GCE A/L Bio Systems Technology cheat sheet

Bio systems technology applies engineering principles to living systems or their components; it integrates cell biology, microbiology, biochemistry and process engineering into products and services.

Risk assessment hierarchy: eliminate hazard, substitute, use engineering controls (fume hood, biosafety cabinet), then administrative controls, then PPE as last barrier.

Material Safety Data Sheet (SDS) sections include hazard identification, first-aid measures, fire-fighting measures, handling and storage, exposure controls and disposal.

Chemical storage rule: acids separated from bases; oxidisers separated from flammables and organic solvents; water-reactive reagents kept dry; flammable liquids in fire-rated cabinets.

Biological spill kit contents: absorbent, disinfectant (e.g. 10% hypochlorite or 70% ethanol), forceps, autoclavable bags, gloves and eye protection; spill is flooded with disinfectant, held for contact time, then absorbed outward to inward.

Autoclave standard cycle for biohazard waste: 121 °C at 15 psi (103 kPa) for 15–20 minutes; effectiveness confirmed with biological indicators such as Geobacillus stearothermophilus spores.

Biosafety levels: BSL-1 non-pathogenic; BSL-2 moderate hazard with class II cabinet for aerosols; BSL-3 airborne pathogens with controlled access and directional airflow; BSL-4 dangerous/exotic agents with positive-pressure suits or class III cabinets.

Laboratory waste streams are segregated at source: sharps in puncture-proof containers, biohazard waste in yellow/red-coded bags, chemical waste by compatibility, and radioactive waste by isotope half-life.

Prokaryotic cell: no membrane-bound nucleus or organelles, 70S ribosomes, peptidoglycan wall in bacteria; eukaryotic cell: nucleus, 80S ribosomes, membrane-bound organelles.

Membrane model is the fluid mosaic: phospholipid bilayer with integral and peripheral proteins, cholesterol modulating fluidity, and glycoproteins for recognition.

Mitochondrial ATP yield from one glucose: glycolysis 2 net ATP + 2 NADH; pyruvate oxidation 2 NADH; Krebs cycle 2 ATP + 6 NADH + 2 FADH₂; oxidative phosphorylation gives roughly 30–32 ATP in total.

Osmosis rule: water moves from low solute concentration to high solute concentration across a semipermeable membrane; plant cells become turgid in hypotonic and plasmolyse in hypertonic solutions.

Cell cycle checkpoints: G1/S (size, nutrients, DNA damage), G2/M (replication complete, damage), spindle assembly checkpoint at metaphase; failure leads to mutation or apoptosis.

Organelle functions: rough ER protein synthesis and folding, smooth ER lipid synthesis and detoxification, Golgi modification and sorting, lysosome acid hydrolases, peroxisome catalase and β-oxidation.

Apoptosis is programmed and caspase-mediated with membrane blebbing and no inflammation; necrosis is passive, causes swelling, lysis and inflammation.

Cell wall composition differs: cellulose in plants, chitin in fungi, peptidoglycan in bacteria, and no wall in animal cells; this determines antibiotic and enzyme selectivity.

Resolution d = 0.61λ/NA; shorter wavelength and higher numerical aperture improve resolution; oil immersion raises NA to about 1.25–1.4.

Total magnification = objective magnification × eyepiece magnification; a 100× objective with a 10× eyepiece gives 1000×.

Light microscope resolving limit is about 200 nm; electron microscope reaches ~0.1–0.2 nm (TEM) and ~1–10 nm practical (SEM).

Stains: Gram stain differentiates Gram-positive (purple, thick peptidoglycan) from Gram-negative (pink, thin wall, outer membrane); methylene blue and safranin are simple/contrast stains.

Centrifugation separates by sedimentation coefficient; relative centrifugal force RCF = 1.118 × 10⁻⁵ × r (cm) × (rpm)², measured in ×g rather than rpm alone.

Chromatography separates by differential partitioning: paper and thin-layer by polarity, gel filtration by size, ion exchange by charge, affinity by specific binding.

