Chapter 8 – Cell: The Unit of Life

Vocabulary flashcards covering key terms, scientists, structures, and concepts from Chapter 8: Cell – The Unit of Life.

Cell

Fundamental structural and functional unit of all living organisms.

Unicellular organism

Living organism made up of a single cell capable of independent existence.

Multicellular organism

Organism composed of many cells that work together to perform life functions.

Antonie van Leeuwenhoek

First person to observe and describe a living cell.

Robert Brown

Discovered the cell nucleus.

Cell theory

Concept stating that all living organisms are composed of cells and all cells arise from pre-existing cells.

Matthias Schleiden

Botanist who proposed that all plants are made of cells.

Theodor Schwann

Zoologist who concluded that animals are composed of cells; co-formulated cell theory.

Rudolf Virchow

Added the idea that new cells come only from pre-existing cells (Omnis cellula e cellula).

Prokaryotic cell

Cell lacking a membrane-bound nucleus and organelles; exemplified by bacteria and cyanobacteria.

Eukaryotic cell

Cell possessing a membrane-bound nucleus and membrane-bound organelles.

Plasma membrane

Selectively permeable phospholipid bilayer forming the cell’s outer boundary.

Cell wall

Rigid outer layer that provides shape and protection, present in plants, bacteria, and fungi.

Nucleus

Membrane-bound organelle containing chromosomes and genetic material (DNA).

Chromosome

DNA–protein structure carrying hereditary information.

Cytoplasm

Semi-fluid matrix inside the cell where most metabolic reactions occur.

Organelle

Specialized sub-cellular structure performing a distinct function.

Endoplasmic reticulum (ER)

Membrane network involved in protein (rough ER) and lipid (smooth ER) synthesis.

Golgi complex

Stacked membranes that modify, sort, and package proteins and lipids.

Lysosome

Membrane-bound vesicle containing hydrolytic enzymes for intracellular digestion.

Mitochondrion

Double-membrane organelle that produces ATP through cellular respiration.

Ribosome

Non-membranous particle made of rRNA and protein; site of protein synthesis.

Centrosome

Animal-cell organelle containing centrioles, crucial for spindle formation during cell division.

Mycoplasma

Smallest known bacteria (≈0.3 µm) lacking a cell wall.

PPLO

Pleuro-Pneumonia-Like Organisms; another term for mycoplasma.

Bacillus

Rod-shaped bacterium.

Coccus

Spherical bacterium.

Vibrio

Comma-shaped bacterium.

Spirillum

Spiral-shaped bacterium.

Plasmid

Small circular DNA in bacteria conferring extra traits such as antibiotic resistance.

Mesosome

Plasma-membrane infolding in prokaryotes involved in respiration, DNA replication, and cell wall formation.

Cell envelope

Three-layered structure of glycocalyx, cell wall, and plasma membrane in bacteria.

Glycocalyx

Outermost sugar-rich layer of bacterial cell envelope; may be slime layer or capsule.

Slime layer

Loosely attached, thin glycocalyx in some bacteria.

Capsule

Thick, tough glycocalyx that protects bacteria from desiccation and phagocytosis.

Gram-positive bacteria

Bacteria that retain Gram stain due to thick peptidoglycan cell wall.

Gram-negative bacteria

Bacteria that do not retain Gram stain; have thin peptidoglycan and outer membrane.

Chromatophore (prokaryote)

Pigmented membrane extension in cyanobacteria aiding photosynthesis.

Flagellum

Long, whip-like filament used for bacterial motility; consists of filament, hook, and basal body.

Pili

Elongated protein tubes on bacteria involved in DNA transfer and attachment.

Fimbriae

Short bristle-like projections helping bacteria adhere to surfaces or hosts.

Polyribosome (Polysome)

Chain of ribosomes simultaneously translating a single mRNA molecule.

Inclusion bodies

Membrane-less cytoplasmic reserves such as glycogen, phosphate, or cyanophycean granules in prokaryotes.

Gas vacuole

Protein-bounded, gas-filled structure providing buoyancy in aquatic photosynthetic bacteria.

70S ribosome

Prokaryotic ribosome composed of 50S and 30S subunits.

50S subunit

Large subunit of the 70S prokaryotic ribosome.

30S subunit

Small subunit of the 70S prokaryotic ribosome.

Ostrich egg

Largest known isolated single cell in nature.

Red blood cell

Biconcave human cell ~7 µm in diameter specialized for oxygen transport.

Nerve cell

Highly elongated, branched cell specialized for rapid signal transmission.