Microbiology Study Guide Test 1 (Cell structure and function)

glycocalyx

"sugar cup" composed of polysaccharides and/or polypeptides

axial filaments

responsible for motility of spirochetes

arrangements of flagella

Monotrichous - single flagellum at only one end of the cell Lophotrichous - multiple flagella grouped at one end of the cell Amphitrichous - single or multiple flagella at both ends of the cell Endoflagella - special flagella found on spirochetes that enable "corkscrew" motion Peritrichous - multiple flagella covering the entire cell

what isnt true about growth and reproduction?

a living organism must reproduce to be considered alive

cytoskeleton

allows contraction of the cell

endospores

are dormant, resistant cells

fimbriae

bristlelike projections found in quantities of 100 or more, numerous "grabbing-hook" projections

what is associated with diffusion?

carrier proteins

what cellular structure is important in classifying a bacterial species as Gram-positive or gram-negative

cell wall

peoxisome

contains enzymes to neutralize hydrogen peroxide

centriole

contains microtubules in "9+0" arrangment

dipicolinic acid is an important component of

endospores

a "9 +2" arrangement of microtubules is seen in

eukaryotic flagella

Al cell may allow a larger or charged chemical to move across the cytoplasmic membrane, down the chemical's electrical and chemical gradients, in a process called

facilitated diffusion

ER

functions as the transport system within a eukaryotic cell

gram positive bacteria

have a thick cell wall, which retains crystal violet dye, contains teichoic acids in their cell walls, and appear purple after gram staining

mitochondrion

its internal membranes are sites for ATP production

chloroplast

light-harvesting organelle

flagella

long whip, made of tubulin in eukaryotes, made of flagellin in bacteria, Complex molecular machines that often translate rotary motion into directional movements

cilia

made of tubulin in eukaryotes •Shorter and more numerous than flagella •Composed of both "9 + 2" and "9 + 0" arrangements of microtubules •Coordinated beating functions to propel cells through their environment •Ciliary action also functions to move substances past the surface of the cell for nutrient uptake (feeding)

what is associated with prokaryotic organisms?

nucleiod, glycocalyx, and circular DNA

hami

numerous "grabbing-hook" projections

what are the functions of glycocalyx?

peptidoglycan is a fatty acid, gram-positive bacterial walls have a relatively thin layer of peptidoglycan anchored to the cytoplasmic membrane by teichoic acid, peptidoglycan is found mainly in the cell walls of fungi, algae, and plants.

pili

responsible for conjugation, extensions not used for cell motility

nucleus

site of most DNA in eukaryotes

ribosome

site of protein synthesis

inclusions have been found to contain

sulfur globules

a gram negative cell is moving uric acid across the cytoplasmic membrane against its chemical gradient.

the acid moves by an active process such active transport

Svedbergs

they are an expression of sedimentation rate during high-speed centrifugation

extracellular matrices

•Comparable to prokaryotic glycocalyces, but never as organized as bacterial capsules •Helps animal cells anchor themselves to substrates and/or adhere to each other •Strengthens cell surface and protects underlying fluid cell membrane •Provides protection against dehydration (dessication) •Play important roles in cell-to-cell recognition and communication

flagellar structure

•Composed of filament, hook, and basal body •Flagellin protein (filament) arranged in chains and forms helix around hollow core •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 •Filament rotates 360º to generate forces needed for propulsion

slime layer

•Composed of water-soluble organic compounds •Loosely attached to cell surface •Protects cells from dessication (drying out) •Sticky layer that allows prokaryotes to attach to surfaces

cytoplasm of Eukaryotes

•Consists of all non-nuclear intracellular components, including membrane-bound organelles, confined within the cell membrane •Here, "cytosol" refers to the non-organellar liquid portions of the cytoplasm •Organelles fall into two categories . . . -Nonmembranous - ribosomes, cytoskeleton, centrioles and centrosome -Membranous - nucleus, endoplasmic reticulum, golgi bodies, lysosomes, peroxisomes, vacuoles, vesicles, mitochondria, chloroplasts

