Cell Organelles (T1)

Vocabulary-style flashcards covering key terms and definitions from the lecture notes on cellular organelles and the cytoskeleton.

Cytoskeleton

Network of protein filaments (actin, intermediate filaments, microtubules) that gives the cell shape, support, and tracks for movement.

Microtubule

Hollow tubule of tubulin (~25 nm) that provides structural support, serves as tracks for motor proteins, and forms the mitotic spindle and cilia/flagella.

Microfilament (Actin filament)

7 nm filament formed from actin; involved in cell shape, movement, and microvilli core; polymerizes dynamically.

Intermediate filament

8–12 nm filaments of various proteins; provide mechanical strength and nuclear/cell integrity.

Microvilli

Membrane protrusions supported by an actin core that increase cell surface area.

Pericentriolar material

Protein matrix around centrioles in the centrosome; nucleates microtubules via gamma-tubulin.

Centrioles

9 triplets of microtubules; organize the centrosome and form basal bodies for cilia/flagella.

Centrosome

Microtubule organizing center; contains a pair of centrioles and gamma-tubulin ring complexes for nucleation.

Plasma membrane

Phospholipid bilayer enclosing the cell; controls movement of substances in and out.

Secretory vesicle

Vesicle that transports proteins from the Golgi to the plasma membrane or extracellular space.

Lysosome

Membrane-bound organelle with acidic hydrolases for intracellular digestion.

Smooth endoplasmic reticulum

ER region without ribosomes; lipid synthesis, detoxification, and calcium storage.

Rough endoplasmic reticulum

ER region studded with ribosomes; synthesizes proteins destined for secretion, lysosomes, or membranes.

Peroxisome

Small organelle for fatty acid oxidation and detoxification; contains catalase.

Mitochondrion

ATP-producing organelle with double membranes; site of TCA cycle and oxidative phosphorylation.

Flagellum

Motile cellular appendage built on a microtubule core; enables cell movement.

Cilium

Hair-like projection, often motile or sensory, with a 9+2 (motile) or 9+0 (primary) arrangement.

Proteasome

ATP-dependent proteolytic complex that degrades ubiquitinated proteins.

Free ribosomes

Ribosomes in the cytosol that synthesize cytosolic, nuclear, mitochondrial, and peroxisomal proteins.

Nuclear envelope

Double membrane surrounding the nucleus; outer membrane continuous with the ER; contains pores.

Nuclear lamina

Meshwork of lamin intermediate filaments underlying the inner nuclear membrane; supports the envelope.

Nuclear pores

Protein channels spanning the nuclear envelope that regulate nucleo-cytoplasmic transport.

Nucleolus

Site of ribosome biogenesis; rRNA transcription and ribosomal subunit assembly.

Chromatin

DNA–protein complex; exists as euchromatin (less condensed) or heterochromatin (condensed).

Euchromatin

Less condensed chromatin that is transcriptionally active.

Heterochromatin

Condensed chromatin that is largely transcriptionally inactive.

Nucleosome

DNA wrapped around a histone octamer; basic unit of chromatin; “beads on a string.”

Centromere

Constricted region of each chromosome holding sister chromatids together; site of kinetochore formation.

Telomere

Repeated chromosome-end sequences that protect ends and influence replication.

Replication origin

Starting point where DNA replication begins.

Ribosome

Ribonucleoprotein complex that catalyzes protein synthesis; two subunits in eukaryotes.

Membrane-bound ribosomes

Ribosomes attached to the rough ER; synthesize secretory, lysosomal, and membrane proteins.

Golgi apparatus

Stack of flattened cisternae that modifies, sorts, and packages proteins for secretion or delivery.

COP-I coated vesicles

Vesicles mediating retrograde transport from CGN to the rough ER.

COP-II coated vesicles

Vesicles mediating anterograde transport from the ER to the CGN.

ER signal sequence

Amino-terminal sequence that directs ribosome to the ER for secretion or membrane insertion.

Lysosomal enzymes

Acid hydrolases that function optimally at low pH inside lysosomes.

Mannose-6-phosphate (M6P)

Tag added in the Golgi that targets hydrolases to lysosomes via receptor recognition.

Lysosomal storage diseases

Disorders from defective lysosomal enzymes causing substrate accumulation and cellular dysfunction.

Tay-Sachs disease

LSD caused by HEXA deficiency; GM2 ganglioside accumulation leading to neurodegeneration.

Ubiquitin

Small protein that tags substrates for degradation by the proteasome.

Proteasome inhibitors

Drugs that block proteasome activity; used in cancer therapy to accumulate damaged proteins.

Autophagy

Lysosome-dependent degradation and recycling of cellular components.

Endocytosis

Process by which cells take up extracellular material in vesicles.

Phagocytosis

Engulfment of large particles (bacteria) by phagocytes.

Pinocytosis

Non-specific uptake of extracellular fluid via vesicles.

Lipofuscin

Wear-and-tear pigment; brownish-gold accumulates in aging/non-dividing cells.

Glycogen

Stored form of glucose; granules in cytoplasm; energy reserve.

Lipid droplets

Non-membrane-bound organelles storing triglycerides for energy and membranes.

Mitochondrial DNA

Circular DNA in mitochondria; maternally inherited; encodes a subset of RNAs/enzymes.

Cytochrome c

Intermembrane space protein involved in intrinsic apoptosis pathway.

Mitochondrial diseases

Disorders from mutations in mitochondrial genes impairing ATP production.

Primary cilium

Non-motile 9+0 cilium acting as a sensory antenna; develops from centriole.

Basal body

Centriole-derived structure that anchors cilia/flagella to the cell.

Dynein

Motor protein moving toward the minus end of microtubules; key in cilia/flagella motion.

Kinesin

Motor protein moving toward the plus end of microtubules; transports organelles/vesicles.

Cilia/axoneme 9+2

Motile cilia with microtubule core arranged as 9+2; dynein arms drive bending movement.

Rho family proteins

Monomeric GTPases (Rho, Rac, Cdc42) regulating actin dynamics and cell motility.

Actin polymerization

Addition of actin monomers at the leading edge driving membrane protrusions.

ARP complex

Actin-related protein complex initiating branching of actin filaments at the leading edge.

Filopodia

Thin, finger-like actin-rich protrusions involved in sensing the environment.

Lamellipodia

Sheet-like actin-rich protrusions that drive cell migration.

Pseudopodia

3D cellular extensions used for movement and feeding in some cells.

Focal adhesions

Sites where the actin cytoskeleton connects to the ECM via integrins.

Treadmilling

Dynamic cycle of actin growth at the front and disassembly at the rear of a filament.

Beaded filaments

Eye lens-specific intermediate filaments that contribute to lens structure.

Lamin A/B

Nuclear lamins forming the nuclear lamina; scaffold for envelope and chromatin; disassemble during mitosis.

Golgi CGN/TGN

Cis Golgi Network (entry) and Trans Golgi Network (exit) within the Golgi apparatus.

Neutrophil migration

Process of rolling, activation, adhesion, and diapedesis to reach sites of inflammation.

Chemotaxis

Directed cell movement along a chemical gradient toward attractants.

Microtubule poisons

Agents that disrupt microtubule dynamics, arresting cells in mitosis.

Colchicine

Mitotic spindle disruptor that prevents tubulin polymerization.

Taxol

Stabilizes microtubules, blocking disassembly and mitosis, used in cancer therapy.

Dexterity of motor proteins

Dynein moves toward the minus end; kinesin moves toward the plus end of microtubules.