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Home , Cell membrane, Fimbria (bacteriology), Glycocalyx, Pilus, Slime layer, Spiral bacteria

Distinguishing Features of Procaryotic Cells: Chapter 4: Functional 1. DNA is: u Not enclosed within a nuclear . Anatomy of Procaryotic and u A single circular . Eucaryotic Cells u Not associated with histone . 2. Lack membrane-enclosed like mitochondria, , Golgi, etc. 3. walls usually contain , a complex . 4. Divide by binary fission.

Distinguishing Features of Eucaryotic The Procaryotic Cell: Size, Shape, and Cells: Arrangement of Bacterial Cells 1. DNA is: Cell Size: u Enclosed within a nuclear membrane. u Dimensions of mostbacterial cells: u Several linear . u Diameter: 0.2 to 2.0 mm. u Associated with histones and other proteins. u Human is about 7.5-10 mm in diameter. u 2. Have membrane-enclosed organelles like Length : 2 to 8 mm. u Some cyanobacteria are up to 60 mm long. mitochondria, chloroplasts, Golgi, , etc. u Bacterial cells have large surface to volume ratios. Therefore all parts of the cell: 3. Divide by . u Are close to the surface. u Can be quickly reached by .

Bacterial Cell Size Compared to The Procaryotic Cell: Size, Shape, Eucaryotic Cells and and Arrangement of Bacterial Cells Bacterial Cell Shapes & Arrangements: u (plural: cocci): Spherical. May have the following arrangements: u Diplococci : A pair of attached cocci. Remain attached after dividing. u Streptococci : Chainlike arrangement. u Tetrads : Groups of four. Divide in two planes. u Sarcinae : Groups of eight. Divide in three planes. uStaphylococci : Grapelike clusters. Divide in multiple planes.

1 Common Arrangements of Cocci The Procaryotic Cell: Size, Shape, and Arrangement of Bacterial Cells Bacterial Cell Shapes & Arrangements: u (plural: bacilli): Rod-shaped. Most bacilli appear as single rods but may see: u Diplobacilli: A pair of attached bacilli. Remain attached after dividing. u Streptobacilli: Chainlike arrangement. u : Intermediate shape between coccus and bacillus. Oval rods.

Different Types of Bacilli The Procaryotic Cell: Size, Shape, and Arrangement of Bacterial Cells Bacterial Cell Shapes & Arrangements : u Spiral : Have one or more twists: u Vibrio: A comma shaped cell. Look like curved rods. u Spirilla: Helical, corkscrew shaped bacteria with rigid bodies. u Use whiplike external flagella to move. u Spirochetes: Helical bacteria with flexible bodies. u Use axial filaments (internal flagella) to move.

Spiral Shaped Bacteria The Procaryotic Cell: Size, Shape, and Arrangement of Bacterial Cells Bacterial Cell Shapes & Arrangements : u Other less common shapes: u Star u Flat and square u Triangular u Pleomorphic bacteria: Have several possible shapes. Found in a few groups: u Corynebacterium u Rhizobium Most bacteria are monomorphic: Maintain a single shape. However environmental factors may affect cell shape.

2 The Procaryotic Cell Structure Procaryotic Cell Structure I. Structures External to the 1. : “Sugar coat”. u All polysaccharide containing substances found external to the cell wall, from the thickest capsules to the thinnest slime layers . u All bacteria have at least a thin . u Chemical composition varies widely with species. u A glycocalyx made of sugars is called an extracellular polysaccharide (EPS). u The glycocalyx may have several functions: u Attachment to host cells. u Source of nutrition. u Prevent dehydration. u Escape host .

