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Questions and Answers
What is the primary function of the phospholipid bilayer in a prokaryotic cell membrane?
What is the primary function of the phospholipid bilayer in a prokaryotic cell membrane?
Which of the following molecules can typically diffuse directly through the cell membrane due to passive diffusion?
Which of the following molecules can typically diffuse directly through the cell membrane due to passive diffusion?
What is the proton motive force (PMF) primarily used for in prokaryotic cells?
What is the proton motive force (PMF) primarily used for in prokaryotic cells?
In a hypertonic environment, what will be the net movement of water in relation to a prokaryotic cell?
In a hypertonic environment, what will be the net movement of water in relation to a prokaryotic cell?
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Which cellular component is NOT a primary structural feature of prokaryotic cells?
Which cellular component is NOT a primary structural feature of prokaryotic cells?
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Which of the following structures is NOT found in all prokaryotic species?
Which of the following structures is NOT found in all prokaryotic species?
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What is the primary function of pili or fimbriae in bacteria?
What is the primary function of pili or fimbriae in bacteria?
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Which bacterial genus is NOT known for forming endospores?
Which bacterial genus is NOT known for forming endospores?
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What is the energy source for flagellar rotation in bacteria?
What is the energy source for flagellar rotation in bacteria?
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Which photosynthetic bacteria uses bacteriochlorophyll and does NOT produce oxygen?
Which photosynthetic bacteria uses bacteriochlorophyll and does NOT produce oxygen?
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What is the primary purpose of bacterial storage inclusions?
What is the primary purpose of bacterial storage inclusions?
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Which of the following is a characteristic trait of bacterial endospores?
Which of the following is a characteristic trait of bacterial endospores?
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Which of these describes the membrane found within a cyanobacteria?
Which of these describes the membrane found within a cyanobacteria?
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What is the primary role of lipopolysaccharide (LPS) in the context of bacterial infections?
What is the primary role of lipopolysaccharide (LPS) in the context of bacterial infections?
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Which of the following best describes the function of the S layer in bacteria?
Which of the following best describes the function of the S layer in bacteria?
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What is a typical characteristic of bacterial capsules and slime layers?
What is a typical characteristic of bacterial capsules and slime layers?
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What is a key feature of acid-fast bacteria that makes them difficult to detect and treat?
What is a key feature of acid-fast bacteria that makes them difficult to detect and treat?
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Which characteristic is unique to Mycoplasma species?
Which characteristic is unique to Mycoplasma species?
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Where is bacterial DNA typically stored?
Where is bacterial DNA typically stored?
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What is the function of plasmids in bacteria?
What is the function of plasmids in bacteria?
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What is the main function of bacterial ribosomes?
What is the main function of bacterial ribosomes?
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What is the primary function of peptidoglycan in bacteria?
What is the primary function of peptidoglycan in bacteria?
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Which of the following components are the 'bricks' that form the glycan chains in peptidoglycan?
Which of the following components are the 'bricks' that form the glycan chains in peptidoglycan?
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A bacterium is placed in a hypotonic solution. What is the likely outcome?
A bacterium is placed in a hypotonic solution. What is the likely outcome?
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Which of the following is a component of Gram-negative bacteria, but not Gram-positive bacteria?
Which of the following is a component of Gram-negative bacteria, but not Gram-positive bacteria?
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What is the function of the lipid A portion of lipopolysaccharide (LPS)?
What is the function of the lipid A portion of lipopolysaccharide (LPS)?
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Which of the following describes the structure of the peptidoglycan layer in Gram-positive bacteria?
Which of the following describes the structure of the peptidoglycan layer in Gram-positive bacteria?
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What is the role of the peptide crosslinks in peptidoglycan?
What is the role of the peptide crosslinks in peptidoglycan?
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What is the effect of lysozyme on bacteria?
What is the effect of lysozyme on bacteria?
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Study Notes
Prokaryotic Structure
- Prokaryotes lack a nucleus, storing DNA in a nucleoid, often as a single circular chromosome.
