Biologie Cellulaire 1: Comprehensive Course Flashcards

Comprehensive vocabulary flashcards covering the cell cycle, mitosis, meiosis, prokaryotic and eukaryotic cellular organization, intercellular communication, the cytoskeleton, and nuclear structure from the Biologie Cellulaire 1 course.

Cell Theory

The foundational biological principle formulated between 1838 and 1861 by Schleiden, Schwann, Virchow, and Pasteur stating that the cell is the structural, functional, and reproductive unit of all living organisms, delimited by a plasma membrane, containing genetic information as DNA, and originating exclusively from pre-existing cells through division.

Peptidoglycan

A bacterial cell wall polymer composed of alternating linear chains of N-acetylglucosamine (NAG) and N-acetylmuramic acid (ANAM) connected by $\beta(1\rightarrow 4)$ glycosidic bonds and cross-linked by species-specific peptide side chains.

Gram Staining

A differential staining procedure developed by Hans Christian Gram (1853–1938) that classifies bacteria into Gram-positive (purple) and Gram-negative (pink) based on wall structure, using heat fixation, gentian violet, Lugol stabilization, alcohol/acetone decolorization, and safranin/fuchsine counterstaining.

Archaeal Cell Membrane

A unique membrane structure characterized by branched phytanyl sidechains linked to glycerol by ether bonds (rather than ester bonds), often organizing into a rigid lipid monolayer suited to extreme environments.

Lynn Margulis

The biologist who formulated the endosymbiotic theory (1960–1980), positing that eukaryotic plastids and mitochondria originated from ancestral archaea engulfing aerobic and photosynthetic bacteria.

Tonoplast

The single limiting membrane surrounding the central vacuole in plant cells that regulates turgor pressure, stores metabolites, and maintains acidic lytic compartments analogous to animal lysosomes.

Plasmodesma

A microscopic channel traversing the pectin-cellulosic cell walls of plant cells that provides membrane, endoplasmic reticulum, and cytoplasmic continuity between adjacent cells.

Glyoxysome

A specialized peroxisome found in plant seeds that converts stored lipid reserves into carbohydrates during seed germination.

Juxtacrine Signaling

A contact-dependent mode of cell communication occurring between directly adjacent cells via membrane-bound ligands, adhesion molecules, or gap junctions.

Protein Kinase

An enzyme that transfers a phosphate group from $\text{ATP}$ to accessible hydroxyl groups of serine, threonine, or tyrosine residues on target proteins to modulate their activity.

G-Actin

Globular monomeric actin with a molecular weight of $42\text{ kDa}$ that possesses an ATPase function and always binds $\text{ATP}$ prior to filament incorporation.

F-Actin

Filamentous actin consisting of two parallel protofilaments arranged into a polar, right-handed double helix with an outer diameter of $7\text{ nm}$.

Actin Treadmilling

A dynamic steady-state behavior where G-actin-ATP monomers assemble rapidly at the barbed ($+\text{ end}$) while G-actin-ADP monomers dissociate from the pointed ($-\text{ end}$), driven by delayed $\text{ATP}$ hydrolysis.

Profilin

An actin-regulatory protein that stimulates the exchange of $\text{ADP}$ for $\text{ATP}$ on free G-actin monomers, thereby promoting polymerization at the barbed ($+\text{ end}$).

Cofilin

An actin-binding protein that preferentially binds to F-actin-ADP, induces mechanical twisting of the filament, and accelerates local severing and depolymerization.

Fimbrin

An actin-bundling protein that cross-links microfilaments into tight, parallel, non-contractile bundles with an inter-filament spacing of $20\text{ nm}$, typical of filopodia and microvilli.

\alpha-Actinin

An actin-cross-linking protein that organizes microfilaments into loose, antiparallel contractile bundles spaced $40\text{ nm}$ apart, accommodating myosins in stress fibers and adherens junctions.

Filamin

A flexible V-shaped actin-crosslinking homodimer that binds microfilaments at wide angles to form a three-dimensional, viscoelastic gel network in the cell cortex and lamellipodia.

Microtubule

A hollow cylindrical cytoskeletal fiber with an outer diameter of $25\text{ nm}$ composed of 10 to 15 (typically 13) parallel protofilaments made of alternating $\alpha$- and $\beta$-tubulin heterodimers.

Kinesin

A dimeric motor protein with ATPase activity that hydrolyzes $\text{ATP}$ to transport vesicles and organelles processively toward the plus end ($+\text{ end}$) of microtubules in anterograde transport.

Dynein

A minus-end-directed ($-\text{ end}$) microtubule motor protein complex that couples $\text{ATP}$ hydrolysis to retrograde intracellular transport toward the centrosome.

Taxanes

A class of microtubule-targeting antineoplastic agents that bind and stabilize microtubules, stimulate tubulin polymerization, and inhibit GTP-to-GDP conversion.

