MTEL Biology cheat sheet

Cell theory: all living things are made of cells, cells arise from pre-existing cells, and the cell is the basic unit of structure and function.

Prokaryotes lack membrane-bound organelles and a nucleus; eukaryotes have a nucleus and organelles such as mitochondria, ER, and Golgi.

Mitochondria and chloroplasts carry their own DNA and ribosomes, supporting the endosymbiotic theory of their bacterial origin.

Membrane transport: simple diffusion moves solutes down a gradient; osmosis moves water; facilitated diffusion uses channels; active transport uses ATP (e.g., Na+/K+ pump).

Enzymes lower activation energy and are not consumed; they are substrate-specific at the active site and denature with heat or extreme pH.

Photosynthesis: light reactions in thylakoids produce ATP and NADPH and release O2; the Calvin cycle in the stroma fixes CO2 via rubisco.

Cellular respiration: glycolysis (cytoplasm) yields 2 ATP and 2 pyruvate; the Krebs cycle and oxidative phosphorylation (mitochondria) yield most ATP.

DNA replication is semiconservative; transcription makes mRNA from a DNA template; translation at ribosomes uses codons matched to tRNA anticodons.

Mitosis produces two genetically identical diploid cells; meiosis produces four haploid gametes with crossing over and independent assortment.

Mendelian ratios: monohybrid cross of two heterozygotes gives 3:1 phenotype and 1:2:1 genotype; dihybrid heterozygote cross gives 9:3:3:1.

Punnett squares predict offspring probabilities; testcross with a homozygous recessive reveals an unknown dominant genotype.

Non-Mendelian patterns include incomplete dominance (blended phenotype), codominance (both expressed), and sex-linked traits (more common in males).

Mutations are the ultimate source of genetic variation; natural selection acts on existing phenotypic variation in a population.

Hardy-Weinberg equilibrium (p^2 + 2pq + q^2 = 1) holds only with no mutation, no migration, random mating, large population, and no selection.

Genetic drift (bottleneck, founder effect) and gene flow change allele frequencies; directional, stabilizing, and disruptive selection are selection modes.

Speciation occurs via geographic isolation (allopatric) or reproductive isolation within a range (sympatric); reproductive isolation defines species.

Evidence for evolution includes fossil records, homologous and vestigial structures, embryology, biogeography, and molecular (DNA/protein) comparisons.

Trophic levels transfer energy; roughly 10% passes to the next level, so energy pyramids taper sharply while biomass pyramids vary by ecosystem.

Photosynthesis and respiration drive the carbon cycle; nitrogen fixation by bacteria converts N2 to ammonia; decomposition returns nutrients to soil.

Population growth: exponential (J-curve) under unlimited resources; logistic (S-curve) approaches carrying capacity K.

Symbiosis types: mutualism (both benefit), commensalism (one benefits, other unaffected), parasitism (one benefits, host harmed).

Homeostasis uses negative feedback (e.g., insulin/glucagon, thermoregulation); positive feedback amplifies change (e.g., childbirth, blood clotting).

Human organ systems: circulatory, respiratory, digestive, excretory, nervous, endocrine, immune, reproductive, skeletal, and muscular each have distinct structure-function roles.

Plant structures: xylem transports water and minerals upward; phloem transports sugars; stomata regulate gas exchange and transpiration.

Immune response: innate (barriers, inflammation) versus adaptive (B cells produce antibodies, T cells mediate cell destruction and helper signaling).