Microbiology - Bacterial Structure and Function

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Questions and Answers

What is a key feature of bacterial DNA compared to eukaryotic DNA?

Bacterial DNA is double stranded but not helical.

Bacterial DNA does not contain any proteins.

Bacterial DNA is circular and represented by only one chromosome. (correct)

Bacterial DNA is linear and present in multiple chromosomes.

Which of the following statements about plasmids is true?

Plasmids are always linear molecules.

Plasmids can encode for antibiotic resistance. (correct)

Plasmids are essential for bacterial growth and metabolism.

Plasmids cannot be transferred between cells.

The nucleolus within the eukaryotic nucleus is responsible for what function?

Storage of chromatin.

Production of ATP.

Replication of DNA.

Synthesis of ribosomal RNA components. (correct)

What distinguishes Gram-positive bacteria from Gram-negative bacteria?

Gram-positive bacteria have a thicker peptidoglycan layer. Signup and view all the answers

Which of the following statements describes the composition of the cytoplasm in eukaryotic cells?

Cytoplasm includes membranous organelles such as the nucleus. Signup and view all the answers

What role does Gram's iodine play in the Gram staining process?

It serves as a stabilizer to form dye complexes. Signup and view all the answers

What occurs when alcohol is applied to gram-negative bacteria during the Gram stain procedure?

The outer membrane is dissolved, and dye is removed. Signup and view all the answers

Which characteristic of gram-positive bacteria aids in trapping dye during Gram staining?

Lack of an outer membrane. Signup and view all the answers

What is the purpose of using safranin in the Gram staining process?

To provide a secondary color for gram-negative bacteria. Signup and view all the answers

What happens to the dye complexes in the gram-negative cell walls during Gram staining?

They are formed but not stabilized effectively. Signup and view all the answers

What does pleomorphism refer to in bacteria?

Variation in the size and shape of cells of a single species Signup and view all the answers

Which arrangement describes a pair of spherical bacterial cells?

Diplococci Signup and view all the answers

What type of flagellation features a single flagellum at one end?

Monotrichous Signup and view all the answers

What are fimbriae primarily involved in?

Adhesion to other cells and surfaces Signup and view all the answers

Which of the following best describes a capsule in bacteria?

A highly organized, tightly attached coating of molecules Signup and view all the answers

Which arrangement describes a chain of rod-shaped bacterial cells?

Streptobacilli Signup and view all the answers

What is the function of the glcocalyx in bacteria?

To serve as a component of the bacterial slime layer or capsule Signup and view all the answers

What is the primary characteristic of peritrichous flagellation?

Flagella are dispersed over the entire surface Signup and view all the answers

What is a characteristic feature of Gram-positive bacterial cell walls?

Thick layer of peptidoglycan Signup and view all the answers

What color do Gram-negative bacteria appear after the Gram staining procedure?

Pink Signup and view all the answers

What significant component is found in the outer membrane of Gram-negative bacteria?

Lipid A Signup and view all the answers

Which of the following is true about the S-layer in some bacteria and archaea?

It contains only one or two identical proteins Signup and view all the answers

What is the primary chemical reaction involved during the Gram staining process with crystal violet?

It stains all cells the same color. Signup and view all the answers

What role does mycolic acid play in acid-fast bacteria?

It aids in survival during desiccation. Signup and view all the answers

What is the composition of the periplasmic space in Gram-negative bacteria?

A mixture of enzymes and proteins Signup and view all the answers

Which of the following statements is incorrect regarding bacterial cell walls?

Gram-negative bacteria contain teichoic acids. Signup and view all the answers

What is the primary function of the slime layer glycocalyx in Streptococcus mutans?

Helps in attachment to surfaces Signup and view all the answers

Which of the following is NOT a component of the taxonomic hierarchy?

Species type Signup and view all the answers

Which organism is known for producing endospores?

Clostridium Signup and view all the answers

Which of the following best defines chemotaxis?

Movement in response to a chemical signal Signup and view all the answers

Which of the following best describes the life cycle of endospores?

Presence of vegetative and endospore phases Signup and view all the answers

Which of the following is a characteristic of saprophytic organisms?

They live on dead, decomposing matter Signup and view all the answers

Which organism can utilize pseudopodia for movement?

Amoeba Signup and view all the answers

Which of the following best describes the function of receptors in the slime layer?