Procaryotic Cell Structure Procaryotic Cell Structure I. Structures External to the Cell Wall I. Structures External to the Cell Wall 1. Glycocalyx: “Sugar coat”. 1. Glycocalyx: u A. Capsules: Organized polysaccharide substance B.Slime Layer:Thin polysaccharide substance that is loosely attached to the cell wall. that is firmly attachedto the cell wall. u Not formed by all bacteria. u Not formed by all bacteria. u Important for . u Important in virulence. u Oral bacteria stick to teeth due to slime layer and with time u Anthrax bacteria only cause anthrax if have capsule. produce dental plaque. u Only pneumoniae with capsule cause pneumonia. u Allow bacteria to adhere to objects in their environment so they can remain near sources of u Help bacteria escape the host immune system, by nutrients or oxygen. preventing destruction by . u Rock surfaces u When bacteria lose their capsules they become less likely u roots to cause and more susceptible to destruction. u Help bacteria trap nutrients near cell and prevent dehydration.

Procaryotic Cell Structure Procaryotic Cell Structure I. Structures External to the Cell Wall I. Structures External to the Cell Wall 2. Flagella (Sing. ): 2. Flagella (Sing. Flagellum): u About half of all known bacteria are motile, most u Flagella have three basic parts: use flagella. 1. Filament: Outermost region. u Long, thin, helical appendages. u Contains . u Not covered by a sheath like eucaryotic filaments. u A bacterium may have one or several flagella, 2. Hook: Wider segment that anchors filament to basal which can be in the following arrangements: body. u Monotrichous: Single polar flagellum at one end. 3. : Complex structure with a central rod u Amphitrichous: Two polar flagella, one at each end. surrounded by a set of rings. u Lophotrichous: Two or more flagella at one or both u Gram negative bacteria have 2 pairs of rings. ends. u Gram positive bacteria only have one pair of rings. u Peritrichous: Many flagella over entire cell surface.

3 Flagellum of Gram-Negative Bacterium Procaryotic Cell Structure I. Structures External to the Cell Wall 2. Flagella (Sing. Flagellum): u Bacterial flagella move by rotation from basal body. u Flagellar movement may be either clockwise or counterclockwise. u Bacteria may be capable of several patterns of . u Runs or swims: Bacterium moves in one direction. u Tumbles: Bacterium changes direction. Caused by reversal of flagellar rotation.

Patterns of Procaryotic Cell Structure I. Structures External to the Cell Wall 2. Flagella (Sing. Flagellum): u Taxis: Movement of a cell toward or away from a particular stimulus. u : Movement in response to a chemical stimulus. u Phototaxis: Movement in response to a light stimulus. u Flagellar protein H are used to identify important pathogens. u E. coli O157:H7: Causes bloody diarrhea associated with foodborne epidemics. Causes 200-500 deaths per year.

Procaryotic Cell Structure Axial Filaments in Spirochetes I. Structures External to the Cell Wall 3. Axial Filaments (Endoflagella): u Bundles of fibers that are anchored at ends of the cell beneath the outer sheath. u Spiral around the cells. u Have similar structure to flagella. u Rotation of endoflagella produces a corkscrew motion. u May enable bacteria to penetrate body tissues. u Found in spirochetes: u pallidum: Cause of . u burgdorferi: Cause of .

4 Procaryotic Cell Structure Procaryotic Cell Structure I. Structures External to the Cell Wall 4. Fimbriae and Pili: u Hairlike appendages that are shorter, straighter, and thinner than flagella. u Used for attachment rather than motility. u Found in Gram-negative bacteria. A. Fimbriae (Sing: ) u May occur at poles or over entire cell surface. u Like glycocalyx, enable bacteria to adhere to surfaces. Important for colonization of host . u gonorrhoeae: Causes gonorrhea. Attach to cells and mucous through fimbriae. u Bacteria can attach to broth surface via fimbriae, forming a film-like layer called pellicle.

Procaryotic Cell Structure Procaryotic Cell Structure I. Structures External to the Cell Wall II. The Cell Wall 4. Fimbriae and Pili: General Characteristics: B. Pili (Sing: ): Conjugation or sex pili u Semirigid structure that lies outside the cell u Only found in certain groups of bacteria. membrane in almost all bacteria. u Longer than fimbriae. u Two major functions: u Cells only have one or two sex pili. 1. Maintains characteristic shape of cell. u Attach two cells together, and allow the transfer 2. Prevents the cell from bursting when fluids flow into the cell by . of genetic material (DNA) between cells. u Contributes to bacterial ability to cause disease. u Medically important because allow for the transfer of resistance from one u Site of action of some . cell to another. u Very porous and does not regulate passage of materials into the cell.

