Bacterial Structure and Function Quiz

Prokaryotes lack a nucleus and membrane-bound organelles, while eukaryotes have both.

Streptococci are spherical bacteria that form chains.

A glycocalyx is a sticky, protective layer outside the bacterial cell wall. It can be a capsule (organized, firmly attached) or a slime layer (loosely attached).

Flagella are long, whip-like structures that propel bacteria. Axial filaments are bundles of flagella within the periplasmic space of spirochetes. Fimbriae are hair-like structures for attachment. Pili are involved in DNA transfer between bacteria.

Gram-positive bacteria have a thick peptidoglycan layer and no outer membrane. Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane containing lipopolysaccharides. Acid-fast bacteria have a waxy layer, archaea have pseudopeptidoglycan, and mycoplasmas lack a cell wall.

Protoplasts are bacterial cells without cell walls. Spheroplasts are Gram-negative bacteria with partially degraded cell walls. L forms are bacteria that have lost their cell wall permanently.

The prokaryotic plasma membrane is a phospholipid bilayer that regulates the passage of substances into and out of the cell. It contains proteins involved in transport, energy production, and signal transduction.

Simple diffusion is the movement of molecules from high concentration to low concentration, down their concentration gradient. Facilitated diffusion also moves molecules down the gradient but requires the assistance of membrane proteins. Osmosis is the movement of water across a selectively permeable membrane from high water concentration to low water concentration. Active transport moves molecules against their concentration gradient and requires energy. Group translocation modifies the molecule as it is transported across the membrane.

A structure found in some cells that helps in movement. They are hair-like projections, but prokaryotic flagella are made of a different protein called flagellin compared to the tubulin found in eukaryotic flagella.

A rigid outer layer that provides structural support and protection for prokaryotic cells. It is primarily composed of a unique molecule called peptidoglycan, which is absent in eukaryotic cell walls.

The outermost boundary of a cell, regulating the passage of molecules in and out. Both prokaryotic and eukaryotic plasma membranes are composed of a phospholipid bilayer, but the proteins embedded in the membrane differ, leading to variations in their functions.

The gel-like substance within the cell, encompassing all the organelles and structures. Both prokaryotic and eukaryotic cytoplasms contain water, enzymes, and other molecules, but the composition and organization can vary.

The site of protein synthesis, responsible for translating genetic information into functional proteins. Both prokaryotic and eukaryotic ribosomes have a small and large subunit, but they differ in their size and composition. The antibiotic erythromycin targets the 50S subunit of prokaryotic ribosomes, inhibiting their function.

A membrane-bound structure that contains the cell's genetic material (DNA) in eukaryotic cells. It is the control center of the cell, dictating cellular activities. In prokaryotes, the genetic material is located in a region called the nucleoid, which doesn't have a membrane.

A specialized structure within a eukaryotic cell that performs a specific function. It is often membrane-bound and can be likened to a miniature organ within a cell.

The endosymbiotic theory proposes that some eukaryotic organelles, like mitochondria and chloroplasts, originated from free-living prokaryotic cells that were engulfed by larger cells and established a symbiotic relationship. The evidence includes similarities in structure, size, and genetic material between these organelles and certain prokaryotes.

The glycocalyx is a sticky, protective layer outside the bacterial cell wall. It can be a capsule (organized, firmly attached) or a slime layer (loosely attached).

Capsules help bacteria evade the host's immune system by preventing phagocytosis, the process where white blood cells engulf and destroy bacteria.

Flagella are long, whip-like structures that propel bacteria. They consist of a filament, hook, and basal body.

A bacterial cell wall is essential for maintaining the cell's shape and protecting it from osmotic stress.

Peptidoglycan is a unique polymer found in bacterial cell walls. It consists of alternating sugars (NAG and NAM) linked by short chains of amino acids.

Gram-positive bacteria have thick cell walls with many layers of peptidoglycan. Their cell walls also contain teichoic acids.

Gram-negative bacteria have thin cell walls with a single layer of peptidoglycan. They also have an outer membrane containing lipopolysaccharides.

Porins are proteins found in the outer membrane of Gram-negative bacteria. They act like gates, allowing small molecules to pass through the membrane.

