Biology 1090: Cell Structure, Organelles, and Cellular Dynamics

Comprehensive vocabulary flashcards reviewing cell biology, membrane dynamics, organelle function, vesicular trafficking, and cytoskeletal structures based on Biology 1090 lecture notes.

Central Dogma of Biology

The core cellular principle describing the directed flow of genetic information: DNA is transcribed into RNA, which is subsequently translated into functional proteins.

Primordial Soup Hypothesis

The hypothesis proposed by Oparin and Haldane stating that more complex chemical reactions were favored under early Earth conditions, allowing core molecules combined with energy to generate simple organic compounds such as amino acids.

Cell Theory

The fundamental doctrine founded on observations by Robert Hooke and later researchers, stating that all living organisms are composed of one or more cells, the cell is the most basic unit of life, and all cells arise from pre-existing cells.

Plasmid

A circular DNA molecule found in prokaryotic cells such as bacteria, which lack membrane-bound organelles and true linear chromosomes.

Heterochromatin

The darker, densely packed region of the nucleus containing DNA that is transcriptionally inactive and not required for immediate cellular function.

Euchromatin

The lighter, loosely packed region of the nucleus containing transcriptionally active DNA that the cell needs to function.

Virion

An inanimate viral particle existing outside the host cell, composed of a small amount of DNA or RNA enclosed within a protective protein capsule called a capsid.

Baltimore Classification

A virus categorization system that groups viruses based on their genome type (RNA versus DNA) and their specific method of replication.

Lytic Infection

A viral infection pathway where the rapid production and assembly of viral particles ruptures and kills the host cell to release progeny.

Non-Lytic Infection

A viral infection pathway (integrative or lysogenic) in which viral DNA integrates into the host genome, permitting host survival while continuously releasing viral particles and establishing a persistent infection.

Fluid Mosaic Model

A model of biological membranes describing a two-dimensional liquid bilayer of dynamic lipids interspersed with diverse proteins, carbohydrates, and cholesterol that restricts diffusion while permitting lateral movement.

Flippase

A membrane-associated enzyme that catalyzes the transbilayer movement of specific phospholipids from one leaflet of the lipid bilayer to the other.

Integral Membrane Proteins

Proteins integrated directly into the hydrophobic core of the lipid bilayer, typically spanning it via hydrophobic $\alpha$-helical domains, making them the most difficult proteins to dissociate from the membrane.

Peripheral Membrane Proteins

Non-embedded membrane proteins that associate non-covalently with integral proteins or membrane phospholipid headgroups, making them the easiest proteins to detach.

Antiporter

A secondary active transport carrier protein that harnesses the concentration gradient of one molecule to drive the movement of a second molecule in the opposite direction across the membrane.

Adenylyl Cyclase

An effector membrane enzyme activated by a G protein subunit that catalyzes the conversion of ATP into cyclic AMP ($\text{cAMP}$), which functions as an intracellular second messenger.

Extracellular Matrix (ECM)

An organized network of macromolecules (including collagen, laminin, fibronectin, and proteoglycans) secreted by cells that mediates adhesion, provides mechanical support, and regulates cell-to-cell communication.

Endosymbiotic Theory

The evolutionary framework proposing that double-membraned eukaryotic organelles (mitochondria and chloroplasts) evolved from symbiotic prokaryotes that were engulfed by ancestral host cells.

Cardiolipin

A specialized, bacterial-like phospholipid present in high amounts within the inner mitochondrial membrane that is essential for the proper enzymatic function of respiratory chain complexes.

Bax

A pro-apoptotic protein located in the outer mitochondrial membrane that oligomerizes to form pores, depolarizing the membrane and allowing cytochrome c to leak into the cytoplasm.

Caspases

Executioner protease enzymes activated during apoptosis that dismantle cellular architecture by degrading cytoskeletal elements, cell adhesion complexes, and the nuclear envelope.

COPI

A coatomer vesicle protein complex that coats vesicles mediating retrograde transport, moving cellular membranes and cargo backward from the Golgi apparatus to the endoplasmic reticulum.

COPII

A coatomer vesicle protein complex assembled with Sar1, Sec23, and Sec24 that coats vesicles mediating anterograde transport, moving cargo forward from the rough ER to the Golgi apparatus.

Co-Translational Protein Translocation

A mechanism where a signal recognition particle (SRP) binds an N-terminal signal sequence on a nascent polypeptide, halts translation, and docks the ribosome to the ER translocon, permitting synthesis directly into the ER lumen.

Translocon

A protein-conducting channel located in the ER membrane featuring an aqueous pore, a central plug, and a lateral gate that permits hydrophobic $\alpha$-helices to partition directly into the lipid bilayer.

Acid Hydrolases

Hydrolytic enzymes sequestered within lysosomes that require an acidic environment of $\text{pH } 4.6$ to adopt their active conformation and digest macromolecules.

Autophagy

A regulated catabolic process wherein the cell encapsulates worn-out organelles or internal components within an ER-derived autophagosome, which subsequently fuses with a lysosome for degradation.

Tonoplast

The semipermeable vacuolar membrane in plant cells that actively transports ions and solutes, mediates intracellular digestion at $\text{pH } 5$, and maintains turgor pressure for mechanical support.

Dynamic Instability

The rapid turnover behavior of microtubules characterized by alternating periods of polymerization and rapid depolarization/shrinkage (known as catastrophe) at the plus ($+$) end.

Kinesin

An ATP-dependent motor protein that generates mechanical force to transport cargo along microtubules toward the plus ($+$) end, directed away from the nucleus toward the cell periphery.

Dynein

An ATP-dependent motor protein that walks along microtubules toward the minus ($-$) end, transporting cargo inward toward the microtubule organizing center.

Arp2/3 Complex

A major actin-nucleating complex that binds along existing microfilaments in response to nucleation promoting factors (NPF) to initiate actin filament branching for directed cell motility.

Nuclear Pore Complex (NPC)

A large macromolecular gateway composed of nucleoporins exhibiting octagonal symmetry that spans the inner and outer nuclear membranes to regulate nucleocytoplasmic transport.

Nuclear Localization Signal (NLS)

A specific sequence of positively charged amino acids on a nuclear-destined cargo protein that is recognized and bound by importin to facilitate translocation into the nucleus.

Nucleolus

The largest subnuclear compartment in eukaryotic cells, functioning as the primary site for ribosomal RNA transcription, processing, and ribosome subunit assembly.