Procaryotic Cell Structure NAG-NAM Peptidoglycan Disaccharide II. The Cell Wall Composition: u Peptidoglycan (Murein): Made up of a repeating disaccharide attached by polypeptides to form a lattice. u Peptidoglycan is one immense covalently linked molecule, resembling multiple layers of chain link fence. u Disaccharide component: Made up of two monoscaccharides: u N-acetylglucosamine (NAG) u N-acetylmuramic (NAM) u Alternating disaccharides (NAG-NAM) are linked together in rows of 10 to 65 molecules.

5 A. Peptidoglycan Structure Procaryotic Cell Structure B. Gram-Positive Cell Wall Structure II. The Cell Wall Composition: u Peptidoglycan (Murein):. u Adjacent disaccharide rows are linked together by polypeptide chains which vary in composition, but always contain tetrapeptide side chains. u Parallel tetrapeptide side chains may be directly linked together or linked by a polypeptide cross-bridge. u Penicillininterferes with the final linking of peptidoglycan rows by peptide cross bridges. As a result, the cell wall is greatly weakened and cell undergoes .

Procaryotic Cell Structure Procaryotic Cell Structure II. The Cell Wall II. The Cell Wall Gram-Positive Cell Walls: Gram-Negative Cell Walls: u Consist of several layers of peptidoglycan, u Cell wall is thinner, more complexand more which form a thick , rigid structure (20-80 nm). susceptible to mechanical breakage than that of u Also contain teichoic , which are made up Gram-positive bacteria. of an alcohol and a phosphate group. Two types: u Consist of one or a few peptidoglycan layers and u Lipoteichoic acids: Span cell wall, linked to cell an outermembrane. membrane. u Peptidoglycan is bonded to in: u Wall teichoic acids: Linked to peptidoglycan layer. u Outer membrane u Teichoicacids are negatively charged and: u Periplasmic space: Region between outer membrane u Bind to and regulate movement of cations into cell. and plasma membrane. u Regulate and prevent cell lysis. u Periplasmic space contains degradative u Can be used to identify bacteria. and transport proteins.

II. The Cell Wall Gram-Negative Cell Wall Structure Gram-Negative Cell Walls: Outer Membrane (OM): u Consists of: u bilayer u (LPS) with two components: u O : Antigens, used to identify bacteria. u A: Endotoxin causes fever and shock. u Porins: Membrane proteins that allow the passage of , disaccharides, peptides, amino acids, vitamins, and iron. u Lipoproteins u Functions of Outer Membrane: u Evade phagocytosis and complement due to strong negative charge. u Barrier to antibiotics (penicillin), digestive enzymes (lysozyme), , heavy metals, dyes, and bile salts.

6 II. The Cell Wall II. The Cell Wall Atypical Cell Walls: Atypical Cell Walls: 1. Acid-Fast Bacteria: 2. : u Cell wall is thick like that of Gram-positive u Smallest known bacteria that can grow and bacteria. reproduce outside of host cells. u Contains 60% and much less peptidoglycan. u They have no cell wall. Has a waxy consistency. u Pass through most bacterial filters. Originally u Lipids make cells impermeable to many stains, and mistaken for viruses. protect them from acids, alkalis, and antibiotics. u Unique plasma membrane contains lipids called u grow slowly because nutrients penetrate , which protect them from osmotic lysis. inefficiently and cells spend a lot of energy making 3. Archaebacteria lipids. u May lack cell walls or have cell walls without u Stain as Gram-positive. peptidoglycan. u Instead of peptidoglycan, may have pseudomurein.