Gram-positive bacteria have a thick peptidoglycan layer, making them retain the crystal violet stain during the Gram stain procedure, resulting in a purple appearance.

Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane, causing them to lose the crystal violet stain during the Gram stain procedure, resulting in a pink appearance.

The outermost layer of Gram-negative bacteria, composed of lipids and polysaccharides, and is responsible for the negative staining characteristic.

Lysozyme, an enzyme found in tears and saliva, breaks down the peptidoglycan layer in the bacterial cell wall, destroying the cell.

Penicillin, a common antibiotic, inhibits the synthesis of peptidoglycan, weakening the cell wall and causing bacterial death.

The cell wall acts as a barrier that prevents the cell from bursting due to osmotic pressure, maintaining the cell's shape and integrity.

The plasma membrane, a phospholipid bilayer, is selectively permeable, controlling the movement of substances into and out of the cell.

Passive transport processes, like diffusion and osmosis, move substances across the membrane without cellular energy expenditure, while active transport requires energy to move substances against their concentration gradient.

Centrioles are cylindrical structures composed of nine triplets of microtubules, playing a crucial role in the formation of the mitotic spindle during cell division, which is essential for separating chromosomes and creating two daughter cells.

The endosymbiotic theory proposes that eukaryotic cells evolved through a process where prokaryotic cells were engulfed by other prokaryotic cells, forming a symbiotic relationship. Over time, these engulfed prokaryotes became organelles like mitochondria and chloroplasts.

Sporogenesis is the process by which bacteria form endospores, a dormant, highly resistant structure that allows them to survive harsh environmental conditions. This process is crucial for survival and dispersal.

An endospore is a dormant, resistant structure formed within certain bacteria, particularly Bacillus and Clostridium. Endospores are highly resistant to heat, radiation, chemicals, and desiccation, allowing bacteria to survive harsh conditions for long periods.

Germination is the process where an endospore reverts back to its vegetative state, a normal, actively growing bacterium. This occurs when favorable environmental conditions are present, allowing the bacteria to resume normal growth and reproduction.

Facilitated diffusion is a type of passive transport that moves molecules across the cell membrane from high to low concentration with the help of carrier proteins. This process doesn't require energy. Active transport, on the other hand, moves molecules against their concentration gradient, requiring energy. Group translocation modifies the molecule during transport across the membrane.

Gram-positive bacteria have a thick peptidoglycan layer in their cell wall, which retains the crystal violet stain during the Gram staining process. Gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane, causing them to lose the violet stain and appear pink after counterstaining.

Penicillin is ineffective against gram-negative bacteria because the outer membrane of these bacteria prevents the drug from reaching the peptidoglycan layer, where it typically inhibits cell wall synthesis. Penicillin targets the synthesis of peptidoglycan, which is essential for bacterial cell wall integrity, leading to cell lysis (bursting).

Coxiella burnetii exists in two forms: the Large Cell Variant (LCV) and the Small Cell Variant (SCV). LCVs are metabolically active and divide rapidly within host cells. SCVs are more resistant to environmental stress and can survive outside of a host. SCVs are essential for transmission of Q fever.

Coxiella burnetii can stain either gram-positive or gram-negative depending on its form. LCVs stain gram-negative due to having a thin peptidoglycan layer and an outer membrane. Conversely, SCVs stain gram-positive due to having a thick peptidoglycan layer. However, Coxiella is classified as gram-negative overall due to its basic structural features.

Coxiella burnetii causes Q fever, a zoonotic disease commonly transmitted through inhalation of contaminated aerosols. This bacterium's ability to survive outside a host in a spore-like form (SCV) makes airborne transmission possible. In contrast, other related bacteria, like rickettsia, require insect vectors for transmission because they cannot survive independently in the environment.

The life cycle of Coxiella burnetii involves both LCV and SCV forms. LCVs multiply rapidly within host cells. When conditions become unfavorable, LCVs differentiate into SCVs, which are resistant to environmental stress. These SCVs are released from the host and can survive outside. When conditions are favorable, SCVs transform back into LCVs, enabling infection of new hosts.

Coxiella burnetii undergoes binary fission, a form of asexual reproduction, within the phagolysosome of a host cell. This process involves the division of a single cell into two identical daughter cells. The LCV form is metabolically active and divides more rapidly than the SCV form.