UAE TLS Biology Test cheat sheet

Prokaryotic cells have no membrane-bound nucleus or organelles and use 70S ribosomes; eukaryotic cytoplasm contains membrane-bound organelles and 80S ribosomes.

Fluid mosaic model: a phospholipid bilayer with hydrophilic heads facing outward and hydrophobic tails inward, plus embedded proteins, cholesterol and glycoproteins.

Aerobic respiration ATP yield per glucose is about 30-32: glycolysis gives 2 net ATP plus 2 NADH, the link reaction 2 NADH, the Krebs cycle 2 ATP plus 6 NADH and 2 FADH2, with the remainder from the electron transport chain.

Enzymes lower activation energy; rate peaks at optimum temperature and pH, and denaturation above the optimum permanently distorts the active site.

Competitive inhibitors raise Km with Vmax unchanged; non-competitive inhibitors lower Vmax with Km unchanged.

Biological polymers: monosaccharides join by glycosidic bonds, amino acids by peptide bonds, and nucleotides by phosphodiester bonds.

The sodium-potassium pump moves 3 Na+ out and 2 K+ in per ATP hydrolysed, an example of active transport against the concentration gradient.

Water is a polar solvent with high specific heat capacity and strong cohesion; these properties support xylem transport and temperature stability in organisms.

Law of segregation: the two alleles of a gene separate in meiosis so each gamete carries one; the law of independent assortment applies to genes on different chromosomes.

Monohybrid cross Aa x Aa gives a 3:1 phenotypic ratio and a 1:2:1 genotypic ratio.

Dihybrid cross AaBb x AaBb gives a 9:3:3:1 phenotypic ratio when the genes assort independently.

Codominance expresses both alleles, as in AB blood group; incomplete dominance produces an intermediate phenotype, as when red x white gives pink.

X-linked recessive conditions appear more often in males because males carry only one X chromosome and are therefore hemizygous.

Base pairing: adenine pairs with thymine by two hydrogen bonds and guanine with cytosine by three; DNA replication is semi-conservative.

Translation begins at the AUG start codon and ends at UAA, UAG or UGA; each codon specifies one amino acid.

A substitution may be silent, missense or nonsense; an insertion or deletion not a multiple of three causes a frameshift.

Blood pathway: right atrium, right ventricle, pulmonary artery, lungs, pulmonary vein, left atrium, left ventricle, aorta.

Cardiac output (mL/min) = heart rate (beats/min) x stroke volume (mL/beat); the resting value is about 5 L/min.

ECG waves: P = atrial depolarisation, QRS = ventricular depolarisation, T = ventricular repolarisation.

Alveoli provide a large surface area of about 70 m2, thin walls and a moist surface for gas exchange by diffusion.

Nephron: filtration at the glomerulus, selective reabsorption of glucose and amino acids in the proximal tubule, and water reabsorption controlled by ADH in the collecting duct.

Digestive enzymes: amylase hydrolyses starch to maltose, pepsin digests protein at pH 2, lipase breaks fats into fatty acids and glycerol, and bile emulsifies fats.

Neuron potentials: resting membrane potential about -70 mV, threshold about -55 mV, peak action potential about +40 mV.

Insulin lowers blood glucose by promoting cellular uptake and glycogen formation; glucagon raises it by stimulating glycogen breakdown; both act through negative feedback.

Natural selection requires heritable variation, competition for limited resources and differential reproductive success.

Hardy-Weinberg: p + q = 1 and p2 + 2pq + q2 = 1; equilibrium requires no mutation, no migration, random mating, no selection and a large population.

Allopatric speciation follows a geographic barrier; sympatric speciation occurs without one, for example through polyploidy in plants.

Homologous structures indicate divergent evolution from a common ancestor; analogous structures indicate convergent evolution.

Classification hierarchy: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

Binomial names are italicised with a capitalised genus and lower-case species, for example Homo sapiens.

The three domains are Bacteria, Archaea and Eukarya; antibiotic resistance spreads through mutation and horizontal gene transfer.

Endosymbiotic theory: mitochondria and chloroplasts originated from engulfed prokaryotes, supported by their own circular DNA and 70S ribosomes.

Energy transfer between trophic levels is about 10 per cent, so pyramids of energy are always upright.

Population growth is exponential (J-shaped) when resources are unlimited and logistic (S-shaped) as the carrying capacity K is approached.

Carbon cycle processes: photosynthesis fixes CO2, respiration and combustion release it, and decomposition returns carbon to soil and air.

Nitrogen cycle order: fixation, nitrification, assimilation, ammonification, denitrification.

Symbiosis types: mutualism (+/+), commensalism (+/0) and parasitism (+/-).

Survivorship curves: Type I shows high early survival, Type II constant mortality and Type III high early mortality.

Biodiversity has two components: species richness (number of species) and species evenness (relative abundance).

Major greenhouse gases are carbon dioxide, methane, nitrous oxide and water vapour; methane has a higher warming potential per molecule than carbon dioxide.

