Cell and Its Structure: Cytology, Cell Theory, and Cellular Classification

Vocabulary practice flashcards covering cell history, key cytological definitions, early Earth abiogenesis experiments, endosymbiosis, cell theory, and cellular classifications based on physiology and nuclear organization.

Robert Hooke's Cell Discovery ($1665$)

In $1665$, while serving as keeper of instruments at the Royal Society of London, Robert Hooke observed thin sections of cork under a microscope, discovered small honeycomb-like compartments resembling monastic cells, and coined the term 'cell' from the Latin word Cellula (meaning small room), publishing his findings in the book Micrographia.

Micrographia

The book published by Robert Hooke in $1665$ detailing his microscopic observations, including the original description and naming of cork cells.

Antony Van Leeuwenhock

The Dutch scientist who in $1674$ was the first to observe live cells containing complete internal cellular contents, advancing beyond the observation of empty cell walls.

Robert Brown

The scientist who discovered the presence of a distinct spherical nucleus in plant cells in $1833$, confirming an earlier inference by Felice Fontana in $1781$.

Sarcode

The term given in $1835$ by French cytologist Felix Dujardin to describe the thick, jelly-like living substance observed within cells.

Protoplasm

The scientific name introduced in $1840$ by Johannes Purkinje for the living, fluid cellular substance previously called sarcode.

Electron Microscope Invention ($1931$)

A major technological advancement developed in $1931$ by German scientists Max Knol and Ernst Ruska that allowed scientists to observe the ultra-fine structure of cells and cell organelles.

Ostrich Egg Dimensions

Recognized as the largest known single cell, measuring $17\,\text{cm} \times 12.5\,\text{cm}$.

Human Motor Neuron Length

An exceptionally long single human cell that can reach approximately $1.37\,\text{m}$ in length.

Cell (Jean Brachet's Definition, $1961$)

Defined as the basic structural unit of living organisms.

Cell (Loewy and Siekevitz's Definition, $1963$)

Defined as a unit of biological activity delimited by a semi-permeable membrane and capable of self-reproduction in a medium free of other living systems.

Cell (C. P. Hickman's Definition, $1970$)

Defined as the structural and functional unit of biological activity, representing the minimal living unit capable of self-regulation and reproduction.

Primordial Atmospheric Composition (Oparin and Haldane, $1920$)

The primitive prebiotic atmosphere described by Alexander Oparin and J.B.S. Haldane containing methane ($\text{CH}_4$), ammonia ($\text{NH}_3$), hydrogen ($\text{H}_2$), and water vapor ($\text{H}_2\text{O}$), but lacking free oxygen ($\text{O}_2$).

Miller and Urey's Experiment ($1953$)

A laboratory experiment conducted in $1953$ by Stanley Miller and Harold Urey in which electric discharges were passed through a mixture of $\text{CH}_4$, $\text{NH}_3$, $\text{H}_2$, and $\text{H}_2\text{O}$ vapor, successfully synthesizing amino acids from abiotic precursors.

RNA-World Hypothesis

The scientific hypothesis proposing that primitive ancestral life was composed of simple RNA molecules, which later facilitated the production of proteins.

Endosymbiosis

The evolutionary mechanism wherein an ancient nucleated host cell engulfed an aerobic bacterium that evolved into a mitochondrion, and subsequently engulfed a photosynthetic bacterium that evolved into a chloroplast, establishing eukaryotic animal and plant cell lineages.

Homeostasis

The fundamental cellular characteristic of maintaining a stable internal physiological state despite fluctuations in the external environment.

Cell Organelles

The living, specialized, active subcellular structures situated in the cytoplasm that are essential for sustaining the life of the cell (such as mitochondria, ribosomes, and the endoplasmic reticulum).

Cytology

The scientific discipline focused on the structure, types, division, development, physiological function, and growth of cells, derived from the Greek words Kytos (cell or hollow) and logos (discourse).

Carl P. Swanson

The biologist recognized as the father of modern cytology ($1911\text{--}1996$).

Cell Theory

The biological doctrine formulated by Mathias Jacob Schleiden ($1838$) and Theodor Schwann ($1839$), and expanded by Rudolf Virchow ($1855$), stating that all organisms are composed of cells, the cell is the smallest structural and functional unit of life, and all cells arise from pre-existing cells.

Cell Metabolism

The collective sum of thousands of biochemical reactions occurring simultaneously within a cell that keep living tissues active and viable.

Somatic Cell (দেহকোষ)

Any biological cell forming the body structures, organs, and organ systems of an organism that is not a gamete; in humans, somatic cells possess a diploid chromosome complement of $2n = 46$.

Reproductive Cell or Gamete (জননকোষ বা গ্যামিট)

A specialized haploid cell produced via meiosis in the sex organs of diploid organisms for sexual reproduction (such as sperm and ovum), containing $n = 23$ chromosomes in humans.

Prokaryotic Cell (আদিকোষ)

A primitive cell type lacking a membrane-bound nucleus and membrane-bound organelles, containing circular non-histone DNA located freely in the cytoplasm, $70S$ ribosomes, and undergoing amitosis or binary fission (e.g., Escherichia coli, cyanobacteria, Mycoplasma).

Nucleoid

The defined non-membrane-enclosed area within the cytoplasm of a prokaryotic cell where the single circular coiled DNA resides.

Eukaryotic Cell (প্রকৃতকোষ)

A cell possessing a distinct membrane-enclosed nucleus with a double-layered nuclear envelope, linear chromosomes composed of DNA and histone proteins, $80S$ ribosomes, and membrane-bound organelles, dividing via mitosis and meiosis.

Bongiomorpha pubescens

A fossil red alga discovered in rocks dating back $1200$ million years, recognized as likely the earliest known eukaryotic and multicellular organism that reproduced sexually using large female gametes and small male gametes.