L2-Cell Structure/Function of Bacteria and Archaea Flashcards
How do prokaryotic and eukaryotic cells differ?
- E-DNA is enclosed the nucleus
- E-generally much larger/structurally more complex
- E-presence of organelles/membrane-enclosed structures esp. mitochondria and chloroplasts
- P-organelles are absent
- P-can couple transcription directly to translation because DNA is in cytoplasm
- P-small circular DNA
- P-employ energy conservation reactions in the membrane
How is DNA arranged inside of microbial cells and how does this differ from eukaryotes?
- Microbes-small circular DNA in the cytoplasm called the chromosome; some prokaryotes have a linear chromosome. Highly condensed visible portion is called the nucleoid. Also contain one or more small circles of DNA (plasmids) distinct from the chromosome. They confer a special property (ex. unique metabolism) on a cell. Generally contain 1 copy of each gene (haploid).
- Eukaryotes-DNA is arranged in linear molecules wrapped tightly around histone proteins to form chromosomes inside the nucleus. Generally contain 2 copies of genes to be diploid.
Are prokaryotes more primitive than eukaryotes? Why or why not?
Prokaryotes are NOT more primitive than eukaryotes. Both are highly evolved. The difference is made to sort out structural rather than evolutionary differences.
How could you determine the relationship of microorganisms?
- Extract rRNa from the organisms
- Amplify the DNA by PCR
- Sequence the gene and align the sequences
- Computer-scores sequence differences base by base
- Use treeing algorithm to make a phylogenetic tree/determine divergence
Describe metabolic diversity of microbes. Explain the difference between chemoorganotrophs, chemolithotrophs and phototrophs. Also give an example of an organism that utilizes each of these types of metabolism.
- • Chemoorganotrophs-organisms that use organic chemicals to generate energy (ex. glucose, acetate, etc) ex. humans
- • Chemolithotrophs-tap the enrgy available from oxidation of inorganic compounds. Occurs only in prokaryotes (H2, H2S, Fe2+, NH4+). Live in close proximity to chemoorganotrophs
- • Phototrophs-contain pigments that allow them to cconert light energy into chemical energy (thus their cells appear colored). Does not require chemicals as a source of energy. Oxygenic (produces O2)-cyanobacteria, algae. Anoxygenic-purple bacteria, green bacteria, helio bacteria
Know the major phylogenetic divisions of bacteria and an example of each.
- • Proteobacteria-largest phylum of Bacteria. Includes many chemoorganotrophic, chemolithotrophic and phototropic bacteria. Inclues species that live in plants, animals, soil, water and are harmless or disease causing (mitochondrion has evolutionary roots in p) Ex. E. coli, Salmonella, Pseudomonas
- • Gram-Positive Bacteria-Related by common phyologeny and cell wall structure. Includes endospore-forming, Streptococcus and Lactobacillus. Many lack a cell wall and are pathogenic
- • Cyanobacteria-phylogenetic relatives of gram-positive bacteria. Oxygenic phototrophs Ex. Prochloron
- • Other: aquatic planctomycetes (distinct stalk ), helically shaped spirochetes (ex. syphilis and lyme disease), green sulfur bacteria and green nonsulfur bacteria (Ex. Chloroflexus) both of which are phototrophic autotrophs, Chlamydiae STD, Denococcus-Thermus (D. radiodurans-survives high doses of radiation), and hypothermophiles (Aquidwz, Rhwemorof)
Know the major phylogenetic divisions of archaea and an example of each.
- • Eurarchaeota-contains methanogens, extreme halophiles, thermoacidophiles, hyperthermophiles Ex. Methanobacterium-strict anaerobes (cannot tolerate low levels of O2)
- • Crenarchaeota- majority are hyperthermophiles (chemolithotrophs or chemoorganotrophs) many prokaryotes in open ocean are Crenarchaeota. Ex. Sulfolobus solfataricus (thermophile but groes aerobically/chemoorganotrophically)
Know main cell morphologies.
