Key Concepts & Self-Assessment15 Key Facts
Review key Cell Biology: Prokaryotes, Eukaryotic Organelles & Mitosis/Meiosis Division exam facts and rate your mastery to track revision.
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#1
Classical Cell Theory formulated by Schleiden, Schwann, and Virchow asserts that all living organisms are composed of cells derived from pre-existing cells.
#2
Prokaryotes (e.g., bacteria) lack membrane-enclosed organelles and possess 70S ribosomes, whereas eukaryotes contain compartmentalized organelles and 80S ribosomes.
#3
Mitochondria produce cellular energy in the form of ATP through oxidative phosphorylation along the inner mitochondrial cristae.
#4
Mitosis constitutes equational cell division generating two genetically identical diploid (2n) somatic daughter cells.
#5
Meiosis is a reductional division producing four haploid (n) gametes, with genetic recombination occurring during the pachytene stage of prophase I.
#6
S.J. Singer and Garth L. Nicolson proposed the Fluid Mosaic Model of the plasma membrane in 1972, describing a quasi-fluid phospholipid bilayer embedded with peripheral and integral proteins.
#7
The Endosymbiotic Theory, popularized by Lynn Margulis, posits that mitochondria and chloroplasts originated as free-living prokaryotes engulfed by ancestral eukaryotic host cells.
#8
The Endoplasmic Reticulum is differentiated into Rough ER (studded with ribosomes for protein synthesis) and Smooth ER (lacking ribosomes, synthesizing lipids and steroids while detoxifying drugs).
#9
Camillo Golgi discovered the Golgi apparatus in 1898, which functions in modifying, sorting, and packaging glycoproteins and glycolipids synthesized in the endoplasmic reticulum.
#10
Christian de Duve discovered lysosomes in 1955, membrane-bound vesicles containing acidic hydrolase enzymes active at pH 4.5 to 5.0 for intracellular macromolecular digestion.
#11
Ribosomes are non-membrane-bound ribonucleoprotein complexes composed of ribosomal RNA (rRNA) and proteins, serving as the universal catalytic sites for peptide chain translation.
#12
The eukaryotic cell cycle consists of Interphase—divided into Gap 1 (G1), Synthesis (S, where nuclear DNA replication occurs), and Gap 2 (G2)—followed by the mitotic (M) phase.
#13
During mitotic metaphase, chromosomes align along the equatorial metaphase plate and attach to spindle fibers at their centromeric kinetochores.
#14
Meiosis I separates homologous chromosome pairs, whereas Meiosis II separates sister chromatids, halving the somatic diploid chromosome number (2n) to haploid (n).
#15
Synapsis of homologous chromosomes and formation of the synaptonemal complex occur during the zygotene stage of prophase I, followed by crossing over mediated by the enzyme recombinase in pachytene.
Subject Specialist Commentary
Analytical perspective & practical exam advice from the Master10 academic board
The cell is the basic structural and functional unit of all living organisms. While primitive prokaryotes like bacteria lack a distinct nucleus and membrane-bound organelles, complex eukaryotic cells house specialized compartments to perform distinct biochemical duties. Mitochondria generate cellular fuel known as ATP through cellular respiration, the endoplasmic reticulum manufactures proteins and lipids, and the Golgi apparatus modifies and packages these molecules for transport throughout the cell.
In UPSC Prelims and SSC science papers, cell division stages are frequent question favorites. Pay close attention to the distinction between mitosis and meiosis. Mitosis produces two identical diploid cells for growth and tissue repair, whereas meiosis creates four unique haploid gametes for sexual reproduction. A recurring exam trap asks where genetic crossing over occurs: remember that crossing over happens specifically during the pachytene stage of prophase I, driving evolutionary variation.
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