Foundations of Medicine – Cells, Organelles & Levels of Organisation

Vocabulary flashcards summarising essential terms, structures and concepts from the lecture on cellular and organisational foundations of medicine.

Carbon

Element that forms four strong covalent bonds; backbone of organic molecules and life chemistry (≈19 % of human body).

Hydrogen

Lightest element (≈9 % of body); part of water and most organic molecules.

Nitrogen

Element (≈5 %) found in amino acids, nucleotides and many biomolecules.

Oxygen

Most abundant body element (≈63 %); key to water and aerobic energy production.

Phosphorus

Element in phosphate groups of nucleotides and membrane phospholipids (≈0.6 %).

Sulphur

Element in certain amino acids (cysteine, methionine) and many co-factors (≈0.6 %).

Ionic bond

Chemical bond formed by electron transfer; produces salts/electrolytes weakened by water.

Covalent bond

Chemical bond formed by electron sharing; strong and water-insensitive.

Amino acid

Monomer with amino and carboxyl groups around a central carbon; builds proteins.

Nucleotide

Monomer of nucleic acids; nitrogenous base + 5-carbon sugar + phosphate.

Sugar (Monosaccharide)

Poly-hydroxylated aldehyde/ketone (e.g., glucose); carbohydrate building block.

Fatty acid

Long hydrophobic hydrocarbon with reactive carboxylic acid head; builds lipids.

Protein

Macromolecule of folded polypeptides performing structural or catalytic roles.

Nucleic acid

Polymer of nucleotides (DNA or RNA) storing and expressing genetic information.

Carbohydrate

Macromolecule of sugars; energy source and structural component (e.g., glycogen, cellulose).

Lipid

Hydrophobic biomolecule class including fats, phospholipids and steroids.

Phospholipid bilayer

Double layer of amphipathic phospholipids forming cellular membranes.

Amphipathic

Describes molecules with both hydrophilic and hydrophobic regions (e.g., phospholipids).

Cell membrane (Plasma membrane)

Selective phospholipid bilayer enclosing the cell; maintains internal environment.

Selective permeability

Property of membranes allowing regulated passage of ions and molecules.

Nucleus

Largest organelle; double-membrane envelope housing DNA and regulating gene expression.

Nuclear lamina

Meshwork of intermediate filament proteins underlying the inner nuclear membrane; provides nuclear shape.

Nuclear pore

Protein complex forming regulated gateways across the nuclear envelope.

Nucleolus

Non-membranous nuclear subdomain for rRNA transcription and ribosome assembly.

Endoplasmic reticulum (ER)

Network of membrane cisternae continuous with nuclear envelope; rough and smooth regions.

Rough ER

ER studded with ribosomes; synthesises secreted and membrane proteins.

Smooth ER

ER lacking ribosomes; lipid, steroid, carbohydrate metabolism, Ca²⁺ storage, detoxification.

Golgi apparatus

Stack of flattened cisternae that processes, sorts and dispatches proteins and lipids.

Vesicle

Small membrane sphere for transport, secretion, endocytosis or transcytosis.

Endocytosis

Uptake of extracellular material via vesicle formation at the plasma membrane.

Exocytosis

Fusion of vesicles with plasma membrane to release contents outside cell.

Lysosome

Acidic, enzyme-rich vesicle digesting macromolecules from endocytosis, phagocytosis or autophagy.

Autophagy

Self-digestion pathway where autophagosomes deliver cytoplasmic cargo to lysosomes.

Lysosomal storage disorder

Genetic defect in lysosomal enzyme or trafficking causing substrate accumulation and cellular toxicity.

Proteasome

Cylindrical protein complex degrading ubiquitin-tagged mis-folded or short-lived proteins.

Ubiquitin

Small protein covalently attached to targets, labelling them for proteasomal degradation.

Peroxisome

Single-membrane organelle rich in oxidative enzymes and H₂O₂ metabolism; β-oxidises very long fatty acids.