Procaryotic Cell Structure III. Structures Internal to the Cell Wall Structure of Plasma Membrane 1. The Plasma (Cytoplasmic) Membrane: u Thin structure inside of cell wall that surrounds the . u Phospholipid bilayer with proteins (). u Integral membrane proteins: Penetrate membrane completely. u Peripheral membrane proteins: On inner or outer membrane surface. u Lack sterols and are less rigid than eucaryotic membranes. u Exception: Mycoplasmas

Procaryotic Cell Structure Procaryotic Cell Structure III. Structures Internal to the Cell Wall III. Structures Internal to the Cell Wall Functions of the Plasma (Cytoplasmic) Membrane: Functions of the Plasma (Cytoplasmic) Membrane: 1. Selective barrierthat regulates the passage of 5. Site of : Photosynthetic bacteria materials in and out of the cell. have membrane extensions calledthylakoids, where u Impermeable to large proteins, ions, and most polar molecules. photosynthesis occurs. u Permeable to water, oxygen, carbon dioxide, some 6. Secretes proteins simple sugars, and small nonpolar substances. 7. Contains bases of flagella 2. breakdown and energy (ATP) production: Site of . 8. Responds to chemical substances in the 3. Synthesis of cell wall components environment 4. Assists with DNA replication

7 Procaryotic Cell Structure Procaryotic Cell Structure III. Structures Internal to the Cell Wall III. Structures Internal to the Cell Wall Destruction of the Plasma Membrane: Several Movement of Materials Across Membranes: antimicrobial agents damage the integrity of the Can be either a passive or an active process. plasma membrane. Processes: They commonly cause leakage of intracellular contents u Substances move spontaneously from an area of and cell death: high concentration to one of low concentration. 1. Alcohols u Do not require energy expenditure (ATP) by the 2. Quaternary ammonium compounds cell. 3. Antibiotics () u Include the following processes: u Simple u u Osmosis

Procaryotic Cell Structure Active versus Passive Transport III. Structures Internal to the Cell Wall Movement of Materials Across Membranes: Passive Transport Processes: 1. Simple diffusion: u Net movement of molecules or ions from an area of high concentration to one of low concentration. u Equilibrium: Net movement stops when molecules are evenly distributed. u Used by cells to transport small molecules (oxygen, carbon dioxide) across their membranes. u Example: Diffusion of perfume into the air after the bottle is opened.

Simple Diffusion is a Passive Process Procaryotic Cell Structure Equilibrium is Eventually Reached III. Structures Internal to the Cell Wall Movement of Materials Across Membranes: Passive Transport Processes: 2. Facilitated diffusion: u Net movement of molecules or ions from an area of high concentration to one of low concentration. u Substance to be transported combines with a carrierprotein in plasma membrane. u Extracellular enzymes may be used to break down large substances before they can be moved into the cell by facilitated diffusion.

8 Facilitated Diffusion Requires a Procaryotic Cell Structure Membrane Carrier Protein III. Structures Internal to the Cell Wall Movement of Materials Across Membranes: Passive Transport Processes: 3. Osmosis: u Net movement of water (solvent) molecules across a from an area of high concentration to one of low concentration of water. u : Pressure required to prevent the movement of pure water into a solution.

Passive Transport Processes: Osmosis: The diffusion of water across 3. Osmosis (Continued): a semipermeable membrane u Bacterial cells can be subjected to three different types of osmotic solutions: 1. Isotonic: Concentration of solutes (and water) are equal on both sides of a (e.g.: 0.9% NaCl, 5% ). Result: No net movement of water into or out of the cell. 2. Hypotonic: Solute concentration is lower outside the cell (e.g.: pure water). Result: Net movement of water into the cell. Most bacteria live in hypotonic environments. Cell wall protects them fromlysis. 3. Hypertonic: Solute concentration is higher outside the cell. Result: Net movement of water out of the cell.

Movement of Materials Across Membranes: Effects of Osmosis on Cells Active Processes: u Substances are concentrated, i.e.: moved from an area of low concentration to one of high concentration. u Require energy expenditure (ATP ) by the cell. u Include the following: 1. 2. Group translocation 1. Active Transport u Requires carrier proteins or pumps in plasma membrane.