cell membrane function

•Controls passage of substances into and out of the cell; selectively permeable •Harvests light energy in photosynthetic bacteria •Functions in energy production (ETC) -Maintains a concentration gradient and electrical gradient; collectively known as electrochemical gradient •Transport across the cell membrane -Membrane is naturally impermeable to most substances -Proteins are required for some substances to cross membrane -Transport occurs by passive or active processes

prokaryotes

•Do not have membrane surrounding their DNA; no nucleus •Lack various internal membrane-bound structures •Small; ~1.0 μm in diameter •Simple structure •Comprised of bacteria and archaea

cytoskeleton

•Extensive network of structural filaments and cables that function to . . . -Provide overall shape and anchor organelles in specific positions -Move organelles and cytoplasmic contents (streaming) -Contract or expand regions of the cell membrane during endocytosis, exocytosis, and amoeboid movement •Three main structural elements -Microtubules composed of tubulin protein -Microfilaments composed of actin protein -Intermediate filaments composed of various proteins

external structures of eukaryotes

•Extracellular Matrix (ECM) •Flagella •Cilia

nonmotile extensions

•Fimbriae -Sticky, proteinaceous, bristlelike projections -Used by bacteria to adhere to one another, to hosts, and to substances in the environment -May be hundreds per cell and are shorter than flagella -Serve an important function in biofilms •Pili -Long hollow tubules composed of pilin -Longer than fimbriae but shorter than flagella -Bacteria typically only have one or two per cell -Join two bacterial cells and mediate the transfer of DNA from one cell to another (conjugation) -Also known as conjugation pili or sex pili

capsule

•Firmly attached to cell surface •Protects cells from dessication (drying out) •May prevent bacteria from being recognized and destroyed by host

eukaryotic cell membrane

•Fluid mosaic boundary composed of phospholipids and peripheral and integral proteins •Contains cholesterol and other steroid-derived lipids for dynamic maintenance of membrane fluidity •Controls movement of materials into and out of cell through . . . -Passive and facilitated diffusion, osmosis, and active transport -Endocytosis - invagination of membrane engulfs extracellular materials for import (e.g., amoebas and macrophages) -Exocytosis - evagination of membrane expels intracellular materials for export

eurkaryotic cell walls

•Fungi, algae, and plants have cell walls but no extra-cellular matrices (ECMs) •Composed primarily of polysaccharides that vary by cell type . . . -Plant cell walls mostly contain cellulose -Fungal cell walls composed of chitin, cellulose, and/or glucomannan -Algal cell walls composed of cellulose, agar, carrageenan, silicates, algin, calcium carbonate, or combination of these •Permeable to water and most small metabolites, but not organic macromolecules (e.g., antibodies) •Provide multicellular eukaryotes with rigid structure that counteracts gravity (think cellular exoskeleton)

active transport

•In active transport, carrier proteins in the membrane burn ATP to move molecules against their concentration gradients •Types of carrier proteins -Uniporters - single molecule transport -Antiporters - coordinated transport of multiple molecules in opposite directions -Symporters - coordinated transport of molecules in the same direction

Golgi body

•In most cells, consists of flattened hollow sacs that are surrounded by single phospholipid bilayers Receives, processes, and packages immature proteins for transport to the cell membrane and subsequent export from the cell -Processing involves addition and subtraction of sugars for glycoprotein synthesis -Packaging involves inserting molecules into secretory vesicles that later fuse with the cell membrane during exocytosis

Ribosomes

•Larger than prokaryotic ribosomes (80S versus 70S) -"S" refers to a "Svedberg" or "sedimentation coefficient", a unit that defines the relative size of a macromolecule based upon how quickly it sediments out of solution in a centrifuge •Composed of RNA and protein molecules that assemble into 60S and 40S subunits •Critically important sites for protein synthesis -Decoding of genetic information via "translation" - conversion of nucleotide code into specific string of amino acids -Joining of amino acids into unfolded, immature proteins •Many important antibiotics are ribosomal inhibitors!!!

