Functional Anatomy of Prokaryotic Cells

What distinguishes prokaryotic cells from eukaryotic cells?

Prokaryotic cells are smaller, lack cellular organelles, and have one circular chromosome not enclosed in a membrane.

What are the main structural differences between prokaryotic and eukaryotic cells?

Prokaryotic cells have no cellular organelles, one circular chromosome, peptidoglycan or pseudopeptidoglycan cell walls, and reproduce by binary fission. Eukaryotic cells have subcellular organelles, paired chromosomes in a nuclear membrane, and may have polysaccharide cell walls.

Which statement about prokaryotic cells is false?

Prokaryotic cells have subcellular organelles.

How do bacteria reproduce?

Bacteria reproduce by binary fission.

What are the basic shapes of prokaryotic cells?

Bacillus (rod-shaped), Coccus (spherical), Spiral (twisted), Vibrio, Spirillum, Spirochete.

What does pleomorphic mean in the context of bacteria?

Pleomorphic refers to bacteria that can assume several shapes.

What are the arrangements of cocci?

Cocci can be arranged in pairs (diplococcus), chains (streptococcus), or clusters (staphylococcus).

What are the common structures found in bacterial cells?

Common structures include the capsule, cell wall, plasma membrane, flagella, nucleoid containing DNA, ribosomes, and various inclusions.

What is the role of the bacterial cell wall?

The cell wall maintains cell shape and prevents osmotic lysis.

What is peptidoglycan composed of?

Peptidoglycan is a polymer of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) linked by peptide chains.

What crosslinks the major carbohydrate backbone in peptidoglycan?

Peptide cross-bridges link the carbohydrate backbone.

To which sugar is the peptide attached in the peptidoglycan structure?

The peptide is attached to N-acetylmuramic acid (NAM).

What is the basic subunit of the carbohydrate in peptidoglycan?

The basic subunit is N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM).

What are the two types of cell walls in prokaryotes?

Bacteria have peptidoglycan cell walls, while Archaea have pseudopeptidoglycan cell walls.

What types of spiral bacteria exist?

Vibrio, Spirillum, and Spirochete.

What is the significance of drugs that target cell wall synthesis?

They are useful for killing bacteria by disrupting the integrity of the cell wall.

How can you identify streptococci with a microscope?

By observing their arrangement in chains due to their planes of division.

What is the structural difference between bacillus and coccobacillus?

Bacillus is rod-shaped, while coccobacillus is a short rod that resembles a sphere.

How many planes of division does a streptobacillus have?

Streptobacillus typically has one plane of division.

What types of bacteria form grapelike structures?

Staphylococci form grapelike structures.

Which material is not used to make the peptidoglycan cell wall?

Lipid is not used to make the peptidoglycan cell wall.

What are the major structural differences between gram-positive and gram-negative cell walls?

Gram-positive cell walls have a thick peptidoglycan layer and teichoic acids, while gram-negative cell walls have a thin peptidoglycan layer, an outer membrane containing lipopolysaccharides (LPS), and porins.

Which type of bacterial cell wall provides a greater permeability barrier?

The gram-negative cell wall provides a greater permeability barrier due to its outer membrane.

Which bacterial cell wall is physically stronger?

The gram-positive cell wall is physically stronger due to its thick peptidoglycan layer.

What are teichoic acids composed of?

Teichoic acids are composed of sugars, phosphates, and amino acids.

What is the difference between lipoteichoic acid and wall teichoic acid?

Lipoteichoic acid links to the plasma membrane, while wall teichoic acid links to peptidoglycan.

What components are found in the cell walls of gram-positive bacteria?

Gram-positive bacteria contain mannan, teichoic acid, cellulose, and chitin.

What can teichoic acid bind to?

Teichoic acid can bind to anions, cations, water molecules, and vitamin C.

What is the composition of the gram-negative outer membrane?

The gram-negative outer membrane is composed of phospholipids, lipopolysaccharides, and lipoproteins.

What is the periplasm?

The periplasm is the space between the outer membrane and the plasma membrane in gram-negative bacteria.

How does the outer membrane protect bacteria from harmful chemicals?

The outer membrane confers a barrier to chemicals, protecting bacteria from harmful substances, antibiotics, lysozymes, and immune factors.

What is degraded by lysozymes?

Lysozymes degrade the peptidoglycan layer.

What are the components of lipopolysaccharides?

Lipopolysaccharides consist of Lipid A, a core polysaccharide, and an O polysaccharide antigen.

Which part of lipopolysaccharides is considered an endotoxin?

Lipid A is considered an endotoxin.

What is the role of porins in the outer membrane?

Porins form channels through the outer membrane, allowing the passage of small molecules.

What is the role of crystal violet in the Gram-staining process?

Crystal violet stains all bacterial cells initially.

What is the role of iodine in the Gram-staining process?

Iodine forms crystal violet-iodine complexes that are retained in gram-positive bacteria.

What happens to gram-negative bacteria during the Gram-staining process?

Alcohol dissolves the outer membrane of gram-negative bacteria, allowing the crystal violet-iodine complex to wash out.

What is the counterstain used in Gram-staining?

Safranin is used as the counterstain in Gram-staining.

Which microorganisms have acid-fast cell walls?

Mycobacterium species, such as Mycobacterium tuberculosis and Mycobacterium leprae, have acid-fast cell walls.

What component in Mycobacterium spp. cell walls helps resist drying and immune attack?

Mycolic acid, a thick layer of waxy lipid, helps resist drying and immune attack.

What chemicals are used in acid-fast staining?

Carbolfuchsin is used to stain, and acid alcohol is used to destain microorganisms.

What are the main components of acid-fast cell walls?

Mycolic acid and peptidoglycan.

