Chapter 4 – Prokaryotes, Eukaryotes & Cell Structures

Vocabulary flashcards covering major terms and definitions from Chapter 4 lecture on prokaryotic and eukaryotic cells, their structures, and related cellular processes.

Prokaryote

Single-celled organism lacking a true nucleus; DNA is circular, not membrane-bound; no organelles; divides by binary fission; peptidoglycan cell wall (bacteria).

Eukaryote

Organism with true nucleus containing linear chromosomes; DNA associated with histones; possesses membrane-bound organelles; divides by mitosis; no peptidoglycan in cell walls.

Nucleoid

Region in prokaryotes where the single circular chromosome is located; not membrane-bound.

Histone

Protein around which eukaryotic DNA wraps to organize into linear chromosomes; absent in bacteria.

Binary Fission

Asexual prokaryotic division where DNA is copied and the cell splits into two identical cells.

Mitosis

Eukaryotic process that distributes replicated chromosomes into two nuclei followed by cytokinesis.

Monomorphic

Bacterial species that maintain a single, constant shape.

Pleomorphic

Bacteria capable of assuming multiple shapes.

Coccus

Spherical bacterial shape.

Bacillus (shape)

Rod-shaped bacterium.

Spiral Bacteria

Group including vibrio, spirillum, and spirochete shapes.

Vibrio

Curved-rod (comma-shaped) bacterium.

Spirillum

Rigid corkscrew-shaped bacterium with external flagella.

Spirochete

Flexible spiral bacterium with internal axial filaments.

Diplococci

Pair of cocci resulting from one division plane.

Streptococci

Chain of cocci formed by repeated divisions in one plane.

Staphylococci

Grape-like cluster of cocci from multiple division planes.

Tetrad

Group of four cocci arranged in a square.

Sarcinae

Cube of eight cocci (2x2x2 arrangement).

Diplobacilli

Pair of rod bacteria attached end to end.

Streptobacilli

Chain of rod-shaped bacteria.

Coccobacillus

Short rod that resembles a coccus.

Palisade

Side-by-side fence-like arrangement of bacilli.

Stella

Star-shaped bacterial genus.

Haloarcula

Square-shaped archaeal genus.

Glycocalyx

Viscous, sticky external coating of polysaccharide and/or polypeptide secreted by many bacteria.

Capsule

Organized, firmly attached glycocalyx that inhibits phagocytosis; visualized by negative stain.

Slime Layer

Unorganized, loosely attached glycocalyx.

Extracellular Polymeric Substance (EPS)

Glycocalyx within biofilms that aids adhesion, protection, and communication.

Flagellum

Long filamentous appendage for bacterial motility; composed of flagellin, hook, and basal body.

Monotrichous

Single flagellum at one pole.

Amphitrichous

Single flagellum at each pole.

Lophotrichous

Tuft of flagella at one or both poles.

Peritrichous

Flagella distributed over the entire cell surface.

Chemotaxis

Movement toward (attractant) or away from (repellent) chemical stimuli via flagellar rotation.

Phototaxis

Movement in response to light stimuli.

Axial Filament (Endoflagellum)

Internal flagella wrapped around spirochetes, causing corkscrew motility.

Fimbriae

Short, hair-like protein appendages (pilin) for adhesion, not motility.

Pilus (Sex Pilus)

Long pilin tube that attaches to another bacterium to transfer DNA (conjugation).

Twitching Motility

Jerky movement using extension and retraction of a pilus.

Gliding Motility

Smooth surface movement (e.g., myxobacteria) without flagella in low-water environments.

Cell Wall (Bacteria)

Semi-rigid structure outside plasma membrane; maintains shape and prevents osmotic lysis; composed of peptidoglycan in bacteria.

Peptidoglycan

Bacterial cell wall polymer of NAG-NAM disaccharides cross-linked by peptides.

Gram-Positive Cell Wall

Thick peptidoglycan layers with teichoic acids; no outer membrane.

Teichoic Acid

Polymer in Gram-positive walls that links peptidoglycan or plasma membrane and regulates cation movement.

Gram-Negative Cell Wall

Thin peptidoglycan plus outer membrane containing lipopolysaccharide, lipoprotein, and phospholipid; forms periplasmic space.

Lipopolysaccharide (LPS)

Outer membrane molecule; Lipid A is an endotoxin, O-polysaccharide functions as antigen.

Periplasm

Gel-like space between outer membrane and plasma membrane in Gram-negative bacteria.

Crystal Violet

Primary dye in Gram stain that complexes with iodine inside cells.

Safranin

Counterstain that colors Gram-negative bacteria pink after decolorization.

Mycoplasma

Smallest bacteria lacking cell walls; plasma membrane contains sterols for stability.

Pseudomurein

Archaeal cell-wall material distinct from peptidoglycan.

Mycolic Acid

Waxy lipid in Mycobacterium cell walls; basis for acid-fast staining.

Protoplast

Wall-less Gram-positive cell produced by lysozyme/penicillin action.

Spheroplast

Gram-negative cell stripped of peptidoglycan but retaining outer membrane remnants.

Plasma Membrane

Phospholipid bilayer with embedded proteins; selective barrier; site of ATP synthesis in prokaryotes.

Fluid Mosaic Model

Concept that membrane lipids and proteins move laterally, creating a dynamic, oil-like mosaic.

Selective Permeability

Property allowing some substances to cross the membrane more easily than others.

Simple Diffusion

Net movement of molecules from high to low concentration without energy or carriers.

Facilitated Diffusion

Passive transport aided by membrane transporter proteins; no ATP required.

Net diffusion of water across a semipermeable membrane from high to low water concentration.

