Micro Cell Bio Flashcards
Comparing Prokaryotic and Eukaryotic Cells
- They both contain nucleic acids, proteins, lipids, and carbohydrrates
- use same chemical reactions to metabolize food, build proteins, and store energy
- the structure of the cells and the absence of organelles specialized cellular structures that have specific functions is where they differ.
DISTINGUISHING CHARACTERISTICS OF PROKARYOTES
- dna is not enclosed within a membrane and is a circularly arranged chromosome…usually singular
- the dna is not associated with histones (special chromosomal proteins found in eukaryotes)
- lack organelles…lack membrane enclosed organelles such as nuclei, mitochondria, and cholorplast
- their cell walls almost always contain the complex saccharide peptidoglycan
- usually divide by binary fission, where DNA is copied and the cell splits into two cells.
- invloves fewer structures and processes than eukaryotic cell division
Prokaryotes
- likely have a chemically complex cell wall
- cytoplasm: ribosomes, protein, lipids, nuclei
- have different mass density in ribosomes 70s
- has dna can’t be a living organism without it
DISTINGUISHING CHARACTERISTICS OF EUKARYOTIC CELLS
- dna is found in the cells nucleus which is separated from the cytoplasm by a nuclear membrane and the dna is found in multiple chromosomes.
- dna is consistently associated with chromosomal proteins called histones and with nonhistones
- have several of membrane enclosed organelles like mitochondria, endoplasmic reticulum, golgi complex, lysosomes, and sometimes chloroplast
- have chemically simple cell walls
- their cell division involves mitosis where a chromosome replicates and an indentical set is distributed into each of two nuclei. Division of the cytoplasm and other organelles follow so the two cells produced are indential to each other
Prokaryotic Cells are most likely ___?
- unicellular
- bacteria or archaea
DNA of Prokaryotes
- not linear and not located in nucleus
- each chromosome has one long molecule of DNA making it a circle so one large circular molecule of DNA
- the dna sits in the nucleiod thats in the center of the cytoplasm
- has naked/unsupported proteins so no histones
WHAT DEFINES A GENERALIZED PROKARYOTE?
Ribosomes (70s), Nuceloid w DNA, Plasma Membrane, and Cytoplasm
- core genetic info that dictates shape cell and whether its gram negative/ positive
- every damn prokaryote has this….this what defines the prokaryote.
- Think of a car with the basic package
WHAT IS THE EXTRA SHIT THAT A PROKARYOTE CAN DEVELOP?
- Car with the upgraded shit
- extra shit is the plasmid or plasmids
- Gives extra like capsules
- ability to be resistant to antibiotics
- ability to perform rare asexual behavior
Prokaryote Genome
- the main genetic information is not really a chromosome rather it is a chromomene which is the main genetic element of the cell
- circular dna packed to the nucleiod region
- in the chromomeme all the genes to define a species not the extra shit
Chromomeme
- all the genes to define a species not the extra shit
- shape, gram neg/pos or acid fast
Other Prokaryote Genetic Elements
-plasmids and transposons
Plasmids
- tiny circles of DNA that code things you won’t find in all prokaryotes
- gives extra DNA and extra info from somewhere and this how some bacteria become resistant to some antibiotics
- gets new ability not related to that species from plasmid
- has significant less genes but for unusual abilities
What are the two different type of plasmids?
