T-Level Core Science Concepts: Cellular Biology, Biochemistry, Homeostasis, and Pathophysiology

Comprehensive practice flashcards matching vocabulary terms and exact definitions across cell biology, molecular genetics, transport mechanisms, homeostasis, injury versus trauma, infection control, and infectious pathogens.

Antigen

A substance recognized by the immune system that has the ability to stimulate an immune response, including self-antigens and foreign antigens.

Phagocytosis

The multi-step immune process where a phagocyte engulfs a foreign pathogen via receptors, encloses it within a phagosome, digests it with lysosomal enzymes in a phagolysosome, and expels soluble debris via exocytosis.

Antibody

A specialized blood protein produced by B cells in response to, and counteracting, a specific complementary antigen.

Cilia

Hair-like epithelial projections that beat in a coordinated brushing motion, such as sweeping trapped pathogens upward along the trachea and down to the stomach.

Erythema

The clinical sign of localized redness during an inflammatory response, caused by increased blood flow to damaged vascular beds.

Oedema

The clinical sign of swelling in an inflamed tissue caused by an accumulation of excess blood plasma leaking into the interstitial space.

Decolonisation (MRSA)

A topical eradication regimen prescribed to eliminate MRSA colonization from skin surfaces and nasal passages to prevent infection and transmission.

Bactroban Nasal®

A topical nasal eradication ointment applied inside each nostril $3$ times daily for $5$ days, followed by rescreening after $48\,\text{hours}$ to verify eradication.

Octenisan®

An antiseptic wash applied undiluted across the entire body for at least $1\,\text{minute}$ before rinsing, accompanied by fresh towels and clothing daily, and used as shampoo on days $1$ and $3$.

Direct Transmission

The transfer of a pathogen between individuals via immediate physical contact, exchange of bodily fluids, sharps injuries, or direct droplet/aerosol exposure.

Indirect Transmission

The transfer of an infectious agent via intermediary pathways, such as contaminated vehicles (water, food, surfaces/fomites) or living insect vectors.

Aerosols

Microscopic airborne particles ($< 5\,\mu\text{m}$) capable of remaining suspended in the air for hours, traveling beyond $1\,\text{meter}$, and being inhaled deep into the respiratory tract.

Droplets

Respiratory particles ($5\text{--}100\,\mu\text{m}$) that travel less than $1\,\text{meter}$, precipitate to ground surfaces in under $5\,\text{seconds}$, and cannot be inhaled.

Healthcare-Associated Infections (HCAIs)

Infections that emerge as a direct consequence of care or medical intervention delivered in clinical environments such as hospitals, care homes, clinics, or GP surgeries.

Methicillin-Resistant Staphylococcus aureus (MRSA)

A bacterial pathogen resistant to commonly used antibiotics that harmlessly colonizes skin and nasal vestibules but causes severe systemic infections when gaining entry via surgical wounds or catheters.

Clostridium difficile (C. diff)

A spore-forming gut bacterium that overproliferates following disruption of native intestinal flora by antibiotic therapy, producing exotoxins that irritate the bowel lining to trigger severe diarrhoea, abdominal cramps, and fever.

Magnetism

A fundamental physical force of attraction and repulsion generated by charged particles and magnetic dipoles, projecting field lines from a north pole and absorbing into a south pole.

Permanent Magnet

A magnetic material (commonly metallic) that persistently maintains its magnetic domain alignment and field without requiring external magnetic stimulation.

Induced Magnet

A material that becomes temporarily magnetic only while positioned within an external magnetic field.

Magnetic Resonance Imaging (MRI)

A non-invasive diagnostic modality where an external magnetic field aligns body tissue protons, radiofrequency pulses perturb their alignment, and emitted realignment signals are reconstructed into detailed diagnostic images.

Injury

Physical damage inflicted on the body by external mechanical force, typically mild to moderate in severity and confined to a localized tissue area.

Trauma

Severe, catastrophic physical injury possessing high potential to cause permanent disability or fatality, frequently accompanied by systemic inflammation, multi-organ compromise, or shock.

Proliferation Phase

The regenerative stage of wound healing characterized by soft tissue repair, phagocytic debridement, fibroblast-driven collagen synthesis, angiogenesis, and the development of vascularized granulation tissue.

Angiogenesis

The biological process wherein new capillary networks sprout and grow into newly forming granulation tissue to supply oxygen and nutrients during wound healing.

Ischaemia

A severe restriction or total occlusion of arterial blood supply to tissues, precipitating cellular hypoxia, metabolic compromise, and potentially necrotic tissue death.