Spectrophotometry uses Beer–Lambert law A = εcl; absorbance at 600 nm estimates bacterial cell density and at 260/280 nm assesses nucleic acid purity (ratio ~1.8 for DNA, ~2.0 for RNA).

Electrophoresis separates charged molecules in a gel; agarose for DNA/RNA, polyacrylamide for proteins; SDS-PAGE separates proteins by mass after denaturation.

Bacterial growth curve phases: lag, exponential (log), stationary and death; generation time g = t/n where n is the number of divisions.

Growth kinetics: N = N₀ × 2ⁿ; specific growth rate μ = ln2/g, and in exponential phase ln N = ln N₀ + μt.

Batch culture has a closed nutrient supply and changing conditions; continuous culture (chemostat) maintains steady state with controlled dilution rate and limiting nutrient.

Sterilisation methods: moist heat autoclaving (121 °C, 15 psi, 15 min), dry heat (160–180 °C, 2 h), membrane filtration (0.22 µm for solutions and heat-labile media), UV for surfaces only.

Microbial enumeration: viable plate count, most probable number, direct microscopic count, turbidity, and dry mass; plate counts report colony-forming units, not total cells.

Selective media suppress unwanted organisms (e.g. MacConkey for Gram-negative, mannitol salt agar for staphylococci); differential media reveal biochemical traits by colour change.

Industrial microbes: Lactobacillus for lactic acid and yoghurt, Saccharomyces cerevisiae for ethanol and baking, Aspergillus niger for citric acid, Streptomyces for antibiotics.

Nitrogen cycle roles: Rhizobium fixes nitrogen symbiotically, Azotobacter free-living, Nitrosomonas oxidises ammonia to nitrite, Nitrobacter nitrite to nitrate, denitrifiers return N₂ to atmosphere.

Plant tissue culture steps: explant selection, surface sterilisation (e.g. 70% ethanol then sodium hypochlorite), inoculation on sterile medium, callus induction, shoot/root regeneration, hardening.

Murashige and Skoog (MS) medium contains macroelements, microelements, iron-EDTA, vitamins, sucrose as carbon source, and a gelling agent such as agar; auxin-to-cytokinin ratio controls root versus shoot formation.

Totipotency is the capacity of a plant cell to regenerate a whole plant; it underpins micropropagation, somatic embryogenesis and protoplast culture.

Micropropagation advantages: clonal uniformity, pathogen-free stock, rapid multiplication, year-round production; risks include somaclonal variation, contamination and high initial cost.

Animal cell culture requires aseptic technique, buffered medium (bicarbonate/HEPES), serum or defined supplements, 37 °C, 5% CO₂ and humidified atmosphere; adherent cells need surface attachment.

Primary cultures have limited lifespan; continuous cell lines are immortalised and can be propagated indefinitely; cryopreservation in liquid nitrogen with DMSO or glycerol preserves stocks.

Somatic hybridisation fuses protoplasts to overcome sexual incompatibility; anther culture produces haploid plants that can be chromosome-doubled to give homozygous diploids.

Contamination control in culture: laminar flow hood, HEPA-filtered air, antibiotic use sparingly, regular mycoplasma screening, and quarantine of new cultures.

Biological macromolecules: carbohydrates (mono-, di-, polysaccharides), proteins (amino acids linked by peptide bonds), lipids (ester bonds in triglycerides), nucleic acids (phosphodiester bonds).

Enzyme kinetics: Michaelis–Menten v = Vmax[S]/(Km + [S]); Km is the substrate concentration at half Vmax and is inversely related to substrate affinity.

Lineweaver–Burk plot is 1/v against 1/[S]; y-intercept = 1/Vmax, x-intercept = −1/Km; competitive inhibition raises apparent Km with unchanged Vmax.

Glycolysis net yield per glucose: 2 ATP, 2 NADH and 2 pyruvate; fermentation regenerates NAD⁺ by converting pyruvate to lactate or ethanol plus CO₂.

ATP is the universal energy currency; energy charge = ([ATP] + 0.5[ADP])/([ATP] + [ADP] + [AMP]) and indicates cellular metabolic state.