9 Active Transport Requires Energy Movement of Materials Across Membranes: Active Transport Processes: 2. Group Translocation u Similar to active transport, but substance transported is chemically alteredduring process. u Aftermodification, the substance cannotleave the cell. u Glucose is phosphorylated during group translocation in bacterial cells. Note: (phagocytosis, , etc.) does not occur in procaryotic cells.

Procaryotic Cell Structure Procaryotic Cell Structure III. Structures Internal to the Cell Wall The Nuclear Area (): Cytoplasm u Contains a single chromosome, a long circular u Substance inside the cell membrane. molecule of double stranded DNA. u The chromosome is attached to the plasma Contains: membrane. u 80% water u May occupy up to 20% of the intracellular volume. u Proteins : u u Small, circular, double stranded DNA molecules. u Lipids Found in many bacterial cells in addition to u Inorganic ions chromosomal DNA. u Low molecular weight compounds u May contain from 5 to 100 genes that are usually not u Lacks a and cytoplasmic streaming. essential for survival. u Antibiotic resistance genes u Toxins

Procaryotic Cell Structure Procaryotic Cell Structure III. Structures Internal to the Cell Wall III. Structures Internal to the Cell Wall : Inclusions: u The site of protein synthesis (translation). Reserve deposits in the cytoplasm of cells. u Found in all eucaryotic and procaryotic cells. Not found in all cell types: u Made up of protein and ribosomal RNA (rRNA). 1. MetachromaticGranules: u Procaryotic ribosomes (70S) are smaller and less u Contain inorganic phosphate that can be used in the dense than eucaryotic ribosomes (80S). synthesis of ATP . u Procaryotic ribosomes have two subunits: u Stain red with blue dyes. u Small subunit: 30S u Found in bacteria, , , and fungi. u Large subunit: 50S u Characteristic of Corynebacterium diphtheriae, u Several antibiotics work by inhibiting protein causative agent of diphtheria. Useful for synthesis by procaryotic ribosomes, without identification purposes. affecting eucaryotic ribosomes.

10 Procaryotic Cell Structure Procaryotic Cell Structure III. Structures Internal to the Cell Wall III. Structures Internal to the Cell Wall Inclusions: 5. Carboxysomes: 2. Polysaccharide Granules: u Contain ribulose 1,5-diphosphate u Contain glycogen and starch. carboxylase, necessary for carbon during photosynthesis. u Stain blue or reddish brown with iodine. 3. Lipid Inclusions: u Found in nitrifying bacteria, cyanobacteria, and thiobacilli. u Contain lipids, detected with fat soluble dyes. u 6. Gas : 4. Sulfur Granules: u Hollow cavities found in many aquatic bacteria. u Contain sulfur and sulfur containing compounds. u Contain individual gas vesicles, hollow cylinders u “Sulfur bacteria” (Thiobacillus) obtain energy by covered by protein. oxidizing sulfur and its compounds. u Used to regulate buoyancy so cells can remain at appropriate water depth.

Procaryotic Cell Structure Procaryotic Cell Structure III. Structures Internal to the Cell Wall III. Structures Internal to the Cell Wall 7. Magnetosomes: : u Contain iron oxide (Fe2O3), which acts like a u Specialized “resting” cells formed by certain Gram- magnet. positive bacteria. u Formed by several aquatic gram-negative bacteria. u Genus Bacillus u Genus Clostridium u Enable bacteria to respond to magnetic fields (magnetotaxis). u Highly durable dehydrated cells with thick cell walls and additional layers. u In Northern hemisphere swim towards North Pole. u In Southern hemisphere swim towards South Pole. u Can survive extreme temperatures, disinfectants, acids, bases, lack of water, toxic chemicals, and u Also swim downwards in water, towards sediments where their food is abundant. radiation. u May help decompose hydrogen peroxide. u Endospores of some thermophilic bacteria can survive 19 hours of boiling. u Used industrially to make magnetic audio tapes. u Concern in food and health industries.

