Chapter 4: Functional Anatomy of Prokaryotic and Eukaryotic Cells Flashcards
Prokaryote:
o One Circular chromosome, not membrane bound.
o No organelles.
o Peptidoglycan cell walls if bacteria.
o Pseudomurein cell walls if archaea.
o Binary fission (split into two daughter cells).
Eukaryote:
o Paired chromosomes, in nuclear membrane.
o Organelles.
o Polysaccharide cell walls.
o Mitotic Spindle.
Prokaryotic Cell Shapes:
o Avg. size: 0.2 –1.0 µm × 2 – 8 µm.
o Most monomorphic - A few are pleomorphic.
Basic Cell Shapes:
o Coccus (spherical). o Bacillus (rod-shaped). • Coccobacillus. o Spiral: • Spirillum. • Vibrio. • Spirochete. • Pleomorphic.
Basic Cell Arrangements:
o Pairs (Diplo-). o Clusters (Strepto-). o Chains (Staphylo-). o Group of 4 (Tetrad). o Group of 8 (Sarcinae).
Structure of Prokaryotic Cells Contain:
o Glycocalyx. o Nucleoid. o Pilus and Flagellum. o Plasmid. o Ribosomes. o Fimbrae. o Inclusion Body. o Cytoplasm. o Cell membrane and Cell wall and LPS layer.
The Bacterial Cell Wall:
o Surrounds plasma membrane.
o Protects cell from changes in water pressure.
o Made of peptidoglycan, also called “murein”.
o Two large groups differentiated by Gram Stain:
• Gram Positive.
• Gram Negative.
The Gram Stain:
o Developed in 1884 By Han Christian Gram.
o Differential Stain.
o Used to classify bacteria into two large groups:
• Gram Positive (Darker Pink).
• Gram Negative (Bright Pinkish-Red).
Peptidoglycan:
o Sugar backbone.
o Protein side-chain.
o Present in most bacteria.
o Provides strength.
Peptidoglycan in Gram-Positive Bacteria:
o Many layers of Peptidoglycan.
o Linked by polypeptides.
o Contain teichoic acids.
Gram-Positive Cell Walls:
o Teichoic acids:
• Lipoteichoic acid links to plasma membrane.
• Wall teichoic acid links to peptidoglycan.
o Thick Peptidoglycan.
o Penicillin Sensitive.
o Disrupted by lysozyme.
o 2 ring basal body.
Gram Negative Outer Membrane:
o Protection from phagocytes, complement, and antibiotics. o O polysaccharide antigen, e.g., E. coli O157:H7. o Lipid A is an endotoxin. o Porins (proteins) form channels through membrane.
Gram Negative Bacterial Cell Walls:
o Lipopolysaccharide- (LPS) surrounds thin Peptidoglycan layer. o LPS provides a barrier against some digestive enzymes and some antibiotics. o Lipopolysaccharide (LPS): • O polysaccharide. • Core polysaccharide. • Lipid A. • Periplasmic space. • Peptidoglygan layer. • Periplasmic space. • Plasma membrane. o Thin Peptidoglycan. o LPS outer membrane. o Endotoxin. o Tetracycline sensitive. o 4 ring Basal body.
The Gram Stain Mechanism:
o Crystal violet-iodine (CV-I) crystals form in cell.
o GRAM-POSITIVE:
• Alcohol dehydrates peptidoglycan.
• CV-Iodine crystals do not leave.
o GRAM-NEGATIVE:
• Alcohol dissolves outer membrane and leaves holes in peptidoglycan.
• CV-I crystals wash out.
Atypical Cell Walls:
o Acid-fast cell walls: • Modified gram-positive structure. • Mycolic Acid / thin peptidoglycan layer. • Mycobacterium, spp. o Mycoplasmas: • Lack cell walls. • Sterols in plasma membrane. o Archaea: • Wall-less of walls of pseudomurein.
Why are drugs that target cell wall synthesis useful?
o Eukaryotic cells (animal cells) don’t have cell walls.
Why are Mycoplasmas resistant to antibiotics that interfere with cell wall synthesis?
o Mycoplasmas don’t have cell walls.