Catalase

Peroxisomal enzyme that decomposes hydrogen peroxide to water and oxygen.

Mitochondrion

Double-membrane organelle generating ATP via Krebs cycle and oxidative phosphorylation; contains its own DNA.

Cristae

Infoldings of the mitochondrial inner membrane, increasing surface area for the electron transport chain.

ATP synthase

Inner-membrane enzyme that uses proton gradient to phosphorylate ADP to ATP.

Cytoskeleton

Dynamic protein network (microfilaments, intermediate filaments, microtubules) providing shape, transport and motility.

Actin filament (Microfilament)

6 nm dynamic filament of globular actin; involved in cell movement, cortex and microvilli.

Intermediate filament

10 nm strong, stable filament (e.g., keratins); resists mechanical stress.

Microtubule

25 nm hollow polymer of tubulin; provides tracks for organelle transport, forms spindle and cilia cores.

Centrosome

Major microtubule-organising centre composed of two centrioles and pericentriolar material.

Centriole

Cylinder of microtubule triplets that nucleates cilia/flagella and organises centrosome.

Motor protein

ATP-dependent protein (myosin, kinesin, dynein) that moves along cytoskeletal tracks.

Kinesin

Microtubule motor that generally moves cargo toward the plus end (cell periphery).

Dynein

Microtubule motor that moves cargo toward the minus end (centrosome) and powers ciliary beating.

Myosin

Actin-based motor protein responsible for muscle contraction and many cellular movements.

Cilium

Hair-like microtubule-based projection from cell surface; sensory or motile functions.

Primary cilium

Single, usually non-motile cilium on most mammalian cells; sensory signalling organelle.

Motile cilium

Multiple beating cilia on epithelial surfaces; move fluid or mucus, require dynein arms.

Flagellum

Long, motile cilium (e.g., sperm tail) used for cell propulsion.

Microvillus

Actin-supported membrane projection that increases absorptive surface area (e.g., intestine).

Tissue

Group of similar cells and extracellular matrix organised to perform a specific function.

Epithelial tissue

Sheet of tightly joined cells with apical–basal polarity; covers surfaces and forms glands.

Connective tissue

Tissue with sparse cells and abundant extracellular matrix providing support and packing.

Nervous tissue

Neurons and neuroglia specialised for electrical communication and integration.

Muscle tissue

Elongated, contractile fibres enabling movement; skeletal, cardiac, or smooth types.

Organ

Anatomically distinct structure composed of at least two tissue types performing specific functions.

Organ system

Group of inter-related organs cooperating to perform major physiological tasks (e.g., cardiovascular).

Prokaryote

Unicellular organism lacking nucleus and membrane organelles; single circular DNA (e.g., bacteria).

Eukaryote

Cell with nucleus, membrane-bound organelles and cytoskeleton; may be uni- or multicellular.

Endosymbiosis

Evolutionary theory that eukaryotic organelles (mitochondria, chloroplasts) originated from engulfed bacteria.

Macromolecule

Large polymeric molecule (proteins, nucleic acids, polysaccharides, lipids) built from small organic monomers.

Signal peptide

Short N-terminal sequence directing nascent polypeptide into the rough ER.

Nuclear localisation signal (NLS)

Amino-acid motif that targets proteins to the nucleus through nuclear pores.

β-Oxidation

Fatty-acid catabolic pathway occurring in peroxisomes (very long chains) and mitochondria (shorter chains).

Mitophagy

Selective autophagic removal of damaged or surplus mitochondria to maintain quality control.

Autophagosome

Double-membrane vesicle that encloses cytoplasmic cargo for delivery to lysosomes.

Endomembrane system

Interconnected membranes (ER, Golgi, vesicles, lysosomes, plasma membrane) coordinating protein and lipid trafficking.

Microtubule Organising Centre (MTOC)

Cellular site (e.g., centrosome) where microtubules are nucleated and anchored.

Axoneme

‘9 + 2’ microtubule core of motile cilia and flagella responsible for bending motions