Cell Biology, Cell Cycle, and Transport Mechanisms

Vocabulary flashcards covering cell structure, organelles, cell cycle, chromosomal mutations, transport mechanisms, cell surface modifications, and cell signaling.

Cell Theory

The principle stating that all living organisms are composed of one or more cells, the cell is the basic structural and functional unit of life, and all cells arise from pre-existing cells.

Prokaryotes

Organisms, such as Bacteria and Archaea, that lack a membrane-bound nucleus and membrane-bound organelles.

Eukaryotes

Organisms, including Protists, Fungi, Plants, and Animals, that possess a true nucleus enclosing genetic material and a compartmentalized organelle system.

Nucleus

Subcellular organelle that houses chromatin/DNA and directs protein synthesis.

Ribosomes

Non-membrane-bound cellular structures that serve as the sites of protein synthesis.

Rough Endoplasmic Reticulum

Organelle involved in protein synthesis via studded ribosomes.

Smooth Endoplasmic Reticulum

Organelle involved in lipid synthesis, carbohydrate metabolism, and drug/toxin detoxification.

Golgi Apparatus

Organelle that modifies, sorts, and packages proteins and lipids into vesicles for transport.

Lysosomes

Vesicles containing hydrolytic enzymes used for intracellular digestion and recycling of cellular debris.

Peroxisomes

Microbodies that break down fatty acids and neutralize dangerous hydrogen peroxide ($\text{H}_2\text{O}_2$) into water and oxygen via catalase.

Central Vacuole

Large vacuole in plant cells that stores water, nutrients, pigments, and waste, and maintains turgor pressure.

Mitochondria

Sites of aerobic respiration and ATP generation enclosed by two membranes, evolved from ancient proteobacteria via endosymbiosis (Ivan Wallin, 1992).

Chloroplasts

Sites of photosynthesis in plants and algae containing thylakoid membranes stacked into grana in a fluid stroma, evolved from cyanobacteria (Andreas Schimper, 1883).

Chromoplasts

Plastids that synthesize and store non-chlorophyll pigments.

Amyloplasts

Plastids that synthesize and store starch grains.

Actin Filaments (Microfilaments)

Cytoskeleton elements composed of two intertwined strands of actin responsible for cellular movements including muscle contraction, crawling, pseudopodia, and cleavage furrow formation.

Microtubules

Cytoskeleton structures made of hollow cylinders of tubulin that organize cytoplasm, form spindle fibers during division, and move organelles/vesicles.

Intermediate Filaments

Fibrous cytoskeleton proteins providing high mechanical strength and structural stability to the cell shape.

Binary Fission

Prokaryotic clonal cell division yielding two identical daughter cells.

G1 Phase

First phase of eukaryotic interphase characterized by active growth, organelle duplication, and metabolic function.

S Phase

Eukaryotic interphase stage during which complete replication of genomic DNA (chromosome duplication) occurs.

G2 Phase

Eukaryotic interphase stage involving synthesis of division-specific proteins and final preparation for mitosis.

Mitosis

Somatic cell division producing 2 identical diploid ($2n$) daughter cells through Prophase, Metaphase, Anaphase, Telophase, and Cytokinesis.

Meiosis

Germ cell division producing 4 genetically distinct haploid ($n$) gametes through two successive rounds of division featuring crossing over and independent assortment.

Proto-Oncogenes

Normal cellular genes that promote cell division, which become hyperactive oncogenes requiring only a single mutated allele (gain-of-function) to promote unregulated division.

Tumor-Suppressor Genes

Normal cellular genes that inhibit division or repair DNA, requiring both alleles to lose function (loss-of-function) to promote cancer.

p53 Gene

Known as the Guardian of the Genome, it operates at the G1/S checkpoint to promote DNA repair or trigger programmed cell death (apoptosis) if damage is unfixable.

Euploidy

The normal, correct chromosome number for a species.

Aneuploidy

An abnormal chromosome count resulting from nondisjunction during Meiosis I or II.

Nondisjunction

The failure of homologous chromosomes or sister chromatids to separate properly during Meiosis I or II.

Karyotype

A visual display used to observe chromosomal variations and numbers.

Turner Syndrome (XO)

A monosomy ($2n - 1$) condition in females with a single X chromosome, characterized by short stature, broad chest with widely spaced nipples, webbed neck, and undeveloped ovaries.

Down Syndrome (Trisomy 21)

The most common viable autosomal trisomy ($2n + 1$) in humans, characterized by short stature, eyelid folds, flat facial profile, stubby fingers, and a wide gap between the first and second toes.

Fluid-Mosaic Model

Plasma membrane model describing a phospholipid bilayer with hydrophilic heads and hydrophobic tails, embedded with cholesterol, glycoproteins, glycolipids, and proteins.

Extracellular Matrix (ECM)

Meshwork of collagen, elastin, and fibronectin embedded in proteoglycans that supports animal cell tissue structure and signaling.

Tight Junctions

Impermeable barriers that rivet adjacent cell membranes together to prevent leakage.

Desmosomes (Adhesion Junctions)

Structures that mechanically attach cells under heavy stress, such as heart muscle and skin.

Gap Junctions

Protein channels (connexons) allowing direct passage of small ions and molecules between adjacent animal cells for rapid communication.

Plasmodesmata

Membrane-lined channels passing through plant cell walls allowing cytoplasmic exchange between neighboring cells.

Simple Diffusion

Passive movement of solutes down their concentration gradient from high to low concentration without ATP.

Osmosis

Net movement of water across a selectively permeable membrane toward higher solute concentration.

Hypertonic Solution

A solution with a higher solute concentration outside the cell, causing water to exit so animal cells crenate and plant cells undergo plasmolysis.

Hypotonic Solution

A solution with a lower solute concentration outside the cell, causing water to enter so animal cells lyse and plant cells remain turgid.

Isotonic Solution

A solution with an equal solute concentration inside and outside the cell, resulting in no net water movement.

Facilitated Transport

Passive movement of specific molecules down a concentration gradient utilizing channel or carrier proteins without ATP.

Primary Active Transport

Transport mechanism that pumps molecules against their concentration gradient using ATP directly, such as the $\text{Na}^+/\text{K}^+$ pump pushing $3\,\text{Na}^+$ out and $2\,\text{K}^+$ into the cell.

Phagocytosis

A type of endocytosis referred to as cell eating, involving the intake of large solids.

Pinocytosis

A type of endocytosis referred to as cell drinking, involving the intake of fluids and solutes.

Receptor-Mediated Endocytosis

Selective intake of materials via endocytosis using specific receptor proteins.

Signal Transduction

The second step of cell signaling where a signal is relayed through internal chemical cascades, often involving second messengers or phosphorylation cascades.