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Transcript
UNIT II – CELL STRUCTURE & FUNCTION • Baby Campbell – Ch 4,5,11 • Big Campbell – Ch 6,7,8,11 I. DISCOVERY OF CELLS • History of Microscopes _____________________________________ First to try stacking several lenses together to view tiny objects. Looked at pond water First scientist to describe living cells as seen through a microscope. _____________________________________ Used the microscope to examine thin slices of cork. He called the tiny boxes he saw cells. He chose the name "cells" because the chambers he saw reminded him of rooms in a monastery which were called cells. • Cell Theory I. DISCOVERY OF CELLS, cont. • Types of Microscopes Compound Light Microscope ___________________ Ratio of an objects image to its real size __________________ Measure of clarity of an image Electron Microscope __________________ Electron Microscope (SEM) Used to study the surface of the specimen __________________ Electron Microscope (TEM) Used to study the internal structure of cells TEM SEM II. CELL TYPES • _________________ Cells Typically smaller than eukaryotes Bacteria Kingdom Archaebacteria Kingdom Eubacteria No true nucleus – DNA found as a single chromosome in region called ________________ II. CELL TYPES, cont • Structure found in all prokaryotic cells _____________ _____________ _____________ _____________ _____________ • Additional structures that may be present _____________ _____________ _____________ II. CELL TYPES, cont • ___________________ Cells Larger, more complex Contain true nucleus and membranebound organelles suspended in cytosol Composed of Nucleus Ribosomes Endomembrane System o o o o ER Golgi Apparatus Lysosomes Vacuoles Mitochondria/Chloroplasts Peroxisomes Cytoskeleton III. EUKARYOTIC CELL STRUCTURES • _____________________ Control center of eukaryotic cell Made up of ________________________ Double membrane that protects nucleus; continuous with ER Contains _____________ to allow RNA to leave nucleus ________________________ Site of ribosome and rRNA production ________________________ DNA wrapped in protein Will condense during cell division to form chromosomes III. EUKARYOTIC CELL STRUCTURES, cont • Endomembrane System – membranes are related either through physical continuity or by the transfer of membrane segments as vesicles Endoplasmic Reticulum (“within the cytoplasm”; “little net”) Interconnected network continuous with nuclear envelope Rough ER Site of __________________________ Smooth ER Synthesis of _______________ Metabolism of _________________ ____________________ of drugs & poisons _________________________________ “Cell postmaster” Receives transport vesicles from ER; modifies, stores, and ships products Receiving side is known as the ________ face; shipping side is known as the __________ face III. EUKARYOTIC CELL STRUCTURES, cont • Endomembrane System, cont ______________________________ Sacs containing hydrolytic enzymes Used for recycling cellular materials, destroying pathogens ______________________________ Storage sac Plants typically have large, central vacuole surrounded by membrane called ___________________. Absorbs water and helps plant cell to grow larger Some protists have contractile vacuole to pump out excess water Endomembrane System The endomembrane system plays a key role in the synthesis (and hydrolysis) of macromolecules in the cell. III. EUKARYOTIC CELL STRUCTURES, cont • ____________________________ Suspended in cytosol or found on rough ER Site of protein production in a cell • _____________________________ Site of ________________________________ (making of ATP) Contain their own DNA, ribosomes Found in virtually all eukaryotes cells Enclosed by 2 membranes; inner membrane has folds called _____________ to increase surface area III. EUKARYOTIC CELL STRUCTURES, cont • _____________________________ Type of plastid that carries out _____________________ by converting solar energy to chemical energy (glucose) Contain membranous system of flattened sacs called _______________ – stack is called a _____________ Fluid surrounding thylakoids is called ___________ Contains its own DNA, ribosomes III. EUKARYOTIC CELL STRUCTURES, cont • ____________________________________ Membrane-bound compartments that use O2 to carry out metabolism H2O2 is produced; broken down by enzymes to produce ______ & ______ • ____________________________________ Provides structural support to cell More extensive in animal cells Composed of three types of proteins • ___________________________ – Thinnest filaments …….AKA………. ____________ filaments. – Bundles of them form microvilli - extensions of the cell membrane found in some cells to increase surface area. – Interact with myosin in muscle cells to create movement • _________________________________ – In between in thickness; more permanent than microtubules/microfilaments. • _________________________________ – Hollow rods that support cell, serve as tracks for movement within cell. – Help separate chromosomes during cell division - occurs in a region called centrosome, which is the location of centrioles in animal cells. – Cilia, flagella are constructed from bundles of microtubules covered by extensions of the cell membrane. IV. CELL BOUNDARIES • Cell Wall Found in ___________, _______, ________________, and some _________________ Functions Rigid structure; protects cell Maintains shape of cells Prevents excess water uptake Plant cell wall _________ - primary component Pectin - Sticky polysaccharide found between cell walls of adjacent cells; found in middle lamella Plasmodesmata - Perforations between adjacent cell walls that allow for movement of materials from one cell to another IV. CELL BOUNDARIES, cont • Extracellular Matrix