Isotonic Solution

Equal solute concentration inside and outside cell; no net water movement.

Hypotonic Solution

Lower external solute concentration; water enters cell causing swelling and possible lysis.

Hypertonic Solution

Higher external solute concentration; water leaves cell causing shrinkage (plasmolysis).

Active Transport

ATP-powered movement of substances against their concentration gradient via carrier proteins.

Group Translocation

Prokaryotic active transport that chemically modifies the substance (e.g., phosphorylates glucose) during entry.

Cytoplasm

80 % water solution inside membrane containing nucleoid, ribosomes, and inclusions.

Plasmid

Small, circular, extrachromosomal DNA molecule that replicates independently and may carry antibiotic-resistance genes.

Ribosome (70S)

Prokaryotic protein-synthesis organelle composed of 50S and 30S subunits of rRNA and protein.

Inclusion

Cytoplasmic nutrient reserve granule such as metachromatic, polysaccharide, lipid, sulfur, etc.

Endospore

Dormant, tough, non-reproductive survival structure produced by certain Gram-positive bacteria; highly resistant.

Sporulation

Process of endospore formation under adverse conditions.

Germination

Return of an endospore to metabolically active vegetative cell.

Endomembrane System

Eukaryotic network of organelles (ER, Golgi, vesicles) that synthesize, modify, and transport proteins/lipids.

Endosymbiotic Theory

Idea that mitochondria and chloroplasts originated from engulfed prokaryotes, explaining their double membranes and DNA.

Vesicle

Small membrane sac that transports or stores substances within eukaryotic cells.

Endocytosis

Vesicular import of materials into eukaryotic cells by membrane invagination.

Phagocytosis

Type of endocytosis where pseudopods engulf solid particles like bacteria or debris.

Pinocytosis

Endocytosis of extracellular fluid and dissolved solutes (‘cell drinking’).

Exocytosis

Vesicular export of substances when secretory vesicles fuse with the plasma membrane.

CV-I crystal interaction with Gram-negative cells

In Gram-negative cells, crystal violet and iodine form a complex. During decolorization, the alcohol damages the outer membrane and the thin peptidoglycan layer cannot retain the crystal violet-iodine complex, allowing it to wash out.

histone

Proteins that help package and order DNA into structural units called nucleosomes, playing a key role in gene regulation.

plasmids

Small, circular DNA molecules found in bacteria that replicate independently of chromosomal DNA, often carrying genes that provide antibacterial resistance or other advantageous traits.

ribosomes

Cellular structures that synthesize proteins by translating messenger RNA into amino acid sequences. They are found in both prokaryotic and eukaryotic cells.

inclusions

Granules or storage bodies within cells that can store nutrients, waste products, or pigments, and vary in composition depending on the type of cell.

types of inclusions

can include polysaccharide granules like glycogen, lipid inclusions, and phosphate granules, serving as energy reserves or metabolic intermediates.

cilia

Hair-like structures that extend from the surface of eukaryotic cells, aiding in movement and sensory functions. They can be found in various organisms, including protozoa and some animal cells.

cell wall in eukaryotes

A rigid outer layer that provides structural support and protection to plant, fungal, and some protist cells, primarily composed of cellulose in plants and chitin in fungi. There is no peptidoglycan in these cell walls

plasma membrane proteins

Proteins embedded in or associated with the plasma membrane that play crucial roles in cell communication, transport, and maintaining cell structure. They can function as receptors, channels, or enzymes, facilitating various cellular processes.

vesicular transport

The process by which materials are moved into or out of a cell enclosed in membrane-bound vesicles. This method allows cells to transport large molecules, such as proteins and hormones, across the plasma membrane.

endocytosis

is the process of vesicular transport by which cells engulf external materials, folding them into the plasma membrane to form vesicles that bring substances into the cell. This mechanism is essential for nutrient uptake and the regulation of cell signaling.

phagocytosis

A specific type of endocytosis where large particles, such as bacteria or dead cells, are engulfed by the cell. During this process, the plasma membrane extends around the particle, creating a vesicle that traps and internalizes it for digestion.

ribosome types in prokaryotes and eukaryotes

Ribosomes in prokaryotes are 70S in size, composed of 50S and 30S subunits, while eukaryotic ribosomes are 80S, made up of 60S and 40S subunits, reflecting their structural and functional differences.

pinocytosis

A type of endocytosis involving the ingestion of liquid substances by cells. In this process, the plasma membrane folds inward to form vesicles that take in extracellular fluid and dissolved solutes.

cytoskeleton

A dynamic network of fibers that provide structural support, shape, and movement to eukaryotic cells. It is composed of microfilaments, intermediate filaments, and microtubules, playing crucial roles in intracellular transport and cellular division.

microfilaments

Thin, thread-like structures in the cytoskeleton that provide movement, support, and shape to the cell. They are composed of actin proteins and are involved in cell movement and division.

intermediate filaments

Cytoskeletal components that provide structural support and helps anchor organelles, composed of various proteins such as keratins and vimentin.

microtubules

Cytoskeletal components made of tubulin that provide structural support, aid in intracellular transport, the movement of cilia and flagella, and are critical for cell division. They form the mitotic spindle and maintain cell shape.

cytoplasmic streaming

The movement of the fluid cytoplasm within a cell, helping to transport nutrients, organelles, and other materials, facilitating cellular processes.

endoplasmic reticulum

An organelle made of a network of membranes within the cell that is involved in the synthesis, folding, modification, and transport of proteins and lipids. It consists of rough and smooth regions, where the rough is studded with ribosomes and the smooth is associated with lipid synthesis.