- F PLASMIDS are for fertility and it allows the donation of dna to cells that doesn’t have plasmids
- R plasmids are for resistance and it carry genes for resistance to antibiotics, disinfectants and antiseptics
Transposons
- are other prokaryotic elements that doesn’t define the species
- highly mobile
- can copy and move themselves from one place to another
RIBOSOMES
- For prokaryotes and eukaryotes the ribosomes perform the same function
- the prokaryotes has a density of 70s and eukaryotes ribosomes has 80s
Mitochondria/chloroplast
have bacterial properties
-evidence for ends symbiosis because we know where those organelles came from because they have the same properties
Glycocalyx
- most prokaryotes secrete this on their surface
- the general term used for substances that surround a cell
- if the substance is organized and is firmly attached to the cell wall it is described as a capsule
- the presence of a capsule can be determined by using negative staining
- if the substance is unorganized and only loosely attachted to the cell wall the glycocalyx is described as a slime layer
- capsules are important in contributing to bacterial virulence(the degree to which a pathogen cause disease)
- protects pathogenic bacteria from digestion and ingestion of MOs of the cell
Endospores
- Not all organisms make endospores on bacillus and clostridium species
- spore position whether it is terminal, subterminal, or central is dependent on the species
- heat resistant and autoclaving (steam under pressure
Sporulation Steps
Begins when cell is under biological diversity
- Spore septum begins to isolate newly replicated DNA and some of the cytoplasm
- Plasma membrane starts to surround DNA and cytoplasm
- spore septum surrounds isolated portion forming forespore
- peptidoglycan layer forms between membranes
- spore coat forms
- endospore is freed from the cell
Outer Cell Membrane
- Fluid mosaic model contains phospholipid bilayer and embedded globular proteins
- no internal membrane compartments
Phospholipid bilayer
Part of the fluid-mosaic model
-Barrier to transport of molecules other than respiratory gasses
Globular proteins
- Regulate cell transport
- cell wall biosynthetic enzymes
- antibiotic efflux pumps which are mechanisms of resistance
Prokaryotic Cell walls
- has chemically complex cell walls full with techie acid and peptiglycan
- it protects against mechanical injury and osmotic lysis (water entering it and rupturing it)
- two types gram neg/ gram pos
Gram Pos Cell Walls
- Abundant peptioglycan
- low lipid content because no outer membrane (Lipopolysacchride)
- susceptible to penicillin
- has covalent bonds between amino acids and peptidoglycan
Gram Negative Cell Walls
- Peptidoglycan content low
- abundant phospholipid
- sensative to tetracycline
- no target for penicullum cuz no covalent bonds between amino acids and peptidoglycan molecules
Flagella
- some prokaryotic cells (some don’t have) have flagella which are long filamentous appendages that move bacteria
- rotation motion
- composed of flagellin protein
atrichous
if they don’t have flagella
peritrichous
flagella distributed all over the cell
polar
flagella at one or both ends of the cell
monotrichous
a single flagellum at one pole
lophotrichous
some flagella coming from one pole
Amphitrichous
flagella at both poles of the cell
Fimbriae and Pilli
- many gram negative bacteria contain hairlike appendages that are shorter, straighter, and thinner than flagella.
- these structures consist of a protein called pilin
- used in attachment to environmental surfaces
Differences in GRAM POS/NEG
- the amount of peptiodglycan
- what it is sensitive too
- how it gram stains because the covalent bonds can’t be decolorized
Acid Fast Cells
- similar to gram pos but has waxes and makes it resistant to conventional and aqueous solutions
- heat or surface active agent used to enhance stain penetration
- all acid fast belong to the genus mycobacterium M.Tuberculosis and M. Leprae
Capsule
- outermost coater layer when present
- plasmid genes make it so not species related structure
- genetically controlled and environmentally influenced
- watery mixture of glycoproteins and glycolipids
Functions of Capsules
Protection against dehydration, phagocytosis (virulence factor)
-source of nutrients and energy…so recycles resources
THE CELL WALL…read and divulge
- The cell wall of the bacterial cell is a complex, semirigid structure responsible for the shape of the cell.
- almost all prokaryotes has a cell wall that surrounds the underlying, fragile plasma membrane and protects it and the interior of the cell from adverse changes in the outside environment
- the major function is to prevent bacterial cells from rupturing when the water pressure inside the cell is greter than the outside the cell
- also maintains the shape and serves as a point of anchorage for flagella
- clinically, it is important because it contributes to the ability of some species to cause disease and is the site of action of some antibiotics
- THE CHEMCIAL COMPOSITION OF THE CELL WALL IS USED TO DIFFERENTIATE MAJOR TYPES OF BACTERIA
Composition and Characteristics
- the cell wall is composed of Peptidoglycan which is present either alone or in combination with other substances
- consists of a repeating disaccharide connected by polypepties to form a lattice that surrounds and protect the entire cell
- the dissacharide portion is made up of monosaccahraides called N acetylglucosamine and N acetylmuramic acid
Difference in layers for Gram pos/neg
-the cell walls consist of many layers of peptidoglycan, forming a thick, rigid structure…gram negative only contains a thin layer and has a outermembrane
Difference in space between cell wall and plasma membrane?