eurkaryotes

•Larger; 10-100 μm in diameter •More complex structure •Have membrane surrounding DNA; have nucleus •Have internal membrane-bound organelles •Comprised of algae, protozoa, fungi, animals, and plants

mitochondria

•Like nucleus, possess two boundary membranes that are composed of two separate phospholipid bilayers •Functions to produce most of the cell's ATP •Interior compartment contains a circular molecule of DNA (mitochondrial chromosome) and 70S ribosomes

other important organelles

•Lysosomes contain catabolic enzymes within acidic interiors for breaking down cellular garbage and contaminants •Peroxisomes contain enzymes that degrade poisonous wastes; very important in oilseed plants for converting storage oils into energy for post-germinative growth •Vacuoles and vesicles respectively store and transfer chemicals and nutrients within cells

endoplasmic reticulum (ER)

•Mesh-like arrangement of hollow sacs and tubules that are continuous with the nuclear envelope •Synthesis platform, preliminary processing plant, and transport system for proteins and lipids •Two major forms . . . -Smooth endoplasmic reticulum (SER) - plays a role in lipid synthesis -Rough endoplasmic reticulum (RER) - ribosomes attached to outer surface; transports proteins produced by ribo- somes to Golgi bodies

bacterial cell walls

•Most have cell wall composed of peptidoglycan; a few lack a cell wall entirely •Peptidoglycan is composed of peptide-linked chains of polysaccharides -Polysaccharide portions consist of chains of two alternating sugars . . . •N-acetylglucosamine (NAG) •N-acetylmuranic acid (NAM) -Chains of NAG and NAM are linked to each other by tetrapeptide crossbridges (four amino acids) •Bridges may be covalently bonded to one another (Unique Enzyme) •Bridges may be held together by short connecting chains of amino acids •Two basic types of bacterial cell walls

passive transport

•No energy (ATP) needed •Molecules move from high concentration to low concentration •Types -Simple diffusion •Osmosis - simple diffusion of water •Solution conditions can be described as isotonic, hypertonic, or hypotonic -Facilitated Diffusion •Requires a protein carrier or a protein channel

chloroplasts

•Possess two boundary membranes that are composed of two separate phospholipid bilayers •Light-harvesting structures found in photosynthetic eukaryotes (algae and plants) that function to store light energy as reducing equivalents for ATP synthesis •Interior compartment contains a chloroplast chromosome and 70S ribosomes

prokaryotic cell walls

•Provides structure and shape and protects cell from osmotic forces •Assists some cells in attaching to other cells or in eluding antimicrobial drugs •Animal cells do not have; can target cell wall of bacteria with antibiotics •Bacteria -Most have cell wall composed of peptidoglycan •Archaea -Have different cell wall chemistry -Cell walls contain variety of specialized polysaccharides and proteins

prokaryotic cell membrane

•Referred to as phospholipid bilayer; composed of lipids and associated proteins •Approximately half the membrane is 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

function of flagella

•Rotation propels bacterium through environment •Rotation can be clockwise or counterclockwise; in some species, rotation is reversible •Prokaryotes move in response to stimuli (taxis) -Runs - movements of cell in single direction; increase with favorable stimuli (positive chemotaxis and/or phototaxis) -Tumbles - abrupt, random, changes in direction; increase with unfavorable stimuli (negative chemotaxis and/or phototaxis)

gram positive cell walls

•Thick layer of peptidoglycan (~200 layers)! •Retains crystal violet dye in Gram staining procedure, causing cells to appear purple

gram negative cell walls

•Thin layer of peptidoglycan (~10-15 layers)! •Also possess a bilayer membrane (Outer Membrane) composed of phospholipids, channel proteins (porins), and lipopolysaccharide (LPS) •Cells appear pink due to safranin dye in Gram staining procedure

nucleus

•Usually the largest, most obvious organelle in the cell •Contains most of the cell's DNA •One or more nucleoli present in nucleoplasm; RNA synthesized in nucleoli •Surrounded by nuclear envelope, a double membrane composed of two phospholipid bilayers •Nuclear envelope contains nuclear pore complexes that are large enough to allow passage of intact macromolecules (proteins!)