Structures External to Cell Wall:
o GLYCOCALYX: • Gelatinous polymer. o FLAGELLA: • Filamentous appendage - propels. o AXIAL FILAMENTS: • Corkscrew movement. o FIMBRIAE: • Adherence. o PILI: • DNA exchange and motility.
Glycocalyx:
o Outside cell wall.
o Sticky.
o Helps Prevent phagocytosis.
o Capsule vs. Slime Layer.
Why Bacterial Capsules are Medically Important:
o May protect pathogens from phagocytosis.
o May help them adhere to surfaces.
o May provide nutrients.
o Helps prevent desiccation.
Flagella in a Prokaryote:
o Long filamentous appendages consisting of a filament, hook, and basal body.
o Rotate to push the cell.
o FLAGELLAR (H) protein is an ANTIGEN that helps serotype species of gram-negative bacteria.
o Think E. Coli.
The Structure of a Prokaryotic Flagellum in the Gram-Positive Bacterium:
o Outside cell wall.
o Made of chains of FLAGELLIN.
o Attached to a protein HOOK.
o Anchored to the wall and membrane by the BASAL BODY.
Motile Cells:
o ROTATE FLAGELLA TO RUN OR TUMBLE.
• Moving in one direction for a long time is a run.
• In a tumble flagella have reversed direction of rotation.
o MOVE TOWARD OR AWAY FROM STIMULI (TAXIS).
• Positive taxis is moving toward an attractant.
• Negative taxis is moving away from a repellent.
Axial Filaments:
o Also called ENDOFLAGELLA.
o In spirochetes.
o Anchored at one end of a cell.
o Rotation causes cell to move.
Fimbrae and Pili:
o FIMBRIAE – attachment. • Few to several hundred. • Biofilms. • Adherence to mucus membranes. o PILI – longer than fimbriae. • One or two per cell. • Transfer of DNA. • Motility.
Prokaryotic Membrane:
o Inside cell wall. o Encloses cytoplasm. o Consists mainly of phospholipids. o Exception – mycoplasmas – Why? • No cell wall and PM contains sterols.
The Plasma Membrane:
o Phospholipid bilayer.
o Peripheral proteins.
o Integral proteins .
• Transmembrane Proteins.
Fluid Mosaic Model:
o Viscous as olive oil. o Ability to form self-sealing bi-layer. • Breaks and Tears heal themselves. o Membrane embedded with proteins. o Glycoproteins and glycolipids. • Protect and lubricate the cell. • Involved in cell-to-cell interaction. o In eukaryotes, PM is an attachment site for Influenza virus and toxins that cause cholera and botulism.
Plasma Membrane Functions:
o Selective Barrier.
o Breakdown of nutrients (production of energy).
o Bacterial PM contains enzymes.
• Catalyze chemical reactions that breakdown nutrients and produce ATP.
• Photosynthesis: chromatophores and enzymes.
Destruction of Plasma Membrane by Antimicrobial Agents:
o Alcohols.
o Quarternary Ammonium.
o Polymyxin antibiotics.
Movement of Materials Across Membranes:
o PASSIVE PROCESSESS: o Substances cross the membrane from area of HIGHER conc. to area of LOWER conc. • SIMPLE DIFFUSION. • FACILITATED DIFFUTION. o ACTIVE PROCESSESS: o Requires energy to move substance from area of LOWER conc. to area of HIGHER conc. • ACTIVE TRANSPORT. • GROUP TRANSLOCATION.
Simple Diffusion:
o Net movement from high concentration to lower concentration.
o Water molecules pass through the lipid bilayer by simple diffusion or aquaporins.
Facilitated Diffusion:
o Solute combines with a transporter.
o Moves down the concentration gradient.
o No energy expended.
Osmotic Solutions:
o Isotonic solution: No net movement of water.
o Hypotonic solution: Net movement into a cell.
o Hypertonic Solution: Net movement out of a cell.
When Simple Diffusion and Facilitated Diffusion Aren’t Enough:
o ACTIVE TRANSPORT: Requires a transporter protein and ATP.
o GROUP TRANSLOCATION: Requires a transporter protein and PEP.
Cytoplasm:
Substance inside the plasma membrane.
The Nucleoid:
o Contains bacterial chromosome.
• Single long Ds DNA, frequently circular.
• Plasmid.