gram pos :The space between the cell wall and plasma membrane contains the granular layer which is composed of lipoteichoic acid….the space between gram negative is periplasm
Teichoic Acids
The cell walls iin gram positive bacteria contain teichoic acids which consist primarily of an alchohol and phosphate
-two classes of teichoic acids: lipoteichoic and teichoic acids
Lipoteichoic acids
which spans the peptidoglycan layer and is linked to the plasma membrane
Teichoic Acid
linked to the peptidoglycan layer
- because of their negative charge teichoic acids may bind and regulate the movement of cations (Positive ions) into and out of the cell
- may also assume a role in cell growth, preventing extensive wall breakdown and possible cell lysis
- teichoic acids makes it possible to identify gram positive bacteria by certain lab test
The anatomy of gram negative cell walls
consist of one or a very few layers of peptidoglycan and an outer membrane
- the peptidoglycan is bonded to lipoproteins in the outer membrane and is in the periplasm, a gel like fluid in the periplasmic space of gram negative bacteria, the region between the outer membrane and the plasma membrane
- contains a high concentration of degradative enzymes and transport proteins
- do not contain teichoic acids
- because they contain a small amount of peptidoglycan they are more susceptible to mechanical breakage
Outermembrane of Gram-Negative cell
- consists of lipopolysaccharides, lipoproteins, and phospholipids
- its strong negative charge is an important factor in evading phagocytosis
- provides a barrier to detergents, heavy metals, bile salts, certain dyes, antibiotics, and digestive enzymes such as lysozyme.
- doesn’t block all enviormental substances because nutrients must enter to sustain the metabolism of the cell
- because of the proteins called porins in the membrane it is very permeable. Permits the passage of nucleotides, disaccharides, peptides, amino acids, vitamin b12, and iron
What are the components of the Outermembrane?
lipopolysaccharide which consists of Lipid a, Core Poly Saccharide,, and O polysaccharide
-has lipids and carbohydrates
Lipid A
is the lipid portion of the LPS and is embedded in the top layer of the membrane
- when gam negative bacteria die they relase lipid A which is called endotoxin - responsible fir the symptoms associated with infections by gram negative bacteria such as fever, dilation of blood vessels, shock, and blood clotting
Core Polysaccharide
is attached to lipid A and contains unusual sugars….function is to provide stability
O polysaccharide
extends outward from the core polysaccharide and is composed of sugar molecules
- functions as an antigen and is useful for distinguishing species of gram negative bacteria - similar in how techoic acids are used to identify gram positive cells
Cell Walls and the Gram Stain Mechanism
- the mechanism of the gram stain is based on differences in the cell wall structure of gram positive and gram negative bacteria and how each reacts to various reagents
- crystal violet stains both gram negative and positive cells purple because the dye enters the cytoplasms of both type of cells
- the iodine is applied it forms large crystals with the dye that are too large to escape within the cell
- the alchohol dehydrates the peptidoglycan of gram positive cells to make it more impermeable to the crystal violet iodine
- but for gram negative cells the alcohol dissolves the outer membrane of gram negative cells and even leaves small holes in the thin peptidoglycan layer through wich crystal violet iodine diffuse
- when safranin is applied both gram negative and positive cells absorb it…but is hidden by the darker purple dye that was absorbed by the gram positive cells
Why do some organisms give negative results even if they are gram positive?
IF THE CELLS ARE DEAD THEY MAY GIVE A GRAM NEGATIVE RESPONSE EVEN THOUGH THEY ARE POSITIVE
Acid Fast Cell Walls
- acid fast stain is used to identify all bacteria of the genus Mycobacterium and pathogenic species of Nocardia
- these bacteria contain high concentrations of hydrophobic waxy lipid called mycolic acid in their cell wall that prevents the uptake of dyes, including those used in the gram stain.
