5A Panoramic View of the Cell Prokaryotic Eukaryotic+only in bacteria/archaebacteria Protists, Fungi, Plantae, Animalia+no true nucleus/nuclear envelope true membrane-bound nucleus+genetic material in nucleoid region genetic material in nucleus+no organelles many organelles
6Animal vs. Plant Cell Unique to Plant Cells: - cell wall - large central vacuoleChloroplastsPlasmodesmataUnique to Animal Cells:CentriolesLysosomes- flagella and/or cilia
12The Nucleus and Ribosomes - enclosed by nuclear envelope- contains most of the genes thatcontrol the entire cell+ DNA organized withproteins into chromatin- nucleolusNuclear lamina – protein filamentsthat give structure to the innernuclear membrane
13The Nucleus and Ribosomes (con’t) - build proteins- RNA/proteincomplexes- free/bound
14The Endomembrane System Includes:nuclear envelopeEndoplasmic reticulumGolgi apparatusLysosomesVacuolesPlasma membrane*
15Endomembrane System (con’t) Endoplasmic reticulummanufactures membranestwo distinct regions+ smooth ER- synthesis of lipids- carbohydrate metabolism- detoxify drugs/poisons- stores calcium ions+ rough ER- manufacture proteins forsecretion- membrane production
16Endomembrane System (con’t) Golgi apparatusfinishes, sorts, and ships cell productstwo poles+ cis face+ trans faceEnzymes in the Golgi modify products of the ER in stagesas they move through the Golgi stack from cis to trans face.
36Cell Surfaces and Junctions Tight junctions – prevent fluid from moving between cell layers in a tissueDesmosomes – anchor adjacent cellsGap junctions – allows the movement of cytoplasm, ions, sugars, amino acids from one cell to the next
47Membrane Structure and Function (con’t) Fluid Mosaic ModelThe Fluid Quality of Membranes+ held together by hydrophobic interactions- lipids/proteins drift about laterally+ unsaturated hydrocarbon tails- maintain fluidity at low temperatures+ cholesterol- stabilizes the membranerestrains movement at high temp.hinders close packing at low temp.
48Membrane Structure and Function (con’t) Fluid Mosaic ModelMembranes as Mosaics+ membrane is collage of proteins- integral proteinstransmembrane- peripheral proteinsappendages
62Traffic Across Membranes Selective Permeabilityhydrophobic, small, lipid molecules pass easily across the membranehydrophilic, large, charged (polar) molecules cannot pass easilyHow do cells get the materials they need inside?
63Traffic Across Membranes (con’t) Passive TransportDiffusion+ the tendency for molecules of anysubstance to spread out into theavailable space- concentration gradient
64Passive Transport Requires no energy Occurs due to natural concentration gradientMolecules move from high concentration to low concentration (DOWN the gradient)3 TypesDiffusionOsmosisFacilitated Diffusion
67DiffusionA.K.A. simple diffusionMovement of small molecules across a selectively permeable membrane from an area of HIGH concentration to an area of LOW concentration w/o the use of energy (DOWN the concentration gradient)e.g. O2, CO2, urea, & alcohol
68Traffic Across Membranes (con’t) Passive TransportOsmosis+ the diffusion of water- hypotonic,hypertonic, isotonicTonicity – the ability of a solution to cause a cell to gain or lose waterOsmoregulation – the control of water balance e.g. contractile vacuole in paramecium
69Osmosis The diffusion of WATER across a selectively permeable membrane OSMOTIC PRESSUREThe pressure exerted on plasma membranes in solutionIsotonic solutionHypertonic solutionHypotonic solution
70Water PotentialThe physical property predicting the direction in which water will flow, controlled by the solute concentration
74Water Potential“Water potential" (Ψ) is a measure of the free energy of water; pure water (which has a high amount of free energy) is arbitrarily assigned a water potential of zero; units pressure: MPa; can be positive or negativeFactors that determine plant water potential: 1) amount of solutes- increasing concentrations will lower the free energy (water potential); termed osmotic potential (ψs)2) turgor pressure (ψp) in plant cell- positive pressure inside plant cells; increases free energy; loss of turgor = wilting
79Hypertonic SolutionsMore solute (salt) molecules outside the cell, which causes water to be sucked out of the cell.In plant cells, the central vacuole loses water and the cells shrink, causing plasmolysis resulting in the plant wilting.In animal cells, the cells also shrink.In both cases, the cell may die.This is why it is dangerous to drink sea water
80PlasmolysisA phenomenon in plant cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall when the cell loses water to a hypertonic environment.
82Hypotonic SolutionsThere are less solute (salt) molecules outside the cell, since salt sucks, water will move into the cell.The cell will gain water and grow larger. In plant cells, the central vacuoles will fill and the plant becomes stiff and rigid, the cell wall keeps the plant from burstingIn animal cells, the cell may be in danger of bursting, organelles called CONTRACTILE VACUOLES will pump water out of the cell to prevent this.
84Osmotic PotentialThe tendency of water to move across a selectively permeable membrane into a solutionDetermined by measuring the pressure required to stop the osmotic movement of water into the solution.
94Traffic Across Membranes (con’t) Active Transportenergy-requiring process+ ATPpumps molecules againstconcentration gradient+ Na+/K+ pump
95Active TransportRequires cell energy (ATP) to move molecules AGAINST the concentration gradient; from an area of LOW concentration to an area of HIGH concentrationSodium–Potassium pump (Exchange 3 sodium ions for 2 potassium ions)Hydrogen ion, or proton pump (Pump hydrogen ion against the concentration gradient)
96PhosphorylationThe addition of a phosphate (PO4) group (From ATP) to a protein or a small moleculeThis changes the protein shape
107Bulk Media TransportEndocytosis – Vesicle is created from the invagination of the plasma membrane, which pinches off, bringing large molecules into the cellPinocytosis – Cell drinking (endocytosis)Phagocytosis – Cell eating (endocytosis)Receptor Mediated Endocytosis – Substrate binds to receptor found on the plasma membrane to be brought into the cellExocytosis – Vesicle binds to the plasma membrane releasing the contents outside of the cell
113Traffic Across Membranes (con’t) Transport of Large MoleculesExocytosis+ the cell exports macromoleculesusing vesicles from Golgi apparatusEndocytosis+ the cell takes in macromoleculesby forming new vesicles from membrane- phagocytosis (“cellular eating”)- pinocytosis (“cellular drinking”)- receptor-mediated endocytosis+ ligands