Cell Structure and Function
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Questions and Answers

A eukaryotic flagellum's movement is driven by which structural component?

  • The sliding of actin filaments powered by ATP hydrolysis associated with dynein.
  • The contraction of a surrounding sheath of contractile proteins, similar to muscle cells.
  • The coordinated beating of tubulin-based microtubules in a '9+2' arrangement, powered by dynein. (correct)
  • The rotation of peptidoglycan chains within the cell wall.

Which characteristic fundamentally differentiates eukaryotic cell walls from bacterial cell walls?

  • Eukaryotic cell walls are composed of a single layer of lipids, contrasting with the multiple layers in bacteria.
  • Eukaryotic cell walls contain chitin, while bacterial cell walls contain cellulose.
  • Eukaryotic cell walls lack peptidoglycan, a component universally found in bacterial cell walls. (correct)
  • Eukaryotic cell walls contain teichoic acids, whereas bacterial cell walls do not.

What distinguishes cilia from flagella in eukaryotic cells?

  • Cilia are composed of actin filaments, whereas flagella are composed of tubulin.
  • Cilia are typically more numerous and shorter than flagella. (correct)
  • Cilia propel cells through their environment, while flagella move substances across the cell surface.
  • Cilia contain a '9+2' arrangement of microtubules, while flagella have a '9+0' arrangement.

Considering both structure and function, what is the primary role of the '9+0' microtubule arrangement in certain eukaryotic cilia?

<p>To act as an anchor, preventing movement while still facilitating movement of substances past the cell surface. (D)</p> Signup and view all the answers

How does the arrangement of microtubules within eukaryotic flagella contribute to their characteristic wave-like motion?

<p>Dynein proteins cause the microtubules to slide past each other, resulting in bending and a whip-like movement. (A)</p> Signup and view all the answers

Which characteristic is MOST likely to remain constant across multiple generations of a monomorphic bacterial species, assuming stable environmental conditions?

<p>The general morphological shape (cocci, bacilli, or spiral). (B)</p> Signup and view all the answers

A microbiologist discovers a new prokaryotic species with a highly variable morphology depending on nutrient availability. Which term BEST describes this characteristic?

<p>Pleomorphic, indicating the ability to assume multiple shapes. (B)</p> Signup and view all the answers

In a mixed bacterial culture, what is the MOST reliable initial method for differentiating between Streptococcus (cocci) and Bacillus (bacilli) species?

<p>Observing cellular morphology under a microscope. (C)</p> Signup and view all the answers

A bacterial species is found to produce a thick, well-organized glycocalyx layer. How would this likely influence the bacteria's interactions within a host organism?

<p>Enhanced protection against phagocytosis, increasing its virulence. (D)</p> Signup and view all the answers

A researcher is studying two bacterial strains: one with a capsule and one without. What is a plausible hypothesis regarding their respective abilities to cause disease?

<p>The strain with a capsule will likely be more virulent due to its enhanced ability to evade the host's immune system. (B)</p> Signup and view all the answers

A bacterium is isolated from a patient's bloodstream and determined to be highly virulent due to its glycocalyx. Further analysis reveals this layer is loosely attached. Which term BEST describes this type of glycocalyx?

<p>Slime layer, indicating a loosely attached and less organized layer. (A)</p> Signup and view all the answers

Considering that bacterial morphology is primarily determined by hereditary factors, what cellular component is MOST directly responsible for maintaining a bacterium's characteristic shape?

<p>The cytoskeleton and cell wall, which provide structural support and rigidity. (D)</p> Signup and view all the answers

How does the presence of a capsule contribute to the virulence of a pathogenic bacterium?

<p>By preventing recognition and destruction by the host's immune system. (A)</p> Signup and view all the answers

What is the primary mechanism by which prokaryotic flagella facilitate bacterial motility?

