Slide 1

Prokaryotic and Eukaryotic Cellular Structure Slide 2 Prokaryotic & Eukaryotic Cells: An Overview Prokaryotes Do not have membrane surrounding their DNA lack a nucleus Lack various internal structures bound with phospholipid membranes Are small, ~1.0 m in diameter Have a simple structure Composed of bacteria and archaea Slide 3 Prokaryotic & Eukaryotic Cells: An Overview Eukaryotes Have membrane surrounding their DNA Have a nucleus Have internal membrane-bound organelles Are larger, 10-100 m in diameter Have more complex structure Composed of algae, protozoa, fungi, animals, and plants Slide 4 Prokaryotic & Eukaryotic Cells: An Overview [INSERT FIGURE 3.1] Slide 5 Slide 6 Prokaryotic Cell Membrane Structure Referred to as phospholipid bilayer; composed of lipids and associated proteins Approximately half composed of proteins that act as recognition proteins, enzymes, receptors, carriers, or channels Integral proteins Peripheral proteins Glycoproteins Fluid mosaic model describes current understanding of membrane structure Slide 7 Cell Membrane Membranes contain a hydrophilic and hydrophobic side Composed of many different types of proteins Proteins in the lipid bilayer move freely within the membrane Slide 8 Cell Membrane Thin pliable lipid and protein envelope that defines a cell. Phospholipid bilayer Functions: Regulates nutrient and water intake Regulates waste removal Site of prokaryotic respiration Site of prokaryotic flagella attachment Involved in the distribution of genetic material during binary fission Slide 9 Prokaryotic Cytoplasmic Membranes Function Energy storage Harvest light energy in photosynthetic prokaryotes Selectively permeable Naturally impermeable to most substances Proteins allow substances to cross membrane Occurs by passive or active processes Maintain concentration and electrical gradient Chemicals concentrated on one side of the membrane or the other Voltage exists across the membrane Slide 10 Cell Membrane Slide 11 Slide 12 External Structures of Prokaryotic Cells Glycocalyces Gelatinous, sticky substance surrounding the outside of the cell Composed of polysaccharides, polypeptides, or both Slide 13 External Structures of Prokaryotic Cells Types of Glycocalyces Capsule Composed of organized repeating units of organic chemicals Firmly attached to cell surface Protects cells from drying out May prevent bacteria from being recognized and destroyed by host Slide 14 Capsule Polysaccharides or polypeptides in composition. Surround the cell wall in some bacteria. Function: Protection from phagocytosis Osmotic barrier Reservoir for nutrients Virulence factor Slide 15 Capsule Stain Slide 16 Slime Layer Consist of polysaccharide fibers that extend form the bacterial surface Functions: Protection Attachment Associated with biofilms Slide 17 External Structures of Prokaryotic Cells Types of Glycocalyces Slime layer Loosely attached to cell surface Water soluble Protects cells from drying out Sticky layer that allows prokaryotes to attach to surfaces Slide 18 Bacterial Appendages Flagella Axial Filaments Pili (Fimbriae) Slide 19 Bacterial Appendages Flagella Structures of locomotion Originate in the plasma membrane In bacteria rotate like a propellar Many different arrangements Slide 20 External Structures of Prokaryotic Cells Flagella Are responsible for movement Have long structures that extend beyond cell surface Are not present on all prokaryotes Slide 21 External Structures of Prokaryotic Cells Flagella Structure Composed of filament, hook, and basal body Flagellin protein (filament) deposited in a helix at the lengthening tip Base of filament inserts into hook Basal body anchors filament and hook to cell wall by a rod and a series of either two or four rings of integral proteins Filament capable of rotating 360 Slide 22 Bacterial Appendages Arrangements of Flagella A.Monotrichous B.Lophotrichous C.Amphitrichous D.Peritrichous Slide 23 Bacterial Appendages Axial filament (endoflagella) Originates in the cell membrane and transverses the length of the cell in the periplasmic space. As the endoflagella rotate to move the cell the characteristic shape is formed. Endoflagella are associated with spirochetes. Slide 24 External Structures of Prokaryotic Cells Endoflagellum is also know as an axial filament. Attached to the plasma embrane and transverses the entire cell. Responsible for the spirochete morphology. Slide 25 External Structures of Prokaryotic Cells Flagella Function Rotation propels bacterium through environment Rotation reversible, can be clockwise or counterclockwise Bacteria move in response to stimuli (taxis) Runs Tumbles Slide 26 Bacterial Appendages Fimbriae and Pili Rod-like proteinaceous extensions Slide 27 Bacterial Appendages Fimbriae Hollow tubes