- • Coccus-spheroid or ovoid (plural cocci)
- • Rod/bacillus-cylindrical shape
- • Spirilla-rods twisted into spiral shapes
- • Filamentous bacteria-long filaments
How does small size and genetics of prokaryotes accelerate their evolution?
The small size of prokaryotes allows them to mature quicker and the greater surface area/volume ratio facilitates a quicker nutrient exchange. Hence, mutations (“raw material” of evolution) that naturally occur each time the chromosome replicates occur much greater in a population of prokaryotes in comparison to a population of eukaryotes. Also, since prokaryotes are generally haploid, they express mutations immediately rather than being masked by a second, unmutated gene copy.
Describe how archaeal and bacterial cell membranes are similar and different.
Similarities-
- • Hydrophilic exterior, hydrophobic interior
- • Fluid movement of the phospholipids
- • Membrane proteins are integrated into lipid or are peripheral
- • Proteins are arranged in clusters
Differences-
- • A-ether bonds between glycerol and the hydrophobic side chain
- • B-ester linkages between fatty acids and glycerol
- • A-diglycerol tetraethers from monolayers highly resistant to heat denaturatuion
- • A-many archaeal lipids also contain rings within the hydrocarbon chain-adjusts viscosity/membrane function
What are the main functional purposes of a cell membrane?
- a) Permeability barrier-prevents the passive leakage of solutes into or out of the cell (only small hydrophobic and water molecules pass the membrane)
- b) Anchor-for many proteins (enzymes and transporters)
- c) Energy conservation-help create proton gradients (proton motive force) such as in mitochondria
Describe the 3 main systems of transport and provide an example of each.
All proton motive force, or ATP, or some other energy-rich organic compound.
1) Simple transport-membrane-spanning transport protein (facilitated diffusion) Ex. lac permease is a symporter of lactose (cotransport of H+)
2) Group translocation-involves a series of proteins in the transport event. Substrate transported is chemically modified during its uptake across the membrane . Ex. phosphotransferase. Phosphate cascade must occur for transportation
3) ABC transport-substrate binding protein, a membrane integrated transporter and an ATP hydrolyzing protein work together for uptake of organic compounds such as sugars, amino acids, and inorganic nutrients such as sulfate, phosphate and trace metals. This system is in a region called the periplasm which lies between the cytoplasmic membrane and a second membrane layer. Ex. MRP1-(multidrug resistance protein) transports lipids and can transport hydrophobic drugs
Describe the functional purpose and structure of cell walls.
- • To withstand internal osmotic pressure due to high concentration of dissolved solutes
- • To prevent bursting (cell lysis)
- • To confer shape and rigidity on the cell
Demonstrate the differences between gram positive and gram negative cell walls.
- • Gram positive-typically much thicker, consists primarily of a single type of molecule. Sheets of peptidoglycan with “cables” for extra support. Also contain teichoic acids embedded in the cell wall
- • Gram negative-chemically complex and consists of at least two layers. Mainly composed of the outer membrane with a phospholipid bilayer and lipids and polysaccharades. Also referred to as the lipopolysaccharide layer or LPS.
Understand the importance of the difference between bacterial and archaeal cell walls.
- B-presence of the peptidoglycan-polysaccharide layer composed of two sugar derivatives, a few amino acids and either lysine or the structurally similar amino acid analog DAP
- B-sometimes the presence of an outer membrane
- A-lacks peptidoglycan and an outer membrane (resistant to lysozyme and penicillin)
- A-May contain pseudomurein which is a polysaccharide similar to peptidoglycan. Other Archaea may lack pseudormurein and have other polysaccharides.
- A-most common cell wall-S-layer (paracrystalline surface layer) (found in some types of bacteria as well) It is always the outermost layer
Describe flagellar structure and function.
- • Long, thin appendage (attached to cell at one end) that are helical/composed of protein flagellan. Wavelength is specific to the microorganism. Wider region at base called the hook and motor is in membrane surrounded by rings.
- • Tiny rotary motor used for movement. Increase or decrease speed in relation to proton motive force
