MTLE Life Science (Grades 9-12) cheat sheet

Prokaryotic cells lack membrane-bound organelles and a nucleus; eukaryotic cells compartmentalize DNA in a nucleus and house oxidative phosphorylation in mitochondria.

Surface area-to-volume ratio decreases as cell size increases, capping diffusion-based exchange; this constraint drives cell division and flattened or folded exchange surfaces.

Fluid mosaic model: phospholipid bilayer is amphipathic, with hydrophilic heads outward; cholesterol modulates fluidity, and integral proteins span the bilayer.

Net osmosis moves water from low to high solute concentration across a selectively permeable membrane; solute movement alone follows its own gradient.

Enzyme kinetics: Km is the substrate concentration at half-maximal velocity (inverse affinity indicator); Vmax rises with enzyme concentration, not with substrate alone.

Competitive inhibitors raise apparent Km with unchanged Vmax; noncompetitive inhibitors lower Vmax without changing Km.

Glycolysis (cytosol) yields 2 ATP net and 2 NADH per glucose; the Krebs cycle and electron transport chain in mitochondria yield most ATP via chemiosmosis.

Photosynthesis: light reactions in thylakoids generate ATP and NADPH and split water, releasing O2; the Calvin cycle in the stroma fixes CO2 using RuBisCO.

Central dogma: DNA to RNA (transcription, nucleus in eukaryotes) to protein (translation at ribosomes); mRNA codons are read 5' to 3' in triplets.

Mendel's law of segregation: allele pairs separate during gamete formation; law of independent assortment applies to genes on different chromosomes or far apart on the same one.

Monohybrid cross of heterozygotes gives a 3:1 phenotype and 1:2:1 genotype ratio; dihybrid heterozygote cross gives 9:3:3:1 with independent assortment.

Punnett square reasoning: testcross against a homozygous recessive reveals an unknown dominant phenotype's genotype.

Sex-linked (X-linked) recessive traits appear more often in males because they carry one X; affected fathers pass the allele to all daughters, none to sons.

Non-Mendelian patterns: incomplete dominance blends phenotypes, codominance expresses both, and multiple alleles (ABO blood groups) produce more than two variants in a population.

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

Natural selection acts on phenotypic variation with heritable basis and differential reproductive success; it changes allele frequencies, not individuals.

Speciation requires reproductive isolation; allopatric isolation is geographic, sympatric isolation arises within a shared range via polyploidy, behavior, or timing.

Evidence for common ancestry includes homologous structures, fossil transitions, biogeography, and shared molecular sequences such as conserved ribosomal RNA genes.

Homeostasis maintains internal set points through negative feedback loops; positive feedback amplifies a change and is rarer (e.g., childbirth, blood clotting).

Plant transport: xylem moves water and minerals upward driven by transpiration pull and cohesion-tension; phloem translocates sugars from source to sink.

Vertebrate circulation: fish have a two-chambered heart and single circuit; mammals and birds have a four-chambered heart separating pulmonary and systemic circuits.

Trophic levels transfer roughly 10 percent of energy upward; energy is lost as heat, so food chains rarely exceed four or five levels.

Population growth: exponential growth is density-independent (dN/dt = rN); logistic growth includes carrying capacity K and slows as N approaches K.

Species interactions: competition (-/-), predation and parasitism (+/-), mutualism (+/+), and commensalism (+/0); the niche is a species' functional role and resource use.

Succession: primary succession begins on bare substrate without soil; secondary succession follows disturbance where soil and seed banks remain.

Carbon cycle fluxes include photosynthesis, respiration, combustion, and decomposition; nitrogen fixation by bacteria converts atmospheric N2 into usable ammonia.

Biomes are classified by climate and dominant vegetation; aquatic zones are defined by depth, light penetration, and salinity.

Controlled experiment design: manipulate one independent variable, measure the dependent variable, and hold all other factors constant; include a control group and repeated trials.

Validity versus reliability: validity means the procedure measures the intended variable; reliability means repeated measurements agree.

A hypothesis must be testable and falsifiable; a prediction states the expected outcome under specified conditions.

Data reporting: use mean with a measure of spread (range or standard deviation) and graph the independent variable on the x-axis and the dependent on the y-axis.

Laboratory safety: know location and use of eyewash, safety shower, fire extinguisher, and fume hood; never return unused chemicals to stock bottles.

Goggles are required whenever chemicals, heat, or glassware under pressure are used; contact lenses are discouraged around volatile solvents.

Chemical hazard communication uses GHS pictograms and Safety Data Sheets (SDS) for handling, storage, and spill response.

Inquiry-based instruction sequences engage, explore, explain, elaborate, and evaluate; formative assessment informs instruction while summative assessment measures mastery.

5E and modeling approaches should include explicit safety briefing and a written risk assessment before any hands-on investigation.

Controlled experiment design: manipulate one independent variable, measure the dependent variable, and hold all other factors constant; include a control group and repeated trials.

Validity versus reliability: validity means the procedure measures the intended variable; reliability means repeated measurements agree.

A hypothesis must be testable and falsifiable; a prediction states the expected outcome under specified conditions.

Data reporting: use mean with a measure of spread (range or standard deviation) and graph the independent variable on the x-axis and the dependent on the y-axis.

Laboratory safety: know location and use of eyewash, safety shower, fire extinguisher, and fume hood; never return unused chemicals to stock bottles.

Goggles are required whenever chemicals, heat, or glassware under pressure are used; contact lenses are discouraged around volatile solvents.

Chemical hazard communication uses GHS pictograms and Safety Data Sheets (SDS) for handling, storage, and spill response.

Inquiry-based instruction sequences engage, explore, explain, elaborate, and evaluate; formative assessment informs instruction while summative assessment measures mastery.

5E and modeling approaches should include explicit safety briefing and a written risk assessment before any hands-on investigation.