Homeostasis

The physiological maintenance of a dynamic, stable internal environment within precise operating parameters (such as human core body temperature between $36\text{--}37.5\,^\circ\text{C}$) despite fluctuating external conditions.

Homeostatic Mechanism

A physiological feedback pathway consisting of a stimulus, a receptor detecting change, a central integration control centre, an effector (muscle or gland), and a corrective response.

Negative Feedback

A physiological homeostatic mechanism that counteracts a detected stimulus by generating an opposite response to return system parameters to their optimal set point.

Positive Feedback

A physiological control mechanism that amplifies, reinforces, and enhances a deviation away from standard baseline parameters.

Islets of Langerhans

Endocrine cell clusters within the pancreas comprising $\alpha$ cells that secrete glucagon to elevate blood sugar and $\beta$ cells that secrete insulin to lower blood sugar.

Antidiuretic Hormone (ADH)

A peptide hormone synthesized by the hypothalamus and secreted by the posterior pituitary that acts on kidney tubule permeability to promote water reabsorption during dehydration.

Monosaccharide

A simple single-unit carbohydrate monomer consisting of carbon, hydrogen, and oxygen atoms in a fixed ratio, exemplified by glucose.

Glycosidic Bond

The covalent chemical bond formed between adjacent monosaccharide units via a condensation reaction with the elimination of a water molecule.

Glycogen

A highly branched polysaccharide of glucose synthesized and stored in hepatocytes and skeletal muscle tissue as an accessible energy reserve.

Triglyceride

A nonpolar lipid macromolecule composed of one glycerol molecule ester-linked to three fatty acid chains through condensation reactions.

Phospholipid

An amphipathic structural lipid composed of a polar hydrophilic phosphate head and two nonpolar hydrophobic fatty acid hydrocarbon tails.

Health Literacy

The degree to which individuals and populations possess the capacity to obtain, process, understand, and apply essential health promotion messaging and preventive guidance.

Vehicle Transmission

Indirect disease transmission resulting from contact with or ingestion of contaminated inanimate media, such as drinking water supplies, food, shared sanitary containers, or linens.

Cell Theory

The unifying biological doctrine stating that all living entities comprise one or more cells, cells are the elemental units of structure and function, and all new cells originate from pre-existing cells.

Eukaryote

A cellular organism (animal, plant, fungus, or protozoan) possessing a distinct double-membrane-bound nucleus enclosing chromosomal DNA, along with specialized membrane-bound organelles.

Prokaryote

A simple unicellular organism (such as a bacterium) that lacks a membrane-bound nucleus and membrane-bound organelles, typically having naked circular DNA and plasmids.

Biological Catalyst

A specialized protein (enzyme) that substantially increases the rate of specific biochemical reactions by depressing the required activation energy threshold without being consumed.

Induced Fit Model

The catalytic enzyme mechanism wherein initial contact with a complementary substrate causes the active site to mould and flex tightly around the substrate to facilitate bond strain and catalysis.

Myosin ATPase

A specialized muscle enzyme that accelerates the hydrolysis of $ATP$ into $ADP$ and inorganic phosphate to provide the kinetic energy required for the sliding filament mechanism.

Choline Acetyltransferase (ChAT)

A nervous system enzyme responsible for catalyzing the synthesis of neurotransmitters essential for synaptic transmission and muscle contraction.

DNA Helicase

An enzyme that unwinds and separates double-stranded DNA by cleaving hydrogen bonds between complementary base pairs ahead of replication or transcription.

Facilitated Diffusion

Passive, energy-independent transmembrane movement of polar or charged molecules down their concentration gradient assisted by membrane channel or carrier proteins.

Osmosis

The passive net diffusion of water molecules across a partially permeable membrane from a more dilute solution to a more concentrated solution.

Active Transport

The carrier-protein-mediated translocation of specific solute molecules across a cell membrane against their concentration gradient ($\text{low to high}$) driven by metabolic energy from $ATP$.

Co-transport

A secondary active transport mechanism wherein two distinct molecular or ionic species are simultaneously moved across a cell membrane by a single coupled carrier protein.

Nucleus

The prominent eukaryotic organelle enclosed by a perforated double membrane that houses chromosomes, safeguards genetic code, and orchestrates protein synthesis via gene expression.

Mitochondrion

A double-membraned eukaryotic organelle with an inner folded membrane forming cristae surrounding an enzymatic matrix, serving as the primary site of aerobic respiration and $ATP$ generation.

Ribosome

A dense intracellular ribonucleoprotein complex consisting of large and small subunits that functions as the translational site of polypeptide chain synthesis.

Rough Endoplasmic Reticulum (RER)

An extensive network of interconnected membranous cisternae studded with ribosomes that folds, modifies, packages, and transports newly synthesized proteins.