Procaryotic Cell Structure Process of Sporulation: One cell produces one spore. Process of Spore Formation 1. Newly replicated DNA is isolated by an ingrowth of the plasma membrane called a spore septum. 2. Spore septum becomes a double-layered membrane that surrounds chromosome and cytoplasm (forespore). 3. Peptidoglycan layer forms between membranes of forespore. 4. Spore coat forms: Thick layer of protein around the outer membrane. Makes resistant to many harsh chemicals. 5. Maturation: Cell wall ruptures, endospore is released.

11 Procaryotic Cell Structure Eucaryotic Cell Structure Sporulation u Include: , fungi, plant, and animal cells u May be part of normal cycle or triggered by u Larger than procaryotic cells. adverse environmental conditions. u Diameter ranges from 10 to 100 um (versus 0.2 to 2.0 um) u Endospores do not carry out metabolic reactions, u Nucleus: Protects and houses DNA. unlike normal vegetative cells. u Membrane-bound Organelles: Internal structures u Endospores can remain dormant for thousands of with specific functions. years. u Compartmentalization of Function: Organelles allow u Germination: Endospore returns to its vegetative special locations for different chemical reactions and state. Usually occurs when environmental conditions functions. become more favorable. Triggered by physical or uSeparate and store compounds chemical damage to the spore coat. uStore energy Sporulation Germination Vegetative Cell ------> Endospore ------> Vegetative Cell uWork surfaces (Metabolically active) (Not metabolically active) (Metabolically active) uMaintain concentration gradients

Membrane-Bound Organelles of Eucaryotic Cells

uNucleus uRough Endoplasmic Reticulum (RER) uSmooth Endoplasmic Reticulum (SER) uGolgi Apparatus uLysosomes uVacuoles uChloroplasts uMitochondria

Eucaryotic Cell Structure The Cell Wall and Glycocalyx u Cell wall is not found in all eucaryotic cells: u Protozoa have a flexible outer layer called a pellicle, instead of a cell wall. u Animal cells have a sticky glycocalyx surrounding the cell membrane. Important for attachment, strength, and cell-cell recognition. u When present, cell wall is chemically simpler than procaryotic cell wall and lacks peptidoglycan. u Eucaryotic cell wall composition: u Algae and : u Fungi: Chitin (polysaccharide) u : Glucan and mannan (polysaccharides)

12 Eucaryotic Cell Structure Eucaryotic Cell Structure The Cell Membrane The Cytoplasm: u Similar to procaryotic cell membranes, but: u Have different membrane proteins u Many enzymes are sequestered in organelles. u Contain carbohydrates that are important for cell-cell u Contains the cytoskeleton: A complex network of recognition and serve as sites for bacterial attachment. thread and tube-like structures, which provides u Contain sterols which increase resistance to osmotic support, shape, and movement. lysis. 1. : Smallest fibers u Movement across eucaryotic cell membranes: u & mysoin fibers in muscle cells u Simple diffusion, facilitated diffusion, osmosis, and u “Amoeboid motion” of white blood cells active transport. 2. Intermediate filaments: Medium sized fibers u Endocytosis: Process in which plasma membrane u Anchor organelles (nucleus) and hold cytoskeleton in place. encircles particles outside of cell. u Abundant in cells with high mechanical stress. u Phagocytosis: Pseudopods engulf particle. Used by WBCs. u Pinocytosis: Small drops of fluid are brought into the cell. 3. : Largest fibers. u u Group translocation does not occur. Work in , moving chromosomes u Flagella and ciliary movement.

The Eucaryotic Cytoplasm Has Three Eucaryotic Cell Structure Cytoskeleton Components Flagella and Cilia u Projections used for locomotion or to move substances along cell surface. u Enclosed by plasma membrane and contain cytoplasm. u Consist of 9 pairs of microtubules in a ring, with 2 single microtubules in center of ring (9 + 2). u Flagella: Long whip-like projections. u Eucaryotic flagella move in wavelike manner, unlike procaryotic flagella. u Cilia: Short hair-like projections. u Human respiratory system uses cilia to remove harmful objects from bronchial tubes and trachea.

