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Questions and Answers
Which characteristic is universally found in all living cells, regardless of whether they are prokaryotic or eukaryotic?
Which characteristic is universally found in all living cells, regardless of whether they are prokaryotic or eukaryotic?
- The presence of membrane-bound organelles
- A nucleus containing multiple chromosomes
- The ability to perform photosynthesis
- Cytoplasm surrounded by a membrane (correct)
A newly discovered cell is found to have a cylindrical shape. Based on this information alone, which classification is most accurate?
A newly discovered cell is found to have a cylindrical shape. Based on this information alone, which classification is most accurate?
- The cell is eukaryotic and multicellular
- The cell could be either prokaryotic or eukaryotic (correct)
- The cell is prokaryotic and lacks metabolic capabilities
- The cell is spherical and contains a nucleus
A scientist is examining a cell under a microscope and observes ribosomes and a DNA chromosome within the cytoplasm. What further information is needed to determine if the cell is prokaryotic or eukaryotic?
A scientist is examining a cell under a microscope and observes ribosomes and a DNA chromosome within the cytoplasm. What further information is needed to determine if the cell is prokaryotic or eukaryotic?
- Whether the cell has a spherical, cubical, or cylindrical shape
- The presence or absence of a membrane surrounding the DNA (correct)
- The metabolic capabilities of the cell
- The size of the ribosomes present
If a cell suddenly lost its metabolic capabilities, which of the following structures would most likely be directly affected?
If a cell suddenly lost its metabolic capabilities, which of the following structures would most likely be directly affected?
Which of the following structures or components are found in both bacterial cells and human cells?
Which of the following structures or components are found in both bacterial cells and human cells?
How does the location of periplasmic flagella contribute to bacterial motility?
How does the location of periplasmic flagella contribute to bacterial motility?
What is the primary function of fimbriae in bacterial cells?
What is the primary function of fimbriae in bacterial cells?
Which characteristic is most closely associated with pili?
Which characteristic is most closely associated with pili?
A researcher discovers a new bacterial species that exhibits twitching motility. Which structure is most likely contributing to this behavior?
A researcher discovers a new bacterial species that exhibits twitching motility. Which structure is most likely contributing to this behavior?
If a bacterium loses its ability to form biofilms, which structure is most likely affected?
If a bacterium loses its ability to form biofilms, which structure is most likely affected?
A bacterial cell is less susceptible to phagocytosis by white blood cells due to the presence of which external structure?
A bacterial cell is less susceptible to phagocytosis by white blood cells due to the presence of which external structure?
What is the primary role of the cell wall in bacteria?
What is the primary role of the cell wall in bacteria?
A scientist is studying a new bacterial species. Gram staining reveals a thin peptidoglycan layer and an outer cell membrane. Which type of bacteria is the scientist most likely studying?
A scientist is studying a new bacterial species. Gram staining reveals a thin peptidoglycan layer and an outer cell membrane. Which type of bacteria is the scientist most likely studying?
What is the main difference between Gram-positive and Gram-negative bacteria regarding their cell wall structure?
What is the main difference between Gram-positive and Gram-negative bacteria regarding their cell wall structure?
A bacterium's glycocalyx is damaged, impairing its ability to form a biofilm. What is the most likely consequence of this damage?
A bacterium's glycocalyx is damaged, impairing its ability to form a biofilm. What is the most likely consequence of this damage?
Which component of the bacterial cell envelope is primarily responsible for protecting the cell from lysis in hypotonic environments?
Which component of the bacterial cell envelope is primarily responsible for protecting the cell from lysis in hypotonic environments?
A researcher discovers a bacterial strain that is highly resistant to phagocytosis. Which cell structure is most likely contributing to this resistance?
A researcher discovers a bacterial strain that is highly resistant to phagocytosis. Which cell structure is most likely contributing to this resistance?
Which characteristic primarily differentiates fimbriae from pili in bacteria?
Which characteristic primarily differentiates fimbriae from pili in bacteria?
A researcher discovers a novel bacterial strain exhibiting twitching motility. Which structure is most likely responsible for this behavior?
A researcher discovers a novel bacterial strain exhibiting twitching motility. Which structure is most likely responsible for this behavior?
If a bacterium loses the ability to adhere to host cells, which structure is most likely affected?
If a bacterium loses the ability to adhere to host cells, which structure is most likely affected?
A bacterial cell is found to have a thick, tightly attached coating. This structure is most likely a:
A bacterial cell is found to have a thick, tightly attached coating. This structure is most likely a:
Which of the following structures is exclusively found in Gram-negative bacteria, not in Gram-positive bacteria?
Which of the following structures is exclusively found in Gram-negative bacteria, not in Gram-positive bacteria?
The formation of pili is governed by which genetic element?
The formation of pili is governed by which genetic element?
