Biology Chapter: Prokaryotic vs Eukaryotic Cells

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Questions and Answers

Which type of cocci are found in chains?

Staphylococci

Streptococci (correct)

Diplococci

Tetrads

What is the characteristic shape of vibroid bacteria?

Tightly coiled

Curved rods (correct)

Clusters resembling grapes

Straight rods

Which term describes bacteria that do not change shape under environmental conditions?

Filamentous

Monomorphic (correct)

Pleomorphic

Coccobacilli

What is the structure of sarcinae bacteria?

In clusters of 8 Signup and view all the answers

Which type of bacilli have a club shape?

Club-shape bacilli Signup and view all the answers

Which structure is present in prokaryotic cells but not in eukaryotic cells?

Plasmid Signup and view all the answers

What is the function of the glycocalyx in prokaryotic cells?

Protection against environmental threats Signup and view all the answers

How do gram-positive and gram-negative bacteria primarily differ?

Type of cell wall structure Signup and view all the answers

Which of the following shapes can bacteria take?

Coccus Signup and view all the answers

What role do flagella play in bacterial cells?

Enabling motility Signup and view all the answers

What is the outcome of the sporulation process in bacteria?

Development of resistance structures Signup and view all the answers

The slime layer is characterized by which of the following?

Unorganized and loosely attached Signup and view all the answers

Which component is NOT typically found in the internal structure of a bacterial cell?

Mitochondria Signup and view all the answers

Which of the following describes fimbriae?

Short, hair-like projections for adhesion Signup and view all the answers

What is the typical size range of bacterial cells?

2 to 8 um Signup and view all the answers

What role does the glycocalyx play in bacterial biofilms?

It helps in communication and protection within the biofilm. Signup and view all the answers

What is the primary function of the plasma membrane in bacterial cells?

To allow for the breakdown of nutrients and energy production. Signup and view all the answers

Which component of the bacterial cell wall is crucial for maintaining its shape?

Peptidoglycan Signup and view all the answers

What defines bacteria that are described as 'atichous'?

They lack flagella entirely. Signup and view all the answers

What is one of the significant functions of the bacterial cell wall concerning antibiotics?

It serves as a site of action for some antibiotics. Signup and view all the answers

How does the capsule of Bacillus anthracis affect its pathogenicity?

It protects against phagocytosis by the host's immune cells. Signup and view all the answers

What is the primary composition of the plasma membrane in bacterial cells?

Phospholipids and proteins Signup and view all the answers

What type of antigens are served by bacterial flagella?

H antigens Signup and view all the answers

What is the primary characteristic that distinguishes spirochetes from other bacteria?

They move by means of axial filaments. Signup and view all the answers

What are fimbriae primarily involved in?

Adhesion to surfaces. Signup and view all the answers

Which statement about plasmids is correct?

Plasmids are extrachromosomal genetic elements. Signup and view all the answers

Which of the following is NOT a characteristic of endospores?

They are used for reproduction. Signup and view all the answers

What is the main function of ribosomes in prokaryotic cells?

Protein synthesis. Signup and view all the answers

Why are endospores significant in the food industry?

They are resistant to heat and chemicals. Signup and view all the answers

Which of the following statements about pili is false?

They are present in high numbers per cell. Signup and view all the answers

What is the role of dipicolinic acid in endospores?

It protects endospore DNA from damage. Signup and view all the answers

How are bacterial chromosomes characterized?

They are usually circular and not histone-associated. Signup and view all the answers

Which bacterium is primarily associated with causing syphilis?

Treponema pallidum. Signup and view all the answers

Study Notes

Prokaryotic Cells

Prokaryotic cells are unicellular organisms
They lack a nucleus or other membrane-bound organelles
They have a cell wall
Examples of prokaryotic cells include bacteria

Eukaryotic Cells

Eukaryotic cells are multicellular
They have a nucleus and membrane-bound organelles
Examples of eukaryotic cells include protists, plants, fungi, and animals

Bacterial Cell Size

Most bacteria are between 2 and 8 micrometers in length
Their diameter ranges from 0.2 to 2.0 micrometers