that protrude from some bacteria Compose of protein Slide 28 External Structures of Prokaryotic Cells Fimbriae Sticky, bristlelike projections Used by bacteria to adhere to one another, to hosts, and to substances in environment Shorter than flagella May be hundreds per cell Serve an important function in biofilms Virulence factor Slide 29 External Structures of Prokaryotic Cells Pili Tubules composed of pilin Also known as conjugation pili Longer than fimbriae but shorter than flagella Bacteria typically only have one or two per cell Mediate the transfer of DNA from one cell to another (conjugation) Slide 30 Bacterial Conjugation Transfer of plasmid DNA from a donor to a recipient. Process strengthens the bacterial cell and alows for survival in a competitive environment. Slide 31 Bacterial Inclusion Bodies 1. poly-Beta-hydroxybutyric acid - stores lipids for use in plasma membrane 2. glycogen - stores starch like polymer of sugar for energy production 3. Polyphosphate granules (metachromatic granules) - storage for phosphates for plasma membrane and the formation of ATP from ADP. 4. Sulfur granules - stores sulfur which is necessary for the metabolic reactions in biosynthesis. Slide 32 5. Mesosome Mesosomes - invagination of the plasma membrane that increases the surfaces area of the plasma membrane during binary fission. The mesosome also serves as a site for the attachment and distribution of genetic material during binary fission. Slide 33 Mesosome In prokaryotic cell division, called binary fission. A diagram of the attachment of bacterial chromosomes, indicating the possible role of the mesosome (an inward fold of the cell membrane) in ensuring the distribution of the "chromosomes" in a dividing cell. Upon attachment to the plasma membrane, the DNA replicates and reattaches at separate points. Continued growth of the cell gradually separates the chromosomes and allocates chromosome copies to the two daughter cells. Slide 34 Inclusion Bodies 6. gas vacuoles - storage of metabolic gases such as methane or hydrogen gas. The gas vacuoles help in the buoyancy of the cell and aids in it motility. 7. ribosomes - responsible for the synthesis of proteins. 8. nucleoid material - the genetic material of bacteria, which usually is balled up in the cell. During binary fission the nucleoid material unravels within the cell in order to be copied and distributed to the daughter cells. 9. Plasmid - small fragments of self-replicating extrachromosomal DNA that codes for the resistance to antibiotics or for the productions of a specific metabolite, i.e. toxins, pigments. These plasmids may be transferred from one bacterial cell to another by the F-pili. Slide 35 Inclusion Bodies 9. Plasmid - small fragments of self-replicating extrachromosomal DNA that codes for the resistance to antibiotics or for the productions of a specific metabolite, i.e. toxins, pigments. These plasmids may be transferred from one bacterial cell to another by the F-pili. Slide 36 Inclusion Bodies These plasmids may be transferred from one bacterial cell to another by the F-pili. Slide 37 Slide 38 Inclusion Bodies 10.Endospores - a survival mechanism of certain genera of bacteria such as Clostridium and Bacillus. The endospores are composed of a complex of dipicolinc acid and calcium and the function of the endospore is to protect the bacterial chromosome. The endospores are very resistant to heat, desiccation, freezing, and other physical properties such as pesticides, antibiotics, dyes, and acids. Slide 39 Inclusion Bodies The endospores may remain dormant for many years until the environment becomes suitable to sustain the life of the bacteria. The endospore will then germinate to form an exact copy of the parent cell that produced it. Slide 40 Slide 41 Slide 42 Eukaryotic Cell Walls & Cytoplasmic Membranes Fungi, algae, plants, and some protozoa have cell walls but no glycocalyx Composed of various polysaccharides Cellulose found in plant cell walls Fungal cell walls composed of cellulose, chitin, and/or glucomannan Algal cell walls composed of cellulose, proteins, agar, carrageenan, silicates, algin, calcium carbonate, or a combination of these Slide 43 Cell Walls Three different types of cell walls and their compositions: Fungal cell walls are composed of cellulose and/or chitin. Plant cell walls are composed of cellulose. Algal cell walls are composed of cellulose, silicon, and calcium carbonate. Slide 44 Plasma Membrane Consist of a lipid bilayer and associated proteins. The Plasma Membrane of Eukaryotic cells resembles and functions in the same manner as the prokaryotic plasma membrane with the following exceptions; Contains high levels of sterols such as cholesterol. No respiratory enzymes are located in the eukaryotic plasma