Considering their respective functions, which structure would be most crucial for the initial step in the formation of a bacterial biofilm?
Considering their respective functions, which structure would be most crucial for the initial step in the formation of a bacterial biofilm?
How does the slime layer differ from the capsule in terms of their structural arrangement?
How does the slime layer differ from the capsule in terms of their structural arrangement?
Flashcards
Cell Characteristics
Cell Characteristics
Living things are composed of cells with spherical, cubical, or cylindrical shapes containing cytoplasm, a membrane, DNA chromosomes, ribosomes and metabolic capabilities.
Two Basic Cell Types
Two Basic Cell Types
The two main types of cells are eukaryotic and prokaryotic.
Cellularity
Cellularity
Cells can be single-celled or multi-cellular.
Cell Internal Content
Cell Internal Content
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Eukaryotic Cells
Eukaryotic Cells
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Periplasmic Flagella
Periplasmic Flagella
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Fimbriae
Fimbriae
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Pili
Pili
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Conjugation
Conjugation
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Outer Sheath
Outer Sheath
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Glycocalyx function
Glycocalyx function
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Glycocalyx & Pathogenicity
Glycocalyx & Pathogenicity
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Glycocalyx role in Attachment
Glycocalyx role in Attachment
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Cell Envelope
Cell Envelope
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Two basic layers of cell envelope
Two basic layers of cell envelope
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Gram-positive Bacteria
Gram-positive Bacteria
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Gram-negative Bacteria
Gram-negative Bacteria
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Fimbriae Function
Fimbriae Function
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Pili Function
Pili Function
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Fimbriae Number
Fimbriae Number
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Pili Number
Pili Number
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Glycocalyx
Glycocalyx
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Slime Layer
Slime Layer
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Study Notes
Characteristics of Cells and Life
- All living things, whether single-celled or multicellular, consist of cells sharing common traits.
- Basic cell shapes include spherical, cubical, and cylindrical forms.
- The cytoplasm is the internal content of a cell, enclosed by a membrane.
- DNA chromosomes, ribosomes, and metabolic capabilities are key components of cells.
- Eukaryotic and prokaryotic cells are the two fundamental cell types.
- Eukaryotic cells are found in animals, plants, fungi, and protists
- Eukaryotic cells contain membrane-bound organelles to compartmentalize the cytoplasm and perform specific functions.
- Eukaryotic cells contain a double-membrane bound nucleus enclosing DNA chromosomes.
- Prokaryotic cells constitute bacteria and archaea.
- Prokaryotic cells do not have a nucleus or other membrane-bound organelles.
- Reproduction and heredity is facilitated by the genome composed of DNA packed in chromosomes for sexual or asexual offspring production.
- Growth and development is a characteristic of life.
- Chemical and physical life processes define metabolism.
- Movement and irritability entails responding to internal and external stimuli, along with self-propulsion in many organisms.
- Cell support, protection, and storage happens via cell walls, vacuoles, granules, and inclusions.
- Nutrient and waste transport is a characteristic of life.
Bacterial Cell Structures
- Bacterial cell structures include the cell wall, cell membrane, ribosomes, capsule, flagellum, pilus, chromosome(DNA), cytoplasmic matrix, inclusion body, mesosome, slime layer and actin filaments.
- Appendages are external structures which include two major types:
- Motility structures: flagella and axial filaments that include periplasmic flagella.
- Attachment or channels: includes fimbriae and pili.
- Additionally, the Glycocalyx serves as a surface coating.
Flagella
- There are three parts to the flagella:
- Filament is a long, thin, helical structure made of the protein flagellin.
- Hook is a curved sheath.
- Basal body is stack of rings firmly anchored in the cell wall.
- Flagella rotate at 360 degrees.
- Flagella provide motility for a cell through the environment.
Flagellar Arrangements
- Monotrichous: single flagellum at one end.
- Lophotrichous: small bunches of flagella emerging from the same site.
- Amphitrichous: flagella are present at both ends of the cell.
- Peritrichous: flagella dispersed over the cell’s surface.
Flagellar Responses
- Bacteria respond to external stimuli by directing their movement.
- Chemical stimuli result in chemotaxis that can be positive or negative.
- Light stimulus results in phototaxis.
- Signal Sets of flagella in motion can be clockwise or counterclockwise.Counterclockwise moves bacteria in smooth linear direction.
- Counterclockwise results in a run.
- Clockwise causes tumbles.
Periplasmic Flagella
- Internal flagella are enclosed in the space between outer sheath and cell wall peptidoglycan.
- Periplasmic flagella cause cellular motility by contracting and imparting twisting or flexing motion.
Fimbriae and Pili
- Fimbriae are fine, proteinaceous, hairlike bristles emerging from the cell surface.
- Fimbriae function in adhesion to other cells and surfaces.
