Chapter 4- Functional Anatomy of Prokaryotic and Eukaryotic Cells Flashcards
Prokaryotic cell shape
Monomorphic mainly, (rhizobium and Corynebacterium are pleomorphic), 0.2 - 2 microns in diameter, about 2-8 microns in length
Glycocalyx
viscous polymer composed of polysaccharide and/or polypeptide external to the cell wall; can be a capsule if tightly attached to the cell wall, or slime layer if unorganized and diffuses easily; important for biofilms, adherence, inhibit nutrient loss, virulence and dehydration.
Flagella (prokaryotic)
Long filamentous appendages outside the cell wall for propulsion. Consists of non membranous filament (globular flagellin that carries H antigen), basal body (rod and series of rings that attaches flagellum to the wall/membrane), hook (flexible coupling between the filament and the basal body.
Bacterial flagella arrangement
Peritrichous- flagella surrounding the whole cell
Lophotrichous/polar- tuft of flagella like a ponytail
monotrichous- single flagellum
amphitrichous- flagella on each end
Axial filaments
Specialized flagella in spirochetes that lie between the cell wall and outer sheath
Fimbriae and Pili
Both: comprised of pilin, hairlike appendages that are shorter/straighter/thinner than flagella, present in most gram-negative bacteria.
Fimbriae: on poles or evenly distributed, few-hundreds, allow attachment to each other and surfaces.
Pili: normally longer than fimbriae, only 1-2 per cell, facilitate DNA transfer, used for twitching/gliding motility.
Gram + cell walls
cell membrane>thick peptidoglycan cell wall.
contains teichoic acids that provide rigidity, negative charge to regulate cation movement, and that are antigenic.
Gram - cell walls
inner cell membrane > thin peptidoglycan layer > outer cell membrane
has periplasm, lipopolysaccharide, strong negative charge (which is beneficial against phagocytes and complement system), provides a barriere against antibiotics/lysozyme but not small metabolites due to porins.
Lipopolysaccharide
Lipid A>Core polysaccharide> O polysaccharide
Lipid a- released when they die which is highly antigenic and is an endotoxin.
Core polysaccharide- contains unusual sugars which provide stability
o polysaccharide- antigen useful for distinguishing gram - species.
Atypical cell walls
Mycoplasma- lacks cell walls/sterols in plasma membrane
Archaea- wall-less or walls of pseudomurein, which has N-acetyltalosaminuric acid instead of NAM and lacks D-amino acids).
Protoplast
cell wall entirely removed (lysozyme digestion of gram + cells)
Spherplasts
cell wall only partially removed (lysozyme digestion of gram - cells) EDTA is necessary for lysozyme efficacy on gram - cells because it’s a divalent cation chelator that removes Mg+ cations so the lipid A portions repel each other, disrupting the outer membrane which will expose the cell wall.
L form
cells that lose their cell walls and swell into irregular shapes in response to lysozyme or penicillin.
Mesosomes
Irregular folds that happen from preparing a specimen for microscopy.
antimicrobial agents that damage the plasma membrane
Disinfectants: alcohols and quarternary ammonium compounds
antibiotics: polymyxins that interact with phospholipids and disrupt membrane structure resulting in leakage of intracellular contents.
Plasmids
self-replicating double-stranded DNA molecules that contain 5-100 genes that can be used for antibiotic resistance; not crucial for survival.
Metachromatic granules
inclusions of inorganic phosphate; formed by cells in phosphate-rich environments
polysaccharide granules
reverse of glycogen/ starch
sulfur granules
sulfur reserves that can be used for energy
carboxysomes
inclusions that contain ribulose 1,5-diphosphate carboxylase for CO2 fixation.
Gas vacuoles
hollow cavities found in aquatic prokaryotes that maintain buoyancy
magnetosomes
inclusions of iron oxide to orient bacteria as well as protect from H2O2
Endospores
Dehydrated cells with thick walls and resistant to desiccation, radiation, heat and chemicals; contain only DNA, little RNA, ribosomes and a few important molecules. NOT METABOLICALLY ACTIVE; found in gram + bacteria; NOT A FORM OF REPRODUCTION
Flagella (eukaryotic) and cilia
Both have 9+2 arrangement of microtubules (tubulin), encased in cell’s membrane, and anchored to membrane via a basal body. Also, the eukaryotic flagellum moves in a wavelike manner, as opposed to the prokaryotic one’s rotation
Eukaryotic cell wall
animal and protozoan cells lack cell walls (protozoans have outer protein coat called a pellicle)
algae and plant cells have cell walls of cellulose
fungi have cell walls of chitin; molds :NAG polymer and/or cellulose; yeasts: chitin, glucan, and mannan
ribosomes (eukaryotic vs prokaryotic)
80S in eukaryotes (can be membrane bound, and the 2 subunits assemble in the nucleolus and join together in the cytoplasm)
70S in prokaryotes and mitochondria and chloroplasts.
Nucleus
Contains most of the cellular DNA, has nuclear pores and a nuclear envelope; has a compact, nonmembrane-bound region of rRNA genes called the nucleolus.
Endoplasmic reticulum
Rough: Site of protein synthesis that’s continuous with the nucleus, where proteins are initially glycosylated and membrane-bound/secretory proteins are synthesized.
Smooth: phospholipid synthesis.
golgi Complex
Receives transport vesicles from the ER, proteins/lipids move from cis-cis via vesicles; rxns yield glycolipids, glycoproteins and lipoproteins.
Lysosomes
a single membranous compartment that contains digestive enzymes that break down cell components or molecules.
Vacuoles
enclosed golgi-derived membrane-bound sac (tonoplast) that is small in animal cells but can be very large in plant cells. Can store proteins, sugars, organic/inorganic ions, act as degradative compartments, or to store poisons. in plants, they can take up water to provide rigidity.
Centrosome
organization center for microtubule formation in nondividing cells and for the mitotic spindle during cell division.
Has pericentriolar area which is a region of small protein fibers, and centrioles (cylindrical structures which has 9 clusters of 3 microtubules arranged in a 9+0 array).
