Bacterial Structure and Function Quiz

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Questions and Answers

Why might a bacterial species that lacks a capsule be more susceptible to immune system attacks compared to a species with a capsule?

The lack of a capsule makes the bacterial cell wall thinner, exposing its peptidoglycan layer to immune cells.
Capsule-deficient bacteria have a reduced ability to produce adhesins, hindering their interaction with host cells.
Capsule-deficient bacteria are unable to adhere to surfaces, making them easier to flush out of the body.
The capsule acts as a barrier against immune recognition and phagocytosis by immune cells. (correct)

Which of the following statements accurately describes the different roles of peptidoglycan in Gram-positive and Gram-negative bacteria?

Gram-positive bacteria have a thicker peptidoglycan layer, which provides greater structural support and protection, while Gram-negative bacteria have an additional outer membrane. (correct)
Gram-positive bacteria have a thinner peptidoglycan layer than Gram-negative bacteria, making them more susceptible to antibiotics that target peptidoglycan synthesis.
Gram-negative bacteria use peptidoglycan as a primary nutrient reserve, whereas Gram-positive bacteria rely on other mechanisms for nutrient storage.
Gram-negative bacteria have a more complex peptidoglycan structure that is resistant to many antimicrobial agents, making them more difficult to treat.

While both capsules and cell walls contribute to bacterial survival and function, how does their role in protecting against hostile environments differ?

The cell wall primarily provides structural support, whereas the capsule functions as a permeability barrier and defense against phagocytosis. (correct)
The cell wall is essential for maintaining cell shape, while the capsule determines the bacterial species' ability to form biofilms.
The capsule acts as the primary barrier to antibiotics, while the cell wall facilitates nutrient acquisition and waste expulsion.
The capsule plays a crucial role in resisting osmotic stress, while the cell wall is responsible for specific interactions with other organisms.

Which of the following mechanisms contributes directly to a bacterium's ability to adhere to surfaces and colonize a host?

<p>Surface proteins called adhesins on the bacterial cell wall bind to receptor molecules on host cells. (B)</p> Signup and view all the answers

How does the ability of some bacteria to be pleomorphic affect their survival and adaptability?

<p>Pleomorphism enables bacteria to adapt to diverse environments, such as nutrient availability or antibiotic exposure, through changes in shape and function. (C)</p> Signup and view all the answers

Flashcards

Capsule

A gel envelope surrounding some bacterial cells.

Functions of Capsule

Promotes adhesion, acts as a barrier, defends against phagocytosis, and stores nutrients.

Cell Wall Composition

Mainly made of peptidoglycan; a protective layer around bacterial cells.

Gram Staining

A technique that distinguishes bacteria based on cell wall composition.

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Bacterial Shapes

Bacteria can be rod-shaped (bacillus), spherical (coccus), or spiral (spirillum).

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Study Notes

Bacterial Structure and Function

Capsule: A layer of loose gel surrounding some bacteria; it aids in adhesion, acts as a barrier, protects against phagocytosis, and can store nutrients. Not all bacteria have a capsule.

Capsule Function

Adherence: Capsule components called adhesins bind to host receptors, enabling bacteria to attach and colonize.
Permeability Barrier: Limits the passage of molecules.
Phagocytosis Resistance: Protects bacteria from being engulfed by immune cells.
Nutrient Reserve: Can store nutrients within the capsule.

Virulence Factor

Capsules protect bacteria from the host's immune system during infection.

Cell Wall

Peptidoglycan (PG): The major component, a complex structure of carbohydrates and amino acids, forming a rigid layer around the cytoplasmic membrane. Essential for bacterial cell shape and integrity.

Gram Staining

Gram-positive: Retain the violet stain due to a thick peptidoglycan layer.
Gram-negative: Lose the violet stain and stain red due to a thinner peptidoglycan layer and an outer membrane.

Cell Wall Functions

Structural Support: Maintains bacterial shape and integrity.
Semipermeable Surface: Allows the passage of molecules into and out of the cell.
Protection: Protects against harmful substances.

Bacterial Shapes

Bacillus: Rod-shaped bacteria
Coccus: Spherical bacteria
Spirillum: Spiral-shaped bacteria
Pleomorphism: The ability of some bacteria to change shape in response to environmental conditions.

Plasma Membrane

Composition: Primarily protein and phospholipid. It performs many functions like transport, biosynthesis, and energy production, and lies beneath the cell wall.

Cytoplasm

Composition: Gel-like matrix containing water, enzymes, nutrients, wastes, and gases.
Components: Contains ribosomes, a nucleoid (bacterial chromosome), and plasmids.

Cytoplasm - Nucleoid

Contains bacterial DNA, associated proteins and RNA crucial for bacterial activity and reproduction.

Plasmids

Small, circular DNA molecules separate from the main chromosome.
Often carry genes for antibiotic resistance or other traits that contribute to virulence.

Extracellular Appendages

Flagella: Filamentous structures used for bacterial motility (movement).
Pili and Fimbriae: Hair-like structures for adherence to surfaces, facilitating infection. They are found in Gram-negative bacteria, not in many Gram-positive bacteria.