<p>Rotation of the flagellar hook, which propels the cell forward. (D)</p> Signup and view all the answers

A researcher is studying two strains of the same bacterial species, one encapsulated and one unencapsulated. If both strains are introduced into a host organism, what is the most likely outcome?

<p>The encapsulated strain will exhibit higher virulence due to its protection from the host's immune system. (A)</p> Signup and view all the answers

If a bacterium loses its capsule, what is the most likely consequence?

<p>Increased vulnerability to the host's immune system. (C)</p> Signup and view all the answers

Which of the following cellular structures is LEAST likely to be directly involved in bacterial motility?

<p>Capsule (B)</p> Signup and view all the answers

A microbiologist is trying to identify a bacterial species based on its flagellar proteins. Which of the following statements is true about this approach?

<p>Different species and strains of bacteria may have unique flagellar protein profiles, allowing for identification. (A)</p> Signup and view all the answers

A bacterial strain is found to be highly virulent due to its ability to evade the host's immune system. Which of the following virulence factors is MOST likely responsible for this?

<p>Presence of a capsule that inhibits phagocytosis. (D)</p> Signup and view all the answers

A researcher discovers a new bacterial species that is non-motile despite possessing flagella. What is the most likely explanation for this observation?

<p>The bacteria lack the necessary energy-generating mechanisms to power the flagellar motors. (C)</p> Signup and view all the answers

Capsules are composed of repeating carbohydrate subunits. What is the advantage of this for the bacteria?

<p>The carbohydrate composition makes the capsule difficult for the immune system to recognize. (A)</p> Signup and view all the answers

How does the structure of eukaryotic flagella differ significantly from that of bacterial flagella?

<p>Eukaryotic flagella exhibit a more complex structure involving multiple proteins including tubulin and dynein, unlike the simpler bacterial flagella. (D)</p> Signup and view all the answers

Which bacterial flagellar arrangement describes flagella distributed evenly over the entire cell surface?

<p>Peritrichous (A)</p> Signup and view all the answers

What is the underlying mechanism that allows bacteria to exhibit chemotaxis?

<p>A biased random walk achieved through regulating the frequency of 'runs' and 'tumbles' in response to chemical gradients. (C)</p> Signup and view all the answers

How do axial filaments contribute to the unique motility observed in spirochetes?

<p>Axial filaments are internal structures that rotate, causing the spirochete's body to flex and twist in a corkscrew-like motion. (A)</p> Signup and view all the answers

What role do fimbriae play in the formation and maintenance of biofilms?

<p>Fimbriae facilitate the initial attachment of bacteria to surfaces and to each other, a crucial step in biofilm formation. (D)</p> Signup and view all the answers

What is the primary functional difference between fimbriae and pili related to bacterial adherence?

<p>Pili are longer and fewer in number, primarily for attachment to specific host cells or surfaces, whereas fimbriae are shorter and more numerous, mediating general adhesion. (C)</p> Signup and view all the answers

How does the presence of a capsule enhance a bacterium's pathogenicity?

<p>By preventing phagocytosis by immune cells, allowing the bacterium to evade the host defense mechanisms. (D)</p> Signup and view all the answers

What is the role of mycolic acid in the cell walls of acid-fast bacteria like Mycobacterium?

<p>Mycolic acid makes the cell wall waxy and impermeable, protecting the bacteria from desiccation and antibiotics. (A)</p> Signup and view all the answers

What is the significance of lipopolysaccharide (LPS) in Gram-negative bacterial infections?

<p>LPS functions as an endotoxin, stimulating a strong inflammatory response in the host, potentially leading to septic shock. (B)</p> Signup and view all the answers

How do bacterial endospores contribute to the survival and persistence of certain pathogenic species?

<p>Endospores are highly resistant structures that enable bacteria to survive extreme environmental conditions and later germinate into vegetative cells when conditions become favorable. (D)</p> Signup and view all the answers

In a scenario where a bacterial cell is in an environment with a lower concentration of nutrients than inside the cell, which transport mechanism is most likely to be employed to maintain nutrient levels, and why?