Protein structure levels: primary sequence, secondary α-helix and β-sheet, tertiary three-dimensional fold, quaternary subunit assembly; denaturation disrupts non-covalent bonds.

Nucleic acid base pairing: A–T (two hydrogen bonds) and G–C (three hydrogen bonds) in DNA; A–U in RNA; higher G+C content raises melting temperature.

Carbohydrate tests: Benedict's for reducing sugars (brick-red), iodine for starch (blue-black), Biuret for protein (purple), Sudan III for lipids (red droplets).

Enzyme classification: oxidoreductases, transferases, hydrolases, lyases, isomerases and ligases; each name ends in -ase and includes an EC number.

Factors affecting enzyme activity: temperature (denaturation above optimum), pH (charge on active site), substrate and enzyme concentration, inhibitors and cofactors.

Immobilised enzymes offer reuse, easy separation, continuous operation and improved stability; methods include adsorption, covalent binding, entrapment and cross-linking.

Fermentation types: batch, fed-batch and continuous; secondary metabolites such as antibiotics are typically produced in fed-batch or stationary phase.

Bioreactor components: vessel, agitation, aeration, temperature and pH control, foam control, sampling port, and sterilisation-in-place; stirred tank is the most common design.

Key fermentation parameters: pH, temperature, dissolved oxygen, foaming, viscosity, and contamination checks; yield coefficients relate product formed to substrate consumed.

Downstream processing sequence: cell harvesting, disruption if intracellular, clarification, concentration, purification (chromatography) and formulation.

Ethanol fermentation stoichiometry: C₆H₁₂O₆ → 2 C₂H₅OH + 2 CO₂; theoretical maximum is 0.511 g ethanol per g glucose.

Mendel's laws: segregation of alleles and independent assortment of genes on different chromosomes; test cross reveals genotype of a dominant phenotype.

Monohybrid cross Aa × Aa gives 3:1 phenotype and 1:2:1 genotype; dihybrid heterozygote cross gives 9:3:3:1 if genes are unlinked.

DNA replication is semi-conservative; the central dogma is DNA → RNA → protein, with transcription in the nucleus and translation on ribosomes.

Mutation types: substitution (missense, nonsense, silent), insertion or deletion causing frameshift; chromosomal changes include deletion, duplication, inversion and translocation.

Human inheritance patterns: autosomal dominant, autosomal recessive, X-linked recessive and X-linked dominant; pedigree analysis distinguishes them.

Hardy–Weinberg equilibrium: p + q = 1 and p² + 2pq + q² = 1; deviations indicate selection, mutation, migration, genetic drift or non-random mating.

Sex determination and linkage: sex-linked genes sit on sex chromosomes; recombination frequency between linked genes indicates map distance in centimorgans.

Epistasis, codominance and incomplete dominance modify simple Mendelian ratios and must be distinguished in cross analysis.

Restriction endonucleases cut specific palindromic sequences; sticky ends allow ligation, and methylation protects host DNA from digestion.

Cloning workflow: isolate gene, cut with restriction enzymes, ligate into vector, transform host, select transformants, screen for insert, express and purify product.

Plasmid vectors require an origin of replication, selectable marker (e.g. antibiotic resistance), multiple cloning site and promoter for expression.

PCR cycle: denaturation ~95 °C, annealing ~50–65 °C, extension ~72 °C; Taq polymerase is thermostable; cycle number and primer design determine specificity.

Gel electrophoresis confirms fragment size; Southern blot detects DNA, Northern blot RNA, Western blot protein; DNA sequencing uses chain termination or next-generation methods.

Transformation methods: heat-shock calcium-competent cells, electroporation, microinjection, gene gun and Agrobacterium-mediated transfer in plants.

CRISPR-Cas9 uses a guide RNA to target a sequence and Cas9 nuclease to create a double-strand break, repaired by non-homologous end joining or homology-directed repair.

Applications include recombinant insulin, vaccines, Bt crops, gene therapy and transgenic animals; regulation and containment are mandatory.

Innate immunity is non-specific and rapid (barriers, phagocytes, complement, inflammation); adaptive immunity is specific and has memory (B and T lymphocytes).

