Ch4 Bacteria vs. Eukaryotes: Cell Structure, Shapes, and Functions

What is the primary difference in the packaging of DNA between bacteria and eukaryotes?

Bacteria and archaea have nuclear material that is free in the cytoplasm, while eukaryotes have a nucleus.

What is the composition of the bacterial cell wall?

The bacterial cell wall is made of peptidoglycan.

Do bacteria have membrane-bound organelles?

No, bacteria and archaea do not have membrane-bound organelles.

What are the life activities that bacterial cells can carry out?

Reproduction, metabolism, and nutrient processing.

What is the average size of bacterial cells?

Approximately 1 μm.

What are the three general shapes of bacteria?

Coccus (spherical), bacillus (cylindrical), and vibrio (curved).

What is a diplococcus?

A pair of cocci bacteria.

What is the arrangement of bacteria known as tetrads?

Groups of four cocci bacteria.

What is the term for chains of cocci bacteria?

Streptococci.

What are the two major groups of appendages in bacteria?

Flagella and axial filaments for motility, and fimbriae and pili for attachment.

What is the function of flagella in bacteria?

Flagella provide motility.

What is chemotaxis?

Movement in response to chemical signals.

What is positive chemotaxis?

Movement of a cell in the direction of a favorable chemical stimulus.

What is the role of fimbriae in bacteria?

Fimbriae provide adhesion but not locomotion.

What is a pilus?

A long, rigid tubular structure made of pilin protein, used in conjugation for DNA transfer.

What is the function of periplasmic flagella?

They impart a twisting or flexing motion to spirochetes.

What are biofilms?

Communities of bacteria that adhere to surfaces and are often formed with the help of fimbriae.

What is the significance of pili in bacteria?

Pili are used for attachment and genetic exchange during conjugation.

What is the size range of Mycoplasma bacteria?

0.15 to 0.30 μm.

What is the size range of Nanobacteria?

0.05 to 0.2 μm.

What is the arrangement of bacilli known as diplobacilli?

Pairs of bacilli with their ends attached.

What is the term for bacilli that form chains?

Streptobacilli.

What are palisades in bacterial arrangement?

Cells of a chain that remain partially attached and fold back, creating a side-by-side row.

What is the S layer in bacteria?

A protective layer composed of thousands of copies of a single protein, produced in hostile environments.

What is the function of the glycocalyx?

It protects the cell from loss of water and nutrients and can form a slime layer or a capsule.

How does a capsule differ from a slime layer?

A capsule is more tightly bound to the cell and denser than a slime layer.

What is a biofilm?

A community of microorganisms that adhere to surfaces, such as plaque on teeth, providing protection.

What are the main components of the cell envelope in bacteria?

The cell wall, cytoplasmic membrane, and outer membrane (in some bacteria).

What is the significance of the Gram stain?

It differentiates bacteria into Gram-positive and Gram-negative based on cell envelope structure.

What characterizes Gram-positive bacteria?

They have a thick cell wall composed of peptidoglycan and an inner cytoplasmic membrane.

What characterizes Gram-negative bacteria?

They have a thin cell wall, an outer membrane, and an inner cytoplasmic membrane.

What is peptidoglycan?

A unique macromolecule in bacterial cell walls composed of glycan chains cross-linked with peptide fragments.

What is the structure of the Gram-positive cell wall?

A thick, homogenous sheath of peptidoglycan, 20 to 80 nm thick.

What is the structure of the Gram-negative cell wall?

A single, thin sheet of peptidoglycan, 1 to 3 nm thick, providing flexibility.

What are nontypical cell walls?

Cell walls that lack the structure of Gram-positive or Gram-negative bacteria, often containing unique lipids.

What are mycoplasmas?

Bacteria that naturally lack a cell wall and are stabilized by sterols.

What is the cytoplasmic membrane's structure?

A flexible lipid bilayer embedded with proteins, containing 30-40% phospholipids and 60-70% proteins.

What are the functions of the cytoplasmic membrane?

Energy reactions, nutrient processing, synthesis, and regulating transport of substances.

What is selective permeability?

The ability of the cytoplasmic membrane to allow certain substances to pass while blocking others.

What is the bacterial chromosome?

A single circular strand of DNA aggregated in a dense area called the nucleoid.

What are plasmids?

Nonessential pieces of DNA that can confer protective traits and are important in genetic engineering.

What are ribosomes in bacteria?

Made of RNA and protein, they are dispersed throughout the cytoplasm and are involved in protein synthesis.

What are inclusion bodies?

Storage sites for nutrients during periods of abundance, varying in size, number, and content.

What are bacterial endospores?

Structures that withstand hostile conditions, facilitating survival through a two-phase life cycle.

What triggers endospore formation?

Depletion of nutrients, especially carbon and nitrogen sources.

What diseases are associated with endospores?

Anthrax (Bacillus anthracis), Tetanus (Clostridium tetani), and Botulism (Clostridium botulinum).

What is the medical significance of endospores?

They resist cleaning methods and can contaminate cultures, posing risks in sterile environments.

What are the divisions in the bacterial diagnostic scheme?

Gram-positive, Gram-negative, and bacteria without cell walls, with subgroups based on shape and oxygen usage.

What is a serotype?

Representatives of a species that stimulate distinct antibody responses due to unique surface molecules.