membrane. Respiration occurs in the mitochondria. Slide 45 External Structure of Eukaryotic Cells Glycocalyces Never as organized as prokaryotic capsules Help anchor animal cells to each other Strengthen cell surface Provide protection against dehydration Function in cell-to-cell recognition and communication Slide 46 Eukaryotic Appendages Flagella There are several different arrangements of flagella in eucaryotes. This diagram represents a biflagellated eukaryotic cell. One of the flagella aids in movement laterally and the other aids in up and down movement. The eukaryotic flagella move like a whip. See Flagellar handout. Slide 47 Eukaryotic Appendages Flagella Function Do not rotate, but undulate rhythmically Slide 48 Eukaryotic Appendages Cilia Similar to flagella both structurally and functionally but are much shorter and more numerous. Cilia are found peritrichously to the cell. Move in an undulating manner and motility by those organisms with cilia is much more rapid than those with flagella. Slide 49 Slide 50 Intracellular Structures of Eukaryotic Organisms (organelles) Membranous Organelles Nucleus Often largest organelle in cell Contains most of the cells DNA Semi-liquid portion called nucleoplasm One or more nucleoli present in nucleoplasm; RNA synthesized in nucleoli Nucleoplasm contains chromatin masses of DNA associated with histones Surrounded by nuclear envelope double membrane composed of two phospholipid bilayers Nuclear envelope contains nuclear pores Slide 51 Intracellular Structures of Eukaryotic Organisms (organelles) Nucleus - double membraned organelle that houses the genetic material of cell. Nuclear membrane contains numerous pores through which proteins and RNA can move. Slide 52 Intracellular Structures of Eukaryotic Organisms (organelles) Membranous Organelles Endoplasmic reticulum Netlike arrangement of flattened, hollow tubules continuous with nuclear envelope Functions as transport system Two forms Smooth endoplasmic reticulum (SER) plays role in lipid synthesis Rough endoplasmic reticulum (RER) ribosomes attached to its outer surface; transports proteins produced by ribosomes Slide 53 Intracellular Structures of Eukaryotic Organisms (organelles) Endoplasmic reticulum - network of cytoplasmic membranes where lipids and proteins are produced. Smooth ER - synthesis of lipids Rough ER - associated with ribosomes and is responsible for the synthesis of proteins.. Slide 54 Intracellular Structures of Eukaryotic Organisms (organelles) Membranous Organelles Golgi body Receives, processes, and packages large molecules for export from cell Packages molecules in secretory vesicles that fuse with cytoplasmic membrane Composed of flattened hollow sacs surrounded by phospholipid bilayer Not in all eukaryotic cells Slide 55 Intracellular Structures of Eukaryotic Organisms (organelles) Golgi apparatus (dictyosome) is associated with the ER. It modifies and packages the lipids and proteins manufactured by the ER and places them in vesicles for cellular use. Slide 56 Intracellular Structures of Eukaryotic Organisms (organelles) Membranous Organelles Lysosomes, peroxisomes,vacuoles, and vesicles Store and transfer chemicals within cells May store nutrients in cell Lysosomes contain catabolic enzymes Peroxisomes contain enzymes that degrade poisonous wastes Slide 57 Intracellular Structures of Eukaryotic Organisms (organelles) Membranous Organelles Mitochondria Have two membranes composed of phospholipid bilayer Produce most of cells ATP Interior matrix contains 70S ribosomes and circular molecule of DNA Slide 58 Intracellular Structures of Eukaryotic Organisms (organelles) mitochondria - involved in the production of chemical energy in the form of ATP. Consist of convoluted inner membrane and outer membrane. Invaginations are called cristae and contain enzymes used to synthesis ATP. All respiratory enzymes are located in the inner membrane of the mitochondria. Slide 59 Cytoplasm of Eukaryotes Membranous Organelles Chloroplasts Light-harvesting structures found in photosynthetic eukaryotes Have two phospholipid bilayer membranes and DNA Have 70S ribosomes Slide 60 Endosymbiotic Theory Eukaryotes formed from union of small aerobic prokaryotes with larger anaerobic prokaryotes smaller prokaryotes became internal parasites Parasites lost ability to exist independently; retained portion of DNA, ribosomes, and cytoplasmic membranes Larger cell became dependent on parasites for aerobic ATP production Aerobic prokaryotes evolved into mitochondria Similar scenario for origin of chloroplasts Not universally accepted Cytoplasm of Eukaryotes Slide 61 [INSERT TABLE 3.5] Slide 62 Cytoplasm of Eukaryotes [INSERT TABLE 3.4] Slide 63 Eukaryotic Cell Walls & Cytoplasmic Membranes [INSERT TABLE 3.3]