Antibody structure: two heavy and two light chains, variable regions for antigen binding, constant regions for effector function; IgG, IgM, IgA, IgE and IgD differ in role.

Primary immune response is slow with IgM first; secondary response is faster, larger and dominated by IgG due to memory cells.

Antigen–antibody reactions include precipitation, agglutination, neutralisation, complement fixation and opsonisation.

ELISA formats: direct, indirect, sandwich and competitive; enzyme label converts substrate to a coloured product measured spectrophotometrically.

Monoclonal antibodies come from a hybridoma of a B cell fused with a myeloma; they are uniform, specific and used in diagnostics and therapy.

Vaccines: live attenuated, inactivated, toxoid, subunit and mRNA; adjuvants enhance immunogenicity; cold chain is required for many vaccines.

Hypersensitivity types I–IV: immediate IgE, cytotoxic, immune complex and delayed cell-mediated; autoimmune disease results from loss of self-tolerance.

Plant tissue culture supports micropropagation, virus elimination via meristem culture, somaclonal variation and germplasm conservation.

Genetic improvement methods: selective breeding, mutation breeding, hybridisation, marker-assisted selection and transgenic modification.

Biofertilisers: Rhizobium, Azotobacter, Azospirillum and mycorrhizae improve nutrient uptake; biocontrol agents reduce chemical pesticide dependence.

Food fermentation products: yoghurt (Lactobacillus bulgaricus and Streptococcus thermophilus), cheese, bread, tempeh, soy sauce, kimchi and vinegar.

Food preservation principles: reduce water activity, control pH, use heat (pasteurisation, sterilisation), cold storage, modified atmosphere, irradiation and preservatives.

Food safety indicators: total plate count, coliforms, Salmonella and Listeria testing, HACCP critical control points and Good Manufacturing Practice.

Animal biotechnology includes artificial insemination, embryo transfer, cloning, transgenic livestock and vaccines; welfare and ethics require assessment.

Post-harvest losses are reduced by controlled atmosphere storage, ripening control with ethylene management, and biopreservation using bacteriocins.

Wastewater treatment stages: primary sedimentation, secondary biological treatment (activated sludge or trickling filter), tertiary nutrient removal and disinfection.

BOD measures oxygen consumed by microbes over 5 days at 20 °C; COD measures chemical oxidation and is always ≥ BOD; the BOD/COD ratio indicates biodegradability.

Activated sludge parameters: mixed liquor suspended solids, sludge age, food-to-microorganism ratio and dissolved oxygen; bulking sludge settles poorly.

Anaerobic digestion stages: hydrolysis, acidogenesis, acetogenesis and methanogenesis; biogas is roughly 50–70% methane and 30–50% carbon dioxide.

Bioremediation uses indigenous or introduced microorganisms to degrade pollutants; phytoremediation uses plants; composting is aerobic thermophilic degradation.

Air pollution control by biofilters and bioscrubbers uses microbial oxidation of volatile organic compounds and odorous gases.

Industrial fermentation products include antibiotics, enzymes, organic acids, amino acids, vitamins, biopolymers and biofuels.

Sustainability measures: energy efficiency, water recycling, waste minimisation, life-cycle assessment and cleaner production.

Informed consent requires voluntariness, disclosure of purpose, risks and benefits, capacity to decide and the right to withdraw.

Ethical principles: autonomy, beneficence, non-maleficence and justice; research ethics adds scientific validity and independent review.

Genetically modified organism regulation covers contained use, deliberate release, labelling and risk assessment for human and environmental safety.

Biosafety cabinets: class I protects operator and environment, class II protects product as well, class III is gas-tight for maximum containment.

Quality assurance covers the whole process; quality control tests the product; Good Laboratory Practice governs organisation and record keeping.

Standard operating procedures, calibration records, chain of custody and audit trails are essential for traceability and reproducibility.

Animal experimentation follows the 3Rs: replacement, reduction and refinement; ethics committees approve protocols.

Intellectual property and benefit sharing: patents, plant variety protection, access and benefit-sharing under the Convention on Biological Diversity and Nagoya Protocol.