synthesis of lipids and steroids Rough endoplasmic reticulum Proteins are chemically modified and tagged for delivery Has ribosomes attached to begin protein synthesis Endomembrane system Includes the nuclear envelope endoplasmic reticulum Golgi apparatus and lysosomes Vesicle Shuttle substances between the various components as well as to the plasma membrane Primary lysosomes Originate from the Golgi apparatus Contain digestive enzymes and are the site where macromolecules are hydrolyzed into monomers Vacuoles 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 owers and fruits contain pigments whose colors attract pollinators and aid seed dispersal Catabolism digestive enzymes in seeds vacuoles hydrolyze stored food for early growth Phagocytosis part of the plasma membrane encloses the material and a phagosome is formed Phagosomes then fuse with primary lysosomes to form secondary lysosomes Enzymes in the secondary lysosome hydrolyze the food molecules Phagocytes are cells that take materials into the cell and break them down Autophagy the programmed destruction of cell components and lysosomes are where it occurs Lysosomal storage diseases occur when lysosomes fail to digest the components Photosynthesis converts light energy into chemical energy Plant and algae cells contain plastids that can differentiate into organelles some are used for storage Cell junctions Specialized structures that protrude from adjacent cells and glue them together seen often in epithelial cells Tight junctions Prevent substances from moving through spaces between cells Desmosomes Hold cells together but allow materials to move in the matrix Gap junctions Channels that run between membrane pores in adjacent cells allowing substances to pass between the cells Chapter 5 Cell Membrane Fluid mosaic model A system that is uid and dynamic Phospholipid bilayer Makes up the cell membrane Flexible Interior is uid allowing lateral movement of molecules Fluidity depends on temperature and lipid composition Composed of a polar phosphate group and a long hydrocarbon chain Held together by van der Waals forces Proteins within the membrane Number of proteins varies With cell function Functional macromolecules Within cells May connect cells together Some cross phospholipid bilayer Transmembrane proteins may have different domains on either side of the membrane The two sides of the membrane can have very different properties Interact With interior cytoskeleton Membranes have carbohydrates on the outer surface that serve as recognition sites for other cells and molecules Glycolipids Glycoproteins Cell arrangement Cells arrange themselves in groups by cell recognition and cell adhesion Binding of cells is usually homotypic the same molecule sticks out from both cells and forms a bond Some binding is heterotypic the cells have different proteins Selective permeability some substances can pass through but not others Passive transport No outside energy is required Diffusion Is net movement from regions of greater concentration to regions of lesser concentration The process of random movement toward equilibrium Particles continue to move but there is no net change in distribution Di usion rate depends on Diameter of the molecules or ions Temperature of the solution Electric charges Concentration gradient Simple diffusion small molecules pass through the lipid bilayer Osmosis The diffusion of water Depends on the number of solute particles present not the type of particles Water crosses membranes at a faster rate than simple diffusion Hypertonic Water leaves cell to the exterior Has more solutes in exterior example salt Hypotonic Water enters cell More solutes in interior Isotonic Same amount of solutes in exterior and interior Aquaporins specific channels that allow large amounts of water to move along its concentration gradient Facilitated diffusion Polar molecules can cross the membrane through channel proteins and carrier proteins Channel proteins have a central pore lined With polar amino acids Carrier proteins in the membrane facilitate diffusion by binding substances Ion channels important channel proteins Most are gated can be closed or open to ion passage 10 Active transport Requires the input of energy to move substances against their concentration gradients Used to overcome concentration imbalances that are maintained by proteins in the membrane Energy source for active transport is often ATP Active transport is directional and moves a substance against its concentration gradient A substance moves in the direction of the cell s needs usually by means of a specific carrier protein Two types of active transport Primary active transport Involves hydrolysis of ATP for energy Secondary active transport Uses the energy from an ion concentration gradient or an electrical gradient Uses energy that is regained by letting ions move across the membrane with their concentration gradients May begin with passive diffusion of a few ions or may involve a carrier protein that transports both a substance and ions Sodium potassium Na K pump An integral membrane protein that pumps Na out of a cell and K in One molecule of ATP moves two K and three Na ions Passage of macromolecules through vesicles Macromolecules that are too large or too charged to pass through biological membranes instead pass through vesicles To take up or to secrete macromolecules cells must use endocytosis or exocytosis Endocytosis Bring molecules into the cell Three types of endocytosis Phagocytosis Part of the membrane engulfs a large particle or cell A food vacuole phagosome forms and usually fuses With a lysosome Where contents are digested Pinocytosis Vesicles also form 11 The vesicles are smaller and bring in uids and dissolved substances as in the endothelium near blood vessels Receptor mediated endocytosis Depends on receptors to bind to specific molecules their ligands The receptors are integral membrane proteins located in regions called coated pits When receptors bind to their ligands the coated pit invaginates and forms a coated vesicle Exocytosis Moves materials out of the cell in vesicles The vesicle membrane fuses with the plasma membrane and the contents are released into the cellular environment Important in the secretion of substances made in the cell Signal transduction pathway A sequence of molecular events and chemical reactions that lead to a cellular response following the receptor s activation by a signal Involves a signal a receptor and a response A signal molecule or ligand fits into a threedimensional site on the receptor protein Ligands are generally not metabolized further but their binding may expose an active site on the receptor Binding is reversible and the ligand can be released to end stimulation An inhibitor or antagonist can bind in place of the normal ligand Receptors can be classified by their location in the cell Cytoplasmic receptors Have ligands such as estrogen that are small or nonpolar and can diffuse across the membrane Membrane receptors Have large or polar ligands such as insulin that cannot diffuse and must bind to a transmembrane receptor at an extracellular site Receptors are also classified by their activity Ion channel receptors Change their threedimensional shape when a ligand binds Protein kinase receptors Change their shape when a ligand binds Protein kinases catalyze the following reaction ATP protein gt ADP phosphorylated protein Each protein kinase has a specific target protein whose activity is changed when it is phosphorylated 12 G protein linked receptors Expose a site that can bind to a membrane protein a G protein The G protein is partially inserted in the lipid bilayer and partially exposed on the cytoplasmic surface Many G proteins have three subunits and can bind three molecules The receptor GDP and GTP used for energy transfer An effector protein to cause an effect in the cell Inhibition Protein kinase A inactivates glycogen synthase through phosphorylation and prevents glucose storage Activation Phosphorylase kinase is activated when phosphorylated and is part of a cascade that results in the liberation of glucose molecules Cells are exposed to many signals and may have different responses Autocrine Signals affect the same cells that release them Paracrine Signals diffuse to and affect nearby cells Hormones Travel to distant cells Cells can alter the balance of enzymes in two ways Synthesis or breakdown of the enzyme Activation or inhibition of the enzymes by other molecules Cell functions change in response to environmental signals Opening of ion channels Alterations in gene expression Alteration of enzyme activities
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