Intermediate Filaments

Apolar, tough, unbranched cytoskeletal fibers measuring $10\text{ nm}$ in diameter assembled from staggered antiparallel tetramers of fibrous proteins without consuming $\text{ATP}$ or $\text{GTP}$.

Desmosome

A rivet-like cell-cell anchoring junction in epithelia connecting intermediate keratin filaments between adjacent cells via cadherins and dense plaque proteins such as desmoplakin.

Epidermolysis Bullosa Simplex

A genetic skin blistering disease affecting approximately $1/50{,}000$ individuals caused by mutations in basal epidermal keratin genes that compromise the mechanical integrity of hemidesmosomes.

Syncytium

A multinucleated mass of cytoplasm formed by the fusion of individual mononucleated cells, observed in skeletal striated muscle fibers, osteoclasts, and placental syncytiotrophoblasts.

Nuclear Lamina

A dense fibrous network of lamins A, B, and C measuring $30-100\text{ nm}$ in thickness lining the inner nuclear membrane that stabilizes the nuclear envelope and anchors heterochromatin.

Nuclear Pore Complex (NPC)

An eight-fold symmetric multiprotein structure of approximately $125\text{ MDa}$ composed of 30 to 50 distinct nucleoporins (Nups) that spans both membranes of the nuclear envelope.

Central Transporter (NPC)

The central aqueous channel of the nuclear pore complex that expands from $9\text{ nm}$ up to $40\text{ nm}$ to mediate energy-dependent, active receptor-mediated transport of macromolecular cargoes larger than $40\text{ kDa}$.

Ran GTPase

A small regulatory GTPase whose asymmetrical nucleocytoplasmic gradient (Ran-GTP in the nucleoplasm maintained by GEF, and Ran-GDP in the cytosol maintained by GAP) drives directional karyopherin transport.

Nucleosome

The elementary structural repeating unit of chromatin comprising an octamer core of basic histones ($2\times\text{H2A}$, $2\times\text{H2B}$, $2\times\text{H3}$, $2\times\text{H4}$) wrapped by $146\text{ bp}$ of DNA in 1.65 turns.

Histone H1

A linker histone protein residing outside the nucleosomal octamer core that binds internucleosomal spacer DNA to facilitate compaction of the $11\text{ nm}$ fiber into a $30\text{ nm}$ chromatin fiber.

Constitutive Heterochromatin

A permanently compacted, transcriptionally inert form of chromatin devoid of genes, characteristically enriched at eukaryotic centromeres and telomeres.

Nucleolus

A dense, non-membrane-bound subnuclear compartment composed of $5\%$ DNA, $10\%$ rRNA, and $85\%$ proteins responsible for the transcription of pre-rRNA and the assembly of ribosomal subunits.

Nucleolar Organizer Region (NOR)

Chromosomal loops containing tandem repeats of rRNA genes located on the short arms of human acrocentric chromosomes 13, 14, 15, 21, and 22.

S Phase

The synthetic phase of the cell cycle lasting $6-8\text{ hours}$ in human cells during which chromosomal DNA is replicated bidirectionally at $500-1000\text{ nt/s}$ and centriole duplication commences.

Centrosome

The principal animal microtubule-organizing center (MTOC) consisting of two perpendicular centrioles surrounded by pericentriolar material, which duplicates semi-conservatively during S and $G_2$ phases.

Cohesin

A ring-shaped protein complex loaded onto chromatin during telophase/$G_1$ that establishes physical cohesion between replicated sister chromatids during S phase until anaphase cleavage.

Kinetochore

A specialized multiprotein disc structure assembled on the centromeric region of each chromatid that anchors 1 to 40 spindle microtubules to coordinate chromosome segregation.

Separase

A protease that is activated at the metaphase-to-anaphase transition to cleave the cohesin rings, allowing sister chromatids to disjoin and migrate toward opposite spindle poles at $1\,\mu\text{m/min}$.

Phragmoplast

A plant-specific cytokinesis structure composed of microtubules and Golgi-derived vesicles that builds the new cell plate from the center of the dividing cell outward to form the middle lamella.

Synaptonemal Complex

A tripartite proteinaceous ladder composed of lateral and transverse elements that stabilizes the synapsis of homologous chromosomes during prophase I of meiosis.

Chiasma

The physical X-shaped cytological manifestation of crossing-over where non-sister chromatids of homologous chromosomes remain connected following reciprocal DNA exchange in meiotic prophase I.

Reductional Division

The first meiotic division (Meiosis I) during which paired homologous chromosomes separate, reducing the chromosome complement from diploid ($2n$) to haploid ($n$).

Equational Division

The second meiotic division (Meiosis II), mechanistically similar to mitosis, wherein sister chromatids of haploid chromosomes are separated into four genetically distinct gametes.