Structure of Eucaryotic Flagella Eucaryotic Cell Structure: Organelles The Nucleus Structure u Envelope: Double nuclear membrane. u Large nuclear pores u DNA (genetic material) is combined with histones and exists in two forms: u Chromatin (Loose, threadlike DNA. Most of cell life) u Chromosomes (Tightly packaged DNA. Found only during cell division) u : Dense region where ribosomes are made u Functions u House and protect cell’s genetic information (DNA). u synthesis

13 Eucaryotic Cell Structure Structure of Ribosomes u The site of protein synthesis (translation). u Found in all eucaryotic and procaryotic cells. u Made up of protein and ribosomal RNA (rRNA). u May be found free in the cytoplasm or associated with the rough endoplasmic reticulum (RER). u Eucaryotic ribosomes (80S) are larger and more dense than procaryotic ribosomes (70S). u Eucaryotic ribosomes have two subunits: u Small subunit: 40S u Large subunit: 60S u Mitochondria and chloroplasts have 70S ribosomes that are similar to procaryotic ribosomes.

Eucaryotic Cell Structure: Organelles Eucaryotic Cell Structure: Organelles The Endoplasmic Reticulum (ER) Rough Endoplasmic Reticulum (RER) u Flat, interconnected, rough membrane sacs u “Network within the cell” u “Rough”: Outer walls are covered with u Extensive maze of membranes that branches ribosomes. throughout cytoplasm. u Ribosomes: Protein making “machines”. u ER is continuous with plasma membrane and u May exist free in cytoplasm or attached to ER. outer nucleus membrane. u RER Functions: u Two types of ER: u Synthesis and modification of proteins. u Synthesis of cell and membranes. uRough Endoplasmic Reticulum (RER) u Packaging, and transport of proteins that are secreted uSmooth Endoplasmic Reticulum (SER) from the cell. uExample:

Smooth and Rough Endoplasmic Reticulum Eucaryotic Cell Structure: Organelles Smooth Endoplasmic Reticulum (SER) u Network of interconnected tubular smooth membranes. u “Smooth”: No ribosomes u SER Functions: u Lipid Synthesis: , fatty acids, and (sex ). u Breakdown of toxic compounds (drugs, alcohol, , sedatives, antibiotics, etc.). u Helps develop tolerance to drugs and alcohol. u Regulates sugar release from liver into the blood u storage for cell and muscle contraction.

14 Eucaryotic Cell Structure: Organelles The : Receiving, Processing, Golgi Apparatus and Shipping of Proteins

u Stacks of flattened membrane sacs that may be distended in certain regions. Sacs are not interconnected. u First described in 1898 by Camillo Golgi (Italy). u Works closely with the ER to secrete proteins. u Golgi Functions: u Receiving side receives proteins in transport vesicles from ER. u Modifies proteins into final shape, sorts, and labels them for proper transport. u Shipping side packages and sends proteins to cell membrane for export or to other parts of the cell. u Packages digestive enzymes in .

Eucaryotic Cell Structure: Organelles Lysosomes: Intracellular Lysosomes u Small vesicles released from Golgi containing at least 40 different digestive enzymes, which can break down carbohydrates, proteins, lipids, and nucleic acids. u Optimal pH for lysosomal enzymes is about 5 u Found mainly in animal cells. u Functions: u Molecular garbage dump and recyclerof (e.g.: proteins). u Destruction of foreign material, bacteria, viruses, and old or damaged cell components. Important in immunity. u Digestion of food particles taken in by cell. u After cell dies, lysosomal membrane breaks down, causing rapid self-destruction.