Smooth Endoplasmic Reticulum (SER)

A tubular membranous organelle devoid of surface ribosomes that synthesises, modifies, stores, and transports lipids, phospholipids, and steroid hormones.

Golgi Apparatus

A eukaryotic organelle composed of flattened membranous stacks (cisternae) that modifies, concentrates, and sorts secretory proteins into vesicles and generates lysosomes.

Lysosome

A membrane-bound hydrolytic organelle containing diverse acidic digestive enzymes responsible for degrading cellular waste products, obsolete organelles, and phagocytosed pathogens.

Centrioles

Cylindrical microtubule-based organelle pairs situated in the centrosome that assemble and organize mitotic spindle fibres during eukaryotic chromosome division.

Cytoskeleton

An integrated cellular framework of actin microfilaments, intermediate filaments, and tubulin microtubules that provides mechanical structure, aids cell division, and guides organelle transport.

Vector-Borne Transmission

Indirect transmission where an infectious pathogen is carried and injected into a host organism by a living vector, typically an arthropod such as a mosquito or tick.

Inadequate Sanitation

A major public health risk characterized by defective waste management, absent sewage systems, and lack of clean water that promotes the propagation of faecal-oral pathogens.

Surface Area to Volume Ratio (SA:Vol)

The mathematical relationship between an organism's or cell's outer surface area and its internal volume, which declines as cell size increases, thereby constraining simple diffusion.

Diffusion

The passive net movement of solute particles from a region of higher concentration to an area of lower concentration driven by random kinetic motion.

Nucleotide

The monomeric constituent of nucleic acids, consisting of a pentose sugar covalently bound to an inorganic phosphate group and a nitrogenous base.

Phosphodiester Bond

The covalent linkage formed via condensation reactions linking the phosphate group of one nucleotide to the sugar residue of an adjacent nucleotide in a polynucleotide chain.

Transcription

The nuclear biosynthetic process wherein RNA polymerase and enzymes use an unwound strand of genomic DNA as a template to produce a complementary messenger RNA ($mRNA$) molecule.

Translation

The cytosolic protein synthesis stage where ribosomes read successive three-base codons on $mRNA$, matching them with amino-acid-bearing $tRNA$ anticodons to polymerize a polypeptide.

Codon

A specific sequence of three adjacent ribonucleotide bases on an $mRNA$ transcript that dictates a complementary amino acid or a termination signal during protein translation.

Amino Acid

A biological monomer possessing a central alpha-carbon bonded to a hydrogen atom, an amine group ($-NH_2$), a carboxylic acid group ($-COOH$), and a variable $R$ group.

Peptide Bond

A covalent amide linkage joining the carboxyl carbon of one amino acid to the amine nitrogen of another, created through a condensation reaction that releases $H_2O$.

Deamination

A hepatic biochemical reaction in which excess amino acids have their amino groups removed to yield urea, which is subsequently transported via the vascular system for renal excretion in urine.

Quaternary Protein Structure

The highest order of protein architectural organization formed when two or more distinct folded polypeptide chains associate into a single functional multi-subunit macromolecule.

Metabolism

The total sum of all intracellular biochemical transformations and pathways operating within an organism to generate energy, build macromolecules, and eliminate waste products.

Fluid Mosaic Model

The structural paradigm describing the plasma membrane as a dynamic phospholipid bilayer with laterally moving phospholipids and an array of embedded integral and peripheral proteins, carbohydrates, and cholesterol.

Aquaporin

A specialized integral membrane channel protein that provides a water-selective pore across the lipid bilayer, greatly accelerating the velocity of transmembrane osmosis.

Pathogen

Any biological infectious microorganism or agent—including bacteria, viruses, fungi, parasites, protoctists, or prions—capable of entering, replicating within, and causing disease in a host.

Capsid

The protective external protein matrix of a virus, assembled from repeating structural protein subunits called capsomeres, that envelops and shields viral genomic nucleic acids.

Bacteriophage (Binal Virus)

A virus that infects bacterial cells, typically characterized by an icosahedral or polyhedral capsid head containing nucleic acid joined to a helical tail sheath, tail fibers, and base pins.

Prion

An infectious, pathologically misfolded protein lacking nucleic acids that possesses the unique ability to induce misfolding in normal homologous cellular proteins, resulting in fatal neurodegenerative pathology.

Protoctist (Protist)

A diverse taxonomic group of eukaryotic organisms, predominantly microscopic and unicellular ($1\text{--}2\,\mu\text{m}$), that are not classified within the animal, plant, or fungal kingdoms.