<p>Active transport, because it enables movement against the concentration gradient, requiring energy expenditure. (A)</p> Signup and view all the answers

If a bacterial cell is placed in a hypertonic solution, what physiological response is most likely to occur as a direct consequence of the osmotic pressure difference?

<p>The cell will lose water, leading to plasmolysis and potential cell shrinkage. (A)</p> Signup and view all the answers

How does the organization of genetic material within the nucleoid of a bacterial cell differ fundamentally from that in a eukaryotic cell nucleus, and what implications does this have for genetic processes?

<p>Bacterial nucleoids have a single, circular chromosome without histones, which simplifies replication and transcription processes compared to eukaryotes. (A)</p> Signup and view all the answers

In the context of bacterial genetics, what is the most significant evolutionary advantage conferred by plasmids, particularly under conditions of environmental stress or selective pressure?

<p>Plasmids carry genes that provide antibiotic resistance or tolerance to toxic substances, enhancing survival in hostile environments. (D)</p> Signup and view all the answers

What is the primary role of the bacterial cytoplasm's cytosol, and how does its composition contribute to essential cellular processes?

<p>The cytosol serves as a medium for metabolic reactions, containing enzymes, nutrients, ions, and other molecules necessary for cellular functions. (A)</p> Signup and view all the answers

A bacterial cell encounters a sudden increase in environmental osmolarity. What immediate response at the cellular level is most critical for preventing cellular damage?

<p>Adjusting internal solute concentration to match the external environment. (B)</p> Signup and view all the answers

How does the absence of histones in bacterial chromosomes affect DNA accessibility and gene expression compared to eukaryotic chromosomes?

<p>The lack of histones in bacteria results in less condensed DNA, generally increasing accessibility for replication and transcription. (C)</p> Signup and view all the answers

A bacterium gains a plasmid carrying a gene for a novel enzyme that degrades an environmental pollutant. Under what conditions would this plasmid be most selectively advantageous?

<p>Under conditions where the pollutant is present, providing the bacterium with a unique metabolic capability. (C)</p> Signup and view all the answers

How does the relatively high water content (80%) of the bacterial cytosol directly support the biochemical reactions necessary for life?

<p>It provides a medium for dissolving and transporting nutrients and waste products, facilitating chemical reactions. (C)</p> Signup and view all the answers

A scientist discovers a new bacterial species with a unique plasmid that seems to enhance its virulence. Which experimental approach would be most effective in determining the specific gene on the plasmid responsible for this increased virulence?

<p>Sequencing the plasmid DNA and then systematically inactivating genes to observe changes in virulence. (B)</p> Signup and view all the answers

Flashcards

Flagella

Long, few structures for cell motility, made of tubulin.

Cilia

Short, numerous structures that help in movement and moving substances.

9+2 arrangement

Structure of microtubules in flagella and cilia, consisting of 9 pairs and 2 central tubules.

Eukaryotic cell wall

The outer layer of eukaryotic cells, lacking peptidoglycan present in prokaryotes.

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Microtubules

Tubulin polymers that are part of the cytoskeleton, forming flagella and cilia.

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Prokaryotic Cell Morphology

The study of the form and structure of prokaryotic cells.

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Cocci

Spherical-shaped bacteria.

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Bacilli

Rod-shaped bacteria.

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Spiral

Twisted or corkscrew-shaped bacteria.

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Pleomorphic

Ability of bacteria to have varied shapes.

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Glycocalyx

A polysaccharide layer surrounding the cell, can be a capsule or slime layer.

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Capsule

A more virulent, tightly attached glycocalyx layer.

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Pathogenic

Microorganisms that cause disease.

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Virulence factor

Attributes that enable a pathogen to cause disease.

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Capsule (bacterial)

A protective layer firmly attached to bacterial cell surface.

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Desiccation protection

Prevention of drying out in bacterial cells.

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Host recognition evasion

Capsules help bacteria avoid detection by the immune system.

