micro ch. 4

cell wall of bacteria

A complex, semi rigid structure responsible for the shape of the cell. It surrounds the underlying, fragile plasma membrane and protects it and the interior of the cell from adverse changes in the outside environment. Major function is to prevent bacterial cells from rupturing when the water pressure inside the cell is greater than that outside the cell. Serves as a point of anchorage for flagella. Contributes to the ability of some species to cause disease and is the site of action of antibiotics. Chemical composition of cell wall helps differentiate major types of bacteria.

lysozyme

A digestive enzyme. Occurs naturally in some eukaryotic cells and is a constituent of perspiration, tears, mucus and saliva. Lysozyme catalyzes hydrolysis of the bonds between sugars in the repeating disaccharide "backbone" of peptidoglycan. Almost completely destroys gram positive cell walls. Disrupts glycan chains.

fimbriae

A fringy collection of short appendages, used for attachment. Can occur at the poles of the bacterial cell or can be evenly distributed over the entire surface of the cell. Tendency to adhere to each other and object and are involved in forming biofilms.

extracellular polymeric substance

A glycocalyx that helps cells in a biofilm attach to their target environment and to each other.

chloroplasts

A membrane- enclosed structure that contains both the pigment chlorophyll and the enzymes required for the light-gathering phases of photosynthesis.

endoplasmic reticulum (ER)

A membranous network in the eukaryotic cells connecting the plasma membrane with the nuclear membrane. rough ER- Endoplasmatic reticulum with ribosomes on its surface. it's studded with ribosomes, the sites pf protein synthesis. usually folded in a series of of flattened sacs. smooth ER- Endoplasmic reticulum without ribosomes. It contains uniquw enzymes that make it functionally more diverse than rough ER. Synthesizes phospholipids (as does roughER) fats and steroids.

endosymbiotic theory

A model for the evolution of eukaryotes, which states that organelles arose from prokaryotic cells living inside a host prokaryotic.

group translocation

A special form of active transport that occurs exclusively in prokaryotes, the substance is chemically altered during transport across the membrane.

plasma (cytoplasmic) membrane

A thin structure lying inside the cell wall and enclosing the cytoplasm of the cell. Plasma membrane in prokaryotes consists primarily of phospholipids. Because they lack sterols, prokaryotic plasma membranes are less rigid than eukaryotic membranes. Its principle marcomolecules are phospholipids and proteins.

What are the distinguishing characteristics of prokaryotes?

Absence or organelles, which are specialized cellular structures that have specific functions. Their DNA is not enclosed within a membrane and is usually a singular circular arranged chromosome. Their DNA is not associated with histones, which are specialized chromosomal proteins found in eukaryotes; other proteins are associated with the DNA. Their cell walls almost always contain the complex polysaccharide peptidoglycan. They usually divide by binary fission. During this process the DNA is copied, and the cell splits into two cells. Binary fission involves fewer structures and processes than eukaryotic cell division.

pili

An appendage on a bacterial cell used for conjugation and gliding motility. Usually longer than fimbriae and number only one or two per cell. Are involved in motility and DNA transfer. Include twitching and gliding motility. Some pili are used to bring bacteria together allowing the transfer of DNA from one cell to another, a process called conjugation (sex) pili.

vacuoles

An intracellular inclusion, in eukaryotic cells, surrounded by a plasma membrane; in prokaryotic cells, surrounded by a proteinaceous membrane. A space or cavity in the cytoplasma of a cell that is enclosed by a membrane called a tonoplast. Derived from the Golgi complex & have several diverse functions.

mitochondria

An organelle containing Krebs cycle enzymes and the electron transport chain. Spherical or rod-shaped organelle.

golgi complex

An organelle involved in the secretion of certain proteins. Includes secretory vesicles, transfer vesicles, cisternae, and transport vesicle from rough ER.

Cell wall structure

Built from peptidoglycan. Long glycan chains cross-linked with short peptide fragments.

What structures are found in all bacteria?

Cytoplasm, 70s ribosomes, plasma membrane, nucleoid containing DNA. Almost all bacteria have cell walls.

bacilli

Divide only across their short axis. Most appear as single rods called single bacilli. Diplobacilli appear in pairs after division, and streptobacilli occur in chains. Some are oval and look like cocci called coccobacilli. When cap and italicized it refers to a specific genus like Bacillus anthracis.

What do plasmids do?