The Prokaryotic Ribosome:
o Protein synthesis. o Prokaryotic = 70S. • 50S + 30S subunits. o Sites of protein synthesis. o Great site for antibiotics: • Streptomycin. • Gentamicin. • Erythromycin. • Chloramphenical.
Metachromatic Granules:
o Phosphate Reserve – VOLUTIN.
o Used in the synthesis of ATP.
o Found in Algae, Fungi, Protozoa and Bacteria.
o Characteristic of Corynebacterium diptheriae.
Polysaccharide Granules:
o Energy Source. o Glycogen and Starch. o Stain with Iodine. • Glycogen – Reddish Brown. • Starch – Blue.
Lipids:
o Energy Source.
o Stain with Sudan Dyes.
o Mycobacterium, Bacillus, Spirillum.
Sulfur Granules:
o Energy Source.
• Derived by oxidizing the sulfur.
• Chromatium, also Thiobacillus.
Carboxysomes:
o Found in Photosynthetic Bacteria.
o Contains An Enzyme Required For CO2 Fixation.
o Ribulose 1,5-diphosphate carboxylase.
o Nitrifying Bacteria, Cyanobacteria and Thiobacilli.
Gas Vacuoles:
o Often found in aquatic prokaryotes.
o Helps maintain buoyancy.
Endospores:
o Unique to bacteria. o Usually gram positive. o Internal to the cell membrane. o Highly durable. o Released into the environment, endospores can survive: • Extreme Heat, Lack of Water, Toxic Chemicals, Radiation o 7,500 year old endospores. o 25-40 Million year old endospores.
Sporulation:
o Endospore Formation.
• Don’t carry on metabolic functions.
• Contain: DNA, RNA, Ribosomes, Enzymes, and a few important molecules (dipicolinic acid, and Ca++)
• Can remain dormant for thousands of years or more.
Germination:
o Endospores return to vegetative state:
• Triggered by physical or chemical damage to the endospore coat.
• Endospore enzymes then break down the extra layers surrounding the endospore.
• Water enters and metabolism resumes.
Eukaryotic Flagella and Cilia:
o Flagella are few and long in relation to cell length.
o Cilia are short and numerous.
o Both are used for motility.
o In addition, Cilia are used to move substances along the surface of cells.
o Both are anchored to the plasma membrane with a basal body.
Eukaryotes:
o Algae, protozoa, fungi, plants, and animals.
o Size: 10-100 um.
o True nucleus, nuclear membrane, nucleolus.
o Membrane-bound organelles.
o Flagella- Complex, multiple microtubules.
o Glycocalyx present in some cells that lack a cell wall.
o Cell wall when present is chemically simple, chitin and cellulose.
o Plasma membrane sterols and carbs.
o Cytoplasm, cytoskeleton, and cytoplasmic streaming.
o Ribosomes- 80s (70s in organelles).
o Chromosome- Multiple linear chromosomes with histones.
o Cell division involves mitosis.
o Sexual Recombination involves meiosis.
Prokaryotes:
o Bacteria, archea.
o Size 0.2-2.0 um.
o No nuclear membrane or nucleolus.
o No membrane-enclosed organelles.
o Flagella – 2 proteins.
o Glycocalyx present as capsule or slime layer.
o Cell wall usually present, chemically complex, peptidoglycan.
o Plasma Membrane, No carboydrates, generally lacks sterols.
o No cytoskeleton, no cytoplasmic streaming.
o Ribosomes Smaller – 70S.
o Chromosome: Circular, single strand.
o Cell Division - Binary fission.
o Sexual Recombination – none, however transfer of DNA possible.
The Cell Wall:
o Animal Cells do not have a Cell Wall. o Protozoans have a flexible outer protein called a “pellicle” that acts as their cell wall. o Algae, Plants and some Fungi. • Cellulose cell walls. o Most fungi as well as the exoskeleton of insects and Crustaceans. • Chitin cell walls. o Yeast. • Glucan and mannan.
Glycocalyx in Eukaryotic Organisms:
o GLYCOCALYX
• Substantial, sticky carbohydrate layer covering the plasma membrane
• Some proteins and lipids are bound to the carbohydrate layer
o Forms glycoproteins and glycolipids.
• Anchor the glycocalyx to the cell.
o Strengthen the cell surface.
o Helps with cell attachment to each other.
o Cell-cell recognition.