- Pili are rigid tubular structures made of pilin protein.
- Pili are mostly found in gram-negative cells
- Pili join cells for partial DNA transfer called conjugation.
- Pili sometimes aid in adherence and movement.
- Fimbriae are tiny bristle-like fibers arising from the surface of bacterial cells.
- Pili are hair-like microfibers that are a thick tubular structure made of pilin.
- Fimbriae are shorter than pili.
- Fimbriae are thinner than pili.
- Fimbriae numbers are 200-400 per cell, while Pili are less, 1-10 per cell
- Fimbriae are made up of Fimbrillin protein, Pili are made up of Pilin protein.
- Fimbriae are less rigid than Pili.
- Fimbriae are found in both gram-negative and gram-positive bacteria, while pili are only found in gram-negative bacteria
- Fimbriae formation is governed by bacterial genes in the nucleoid region, and pili is governed by plasmid genes.
- Fimbriae are responsible for cell-to-surface attachment, Pili are responsible for bacterial conjugation. Specialized to enable the cell to adhere to the surfaces of other bacteria.
- Fimbriae do not function in active motility while Type IV pili shows twitching motility.
Glycocalyx
- Glycocalyx consist of molecules coating external area of a cell wall; composed of sugars and/or protein
- Types can include:
- Slime Layer: Loosely, organized and attached
- Capsule: Highly organized, tightly attached
Functions of Glycocalyx
- Protection from dehydration and nutrient loss
- Glycocalyx inhibits killing by white blood cells via phagocytosis, which attributes to pathogenicity of the cell
- Attachment formation of biofilms is aided by Glycocalyx
Biofilm
- Consist of a catheter surface, fungal cells and staphylococci.
Cell Envelope
- External covering outside of the cytoplasm
- Cell envelopes consist of 2 basic layers:
- Cell wall
- Cell membrane
- Maintained Cell Integrity
- Gram Stain highlights two different groups of bacteria:
- Gram-positive bacteria feature a thick cell wall composed primarily of peptidoglycan and cell membrane
- Gram-negative bacteria feature an Outer Cell Membrane as well as a thin peptidoglycan layer and cell membrane
Structure of Cell Walls
- Determines cell shape, and prevents lysis due to changing osmotic pressures
- The primary component, peptidoglycan, is a repeating framework of long glycan chains cross-linked by short peptide fragments.
Gram Positive Cell Wall
- Gram Positive cell walls are 20-80 nm thick with peptidoglycan.
- Teichoic acid and lipoteichoic acid function in cell wall maintenance, enlargement during cell division, and cation movement across the cell envelope, and to stimulate a specific immune response
- Some cells have a periplasmic space between cell membrane and cell wall.
Gram Negative Cell Wall
- They consist of inner and outer membranes, and a periplasmic space between the membranes containing a thin peptidoglycan layer.
- The outer membrane contains lipopolysaccharides (LPS).
- Lipid portion (endotoxin) may become toxic when released during infections.
- Lipopolysaccharides may function as receptors and block immune response.
- Contain porin proteins in upper layer to regulate molecules entering and leaving cell.
Gram Positive and Gram-Negative Bacteria
- Gram positive bacteria have one major layer while gram-negative bacteria have two.
- The composition of gram positive bacteria include, peptidoglycan, teichoic acid, lipoteichoic acid and mycolic acids and polysaccharides. In contrast gram-negative is lipopolysaccharide, lipoprotein, peptidoglycan, and porin proteins.
- Gram positive is thicker than gram negative.
- Gram positive do not have an outer membrane while gram-negative do.
- Gram positive have a narrow periplasmic space where as gram-negative are extensive.
- Gram positive are more penetrable and gram-negative is less penetrable.
Gram Stain
- Differential stain highlights cells with gram-positive cell wall from those with gram-negative cell wall
- Gram-positive cells retain crystal violet and stain purple
- Gram-negative cells lose crystal violet and stain red from safranin counterstain
- Important basis of bacterial classification and identification
- Practical aid in diagnosing infection and guiding drug treatment
- In step one, both cell walls stain with a dye, because it is a crystal violet primary dye
- Dying cell traps crystals with the presence of iodine
- When alcohol decolorizes crystals remain in the gram positive cells, but removes color from gram negative, because that wall is weakened.
- Red dye stains the now colorless gram-negative cells, but makes no visible effect on the gram positive
Nontypical Cell Walls
- Some bacterial groups i.e. Mycobacterium and Nocardia lack typical cell wall structure
- Contain a gram-positive structure with lipid mycolic acid (cord factor)
- Pathogenicity and high degree of resistance to certain chemicals and dyes
- Acid-fast stain basis used for diagnosis of infections caused by these microorganisms
- Some i.e. Mycoplasma have no cell wall
- stabilized cell wall by sterols
- Pleomorphic
Cell Membrane Structure
- Selectively permeable Phospholipid bilayer with proteins, termed the fluid mosaic model.