Encode information such as genes for resistance to antibiotics or the production of toxins. Plasmids may be exchanged between bacteria.

lysosomes

Formed fromGolgi complexes and look like membrane-enclosed spheres. have only a single membrane and lack internal structure. Contain as many as 40 different kinds of powerful digestive enzymes capable of breaking down various molecules. Human white blood cells, which use phagocytosis to ingest bacteria, contain large numbers of lysosomes.

medically Bergey's manual of Systematic Bacteriology suggests;

Four major categories- Gram-, gram+, no walls, archaea.

ribosomes

Function as the sites of protein synthesis. Are composed of two subunits, each of which consist of protein and ribosomal RNA. Prokaryotic ribosomes differ from eukaryotic ribosomes in the number of proteins and rRNA molecules they contain. Also somewhat smaller and less dense than ribosomes of eukaryotic cells.

gram+ v. gram-

Gram negative has a thin peptidoglycan layer but does have an outer membrane. The outer membrane makes penicillin less effective on gram negative bacteria. Outer membraneis built from phospholipids and LPS molecules. When gram- bacteria die, they release Lipid A, an endotoxin that is responsible for infection symptoms such as fever, dilation of blood vessels, shock, and blood clotting.

gram-negative cell walls

Gram reaction=Can be decolorized to accept counterstain and stain pink or red. peptidoglycan layer= Thin (single layered) teichoic acids= Absent periplasmic space= present outer membrane=present lipopolusaccharide (LPS) content=high lipid and lipoprotein content= High because of the presence of outermembrane flagellar structure= 4 rings in basal body toxins produced= endotoxins & exotoxins resistance to physical destruction= low cell wall disruption by lysozyme= low susceptibility to penicillin and sulfonamide= low susceptibility to streptomycin, chloramphenicol, and tetracycline= high inhibition to basic dyes= low susceptibility to anionic detergents= low resistance to sodium azide= low resistance to drying= low

gram-positive cell walls

Gram reaction=Retain crystal violet dye and stain blue or purple peptidoglycan layer= thick (multilayered) teichoic acids= present in many periplasmic space= absent outer membrane=absent lipopolusaccharide (LPS) content=virtually none lipid and lipoprotein content= Low. Acid fast bacteria have lipids linked to peptidoglycan. flagellar structure= 2 rings in basal body toxins produced= exotoxins resistance to physical destruction= high cell wall disruption by lysozyme= high susceptibility to penicillin and sulfonamide= high susceptibility to streptomycin, chloramphenicol, and tetracycline= low inhibition to basic dyes= high susceptibility to anionic detergents= high resistance to sodium azide= high resistance to drying= high

Spiral

Have on or more twist. Vibrios look like curved rods. Spirilla have a helical shape and rigid bodies and use flagella to move. Spirochetes are helical and flexible and use axial filaments which resemble flagella but are contained within a flexible sheath.

nucleoid

In a bacterial cell, usually contains a single long, continuous, and frequently circularly arranged thread of double-stranded DNA called the bacterial chromosome. bacteria often contain small usually circular, double-stranded DNA molecules called plasmids. Often code for toxins, special enzymes, or resistance factors.

flagella

Long filamentous appendages that propel bacteria. May be peritrichous, distributed over the entire cell or polar, at one or both poles or ends of the cell. If polar, fagella may be monotrichous, a single flagellum at one pole. Lophotrichous, a tuft of flagella at both poles of the cell.

cytoplasm

Major site of metabolic activities. Water is a principle component (80%) that acts as a solvent. Refers to the substance of the cell inside the plasma membrane.

glycocalyx

Means sugar coat. The general term used for substances that surround cells, Bacterial glycocalyx is viscous (sticky), gelatinous polymer that is external to the cell wall and composed of polysaccharide, polypeptide, or both. If the substance is organized and is firmly attached to the cell wall, the glycocalyx is described as a capsule. If the substance is unorganized and only loosely attached to the cell wall, the glycocalyx is described as a slime layer. Capsules contribute to bacterial virulence, the degree to which a pathogen causes disease. Both can help form biofilms.

Major organelles in a eurkaryotic cell

Nucleus, mitochondria, chloroplasts, endoplasmic, recticulum (smooth & rough), ribosomes, lysosomes, golgi apparatus & motility.

Passive vs. active processes

Passive processes-substances cross the membrane from an area of high concentration to low concentration without any expenditure of energy (ATP) of the cell. Active processes- the cell must use ATP to move substances from areas of low concentration to high concentration.

penicillin

Penicillin interferes with the final linking of the peptidoglycan rows by peptide cross-bridges. As a result, the cell wasll is greatly weakened and the cell undergoes lysis, destruction caused by rupture of the plasma membrane and the loss of cytoplasm.

What does prokaryotic mean?

Pro=before karyotic= nucleus

centrosome

Region in a eukaryotic cell consisting of pericentriolar area (protein fibers) and a pair centrioles; involved in formation of the mitotic spindle.

What are the functions of the plasma membrane?