Found in animal cells Holds cells together, protects & supports cells Allows for communication between cells Composed primarily of ______________________ – proteins with carbohydrate chains that are covalently-bonded Must abundant glycoprotein in most animals is _____________ • Intracellular Junctions Tight Junctions – Fuses membranes together tightly; prevents leakage of fluid Desmosomes (Anchoring Junctions) – Fasten cells together in sheets Gap Junctions – Allow for movement of cytoplasm from one cell to another; important in communication between cells IV. CELL BOUNDARIES, cont • ____________________________ Selectively-permeable barrier found in all cells Composed primarily of _______________________ bilayer Fluid Mosaic Model “Fluid” – Not a rigid structure. Organization due to high concentration of water inside & outside cell IV. CELL BOUNDARIES, cont Proteins - “Mosaic” – Assortment of different proteins embedded in bilayer; determine most of membrane’s specific functions. Act as channels, pumps, enzymes in metabolism, binding sites, etc o _____________ Proteins – Embedded in phospholipid layer o _____________ Proteins – Bound to surface of membrane Carbohydrates – “ID tags” that identify cell. Enable cells to recognize each other and foreign cells. May be bonded to lipids (glycolipids) or proteins (glycoproteins) ____________________ – Found in animal cells for stability V. CELL TRANSPORT V. CELL TRANSPORT, cont • ________________ Transport – Movement of materials from _______ to ______ concentration. No energy output required. ___________________ - Random movement of a substance across membrane down concentration gradient until equilibrium is reached. ________________________________________ – Passive transport of molecules across cell membrane with the help of transport proteins. Water is polar – requires protein channels called aquaporins to move in and out of cell. Glucose also requires protein channels due to size. V. CELL TRANSPORT, cont • Passive Transport, cont ______________ – Diffusion of water across a membrane. ______________ refers to tendency of cell to gain or lose water. If the solution is Isotonic to the cell – Solute concentration is same on both sides of membrane. No net movement of water. Hypertonic to the cell – Concentration of solute is greater outside cell → water moves in until equilibrium is reached. Cell may shrivel. Hypotonic to the cell – Concentration of solute is lower outside cell → water moves into cell until equilibrium is reached. Cell may swell to bursting point. Water moves towards the high solute concentration!!!!! V. CELL TRANSPORT, cont • Passive Transport/Osmosis, cont Osmoregulation Cells must have mechanism to prevent excess loss, uptake of water Cell wall, contractile vacuole _______________________ – Seen in plants; excessive water loss causes cell membrane to pull away from cell wall V. CELL TRANSPORT, cont V. CELL TRANSPORT, cont • ____________ Transport – Movement of materials against concentration gradient. Requires energy output by cell Carrier Proteins – Na+ / K+ Pump V. CELL TRANSPORT, cont • Active Transport, cont _________________ – Secretion of biomolecules by fusion of vesicles with cell membrane. Biomolecules “spit out”. _________________ – “Sucking In”. Cell membrane surrounds, engulfs particle or biomolecule, pinches in to form vesicle. ______________________ – “Sucking in” food particles ______________________ – “Sucking in” fluid droplets Receptor-mediated Endocytosis – Very specific VII. CELL SIGNALING • Coordinates cell activities, development • Initiates series of responses known as signal transduction pathway. Typically involves 3 steps: ________________ – Target cell’s detection of signal molecule due to binding of signal molecule to receptor protein in cell membrane ________________– Binding of signaling molecule changes receptor protein; triggers a sequence of events within cell ________________– Results in specific cellular response; for example, activation of genes, enzyme catalysis, etc. • Cyclic AMP – Intracellular compound often involved in signal transduction pathways. VII. CELL SIGNALING, cont VIII. THE WORKING CELL • Metabolism _____________________ Pathway – Breaks down molecules; releases energy _____________________ Pathway – Pathway that synthesizes larger molecules from smaller ones; requires energy • Energy Kinetic Energy – Associated with relative motion of objects Potential Energy – Energy that matter possesses; stored energy Chemical Energy – Potential energy of molecules • Thermodynamics ________ Law of Thermodynamics states that total amount of energy in universe is constant – can be transferred or transformed, but it cannot be created or destroyed ________ Law of Thermodynamics states that energy is lost to the environment as heat; that is, some energy becomes unusable VIII. THE WORKING CELL, cont • Chemical Reactions are classified according to whether they require or produce energy _____________________ – Requires net input of energy. Energy is then stored in products as potential energy. _____________________ - Release energy. _____________________– Often used in cellular metabolism. Energy released in exergonic rxn is used to drive endergonic rxn. VIII. THE WORKING CELL, cont • ATP – Adenosine triphosphate. Nucleotide that stores & provides usable energy to the cell Structure of ATP Adenine – nitrogen base Ribose – pentose 3 Phosphate groups VIII. THE WORKING CELL, cont • ATP, cont Phosphorylation ATP contains potential energy, especially between 2nd and 3rd phosphate groups. P – P bond is unstable and easily broken by hydrolysis. Exergonic. Coupled with endergonic rxn – specifically, by transferring phosphate group from ATP to another molecule. Known as phosphorylation.