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Unencapsulated bacteria

Bacteria lacking a capsule, often more vulnerable.

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Prokaryotic flagella

Whip-like structures that provide motility to bacteria.

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Flagellar movement

Movement of bacteria caused by the rotation of the hook.

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Staining for capsules

Capsules can be visualized by special staining techniques.

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Osmosis

Movement of solvent (H2O) from high to low concentration.

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Isotonic Solution

Solution with equal osmotic pressure across cell membrane.

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Hypertonic Solution

Solution with a higher solute concentration than isotonic solution.

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Hypotonic Solution

Solution with a lower solute concentration than isotonic solution.

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Active Transport

Movement of material from low to high concentration using energy.

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Cytoplasm

The gel-like substance within a cell, mostly water, containing organelles.

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Nucleoid

Non-membrane enclosed area containing bacterial DNA.

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Plasmids

Extrachromosomal DNA that replicates independently of the main chromosome.

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Ribosomes

Cell structures that serve as the site of protein synthesis.

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Inclusions

Reserve chemical deposits within the cytoplasm for storage.

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coli O157:H7

A strain of E. coli known for causing foodborne illness.

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Flagellar Protein

The protein component of bacterial flagella aiding in movement.

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Motility

Self-directed movement of an organism.

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Chemotaxis

Movement of an organism in response to chemical stimuli.

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Phototaxis

Movement of an organism in response to light.

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Axial Filaments

Flagella-like structures found in spirochetes, enabling corkscrew movement.

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Spirochetes

A group of bacteria characterized by their corkscrew shape and motion.

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Fimbriae

Short, hair-like structures aiding in adherence to surfaces.

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Taxis

Movement toward or away from a stimulus.

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Study Notes

Cell Structure & Function

  • Cells are the fundamental units of life, exhibiting characteristics of life, including growth, reproduction, responsiveness, and metabolism.
  • Microbes, like bacteria, archaea, eukaryotes, and viruses, vary in their characteristics and distribution of life functions.
  • Growth, reproduction, and responsiveness occur in all bacteria, archaea, and eukaryotes, but viruses lack growth and rely on host cells for reproduction. Metabolic functions are present in all. Viruses use host cell metabolism, while cellular structure is absent in viruses.
  • Prokaryotic cells (bacteria and archaea) lack a nucleus and membrane-enclosed organelles.
  • Eukaryotic cells (fungi, protozoa, helminths, plants, and algae) contain a nucleus and numerous membrane-bound organelles.
  • Similar chemical composition, including nucleic acids (DNA and RNA) and proteins, is found in both prokaryotic and eukaryotic cells. Similar chemical processes like metabolism, protein production, and energy storage happen in both cells.
  • Prokaryotes have a single circular chromosome, lack membrane-bound organelles, and have cell walls, in most cases containing peptidoglycan. Cell division is by binary fission and prokaryotic cells are less complex than eukaryotic cells
  • Eukaryotes have multiple linear chromosomes, contain membrane-bound organelles, and, when present, cell walls do not contain peptidoglycan. Eukaryotic division is by mitosis.
  • Bacterial species are identified by morphology (shape), chemical composition, and biochemical activities. Shape can be cocci, bacilli, spiral, or pleomorphic.
  • Prokaryotic cells have a cell wall, cell membrane, cytoplasm, ribosomes, glycocalyx, flagella, fimbriae, pili, and plasmids, and sometimes inclusions and endospores
  • Eukaryotic cells have a cell membrane, cytosol, ribosomes, cytoskeleton, membrane-bound organelles (like nuclei, endoplasmic reticulum, Golgi apparatus, vacuoles, lysosomes, peroxisomes, and mitochondria) and sometimes cilia and flagella
  • The glycocalyx, a sugar coat, may be a capsule (firmly attached) or slime layer (loosely attached). It can protect cells from dehydration and enhance pathogenicity.
  • Flagella are whip-like structures for motility, with filaments, hooks, and basal bodies. Movement occurs via hook rotation.
  • Fimbriae are short, numerous, sticky, hairlike appendages aiding in attachment. Pili are longer, few, and also for adhesion, often facilitating conjugation (DNA transfer).
  • Cell walls encase plasma membranes, providing shape and structural support. Peptidoglycan is a key component in bacterial cell walls.
  • Gram-positive cells have thick peptidoglycan layers with teichoic and lipoteichoic acids, while gram-negative cells have thin peptidoglycan layers with an outer membrane. Mycoplasmas lack cell walls, and mycobacteria have mycolic acids in their cell walls. Archaea have pseudomurein instead of peptidoglycan.
  • Plasma membranes enclose the cytoplasm and control entry of materials into and out of the cell, through mechanisms like diffusion and osmosis. Integral proteins, peripheral proteins, and glycoproteins are important membrane components.
  • Cytoplasm is the liquid content of cells, containing water and various compounds including proteins, enzymes, carbohydrates, and ions.
  • Nucleoid area is the location of the genetic material in prokaryotes (circular DNA) compared to eukaryotes' linear chromosomes. Plasmids are extrachromosomal genetic elements replicating independently.
  • Ribosomes are protein synthesis sites, but prokaryotic ones are 70S, and eukaryotic 80S.
  • Endospores are dormant, highly resistant structures produced by some bacteria to survive harsh conditions. They are located centrally, sub-terminally, or terminally in the bacterial cells.
  • Eukaryotic cells have sophisticated internal structures including cilia and flagella made of microtuble arrangements, and a more complex cytoskeleton for internal support and transport than prokaryotic cells. Eukaryotic DNA is organized around histones into linear chromosomes.
  • Eukaryotic cells are larger and typically possess membrane bound organelles such as the nucleus, endoplasmic reticulum, Golgi apparatus, and mitochondria
  • Movement across cell membranes can involve passive processes (simple diffusion, facilitated diffusion, osmosis) or active transport. Active transport involves the use of energy to move substances against a concentration gradient.

