Prokaryotic Cell Structures Quiz

Prokaryotic Cell Structures

• Diplococci: Cocci that remain in pairs post-division.
• Streptococci: Cocci that divide and form chains.
• Tetrads: Cocci divided in two planes forming groups of four.
• Sarcinae: Cocci forming cubelike groups of eight by dividing in three planes.
• Staphylococci: Cocci that form clusters or sheets by dividing in multiple planes.
• Monomorphic: Describes organisms that maintain a single shape.
• Pleomorphic: Refers to organisms with multiple shapes.

Glycocalyx and Extracellular Structures

• Glycocalyx: Sticky polymer (polysaccharide or polypeptide) secreted by prokaryotes, surrounding the cell, often forming capsules or slime layers.
• Extracellular Polymeric Substance (EPS): Glycocalyx aiding in biofilm attachment and cell cohesion.

Characteristics of Prokaryotes and Eukaryotes

• Prokaryotes: One circular chromosome, no histones or organelles, contain peptidoglycan (bacteria) or pseudomurein (archaea) cell walls, reproduce via binary fission.
• Eukaryotes: Paired chromosomes within a nuclear membrane, histones present, contain organelles, and have polysaccharide cell walls and a mitotic spindle.

Cell Wall Structures

• Gram-Positive Cells: Purple, thick peptidoglycan layer, teichoic acids, more susceptible to penicillin.
• Gram-Negative Cells: Pink, thin peptidoglycan, outer membrane, endotoxins, tetracycline sensitive.
• Atypical Cell Walls: Acid-fast wall with mycolic acid, examples include Mycobacterium and Nocardia.
• Mycoplasmas: Lack cell walls, possess sterols in plasma membrane.
• Archaea: Lack peptidoglycan, with walls of pseudomurein, often appear gram-negative.

Movement and Motility

• Flagella: Long appendages for bacterial propulsion; categorized by arrangement (e.g., peritrichous, polar, lophotrichous, amphitrichous).
• Taxis: Movement towards or away from stimuli (e.g., chemotaxis).
• Fimbriae: Shorter than flagella, help bacteria adhere to surfaces and form biofilms.
• Pili: Longer, involved in motility and DNA transfer through conjugation.
• Twitching and Gliding Motility: Mechanisms used by bacteria for movement in low-water environments.

Ribosomes and Genetic Material

• Ribosomes: 70s in prokaryotes (50s + 30s subunits); involved in protein synthesis.
• Nucleoid: Area in bacterial cells containing a single, continuous loop of double-stranded DNA (chromosome).
• Plasmids: Small, circular DNA molecules found in bacteria, often carrying additional genes.

Membrane Transport

• Plasma Membrane: Encloses cytoplasm, thin structure within the cell wall.
• Fluid Mosaic Model: Describes dynamic arrangement of phospholipids and proteins in the membrane.
• Transport Mechanisms: Includes facilitated diffusion, osmosis, simple diffusion, and active transport utilizing ATP.
• Group Translocation: Exclusive to prokaryotes, involves energy use from PEP during transport.

Endospores

• Endospores: Resistant structures formed by certain bacteria (e.g., Bacillus, Clostridium) for survival under adverse conditions.
• Sporulation: Process of endospore formation, forming from vegetative cells.
• Germination: Return of endospores to their vegetative state.

The Endosymbiotic Theory

• Endosymbiotic Theory: Concept proposing eukaryotic origins from engulfed prokaryotic cells, formulated by Lynn Margulis.
• Key to understanding the evolution of cellular life, emphasizing symbiotic relationships.