Prokaryotes and Eucaryotes Flashcards
Prokaryotes: Nucleoid
nuclear area - contains a single long circular molecule of double-stranded (ds) DNA, “chromosome”. - No histone proteins associate with chromosome
Prokaryotes: Plasmid
extra small circular, dsDNA molecules - replicate independently of chromosome (Fig. 4.6) - usually contain 5 to 100 genes which are usually not essential for survival of the bacteria - may carry genes for antibiotic resistance, tolerance to toxic metals, production of toxins, synthesis of enzymes - horizontal gene transfer via conjugation
Ribosome
sites of protein synthesis
70S
ribosomes composed of 2 subunits: 50S + 30S subunits - Each subunit is composed of a set of proteins complexed with one or more ribosomal RNAs (rRNA).
“S” =
Svedberg units: measurement of mass based on density gradient centrifugation.
Inclusions:
reservedeposits(nutrients)withinthecytoplasm
Types of inclusions:
Metachromatic granules: volutin
eserve of inorganic phosphate (polyphosphate) that can be
used in the synthesis of ATP
- “change color” = named b/c sometimes stain red with certain
blue dyes such as methylene blue
- are found in algae, fungi, protozoans, and bacteria.
- are characteristic in Corynebacterium diphtheriae, the causative agent of dipththeria.
Polysaccharide granules:
consist of glycogen and starch - iodine + starchgranules appear blue
Lipid Inclusions:
stores lipid
- can be stained with fat-storage dyes such as Sudan dyes
- found in various species of Mycobacterium, Bacillus, Azotobacter, Spirillum.
Sulfur Granules:
stores sulfur
- can serve as source of energy
- bacteria in the genus Thiobacillus derive energy by oxidizing sulfur and sulfur containing compounds.
Carboxysomes
contain the enzyme ribulose 1,5-diphosphate
carboxylasecarbon dioxide fixation
- enzyme is necessary for bacteria that use carbon dioxide as
their source of carbon for photosynthesis.
- are found in nitrifying bacteria, cyanobacteria, and thiobacilli.
Gas Vacuoles:
hollow cavities used to maintain buoyancy
- found in many aquatic procaryotes, including cyanobacteria,
anoxygenic photosynthetic bacteria, and halobacteria
- allows organism to remain at the depth in the water appropriate for them to receive sufficient amounts of oxygen, light, and nutrients.
Endospores
specialized “resting” cells found with bacterium - Unique to bacteria
- are formed when nutrients are depleted and when water is
unavailable
- are highly durable, dehydrated bodies with thick walls or
additional layers
- are formed inside the bacterial cell membrane by
sporulation or sporogenesis).
- can survive extreme heat, lack of water, and exposure to
toxic chemicals and radiation
- certain gram (+) bacteria such as those of the genera Clostridium and Bacillus form endospores
- gram (-) generally do no have endospores
Endospores can be: location
- terminally located (at one end)
- subterminally located (near one end)
- centrally located inside the vegetative cell.
Sporogenesis or sporulation:
process of spore formation
1st stage of sporogenesis, a newly replicated bacterial chromosome and a small portion of the cytoplasm are
isolated by a spore septum.
- The spore septum becomes a double-layered membrane called a forespore.
- Thick layers of peptidoglycan are laid down between the two membrane layers.
- A thick spore coat of protein forms around the outside membrane (this coat is responsible for the resistance of endospores to many harsh chemicals.
- When the endospore matures, the vegetative cell wall dissolves (lyses) and the endospore is
released.
- Endospores contain DNA, small
amounts of RNA, ribosomes,
enzymes, and a large amount of small molecules
- Endospores can remain dormant for a long time…1000s of yrs.
sporeulation stage 1
sporulation stage 2
sporulation stage 3
sporulation stage 4
sporulation stage 5
sporulation stage 6
Germination
return of the endospore to vegetative state
- triggered by physical and chemical damage to the endospore’s coat
b. Endospore’s enzymes break down the extra layers surrounding the endospore, water enters, and metabolism resumes. - One vegetative cell forms one endospore.
- Endospores are important clinically because they are resistant
to the processes that normally kill bacteria;
General Characteristics:Eukaryotes
- Greek for “true nucleus”
- include algae, protozoans, fungi, plants, and animals
- typically larger and structurally more complex than the prokaryotic cell
- contain membrane bound organelles – specialized structures that perform specific functions
- genetic material is organized into chromosomes by closely associating with histones and other proteins
- DNA housed in nucleus
Flagella and Cilia:
- used for locomotion & moving substances - flagella are long projections
- cilia are short numerous projections
- eukaryotic flagella move in a wave-like manner but prokaryotic flagella rotate
flagella and cilia contain cytoplasm and enclosed by plasma membrane
- are arranged in 9 (pairs) + 2 arrangement of microtubules - microtubules composed of tubulin protein