Special Cell Structures

  • Glycocalyx: A sugar coat that aids in attachment and protection.
  • Flagella: Whip-like structures for movement.
  • Fimbriae: Short, numerous, sticky, hairlike appendages for attachment.
  • Pili: Longer, thinner structures involved in adherence and conjugation.
  • Endospores: Dormant, resistant structures formed by bacteria to survive unfavorable conditions.
  • Different types of specialized structures exist, especially in bacteria.

Types of Cells

  • Prokaryotic cells (bacteria and archaea)
  • Eukaryotic cells (fungi, protozoa, helminths, plants, algae)

Movement Across the Membrane

  • Passive processes: diffusion, osmosis, and facilitated diffusion.
  • Active transport: using energy to move substances against the concentration gradient.

Typical Bacterial Cell

  • Cell wall (peptidoglycan)
  • Cell membrane (sites of cellular respiration)
  • Cytoplasm (rich in 70S ribosomes)
  • Nucleoid (single circular chromosome)
  • Plasmid
  • Inclusions
  • Flagella
  • Glycocalyx
  • Ribosomes

Eukaryotic Cell structures

  • Plasma membrane
  • Cytoplasm
  • Cytoskeleton
  • Ribosomes
  • Nucleus
  • Nucleolus
  • Endoplasmic reticulum (rough and smooth)
  • Golgi apparatus
  • Lysosomes
  • Peroxisomes
  • Mitochondria
  • Vacuoles
  • Cilia
  • Flagella

Concept Checks

  • Answers to specific questions about cell structures and functions are present.

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Cell Structure and Function 2024 PDF

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Explore the fundamental units of life, cells. Learn about the characteristics of microbes, including bacteria, archaea, eukaryotes, and viruses, examining their diverse life functions. Understand the differences between prokaryotic and eukaryotic cells, focusing on the presence or absence of a nucleus and membrane-enclosed organelles.

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