- Plasmids, extrachromosomal DNA, may be present, carrying genes for metabolism or pathogenicity. They can be transferred between species.
- Bacterial genomes typically range from 3 to 5 million base pairs in size.
- Prokaryotes have ribosomes, involved in protein synthesis, that can be free in the cytoplasm; sometimes associating with mRNA, forming polysomes.
Prokaryotic Cell Wall
- Bacteria have cell walls, primarily composed of peptidoglycan.
- Peptidoglycan is a rigid structure, offering protection from osmotic stress.
- Its composition differs between Gram-positive and Gram-negative bacteria.
- Gram-positive walls are thick and retain crystal violet during Gram staining.
- Gram-negative walls are thinner, appearing reddish-pink after Gram staining.
- Gram-positive cells lack an outer membrane, unlike gram-negative cells.
- In Gram-negative bacteria, an outer membrane containing lipopolysaccharide (LPS) provides protection.
- LPS is toxic when released and can trigger septic shock.
- Teichoic acids are embedded in Gram-positive walls, contributing to rigidity.
Additional Layers
- Some bacteria have additional layers like capsules, slime layers, and s-layers that enhances stability, aid attachment, and resist drugs.
- Capsules are polysaccharide layers, promoting attachment, reducing phagocytosis, and assisting in colony formation.
- Slime layers are also polysaccharide, similarly promoting attachment, pathogenicity, and colony formation.
- S-layers are protein layers, vital to stability, attachment, and drug resistance, for prokaryotes.
Bacterial Storage Inclusions
- Prokaryotes contain inclusions, vacuoles that store various materials including energy substrates, metabolic precursors, sulfur crystals, and polyphosphate crystals.
- Inclusions may also aid bacterial orientation, providing species-specific characteristics.
Bacterial Morphology
- Bacteria exhibit various shapes and arrangements, including cocci (spherical), bacilli (rod-shaped), coccobacilli (short rods), vibrios (curved rods), spirilla (spiral shapes), and spirochetes (flexible spirals).
Bacterial Endospores
- Endospores are metabolically inactive, dormant structures, that enhance long-term survival.
- Endospores typically form within a bacterial cell and are extremely resistant to harsh conditions, disinfectants, and some sterilization procedures.
Bacterial Attachment & Movement
- Pili (or fimbriae) are structures that help bacteria attach to surfaces, enhancing colonization and aiding in pathogenicity.
- Sex pili are specific types of pili that facilitate genetic transfer between bacteria during conjugation.
- Flagella enable bacterial motility, using energy generated by the proton motive force (PMF). Bacteria can move towards or away from attractants or repellents.
Photosynthetic Bacteria
- Cyanobacteria (blue-green algae) are photosynthetic bacteria that produce oxygen.
- They use chlorophyll a for photosynthesis, replicating eukaryotic thylakoids.
- Green and purple sulfur bacteria perform photosynthesis in anaerobic environments and use sulfur compounds like H2S as energy sources.
Archaea
- Archaea form a distinct domain of life differing from Bacteria and Eukarya with unique features including their cell walls not containing peptidoglycan.
- Their cell membranes are constructed from ether-linked lipids instead of ester-linked lipids found in Bacteria and Eukarya.
- Archaea demonstrate a wide range of metabolic adaptations allowing these prokaryotic microorganisms to survive in extreme environments like hot springs, hypersaline areas, and anaerobic conditions.
Bacterial Genome (DNA)
- Bacteria store their DNA within the nucleoid region without a membrane-bound nucleus.
- The DNA is typically organized as a single, circular chromosome.
Bacterial Ribosomes (Protein Synthesis)
- Bacterial ribosomes are protein and RNA complexes responsible for protein synthesis.
- Notably, ribosome size (70S) is distinct from eukaryotic ribosomes (80S).
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Description
This quiz covers fundamental aspects of prokaryotic cells, including their structure, DNA organization, and the characteristics of their cell walls. Understand the differences between Gram-positive and Gram-negative bacteria, and learn about the role of plasmids and ribosomes in prokaryotic function. Prepare to test your knowledge on these essential concepts in microbiology.