Bacterial Cell Structures

Cell Wall
- Prevents the bacterial cell from bursting
- Helps maintain the cell's shape
- Provides a point of anchorage for flagella
- Contributes to disease-causing abilities in some bacteria
- Target for some antibiotics (e.g., penicillin)
- Composed of peptidoglycan
Plasma Membrane
- Innermost layer of the cell
- Serves as a selective barrier for materials entering and exiting the cell
- Plays a role in nutrient breakdown and energy production
Cytoplasm
- Substance inside the cell membrane
- Contains structures such as:
  - Nucleoid: Contains DNA
  - Ribosomes: Site of protein synthesis
  - Inclusions: Reserve deposits
Nucleoid
- Contains the bacterial chromosome
- Not surrounded by a nuclear envelope
- Lacks histones
Ribosomes
- 70S ribosomes (30S and 50S subunits)
Plasmids
- Extrachromosomal DNA (not part of the chromosome)
- Replicate independently
Glycocalyx
- Viscous, gelatinous polymer external to the cell wall
- Composed of polysaccharide, polypeptide, or both
- Can be organized (capsule) or unorganized (slime layer)
- Capsule
  - Firmly attached to the cell wall
  - Contribute to bacterial virulence by protecting bacteria from phagocytosis
  - Examples: Bacillus anthracis, Streptococcus pneumoniae, Klebsiella
  - Important component of biofilms
    - Extracellular polymeric substance (EPS)
    - Helps cells in biofilm attach to surfaces and each other
    - Protects cells and facilitates communication
    - Enhances survival by allowing cells to attach to various surfaces
Flagella
- Long, filamentous appendages
- Propel bacteria
- Arranged in various patterns:
  - Atrichous - No flagella
  - Monotrichous - Single flagellum at one end
  - Lophotrichous - Tuft of flagella at one end
  - Amphitrichous - Flagella at both ends
  - Peritrichous - Flagella distributed around the cell
- H antigen: Flagellar protein used to differentiate among serovars
- Example: E.coli O157:H7
Axial Filaments (Endoflagella)
- Found in spirochetes
- Unique structure and motility (spiral motion)
- Examples: Treponema pallidum (syphilis), Borrelia burgdorferi (Lyme disease)
Fimbriae
- Short, hair-like appendages shorter than flagella
- Allow bacterial cells to attach to surfaces
Pili
- Longer than fimbriae, typically just one or two per cell
  - Involved in motility and DNA transfer
  - Allow bacteria to bring together (conjugation)
Endospores
- Specialized, dormant cells formed by some gram-positive bacteria (Clostridium and Bacillus)
- Highly resistant to harsh conditions (heat, lack of water, toxins, radiation)
- Form when nutrients are depleted
- Contain dipicolinic acid that protects DNA
- Can remain dormant for thousands of years
- Germination: Process of endospore returning to vegetative state
- Not a means of reproduction: One vegetative cell forms one endospore
- Important in food industry due to resistance to processes that kill vegetative cells

Bacterial Shapes

Cocci (spherical)
- Diplococci: Round bacteria in pairs
- Streptococci: Cocci in chains
- Staphylococci: Cocci in clusters resembling grapes
- Sarcinae: Cocci in groups of 8 in cubical packets
- Tetrads: Divide in two planes and remain in groups of 4
Bacilli (rod-shaped)
- Diplobacilli: Paired bacilli
- Streptobacilli: Rods in chains
- Coccobacilli: Short rods
- Bacilli with Rounded Ends: Examples: Salmonella typhi
- Bacilli with Square Ends: Example: Bacillus anthracis
- Filamentous Bacilli: Tend to form long threads
- Club-Shaped Bacilli: Example: Corynebacterium diphtheriae
Helical/Spiral
- Vibroid/Comma-Shaped: Curved rods with less than a complete twist. Example: Vibrio cholerae
- Spirilla: Loosely coiled, helical shape with flagella.
- Spirochetes: Tightly coiled, flexible with axial filaments.
Other Shapes
- Stella: Star-shaped
- Halophilic Archaea: Flat, rectangular shape
- Triangular Shapes

Classification of Bacteria Based on Shape

Monomorphic: Maintain a single shape
Pleomorphic: Have many shapes. Examples: Rhizobium, Corynebacterium
Environmental Conditions Can Influence Shape

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Description

This quiz focuses on the differences between prokaryotic and eukaryotic cells, covering their structures, sizes, and examples. Test your knowledge on the characteristics that define these two fundamental types of cells in biology.