Eucaryotic Cell Structure: Organelles Eucaryotic Cell Structure: Organelles Lysosomes , Aging, and Disease Vacuoles u As we age, our lysosomes become leaky, releasing u Membrane bound sac. enzymes which cause tissue damage and inflammation. u Different types, sizes, shapes, and functions: u Example: Cartilage damage in arthritis u Central : In plant cells. Store starch, water, u Steroids or cortisone-like anti-inflammatory agents pigments, poisons, and wastes. May occupy up to 90% stabilize lysosomal membranes, but have other of volume. undesirable effects. u : Regulate water balance, by u Interfere with normal immune function. removing excess water from cell. Found in many u Genetic from “mutant” lysosome enzymes aquatic . are usually fatal: u Food or Digestion Vacuole: Engulf nutrients in many uPompe’s disease: Defective glycogen breakdown in liver. protozoa (protists). Fuse with lysosomes to digest food uTay-Sachs disease: Defective lipid breakdown in brain. Common genetic disorder among Jewish people. particles.

15 Relationships Between Membrane Bound Central Vacuole in a Plant Cell Organelles of Eucaryotic Cells

Eucaryotic Cell Structure: Organelles Chloroplasts Have Three Sets of Chloroplasts Membranes u Site of photosynthesis in plants and algae.

CO2 + H 2O + Sun Light -----> Sugar + O 2 u Number in cell may range from 1 to over 100. u Disc shaped, with three membrane systems: u Outer membrane: Covers surface. u Inner membrane: Contains enzymes needed to make glucose during photosynthesis. Encloses stroma (liquid) and membranes. u Thylakoid membranes: Contain chlorophyll, green pigment that traps solar energy. Organized in stacks called grana.

Eucaryotic Cell Structure: Organelles Eucaryotic Cell Structure: Organelles Chloroplasts Mitochondria (Sing. ) u Contain own DNA, 70 S ribosomes, and make u Site of cellular respiration: some proteins. Divide by binary fission to form Food (sugar) + O2 -----> CO2 + H2 O + ATP daughter chloroplasts. u Change chemical energy of molecules into the useable u : Organelle that produces and stores food energy of the ATP molecule. in plant and algae cells. u Oval or sausage shaped. Other include: u Contain their own DNA, 70S ribosomes, and make some proteins. Can divide to form daughter mitochondria. u Leukoplasts: Store starch. u Structure: u : Store other pigments that give plants u Inner/outer membrane and color. u Intermembrane space u Cristae(inner membrane extensions) u Matrix (inner liquid)

16 Mitochondria: The Cell’s Energy Plants Evolution of Eucaryotes Endosymbiotic Theory u Ancestors of eucaryoticcells were large procaryotic cells with smaller procaryotic cells living inside of them. u Chloroplasts and mitochondria originated from independent cells that entered and stayed inside a larger cell. u Both organelles contain their own DNA. u Have 70S ribosomes and make their own proteins. u Replicate independently from the cell, by binary fission. u Symbiotic relationship u Larger cell obtains energy or nutrients. u Smaller cell is protected by larger cell.

Eucaryotic Cell Structure: Organelles Important Differences Between Plant and Animal Cells u Found in animal cells, not plant cells. Plant cells Animal cells u Pair of cylindrical structures located near the nucleus. Cell wall No cell wall u Made up of microtubules (9 + 2 pattern). u Important functions: Chloroplasts No chloroplasts u Movement of chromosomes during cell division. Large central vacuole No central vacuole u Formation of cilia and flagella (as basal bodies). Flagella rare Flagella more usual No Centrioles Centrioles present No Lysosome Lysosomes present

Important Differences Between Animal versus Plant Cell Structure Eucaryotic and Procaryotic Cells Procaryotes Eucaryotes Cell size 0.2-2 um in diameter 10-100 um in diameter Nucleus Absent Present Membranous Organelles Absent Present Cell Wall Chemically complex When present, simple Ribosomes Smaller (70S) Larger (80S) in cell 70S in organelles DNA Single circular Multiple linear chromosome chromosomes (histones) Cell Division Binary fission Mitosis Cytoskeleton Absent Present

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