Introduction to Cell Biology, Membrane Transport, Signaling, and Molecular Genetics

Comprehensive vocabulary flashcards generated from lecture notes covering cellular anatomy, membrane transport mechanisms, cell signaling pathways, DNA replication, and eukaryotic transcription.

Nucleus

The organelle that houses the cell's genome, regulates cell growth, intermediary metabolism, protein synthesis, and reproduction by controlling gene expression.

Nucleolus

A distinct structure within the cell nucleus where ribosomes are assembled.

Cisplatin

A chemotherapy drug that crosslinks DNA to prevent it from replicating or transcribing, inducing cell death in rapidly dividing cancer cells.

Rough Endoplasmic Reticulum

A network of sac-like membrane structures studded with ribosomes on its outer surface that serves as the site for translating mRNA into proteins.

Smooth Endoplasmic Reticulum

A region of the endoplasmic reticulum that lacks ribosomes and synthesizes lipids and carbohydrates required by the cell.

Human Ribosome Subunits

Complexes of proteins composed of 60S and 40S subunits that work together to synthesize proteins.

Bacterial Ribosome Subunits

Complexes composed of 50S and 30S subunits that perform protein synthesis in bacteria.

Aminoglycosides

A class of antibiotics, including Streptomycin and Gentamicin, that target the bacterial 30S ribosome subunit to interfere with mRNA reading.

Tetracyclines

A class of antibiotics, represented by Doxycycline, that target the bacterial 30S ribosome subunit to prevent tRNA from binding to the ribosome.

Macrolides

A class of antibiotics, including Erythromycin and Azithromycin, that bind the bacterial 50S ribosome subunit to prevent the growth of the protein chain.

Oxazolidinones

A class of antibiotics, represented by Linezolid, that bind the bacterial 50S ribosome subunit to inhibit the initiation of protein synthesis.

Chloramphenicol

An antibiotic that binds to the bacterial 50S ribosome subunit to inhibit peptide bond formation during protein synthesis.

Mitochondria

Organelles responsible for generating the bulk of cellular ATP via the citric acid cycle and oxidative phosphorylation, and capable of triggering apoptosis.

Microtubules

Cylindrical tubes composed of tubulin dimers that maintain cell shape, facilitate movement, form the mitotic spindle, and act as a highway system for protein transport.

Microfilaments

Cytoskeletal elements consisting of intertwined strands of actin monomers located primarily at the cell periphery that enable movement and muscle contraction.

Intermediate Filaments

Stable, rope-like cytoskeletal structures made of proteins like keratin, vimentin, and desmin that provide mechanical strength and anchor organelles.

Microtubule Destabilizing Agents (MDAs)

Cancer therapeutics that bind tubulin to inhibit microtubule assembly, preventing proper cell division and inducing apoptosis.

Microtubule Stabilizing Agents (MSAs)

Cancer therapeutics that bind tubulin to inhibit microtubule disassembly, halting chromosome separation during division.

Passive Diffusion

The unassisted movement of small, nonpolar molecules across a cell membrane down their concentration gradient without energy consumption.

Facilitated Diffusion

The passive movement of polar or charged molecules down their concentration gradient using channel or carrier membrane proteins without energy input.

Voltage-Gated Sodium (Na+) Channels

Transmembrane channels in axon membranes that open when potential reaches -55 mV, allow Na+ influx, close at +30 mV, and temporarily inactivate during repolarization.

Carrier Proteins

Transmembrane transport proteins that bind specific target molecules and undergo conformational changes to move them across the membrane down a concentration gradient.

Fick's First Law

A transport law stating that the flux or rate of particle movement across an area is proportional to the negative gradient of its concentration.

Primary Active Transport

A membrane transport process that directly utilizes chemical energy, such as ATP hydrolysis, to move solutes against their concentration gradient.

Sodium-Potassium (Na+/K+) Pump

An electrogenic primary active transport pump that consumes ATP to export three Na+ ions and import two K+ ions per cycle, maintaining resting potential.

Secondary Active Transport

A cotransport mechanism that utilizes the potential energy stored in an electrochemical gradient, created by primary active transport, to move molecules against their gradient.

Symporter

A secondary active transport protein that moves two different substances across the cell membrane in the same direction.

Antiporter

A secondary active transport protein that moves two different substances across the cell membrane in opposite directions.

Phagocytosis

A specialized form of endocytosis in which a cell engulfs large particles, such as cell debris or pathogens, inside a membrane-bound vesicle.

Pinocytosis

A non-specific, continuous form of endocytosis where the cell takes in small droplets of extracellular fluid to sample nutrients.

Receptor-Mediated Endocytosis

A selective form of endocytosis triggered when specific extracellular ligands bind to cell surface receptors.

Constitutive Exocytosis

An ongoing exocytosis pathway in nearly all cells that continuously delivers new proteins and lipids from the Golgi complex to the cell membrane.

Regulated Exocytosis

A specialized exocytosis pathway that secretes specific substances, such as hormones or neurotransmitters, only in response to an extracellular signal.

Membrane Receptors

Integral membrane proteins that bind extracellular hydrophilic ligands and initiate intracellular signaling without requiring the ligand to cross the cell barrier.