Selective permeability-Indicates that certain molecules and ions pass through the membrane but that others are prevented from passing through it. Its also important to the breakdown of nutrients and the production of energy. Plasma membranes of bacteria contain enzymes capable of catalyzing the chemical reactions that break down nutrients and produce ATP.

What is the importance of the differences between pro & eukaryotic ribosomes with regard to antibiotics?

Several antibiotics work by inhibiting protein synthesis on prokaryotic ribosomes. Because of the differences in prokaryotic and eukaryotic ribosomes, the microbial cell can be killed by the antibiotic while the euk host cell remains unaffected.

simple vs facilitated diffusion

Simple- the net movement of molecules or ions from an area of high concentration to an are of low concentration. Facilitated- Intergral membrane proteins function as channels or carriers that facilitate the movement of ions or large molecules across the plasma membrane. Called transporters or permeases. Both passive.

active transport

The cell uses energy in the form of ATP to move substances across the plasma membrane. Movement by active transport can go against the concentration gradient, allowing a cell to accumulate needed materials. usually from outside in.

Three basic part of a flagellum

The long outer-most region, the filament, is constant in diameter and contains the globular protein flagellin arranged in several chains that intertwine and form a helix around a hollow core. The filament is attached to a slightly wider hook, consisting of a different protein. The basal body, which anchors the flagellum to the cell wall and plasma membrane.

peptidoglycan

The macromolecular network that makes up bacterial cell walls. Present either alone or in combination with other substances. The structural molecule of bacterial cell walls consisting of the molecules N-acetylglucosamine, N-acetlymuramic acid, tetrapeptide side chain, and peptide side chain. NAG and NAM Are linked by polypeptides.

How do eukaryotic cells differ?

The most characteristic eukaryotic organelle is the nucleus. Nucleus- Usually spherical or oval, is frequently the largest structure in the cell, and contains almost all of the cell's hereditary information (DNA). membrane enclosed organelles and more complex anatomies. greater than 10 um in size. Found in protista, animalia, plantae, and fungi. flagella is complex; consist of multiple microtubes glycocalyx- present in some cells that lack a cell wall. cell wall- when present, chemically simple, includes cellulose and chitin. plasma membrane- sterols and carbohydrates that serve as receptors. cytoplasm- cytoskeletion; cytoplasmic streaming. Cytosol refers to the fluid portion of cytoplasm. Cytoskeleton provides support and shape and assists in transporting substances through the cell. ribosomes- larger. Large size (80s); smaller size (70s) in organelles. chromosome (DNA)- multiple linear chromosomes with histones. cell division- involves mitosis sexual recombination- involves meiosis.

Are all bacteria pro or eukaryotic?

They are prokaryotic.

Cocci

Usually round but can be oval, elongated, or flattened on one side. Divided and remain in pairs are diplococci. Those that divide and remain atttached in chainlike patterns are called streptococci. Divide and remain into two planes and remain in groups of four are tetrads. Divide into 3 planes and in groups of 8 are sarcinae. Divide in multiple planed and form grapelike clusters or broad sheets are staphylococci.

What would happen to bacteria with out peptidoglycan in an aqueous environment?

Water moves into a cell during osmosis, if the wall is weak or damaged, it bursts (osmotic lysis).

endospores

When essential nutrients are depleted, certain gram+ bacteria such as those of the genera Clostridium and Bacillus, form specialized resting cells called endospores. They can withstand extreme conditions like extreme heat, lack of water, & exposure to many toxic chemicals. Resistance dde to dehydration & thick coats and cortex. May survive 250 million years. many are lab & food industry contaminants.

What are the two classifications of prokaryotes?

bacteria and archaea. Most medically important ones belong to the domain bacteria.

inclusions

material held inside a cell, often consisting of reserve deposits.

peroxisomes

organella that oxidizes amino acids, fatty acids, and alcohol.

The basic shapes of bacteria

spherical coccus, plural=cocci, meaning berries. rod shaped bacillus, plural=bacilli, meaning little staffs. Spiral. Determined by heredity.

taxis

the movement of a bacterium toward or away from a particular stimulus. Stimuli include chemicals, known as chemotaxis, and light or phototaxis,

osmosis

the net movement of solvent molecules across a selectively permeable membrane from an area with a high concentration of solvent molecules to an area of low concentration of solvent molecules. osmotic pressure- the pressure required to prevent the movement of pure water into a solution containing some solutes. isotonic solution- A medium in which the overall concentration of solutes equals that found inside a cell. hypotonic solution- outside the cell is a membrane whose concentration of solutes is lower than that inside. hypertonic solution- a medium having a higher concentration of solutes than inside the cell hass.

axial filaments

the structure for motility found in spirochetes; also called endoflagellum.