Cell: The Unit of Life

Vocabulary flashcards for key terms related to cell biology.

Cell

The fundamental unit of life.

Unicellular Organism

An organism that consists of a single cell capable of performing all essential life functions.

Multicellular Organism

An organism that consists of multiple cells.

Virus

An exception to the cell theory; it requires a host to multiply and lacks a complete cellular structure.

Robert Hooke

Observed cork cells and coined the term 'cell,' noting only the cell wall structure.

Anton Von Leeuwenhoek

First observed living cells, including RBCs, WBCs, bacteria, protozoa, and spermatozoa.

Robert Brown

First discovered the nucleus within cells.

Matthias Schleiden

German botanist who, in 1838, determined that plants are composed of different tissues and of different cells.

Theodore Schwann

German zoologist who, in 1839, determined that animal cells have an outer thin layer called the plasma membrane. He also stated that all plants and animals are composed of cells and products of cells.

Cell Theory

Formulated by Schleiden and Schwann, stating that all living organisms are composed of cells and products of cells.

Rudolph Virchow

Modified cell theory in 1855, proposing that all cells come from pre-existing cells (Omnis cellula e cellula).

Modern Cell Theory

Expands on the original theory, including that all living organisms are composed of cells and their products and that all cells arise from pre-existing cells.

Cell Wall

Outermost boundary in certain cells, providing a rigid layer not present in all organisms.

Plasma Membrane

Outer, thin, delimiting layer present in all living organisms.

Nucleus

Dense, membrane-bound structure containing genetic material in the form of chromosomes.

Cytoplasm

Semi-fluid matrix present within all living cells where chemical reactions occur.

Cell Organelles

Specialized structures within cells performing particular functions.

Mycoplasma

Smallest living cell, lacking a cell wall.

PPLO

Pleuropneumonia-like organism, another term for Mycoplasma.

Prokaryotic Cell

Cellular organizational type that is typically smaller than a eukaryotic cell (3-5 μm).

Eukaryotic Cell

Cellular organizational type that is typically larger than a prokaryotic cell (10-120 μm).

Prokaryote

Primitive cell type, always unicellular, with a non-cellulosic cell wall containing peptidoglycan.

Eukaryote

Advanced cell type, uni- or multicellular, with a cell wall (if present) made of various materials like silica, cellulose, chitin, or absent entirely.

Bacterial Chromosome

Circular, double-stranded DNA in prokaryotes, lacking a well-defined nucleus.

Plasmid

Extra-chromosomal DNA present in some bacteria, providing unique phenotypic characteristics.

Cell Envelope

Three-layered structure in bacteria, acting as a single protective unit.

Glycocalyx

Outermost covering of the cell envelope in bacteria; its composition and thickness vary.

Capsule

A tight, rigid layer in the glycocalyx, composed of mucopolysaccharides.

Slime Layer

Loose sheath or covering in the glycocalyx.

Peptidoglycan

Non-cellulosic component present in the cell walls of prokaryotes.

Gram-positive Bacteria

Bacteria with a thick cell wall and more muramic acid, staining blue.

Gram-negative Bacteria

Bacteria with a thin cell wall and less muramic acid, staining pink.

Mesosome

Membranous structure formed by infolding or extension of the plasma membrane into the cell in bacteria.

Chromatophore

Infolding of the plasma membrane in photosynthetic bacteria, containing photosynthetic pigments.

Flagella

Thin filamentous extension from the cell wall, aiding in movement.

Tubulin

protein that is NOT found in bacterial flagella

Pilli

Tubular structures that function in reproduction (conjugation).

Fimbrae

Bristle-like structures that help in adhesion to hosts or substrates.

Ribosome

Cell organelle that functions in protein synthesis.

Svedberg Unit (S)

A unit to measure sedimentation coefficient.

Polysome/Polyribosome

Structure formed when multiple ribosomes are attached to a single mRNA during translation.

Inclusion Bodies

Non-membrane bound structures in prokaryotes that represent reserve material.

Cyanophycean Granules

Reserve material found in cyanobacteria (BGA).

Gas Vacuole

Non-membrane bound structure found in photosynthetic bacteria, providing buoyancy.

Nucleoid

Region in prokaryotes where supercoiled naked DNA is present.

Naked DNA

Genetic material not surrounded by a nuclear membrane.

Genomic DNA / Bacterial Chromosome

Double-stranded circular DNA carrying essential genes in prokaryotes.

Polyamine

Molecule used to condense the bacterial chromosome.

Shapes of bacteria

Rod-shaped (Bacillus), Spherical (Coccus), Spiral (Spirillum), Comma (Vibrio).

Spirillum

Spiral shaped bacteria.