Plasma Membrane in Eukaryotes:
o PHOSPHOLIPID BILAYER – similar to prokaryotes.
o PERIPHERAL PROTEINS.
o INTEGRAL PROTEINS.
o TRANSMEMBRANE PROTEINS.
o STEROLS.
• Adds stability to membrane; helps to resist lysis.
o Selective permeability allows passage of some molecules.
o Simple diffusion.
o Facilitative diffusion.
o Osmosis.
o Active transport.
o Endocytosis:
• Phagocytosis: Pseudopods extend and engulf particles.
• Pinocytosis: Membrane folds inward, bringing in fluid and dissolved substances.
Cytoplasm of Eukaryotes:
o CYTOSKELETON:
• Microfilaments, intermediate filaments, microtubules.
• Provides structure and a transport system – think rails.
o CYTOPLASMIC STREAMING:
• Movement of cytoplasm throughout cells.
• Helps to distribute nutrients throughout the cell.
Organelles of Eukaryotes:
o NUCLEUS: Contains chromosomes.
o ER: Transport network.
o GOLGI COMPLEX: Membrane formation and secretion.
o LYSOSOME: Digestive enzymes.
o VACUOLE: Brings food into cells and provides support.
o MITOCHONDRION: Cellular respiration.
o CHLOROPLAST: Photosynthesis.
o PEROXISOME: Oxidation of fatty acids; destroys H2O2.
o CENTROSOME: Consists of protein fibers and centrioles.
The Eukaryotic Nucleus:
o Spherical or oval.
o Contains chromosomes.
o Consists of: Nuclear Envelope, Nuclear pores, Nucleoli.
Rough E.R.:
o Continuous with Nuclear envelope.
o Outer surface studded with ribosomes.
o Processes and sorts ribosomes.
o Synthesizes secretory proteins, membrane molecules, including phospholipids.
o Enzymes within cisterns attach proteins to Carbohydrates.
Smooth E.R.:
o Smooth ER has no Ribosomes on outer surface.
o Does not synthesize proteins.
o Does synthesize phospholipids, fats and steroids (Estrogens and testosterone).
Golgi Complex:
o Consists of flattened sacs called “cisterns”.
o Functions in membrane formation and protein secretion.
Lysosymes:
o Formed by golgi complexes.
o Contain as many as 40 different digestive enzymes.
Vacuoles:
o Cavity enclosed by a membrane, “tonoplast”.
o Derived from the golgi complex.
o In plants, can be 5-90 percent of the cell volume.
o May serve as temporary storage spaces.
Mitochondria:
o Powerhouse of a cell – central role is ATP production.
o Number varies, 1000-2000 per liver cell.
o Contain ribosomes and their own DNA.
o Can replicate, transcribe, and translate info from their DNA.
Chloroplasts:
o Algae, Green plants.
o Pigment Chlorophyll.
o Enzymes for photosynthesis.
o Contain ribosomes and their own DNA.
o Can replicate, transcribe, and translate info from their DNA.
o Thylakoids: flattened membrane sacs that contain chlorophyll.
o Granum: stacks of thylakoids.
Peroxisome:
o Contain enzymes that can oxidize a variety of organic compounds, H2O2 is often of oxidation reactions.
o Peroxisomes also contain catalase, an enzyme that breaks down H2O2.
Centrosome:
o Pericentriolar area and the centrioles.
o Involved in formation of the mitotic spindle in dividing cells and microtubles in non-dividing cells.
Endosymbiotic Theory of Eukaryotic Evolution:
o EUKARYOTIC CELLS EVOLVED FROM SYMBIOTIC PROKARYOTES LIVING INSIDE OTHER PROKARYOTIC CELLS.
o MITOCHONDRIA AND CHLOROPLASTS:
• Resemble bacteria in size and shape.
• Which contain circular DNA.
• Can replicate independently of their host.
• Ribosomes resemble those of bacteria.
• The same antibiotics that inhibit protein synthesis on bacterial ribosomes, inhibit protein synthesis on their ribosomes.
Origin of Flagella and Cilia:
o Eukaryotic Flagella and Cilia are believed to have originated from symbiotic associations between the Plasma Membrane of early eukaryotes and spirochetes
