2What Are the Basic Attributes of Cells? All cells share common featuresDNA and RNAplasma membranecytoplasm consists of all the fluid and structures that lie inside the plasma membrane but outside of the nucleusThe fluid portion of the cytoplasm (cytosol) contains water, salts, and organic moleculesMost of the cell’s metabolic activities occur in the cell cytoplasm
3The Plasma Membrane Functions: glycoproteincarbo-hydrateextracellular fluid (outside)cytoplasm (inside)cholesterolmembraneproteinchannel proteincytoskeletonA phospholipid bilayerhelps to isolate thecell's contentsProteins help the cellcommunicate withits environmentFunctions:isolates the cell’s contents from the external environmentregulates the exchange of essential substancesallows communication between cellscreates attachments within and between cellsregulates biochemical reactionsPhospholipid bilayer – allows the cell to maintain essential differences in concentrations of material.Proteins are responsible for exchanging and communicating, controlling reactions, and forming connections.10,000 membranes stacked atop one another would scarcely equal the thickness of one page.Membranes vary from one tissue type to another, and their structures can also change dynamically in response to their surroundings.Fig. 4-2
4Eukaryotic cellsPlants, animals, protists, and fungi
5A Generalized Animal Cell microfilamentsnuclear envelopenuclear porenucleuschromatin (DNA)cytosolnucleolusmicro- (cytoskeleton) tubulesflagellumbasal bodyroughendoplasmicreticulumvesicleintermediatefilaments(cytoskeleton)cytoplasmGolgiapparatusOrganelles – membrane-enclosed structures, each specialized for a certain function.centrioleribosomeson rough ERlysosomesmoothendoplasmicreticulumexocytosis ofmaterial fromthe cellmitochondrionplasmamembraneFig. 4-3free ribosome
7What Are the Major Features of Eukaryotic Cells? Cell wallsouter surfaces of plants, fungi, and some protistsPlant cell walls are composed of celluloseFungal cell walls are made of chitinCell walls are porous, allowing oxygen, carbon dioxide, and water carrying dissolved molecules to flow easily through themPlasmodesmata - openings that connect adjacent cells in plantsThe plasma membrane is located just beneath the cell wall1. Nonliving, stiff coating secreted outside cell membrane.2 & 3. some polysaccharides (including prokayrotes) Protists have cellulose, protein, or glassy silica.4. Protective but also ….
8What Are the Major Features of Eukaryotic Cells? microfilamentsintermediatefilamentsmicrotubulesmicrotubules (red)nucleusmicrofilaments (blue)(a) Cytoskeleton(b) Light micrograph showing the cytoskeletonCytoskeletonprovides shape, support, movement, cell divisionThe cytoskeleton is composed of three types of protein fibers:microfilamentsintermediate filamentsmicrotubulesFunctions: shape and support (changes cell shape) cells without cell wallscell movement (cilia & flagella)organelle movementguide chromosomes and separate the dividing cell
10Cilia and Flagella Functions: 0.1 micrometerciliumplasma membranebasal bodysection of ciliumcentral pair ofmicrotubulesprotein“arms”ParameciumFunctions:move the cell through fluidmove fluid past the cellBoth cilia and flagella are slender extensions of the plasma membrane supported by microtubules.Cilia means eyelash (shorter and numerous)Flagella means whip (longer, usually only 1 or 2)Both common in protists.Both contain a ring of 9 fused pairs of microtubules, with an unfused pair in the center.