Soluble (Intracellular) Receptors

Receptors located in the cytoplasm or nucleus that bind hydrophobic messengers, acting directly as transcription factors to regulate gene expression.

G-Protein Coupled Receptors (GPCRs)

A class of membrane receptors containing seven transmembrane alpha-helices that activate an intracellular G-protein upon ligand binding.

Receptor Tyrosine Kinases (RTKs)

Enzyme-linked membrane receptors that dimerize and autophosphorylate upon ligand binding, triggering downstream intracellular protein phosphorylation cascades.

NF-κB

A transcription factor complex activated downstream of TNF-α receptors that regulates genes responsible for immunity, inflammation, and cell survival.

Epinephrine Signaling Pathway

A metabolic cascade where epinephrine binds adrenergic GPCRs to elevate cAMP, activating PKA to stimulate glycogen breakdown and inhibit glycogen synthesis.

Nuclear Envelope

A double-membrane barrier enclosing the nucleus whose outer membrane is contiguous with the endoplasmic reticulum.

Nuclear Pores

Protein complexes spanning the nuclear envelope that form aqueous channels controlling molecule exchange between the nucleus and cytoplasm.

Chromatin

The unwound, relaxed structure of DNA wrapped around histone proteins, present throughout interphase for transcription and replication.

Euchromatin

A loosely packed form of chromatin that comprises most of the genome and remains accessible to replication and transcription machinery.

Heterochromatin

A highly condensed, tightly packed form of chromatin that is inaccessible to enzymes involved in gene expression and replication.

Purines

Nitrogenous bases characterized by a double-ring carbon-nitrogen structure, comprising Adenine (A) and Guanine (G).

Pyrimidines

Nitrogenous bases characterized by a single-ring carbon-nitrogen structure, comprising Cytosine (C), Thymine (T), and Uracil (U).

Origins of Replication (ORI)

Adenine-Thymine (A-T) rich regions on eukaryotic DNA where replication begins due to lower bonding energy required to unwind the strands.

DNA Helicase

The enzyme responsible for unwinding the DNA double helix during replication, creating replication bubbles and forks.

Single-Strand Binding Proteins (SSBs)

Proteins that bind to separated single stranded DNA at the replication fork to prevent complementary bases from rejoining.

Topoisomerase

An enzyme that prevents excessive DNA supercoiling ahead of the replication fork by introducing and resealing temporary nicks in the helix.

RNA Primase

An enzyme that synthesizes short RNA primers onto exposed single stranded DNA to provide initiation points for DNA polymerase.

Leading Strand

The newly synthesized DNA strand built continuously in the 5' to 3' direction toward the advancing replication fork.

Lagging Strand

The template strand synthesized discontinuously away from the replication fork as short 5' to 3' segments called Okazaki fragments.

Okazaki Fragments

Short segments of DNA synthesized on the lagging strand, each initiated by an RNA primer during DNA replication.

DNA Polymerase Alpha (Pol α)

A multiprotein subunit of DNA polymerase that adds a short chain of DNA nucleotides directly to the RNA primers.

DNA Polymerase Epsilon (Pol ε)

The primary DNA polymerase subunit responsible for leading-strand DNA synthesis and repair.

DNA Polymerase Delta (Pol δ)

The primary DNA polymerase subunit responsible for lagging-strand DNA synthesis and repair.

DNA Ligase

An enzyme that connects Okazaki fragments into a continuous strand by forming phosphodiester bonds in the sugar-phosphate backbone.

Central Dogma of Biology

The principle describing the flow of genetic information from DNA to RNA via transcription, and from RNA to protein via translation.

Constitutive Transcription

The continuous transcription of essential housekeeping genes required for constant cell maintenance, such as cytoskeletal or metabolic genes.

Inducible Transcription

Gene transcription that is activated only in response to specific physiological or environmental signals, such as stress or hormones.

Promoter

A regulatory DNA region containing a TATA box located upstream of a gene that serves as the binding site for RNA polymerase II and transcription factors.

7-Methylguanosine Cap

A modified guanine nucleotide added to the 5' end of pre-mRNA to enhance stability, facilitate translation initiation, and assist nuclear export.

Poly(A) Tail

A chain of 100-200 adenine nucleotides added to the 3' end of pre-mRNA by poly(A) polymerase to protect the transcript from degradation.

Spliceosome

A large protein-RNA complex that recognizes consensus junction sequences on pre-mRNA to remove introns and join exons together.

Introns

Non-coding RNA sequences removed from pre-mRNA during splicing that are not translated into the final protein.

Exons

Coding RNA sequences that remain within mature mRNA after splicing and are translated into an amino acid sequence.

Bcl-xL

An anti-apoptotic splice variant of the Bcl-x gene that promotes cell survival and is frequently upregulated in cancer cells.

Bcl-xS

A pro-apoptotic splice variant of the Bcl-x gene that promotes programmed cell death.

REST (RE1-Silencing Transcription Factor)

A repressor transcription factor that binds RE1 elements to block the transcription of neural genes in non-neuronal cells and stem cells.

p53

A tumor suppressor transcription factor that binds enhancer elements to activate genes for cell cycle arrest, DNA repair, and apoptosis.