Cells and Genomes Flashcards

Comprehensive vocabulary flashcards covering the key terms, mechanisms, and structures in cell biology and genomics.

Cell Theory

The biological principle formulated by Matthias Schleiden, Theodor Schwann (1838-39), and Rudolf Virchow (1855) stating that all organisms are composed of one or more cells, the cell is the structural unit of life, and cells arise only by division from preexisting cells.

DNA (Deoxyribonucleic Acid)

A long, unbranched, double-stranded polynucleotide formed by four types of nucleotides (each containing a phosphate, a sugar, and a base) that stores hereditary information.

Templated Polymerization

The process by which cells replicate DNA using a preexisting complementary strand as a template to synthesize a new strand in a semi-conservative manner.

Gene

A DNA segment corresponding to one protein or RNA product, containing coding sequences that specify transcripts and non-coding regions that act as regulatory sequences.

Long Non-coding RNA (lncRNA)

A class of non-coding RNA approximately $1000\text{--}10000$\,nt long with little to no protein-coding potential that functions in gene regulation and chromatin remodeling.

MicroRNA (miRNA)

A small ($18\text{--}25$\,nt) non-coding RNA family in eukaryotes that silences gene expression post-transcriptionally by binding to the 3' untranslated regions of target mRNAs.

Transcription

A form of templated polymerization in which a non-coding strand of DNA serves as a template to produce complementary RNA transcripts.

Messenger RNA (mRNA)

An RNA transcript intermediate that carries genetic code from DNA to guide the synthesis of proteins.

Enzymes

Catalytic proteins that fold into specific conformations to form reactive catalytic sites, accelerating specific chemical reactions in cells.

Organotrophic Organisms

Organisms that obtain free energy by feeding on other living things or the organic chemicals they produce.

Phototrophic Organisms

Organisms that harvest sunlight and convert it into chemical energy usable by cells.

Lithotrophic Organisms

Organisms that capture energy from energy-rich systems of inorganic chemicals in the environment.

Intragenic Mutation

A process of genetic innovation where a DNA sequence is randomly modified by replication errors or other spontaneous alterations.

Gene Duplication

A process generating a pair of identical genes within a single cell, allowing them to diverge independently during evolution.

DNA Segment Shuffling

A genetic modification mechanism where two or more existing genes break and rejoin to produce a hybrid gene.

Horizontal Gene Transfer

The intercellular transfer of a piece of DNA from the genome of one organism or cell into that of another.

Nucleolus

A dense structure inside the cell nucleus that serves as the site of assembly for ribosome subunits.

Nuclear Pore

An opening in the nuclear envelope that serves as a passage for RNA and proteins between the nucleoplasm and cytoplasm.

Endomembrane System

A cellular network of membranes related through direct physical contact or vesicles, dividing the eukaryotic cell into functional compartments.

Rough Endoplasmic Reticulum (RER)

A region of the ER continuous with the outer nuclear membrane that is studded with ribosomes and functions in protein synthesis.

Smooth Endoplasmic Reticulum (SER)

A region of the ER lacking ribosomes that functions in lipid synthesis, sugar processing, drug detoxification, and calcium storage.

Golgi Bodies (Dictyosomes)

Flattened stacks of sac-like membrane cisternae that sort, modify, package, and secrete cellular products to their destinations.

Lysosomes

Membrane-bound organelles containing hydrolytic digestive enzymes that break down macromolecules, cellular debris, old organelles, and foreign substances.

Peroxisomes

Organelles containing peroxidases and catalases that detoxify toxins and free radicals, break down fats, and produce bile salts in liver cells.

Central Vacuole

A large single-membrane organelle in plant cells enclosed by the tonoplast that stores water, ergastic substances, and inclusions.

Mitochondrion

A double-membraned organelle containing mtDNA that generates ATP via cellular respiration and has an inner membrane folded into cristae.

Chloroplast

A double-membraned photosynthetic organelle containing circular DNA, stroma, and thylakoid stacks (grana) where food is produced via photosynthesis.

Plastids

Plant cell organelles containing pigments or food materials, categorized into chromoplasts, leucoplasts, and chloroplasts.

Glyoxysomes

Specialized microbodies in plant cells that store and convert fats into carbohydrates.

Inclusions (Ergastic Substances)

Non-permanent, non-membranous cellular products including stored food reserves (starch, protein, oils), secretory products, excretory products, and mineral crystals.

Cytoskeleton

A dense network of protein fibers comprising microfilaments, intermediate filaments, and microtubules that supports cell shape, anchors organelles, and enables cell movement.

Centriole

An organelle found in animal cells consisting of microtubule triplets that anchors and assembles microtubules and gives rise to spindle fibers during mitosis.

Kinesin

A motor protein that moves vesicles along microtubular tracks toward the cell's periphery.

Dynein

A motor protein that moves vesicles along microtubular tracks toward the interior of the cell.

Tight Junction (Zonula Occludens)

An occluding junction that seals adjacent epithelial cells together to prevent molecule leakage and acts as a diffusion barrier within the plasma membrane.

Adherens Junction (Zonula Adherens)

An anchoring junction that holds cells together using cadherin adhesion proteins and connects to intracellular actin filaments.

Desmosomes (Macula Adherens)

Anchoring junctions that mechanically hold neighboring cells together and serve as attachment sites for intermediate filaments.

Gap Junction

A communicating junction spanned by connexin channels that allows inorganic ions and small water-soluble molecules to pass between animal cells.

Plasmodesma

A microscopic channel traversing the cell wall of plant cells, lined by plasma membrane and containing a desmotubule, that connects the cytoplasm of adjacent cells.

Extracellular Matrix (ECM)

A network of proteins, fibers, and sugar chains secreted outside the plasma membrane of animal cells that coordinates tissue behavior and links to the cytoskeleton via integrins.