11How Cilia and Flagella Move cilia liningtracheapropulsion of fluid(a) Ciliumpower strokereturn strokeplasma membranedirection of locomotionpropulsion of fluidflagellum ofhuman spermRequires energy to continuously undulateCilia – energy similar to oars on a rowboatFlagella – energy compared to a propeller on a motorboatParamecium use cilia to swim through water, others use flagellaCilia used in gills of oystersIn mammals:Cilia – respiratory tract, female reproductiveFlagella – any spermsurface ofhuman eggcell(b) Flagellumcontinuous propulsionFig. 4-7
12The Nucleus Control center Nuclear envelope - consists of a double membrane perforated by nuclear poresChromatinNucleolus(b) Nucleus of a yeast cell(a) The nucleusnuclearenvelopeporesnucleolusribosomeschromatinnucleusnuclear pores withnuclear pore complexStores all information needed to construct the cell and direct the countless chemical reactions for life and reproduction. (make proteins)Largest organelleIsolated from the rest of the cell by a …nuclear pore complex are protein gatekeepers allowing RNA thru for protein synthesis2. (colored substance) – chromosomes made of DNAwhen not dividing – extremely long, thin strands cannot see3. (little nuclei) Site of ribosome assemblyThe nucleolus consists of ribosomal RNA, proteins, ribosomes in various stages of synthesis, and DNA
13Ribosomes small particle composed of ribosomal RNA and proteins site of protein synthesis in the cytoplasmribosomemRNAamino acidpolyribosomegrowingproteinFig. 4-10
14Endoplasmic Reticulum Vesicles are membranous sacs that transport substancesThe endoplasmic reticulum (ER) is a series of interconnected membranes that form a labyrinth of interconnected flattened sacs and channels within the cytoplasmAll the proteins and phospholipids of cell membranes are synthesized in the EREndomembrane system – loosely connected compartments. Segregate molecules from the surrounding cytosol and ensure orderly process of chemical reactions.Vesicles – temporaryReticulum means network
15Endoplasmic Reticulum There are two forms of ER:Smooth endoplasmic reticulum has no ribosomes, detoxifies drugs, and synthesizes lipids like steroid hormones made from cholesterolRough endoplasmic reticulum is studded with ribosomes and synthesizes proteins destined for other membranes or for secretionribosomessmooth ERrough ERvesiclesSmooth ER – scarce in most cells except liver, mammalian reproductive.detoxifies alcohol, metabolic wastes like ammonia
16The Golgi ApparatusFunctions: sorts, chemically alters, and packages important moleculesIt synthesizes some polysaccharides used in plant cell walls, such as cellulose and pectinIt packages the finished molecules into vesicles that are then transported to other parts of the cell (lysosomes) or to the plasma membrane for exportVesicles from theER merge withthe GolgiapparatusVesicles carryingmodified protein leavethe Golgi apparatusGolgiNamed for the Italian cell biologist.
17Lysosomes Serve as the cell’s digestive system Golgi apparatusdigestiveenzymeslysosomefoodvacuolesThe Golgiapparatus modifiesthe enzymes asthey pass throughits compartmentsThe enzymesare packaged intolysosomes, whichbud from the(extracellular fluid)Digestiveenzymes aresynthesized onribosomes andtravel throughthe rough ER(cytoplasm)vesicles and travel tothe Golgi apparatusA lysosome fuseswith a food vacuole,and the enzymesdigest the food54321Serve as the cell’s digestive systemA lysosome fuses with a food vacuole and digests food into basic nutrientsDigest worn-out organellesDigest food from individual proteins to microorganisms like bacteria.Contain enzymes that can break down almost any type of biological molecule.
18VacuolesServe many functions, including water regulation, support, and storageMost cells contain one or moresacs of cell membrane filled with fluid containing various moleculesMany freshwater organisms possess contractile vacuoles composed of collecting ducts, a central reservoir, and a tube leading to a pore in the plasma membrane that carries excess water out of the organismSome vacuoles are temporary large vesicles (food vacuoles)Permanent vacuoles in some freshwater protists and in plant cells:
19Contractile Vacuoles Fig. 4-15 contractile vacuole Water enters the collecting ductsand fills the central reservoir(a) ParameciumcollectingductscentralreservoirporeFreshwater constantly leaks into contractile vacuoles through the cell membrane (osmosis).So much water would cause the organism to burst.Excrete the water by moving salt into collecting ducts then central reservoir.The reservoir contracts, expellingwater through the poreFig. 4-15(b) Contractile vacuole
20Vacuoles Central vacuoles Found in plants Functions: cytoplasm(a) Turgor pressure provides supportcentral vacuolecell wallplasma membraneWhen water is plentiful, it fillsthe central vacuole, pushesthe cytoplasm against the cellwall, and helps maintain thecell's shapeWhen water is scarce, thecentral vacuole shrinks and thecell wall is unsupportedDeprived of the supportfrom water, the plantwiltsWater pressuresupports theleaves of thisimpatiens plant(b) Loss of turgor pressure causes the plant to wiltVacuolesCentral vacuolesFound in plantsFunctions:To maintain water balanceTo store hazardous wastes, nutrients, or pigmentsTo provide turgor pressure on the cytoplasm to keep cells rigidwhich occupy three-quarters or more of the volume of many mature plant cells, are used in several ways:By regulating ion content of cytosol… As well as substances to deter animals from eating their leaves, nutrients (sugar and amino acids) not immediately needed, blue or purple pigments for the colors of flowers.Support. Substances attract water into it -> water pressure – turgor pressureprovides support for the non-woody parts of the plant(when you forget to water your plants)
21Mitochondria Extract energy from food molecules to make ATP “Powerhouse” of the cellDouble membrane with cristaeoutermembraneinnermatrixcristae0.2 micrometerFound in large numbers of cells that are metabolically active (muscle) less in cartilage.