- Functions include:
- A site for energy reactions, nutrient processing, and synthesis
- Regulating the passage of nutrients into the cell and discharge of wastes
Inside a Bacterial Cell
- The cell contains cytoplasm, which is a dense gelatinous solution of sugars, amino acids, and salts.
- The cell is 70-80% water.
- Provides a solvent for all materials used in cell functions.
Nucleoid
- Chromosome
- Single, circular, double-stranded DNA molecule containing all the required genetic information
- Plasmids
- Free small circular, double-stranded DNA that is not essential to bacterial growth and metabolism
- Used in genetic engineering to readily manipulate and transfer from cell to cell
Bacterial Ribosomes
- Bacterial Ribosomes consist of 60% ribosomal RNA and 40% protein.
- Two subunits of bacterial ribosome are: large and small.
- Prokaryotic and Eukaryotic ribosomes differ size and number of proteins.
- Bacterial Ribosomes are the site of protein synthesis
- All cells have Ribosomes
Bacterial Internal Structures
- Inclusions and Granules: -Intracellular Storage Bodies -Vary in size, number, and content -Used by cells when sources become depleted
- Cytoskeleton: -Most bacteria possess an internal network of protein polymers closely associating with the cell wall.
- Endospores:
- Inert resting cells produced by some G+ genera: Clostridium, Bacillus, and Sporosarcina. -A 2-phase life cycle includes: -Vegetative Cell: Growing, metabolically Active. -Endospore: Adverse environmental condition that endures high exposure for long survival.
- Sporulation:
- Endospore formation that is a hard resistant all life-form that withstands extremities in heat, drying, freezing, radiation and chemicals, but it is not considered a form of reproduction.
- Germination: -A return to vegetative growth through the process of Inert resting and metabolically inactive endospores.
- Endospores are dehydrated and metabolically inactive.
- The Endospores’ thick coat give it longevity, verging on immortality for 250 million years.
- They are Resistant to ordinary methods of cleaning and boiling, but can be destroyed via Pressurized Steam in over 120° C for 20-30 Minutes
Bacterial Shapes, Arrangements, and Sizes
- Shape, size, and arrangement vary with three basic shapes
- Coccus - spherical
- Bacillus - rod
- Coccobacillus – very short and plump
- Vibrio – gently curved
- Spirillum – helical, comma, twisted rod
- Spirochete – spring-like
- Variation in cell shape and size within a single species caused by environmental conditions is pleomorphism.
Bacterial Arrangements
- Arrangement depends on pattern of division and how cells remain:
- Cocci which can presents as; singles, Diplococci i.e pairs, Tetrads i.e. Groups of four Irregular clusters; or they may appears as Chains and Cubical packets Bacilli Appear as:Diplobacilli, chains, OR Palisades
Classifications System For Prokaryotes
- Microscopic and Macroscopic Morphology describe individual cells and colony appearance and structure
- Bacterial and Serological Physiology both identify presence of properties due to activities and response (respectively)
- And Genetic And Molecular Analysis is based on identifying both presences of each genetic and molecular traits.
Bacterial Taxonomy Based On Bergey’s Manual
- In "Bergey's Manual Of Determinative Bacteriology", a 5-volume resource covers all known prokaryotes divided by Classification through Domains of Archaea vs. Bacteria
- Five Major Subgroups can be sorted into 25 Different Phyla
Diagnostic and Species
- A Diagnostic Scheme For Medical Uses phenotypic identification and traits. Restricting agents, it divides bacteria based on cell structure, shape, and physiology.
- A Similar Trait pattern amongst bacteria and their collection is key for categorizing by Species and determining strains or varieties.
- Also known through Structure, Metabolism, and type by susceptibility
- By doing so antigen makeup differences by their type are identified
Unusual Prokaryotes and Bacteria
- Nonpathogenic Bacteria are free living
- Use Photosynthesis to require required nutrient compounds from certain sources, (particularly the sulfur bacteria)
- While the rest combined is carried out by all different kinds of bacteria with differing attributes such as blue cyan, etc.
Unusual Forms of Medically Significant Bacteria
- Bacteria with the ability to be intracellular parasites like the Rickettsias (very tiny with negative pathogens) are unable of being a survive without it.
- Rickettis Ricketsii can cause Rockey Mountain spotted fever.
- Other examples include the similar parasite called Chlaymdias trachomatis- that causes severe infections, the most common Sex Transmitted Disease and pneumoniae that results in lung infections.
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Description
Explore cell structures like flagella, fimbriae, and pili. Understand their roles in motility, attachment, and bacterial behavior. Learn about bacterial species and twitching motility.