What are the two types of glycocalyx?

Capsule (neatly organized, firmly attached) and slime layer (unorganized, loosely attached).

What is the main chemical composition of bacterial capsules?

Gelatinous polysaccharide and/or polypeptide.

What roles do bacterial capsules play?

They allow attachment to surfaces, prevent desiccation, and prevent phagocytosis by white blood cells.

Why are bacterial capsules medically important?

They can enhance bacterial virulence by preventing phagocytosis and aiding in attachment.

Which of the following is NOT a role of bacterial capsules?

Cell division

What is the primary function of flagella?

Motility

What are the three main parts of a flagellum?

Filament, hook, and basal body.

Describe the arrangement of flagella known as monotrichous.

A single flagellum at one pole of the cell.

What is the arrangement of flagella called when they are distributed all over the cell surface?

Peritrichous.

What is the term for a bacterium with a tuft of flagella at one end?

Lophotrichous.

What is taxis in the context of bacterial movement?

Movement toward or away from stimuli.

What is positive chemotaxis?

Movement toward a source of food.

How do bacteria move?

By rotating their flagella.

Which part of the flagella acts as a motor?

Basal body.

What is the main function of fimbriae?

Specific adhesion to surfaces or host cells.

What is the main function of bacterial sex pili?

Facilitate the transfer of DNA from one cell to another during conjugation.

Which bacterial structure is not found on the cell surface?

Nucleoid.

What is the difference between fimbriae and pili?

Fimbriae are hair-like projections for adhesion, while pili are fewer in number and can facilitate motility or DNA transfer.

What is the role of axial filaments in spirochetes?

They enable spirochetes to move in a corkscrew motion.

What is the significance of the basal body in flagella?

It anchors the flagellum to the cell wall and membrane.

What is the role of the hook in flagella?

It connects the filament to the basal body and allows for rotation.

What are the primary components of the plasma membrane in prokaryotic cells?

Phospholipids and proteins.

What is the difference between peripheral proteins and integral proteins in the plasma membrane?

Peripheral proteins are located on the outside of the membrane, while integral proteins span the membrane.

What model describes the structure of the plasma membrane?

The Fluid Mosaic Model.

What is the primary function of the plasma membrane?

Selective permeability, providing structural support, and facilitating nutrient transport and energy production.

What is the difference between passive and active transport?

Passive transport does not require energy, while active transport does.

What is simple diffusion?

The movement of a solute from an area of high concentration to an area of low concentration without the need for a mediator.

What is facilitated diffusion?

The process where a solute combines with a protein to be moved across the membrane.

What type of transport proteins are involved in facilitated diffusion?

Transporters or permeases.

What is osmosis?

The movement of water across a permeable membrane from an area of lower salt concentration to an area of higher salt concentration.

What are aquaporins?

Water channels that facilitate the rapid movement of water across the membrane.

What happens to a cell in a hypertonic solution?

Water moves out of the cell, causing the cytoplasm to shrink (plasmolysis).

What occurs in an isotonic solution?

No net movement of water occurs.

What happens to a cell in a hypotonic solution?

Water moves into the cell, which may cause it to swell and burst if the cell wall is weak.

What is the driving force for simple diffusion?

Concentration difference.

Does facilitated diffusion require energy?

No, facilitated diffusion does not require energy.

What is the role of the phospholipid bilayer in the plasma membrane?

It provides a barrier that separates the internal environment of the cell from the external environment.

How do phospholipids and proteins behave in the Fluid Mosaic Model?

They move laterally within the membrane, allowing for flexibility and self-healing.

What is the significance of selective permeability in the plasma membrane?

It allows the cell to control the passage of substances, maintaining homeostasis.

What is the difference between simple diffusion and facilitated diffusion?

Simple diffusion does not require a mediator, while facilitated diffusion requires transport proteins.

What are the two types of transport processes across membranes?

Passive processes and active processes.

What is the primary function of fimbriae in prokaryotic cells?

To aid in attachment and contribute to antibiotic resistance.

What is the role of the conjugation pilus in prokaryotic cells?

It facilitates DNA transfer between bacteria.

What is the function of axial filaments in prokaryotic motility?

They provide a means of movement for certain bacteria.

How are oxygen and most water transported into cells?

Oxygen and most water are transported into cells by simple diffusion.

What is the definition of cytoplasm?

Cytoplasm is the fluid component inside the plasma membrane, mostly water, containing inorganic and organic molecules, DNA, ribosomes, and inclusions.

Where is the chromosomal DNA located in a prokaryotic cell?

The chromosomal DNA is located in the nucleoid.

Which bacterial organelle contains DNA?

The nucleoid contains DNA.

What is the role of the ribosome in prokaryotic cells?

The ribosome's role is protein synthesis.

What are plasmids and why do bacteria have them?

Plasmids are circular, extrachromosomal DNA molecules that are generally not essential for survival but may carry genes for antibiotic resistance and can be transferred between bacteria.

How are plasmids spread among bacteria in nature?

Plasmids can be transferred from one bacterium to another.

How are plasmids used in biotechnology?

Plasmids are used in biotechnology for genetic manipulation, such as insulin production.

Which statement about plasmids is incorrect?

Plasmids are generally essential for the survival of bacteria under normal environmental conditions.

What structure can be used to transfer a plasmid between bacteria?

A pilus can be used to transfer a plasmid between bacteria.

Under what conditions do endospores form?

Endospores form during adverse environmental conditions.

Why are bacterial endospores important in clinical and industrial settings?

Bacterial endospores are important because they are resistant to processes that normally kill vegetative cells and can survive for thousands of years.

What are the characteristics of bacterial endospores?

Bacterial endospores are resistant structures formed internal to the bacterial cell membrane, capable of surviving extreme conditions.