22Chloroplast Site of photosynthesis Double membrane The thylakoid membranes contain the green pigment chlorophyll, which capture sunlight and make sugar from CO2 and water (photosynthesis)outermembraneinnerstromathylakoidchannelinterconnectingthylakoidsgranum(stack of thylakoids)1 micrometerPlants and some protists.Stroma – fluidThylakoid – a stack of hollow membranous sacsChlorophyll captures the energy of sunlight and transfers it to other molecules in the thylakoid membranes. These molecules transfer the energy to ATP which diffuses into the stroma, where their energy is used to drive synthesis of sugar from CO2 and H2O.
23Plastids Storage Only in plants and photosynthetic protists starchglobulesplastid0.5 micrometerStorageOnly in plants and photosynthetic protistsDouble membraneStorage containers for various molecules, such as pigments or starchChloroplasts are highly specialized plastids.3. Pigments that give ripe fruits their yellow, orange, or red colors.store photosynthetic products produced during the growing season for over winterPotatoes are composed almost entirely of cells stuffed with starch-filled plastids
24Review QuestionsDescribe the structures and features shared by all cells.Define organelle.Which organelles are found in plants not animals?Describe each major structure and know its function.DNA, RNA, plasma membrane, cytoplasmMembrane bound specialized structure in the cytoplasmChloroplast, plastids, cell wall, vacuoles
27What Are the Major Features of Prokaryotic Cells? Most prokaryotic cells (bacteria) are less than 5 µm long, with a simple internal structure compared to eukaryotic cellsThey usually have a stiff cell wallProkaryotic cells can take several shapes:Rod-shaped (bacilli)Spiral-shaped (spirilla)Spherical (cocci)Prokaryotic cells are small and possess specialized surface featuresProkaryotic cells have fewer specialized structures within their cytoplasm (no organelles)Eukaryotic cells are umSingle celled2. Antibiotics interfere with cell wall synthesis, causing the bacteria to rupture.
28What Are the Major Features of Prokaryotic Cells? Some bacteria and archaea are propelled by flagellaInfectious bacteria may have polysaccharide adhesive capsules and slime layers on their surfacesPili are protein projections in some bacteria that further enhance adhesionIn the central region of the cell is an area called the nucleoid, which is separate from the cytoplasmWithin the nucleoid is a single, circular chromosome of DNASmall rings of DNA (plasmids) are located in the cytoplasmNone have cilia.Flagella is structured differently from eukaryotes.Capsules and slime layers are similar except that capsules are more organized structurally so more difficult to remove. Allows them to stick to surfaces, protect, and prevent drying out.Pili (hairs) from cell wall.attachment pili: short and abundantsex pili: few and long. Binds to a nearby bacterium of the same type and draws them together to exchange DNA.4. Also has some RNA and proteinThe single DNA carries essential genetic infoPlasmids carry genes that give the cell special properties (like inactivating antibodics)
29What Are the Major Features of Prokaryotic Cells? No nuclear membrane or membrane-bound organellesSome have internal membranes used to capture lightExtensive cytoskeletonThe cytoplasm may containfood granulesribosomes2. Some bacteria use membranes to organize enzymes for reactions. Lined up in order. Example …3. Proteins differ but play similar roles4. Food granules – store energy-rich molecules (glycogen)Ribosomes – protein synthesis but smaller and different RNA and proteins.
30Review QuestionsExplain the major differences between prokaryotic and eukaryotic cells.Describe the structure and function of the major surface features of bacteria.Describe the internal features of bacteria.
31A Protein Is Manufactured and Exported Vesicles merge with theplasma membrane andrelease antibodies into theextracellular fluidVesicles fuse with theGolgi apparatus, andcarbohydrates are addedas the protein passesthrough the compartmentsThe protein ispackaged into vesiclesand travels to the GolgiapparatusAntibody protein issynthesized on ribosomesand is transported intochannels of the rough ERCompleted glycoproteinantibodies are packagedinto vesicles on the oppositeside of the Golgi apparatus(extracellular fluid)(cytoplasm)vesiclesGolgi apparatusformingvesicle54321Fig. 4-13