Photosynthesis: 6CO2 + 6H2O gives C6H12O6 + 6O2, with light-dependent reactions in thylakoid membranes and the Calvin cycle in the stroma.

Chlorophyll absorbs mainly red and blue wavelengths and reflects green light.

Xylem carries water and mineral ions upward by transpiration pull; phloem carries sucrose and amino acids in both directions by pressure flow.

Stomata open when guard cells are turgid and close when they lose water; opening is promoted by light and low internal CO2.

Plant hormones: auxin for elongation and phototropism, gibberellin for stem elongation, cytokinin for cell division, abscisic acid for dormancy and stomatal closure, ethylene for ripening.

Angiosperm flower parts: sepals, petals, stamens (anther and filament) and carpels (stigma, style and ovary).

Monocots have one cotyledon and parallel leaf veins; dicots have two cotyledons and net-like veins.

C4 and CAM photosynthesis reduce photorespiration and water loss in hot, dry habitats.

PCR cycle: denaturation near 94 degrees Celsius, primer annealing near 50-60 degrees Celsius, extension near 72 degrees Celsius by Taq polymerase; product doubles each cycle, giving 2^n copies.

Gel electrophoresis: DNA is negatively charged and migrates toward the positive electrode; shorter fragments travel farther through the gel.

Restriction enzymes cut at specific palindromic recognition sites, often leaving sticky ends suitable for ligation into plasmids.

Plasmid vectors carry an origin of replication, a selectable marker such as antibiotic resistance, and a multiple cloning site.

CRISPR-Cas9 uses a guide RNA to direct the Cas9 nuclease to a complementary target sequence, where it creates a double-strand break.

The lac operon is inducible: lactose binds the repressor, allowing RNA polymerase to transcribe the structural genes.

Sanger sequencing uses dideoxynucleotides that terminate chain elongation, producing fragments separated by size.

DNA profiling commonly compares short tandem repeats (STRs) between samples.

The independent variable is manipulated, the dependent variable is measured, and controlled variables are held constant.

A hypothesis must be testable and falsifiable, and it should generate a prediction about the dependent variable.

A control group receives no treatment and provides the baseline against which the experimental group is compared.

Accuracy is closeness to the true value; precision is closeness of repeated measurements to each other.

Random sampling and a larger sample size increase the reliability and representativeness of results.

Systematic error shifts all readings in one direction; random error scatters readings around the true value and is reduced by averaging repeats.

Correlation does not establish causation, because a third variable may underlie an observed association.

Peer review and independent replication are the main checks on the validity of scientific claims.

Personal protective equipment in a school laboratory includes goggles, a lab coat and gloves; food and drink are never allowed at the bench.

The locations of the eyewash station, safety shower, fire extinguisher and first aid kit must be known before practical work begins.

Always add concentrated acid to water, never water to concentrated acid, to avoid violent spitting and rapid heat release.

Never pipette by mouth; use a pipette filler or bulb.

Autoclaving at 121 degrees Celsius and 15 psi for 15 minutes sterilises equipment and destroys bacterial spores.

Ethidium bromide is a mutagen and must be handled with gloves and disposed of as hazardous waste.

Broken glass goes into a designated sharps bin rather than ordinary waste; chemical spills are reported and cleaned with the correct spill kit.

A Safety Data Sheet lists a chemical's hazards, handling precautions, first-aid measures and disposal routes.

Mean = sum of values divided by the number of values; median = middle value of an ordered set; mode = most frequent value.

Standard deviation measures spread around the mean; about 68 per cent of normally distributed values lie within plus or minus 1 SD and about 95 per cent within plus or minus 2 SD.

Standard error of the mean = standard deviation divided by the square root of n, and it decreases as sample size increases.

Chi-square: chi-squared = sum of (O - E)2 / E, with degrees of freedom equal to the number of categories minus 1.

A t-test compares the means of two samples; a significant result requires the calculated value to exceed the critical value at the chosen probability.

Correlation coefficient r lies between -1 and +1; the sign shows direction and the magnitude shows strength.

Bar charts display categorical data, line graphs display continuous change and scatter graphs show relationships between two variables.

Rate of change = change in value divided by time taken; when converting units, keep prefixes consistent and record significant figures appropriately.

Constructive alignment requires intended learning outcomes, learning activities and assessment tasks to match one another.

Bloom's taxonomy order: remember, understand, apply, analyse, evaluate, create.

Formative assessment supports learning through feedback during a unit; summative assessment judges achievement at the end of a unit.

The 5E inquiry model runs Engage, Explore, Explain, Elaborate, Evaluate.

Differentiation includes scaffolding, extension tasks and multiple representations such as diagrams, models and graphs.

Common misconceptions to address: plants obtain food from soil, dominant alleles are the most common alleles, and evolution occurs within an individual's lifetime.

Practical work must be preceded by a risk assessment covering hazards, control measures and emergency procedures.

Models and analogies are useful teaching tools but must be presented with their limitations made explicit.