Help in sensing environmental changes Signup and view all the answers

Study Notes

Exam 1 Review

The exam covers bacterial cell wall structure (Gram + & Gram -, "Acid fast"), bacterial cellular morphology & arrangement, components of prokaryotic and eukaryotic cells (internal & external), bacterial chemotaxis, endospores, fungi & protozoa, and taxonomy (domains & kingdoms of life).

Bacterial Cell Structure

Prokaryotic cells are simpler than eukaryotic cells, lacking membrane-bound organelles.
Bacterial DNA exists as a single, circular chromosome.
Gram-positive bacteria have a thick peptidoglycan layer in their cell walls and stain purple in Gram staining.
Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane, and stain pink in Gram staining.
Acid-fast bacteria have a waxy outer layer, making them resistant to staining.

Bacterial Cellular Morphology & Arrangement

Bacteria exhibit various shapes (cocci, bacilli, spiral).
Cell arrangements also vary, forming pairs (diplococci), chains (streptococci), clusters (staphylococci), or other patterns.
Variations in shape and size of cells within species (pleomorphism) are common depending on nutritional and genetic differences.

Prokaryotic Cell Components

The image shows a diagram of a typical prokaryotic cell highlighting various components.
Components include ribosomes, cytoplasm, nucleoid, glycocalyx, cell wall, and cytoplasmic membrane.
These components play vital roles in cellular structure, function, and activities.
Inclusions are also found in prokaryotic cells, used for storage.
Flagella and pili allow for movement and attachment.

Eukaryotic Cell Components

A eukaryotic cell is much more complex than a prokaryotic cell.
The image displays a complex diagram of a eukaryotic cell, highlighting various organelles and components.
Key components include the nucleus, containing chromatin and RNA, the nucleolus, the endoplasmic reticulum (rough and smooth), Golgi body, lysosomes, mitochondria, ribosomes, vacuole, cytoskeleton, and the cytoplasmic membrane.
Eukaryotic DNA is linear, not circular.

Plasmids

Plasmids are small, circular, double-stranded DNA molecules, easily manipulated in genetic engineering.
They are not essential for bacterial growth or metabolism.
Plasmids are replicated independently from the bacterial chromosome and often carry genes related to antibiotic resistance, tolerance to metals, or production of toxins.

Bacterial Chemotaxis

Bacteria can move in response to chemical signals (chemotaxis).
A bacterium's movement towards an attractant (positive chemotaxis) or away from a repellent (negative chemotaxis) involves switching between clockwise (tumbling) and counterclockwise (running) rotation of its flagella.

Endospores

Endospores are dormant structures formed by some bacteria (mainly bacilli), serving as a survival mechanism under harsh conditions.
They are highly resistant to heat, drying, and radiation.
Endospores are not a reproductive mechanism; instead, they allow the cells to survive unfavourable conditions.
Different bacterial genera form endospores, for example, Bacillus and Clostridium.

Fungi & Protozoa

Fungi are eukaryotic organisms, including molds (filamentous) and yeasts (unicellular).
Protozoa are unicellular eukaryotic organisms, exhibiting diverse motility methods (pseudopodia, flagella, cilia).
Organisms belonging to these two groups are important parts of the various ecosystems.

Taxonomy

Taxonomy is the science of classifying and naming organisms.
The three domains of life are bacteria, archaea, and eukarya.
Each organism is classified based on its evolutionary relationships and shared characteristics at different taxonomic levels, from domains to species.

Glycocalyx

Glycocalyx is a sugar or protein coating external to a cell wall.
Its primary function is for attachment, and it protects from phagocytes.
Two forms exist: capsule (highly organized, tightly attached) and slime layer (loosely attached).

Chemotaxis

Bacteria can move in response to chemical stimuli.
Bacteria have mechanisms for movement (rotation of flagella).

Fimbrae & Pili

Fimbrae are fine hair like bristles on bacterial cell surfaces for attachment and biofilm formation.
Pili facilitate conjugation (bacterial mating)

Bacterial Mating

Bacteria exchange genetic material (plasmids) through a process called conjugation.
Pili are necessary for this conjugation process.

Differential Gram Staining

Gram staining differentiates bacteria based on cell wall structure.
A series of steps are involved to stain, decolorise, and counterstain the bacteria.

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Description

Test your knowledge on key features of bacterial DNA, the differences between Gram-positive and Gram-negative bacteria, and the role of various components in the Gram staining process. This quiz covers essential concepts in microbiology that highlight the unique characteristics of bacteria compared to eukaryotic cells.