DDDM12: Introductory Biology

Comprehensive vocabulary flashcards covering cellular biology, ultrastructure, organelles, transport systems, and cellular signaling pathways from the Introductory Biology lecture of DDDM12 Pharmaceutical R&D.

Three Domains of Life

The overarching biological classification dividing all cellular life into Bacteria, Archaea, and Eukarya, all branching from a single common ancestor.

Prokaryotic Cell

A cellular life form (Bacteria and Archaea) typically $0.1\text{--}5\,\mu\text{m}$ in diameter that lacks a defined nucleus and membrane-bound organelles, possessing circular DNA without histones and a plasma membrane often lacking receptors.

Eukaryotic Cell

A complex cell type found in animals, plants, and fungi, measuring $5\text{--}100\,\mu\text{m}$ in diameter, containing a defined membrane-bound nucleus, linear DNA packaged with histones, membrane-enclosed organelles, and a receptor-bearing plasma membrane.

Nucleoid

The irregularly shaped, non-membrane-enclosed region within a prokaryotic cell that contains the folded circular chromosome.

Plasma Membrane

A semi-permeable bilayer formed of phospholipids with outward-facing hydrophilic polar heads and inward-facing hydrophobic non-polar fatty acid tails, embedded with functional proteins.

Plasma Membrane Protein Functions

The six vital cellular roles carried out by membrane proteins: communication via ligands and receptors, transport, enzymatic activity, cellular recognition via identity markers, cell junctions, and cell-matrix adhesion.

Integrins

Transmembrane adhesion proteins that anchor eukaryotic cells to the extracellular matrix (ECM) while linking internally to cytoskeletal networks.

Selective Permeability of the Lipid Bilayer

The property of the membrane that allows small hydrophobic molecules ($\text{O}_2$, $\text{CO}_2$, $\text{N}_2$) to permeate freely, permits some small uncharged polar molecules ($\text{H}_2\text{O}$, urea) to cross by diffusion or osmosis, but blocks large uncharged polar molecules and ions without transport proteins.

Uniport, Symport, and Antiport

Mechanisms of membrane transport: uniport moves a single solute across; symport cotransports two different solutes simultaneously in the same direction; antiport cotransports two different solutes in opposite directions.

Nucleus

The command center of a eukaryotic cell enclosed by a double-membrane nuclear envelope containing nuclear pores, housing genomic DNA packaged with proteins into chromosomes.

Nucleolus

A dense non-membrane-bound structure in the nucleus ($1\text{--}6$ per nucleus) that transcribes ribosomal RNA (rRNA) for ribosome synthesis, disassembling at the start of mitosis and reassembling during telophase and early $G_1$ phase.

Rough Endoplasmic Reticulum (RER)

A continuous system of internal membrane cisternae studded on the cytosolic face with ribosomes, specialized for the synthesis of membrane proteins and secreted proteins.

Smooth Endoplasmic Reticulum (SER)

A tubular internal membrane system devoid of ribosomes that aids in the manufacture of carbohydrates and lipids.

Golgi Apparatus

A stack of flattened membrane-bounded cisternae with incoming cis and outgoing trans faces that collects, packages, sorts, and distributes molecules produced in the cell.

Lysosomes

Spherical vesicles containing hydrolytic enzymes maintained at an acidic pH ($\sim 4.5\text{--}5.0$) that degrade endocytosed materials, eliminate cellular waste, and participate in autophagy.

Autophagy

A cellular recycling process meaning 'self eat' in which lysosomes degrade worn-out organelles and cellular debris to salvage and reuse molecular components.

Peroxisomes

Enzyme-filled vesicles ($0.2\text{--}1.0\,\mu\text{m}$ in diameter) present in nearly all animal cells (except erythrocytes) and many plant cells that degrade fatty acids and toxic compounds via oxidases, generating toxic $\text{H}_2\text{O}_2$ which catalase breaks down.

Mitochondria

The primary sites for cellular energy extraction in aerobic cells, producing adenosine triphosphate (ATP) by oxidative phosphorylation and the electron transport chain during cellular respiration.

Endosymbiotic Theory

The evolutionary model proposing that mitochondria originated from aerobic bacteria engulfed by ancestral host cells that adapted to coexist, retaining circular mtDNA and transcription machinery.

Mitochondrial DNA (mtDNA)

Circular genetic material located inside human mitochondria that encodes 37 genes: 2 rRNAs, 22 tRNAs, and 13 protein subunits of the electron transport chain.

Cytoskeleton

An intracellular protein scaffolding composed of three filament types: actin filaments (contractile forces and motion), microtubules (cell shape and mitotic spindle formation), and intermediate filaments (structural strength).

Autocrine Signalling

A short-distance communication mechanism in which a cell responds to the extracellular signalling molecules (such as specific growth factors) that it has released itself.

Paracrine Signalling

A short-distance form of cell communication where signalling molecules diffuse through the interstitial fluid to elicit fast, brief responses from neighbouring target cells.

Synaptic Signalling

A localized form of cell communication wherein extracellular signalling molecules released from a presynaptic terminal cross the synaptic cleft to bind receptors on a postsynaptic target cell.

Cell-Cell Contact Signalling

Direct communication between immediate adjacent cells through specialized protein channels—gap junctions in animals or plasmodesmata in plants—allowing small molecules and ions to diffuse directly between cells.

Endocrine Signalling

Long-distance cellular communication where endocrine cells secrete signalling molecules directly into the bloodstream to reach distant target cells across the body.

Receptor

A cellular component that selectively interacts with a specific extracellular signal molecule to elicit a biological response.

Ionotropic Receptors

Ligand-gated ion channels that undergo a conformational change upon ligand binding to open a central pore, facilitating rapid ion flux down electrochemical gradients within milliseconds.

Nicotinic Acetylcholine Receptor (nAChR)

A pentameric ligand-gated ion channel whose $\alpha$-subunits bind acetylcholine, causing a rapid conformational change that permits the passage of $\text{Na}^+$ and $\text{K}^+$ ions.

G-Protein-Coupled Receptors (GPCRs)

Seven-transmembrane receptors that upon ligand binding trigger the exchange of GDP for GTP on the $\text{G}\alpha$ subunit of an associated heterotrimeric G-protein ($\text{G}\alpha$, $\text{G}\beta$, $\text{G}\gamma$), prompting active $\text{G}\alpha\text{-GTP}$ to dissociate.

Adenylate Cyclase

An effector enzyme activated by $\text{G}\alpha\text{-GTP}$ that catalyzes the conversion of ATP into cyclic adenosine monophosphate (cAMP), subsequently activating Protein Kinase A (PKA).

Receptor Tyrosine Kinases (RTKs)

Transmembrane receptor proteins that dimerize upon ligand binding, activating intrinsic kinase activity that cross-phosphorylates intracellular tyrosine residues to provide docking sites for downstream signalling cascades.

Nuclear Receptors

Intracellular transcription factors activated by lipid-soluble molecules (such as steroid hormones and vitamins) that dimerize, enter the nucleus, and bind hormone response elements (HREs) on DNA.

5$\alpha$-Reductase

The intracellular enzyme that converts testosterone into dihydrotestosterone (DHT) within target tissues such as prostate cells.

Androgen Receptor (AR) Pathway

A nuclear receptor signaling pathway where DHT binding causes heat shock protein (HSP) dissociation, receptor dimerization, phosphorylation, and translocation to the nucleus to bind androgen-response elements; overactivity leads to Benign Prostate Hyperplasia (BPH).