MATSEC AM Biology cheat sheet

Water: high specific heat capacity (~4.2 J g⁻¹ °C⁻¹), high latent heat of vaporisation (~2260 J g⁻¹ at 100 °C), cohesion via hydrogen bonding, and solvent polarity underpin thermoregulation, transpiration pull and transport of ions.

Carbohydrates: monosaccharides (triose, pentose, hexose) join by condensation forming glycosidic bonds; starch is α-1,4/α-1,6 branched, cellulose is β-1,4 straight chains cross-linked by hydrogen bonds into microfibrils.

Proteins: amino acids linked by peptide bonds between amino and carboxyl groups; primary, secondary (α-helix, β-pleated sheet), tertiary (ionic, hydrogen, disulfide, hydrophobic interactions) and quaternary structure determine function; denaturation destroys tertiary bonds, not peptide bonds.

Lipids: triglycerides are glycerol plus three fatty acids joined by ester bonds; saturated chains have no C=C and pack densely; phospholipids are amphipathic and self-assemble into bilayers with hydrophobic tails inward.

Enzymes: globular catalysts lowering activation energy; specificity explained by induced fit; rate rises with substrate and temperature until denaturation; pH shifts alter ionisation of active-site residues; competitive inhibitors raise apparent Km, non-competitive lower Vmax.

Cell structure: prokaryotes lack membrane-bound organelles and have 70S ribosomes; eukaryotes have 80S ribosomes, nucleus, mitochondria and endomembrane system; magnification = image size ÷ actual size.

Membranes: fluid mosaic model with phospholipid bilayer, integral and peripheral proteins, cholesterol, glycolipids and glycoproteins; transport by simple diffusion, facilitated diffusion, osmosis (water potential), and active transport using ATP and carrier proteins.

Cell division: mitosis produces genetically identical diploid cells for growth and repair; meiosis has two divisions with crossing over in prophase I and independent assortment in metaphase I, generating genetic variation in haploid gametes.

Gas exchange: Fick's law states rate is proportional to surface area × concentration gradient ÷ diffusion distance; alveoli and gills maximise area and gradient and minimise distance; haemoglobin saturation curve is sigmoid and shifts right with raised CO₂, temperature and 2,3-BPG (Bohr shift).

Transport in plants: transpiration pull, cohesion-tension and root pressure move water through xylem; stomatal opening driven by K⁺ influx lowering water potential of guard cells; phloem translocation uses pressure flow from source to sink.

Respiration: glycolysis (cytoplasm, net 2 ATP, 2 NADH), link reaction and Krebs cycle (matrix), oxidative phosphorylation via chemiosmosis; ATP yield approximately 30–32 per glucose in eukaryotes; anaerobic pathways regenerate NAD⁺.

Photosynthesis: light-dependent reactions in thylakoids split water, produce O₂, ATP and NADPH; Calvin cycle in stroma fixes CO₂ via rubisco; limiting factors include light intensity, CO₂ concentration and temperature.

Homeostasis: negative feedback loops maintain set points; thermoregulation uses vasodilation, sweating and shivering; blood glucose controlled by insulin (uptake, glycogenesis) and glucagon (glycogenolysis, gluconeogenesis); ADH regulates collecting duct permeability.

Genetics: monohybrid 3:1 and dihybrid 9:3:3:1 ratios assume independent assortment and dominance; test cross distinguishes homozygous dominant from heterozygous; sex-linked traits show different ratios in males and females.

Molecular genetics: semi-conservative DNA replication; transcription to mRNA then translation at ribosomes with tRNA anticodons and codons; the genetic code is degenerate, non-overlapping and universal; mutations include substitution, insertion and deletion, the latter causing frameshifts.

Ecology: energy transfer between trophic levels is about 10 % efficient; pyramids of number, biomass and energy; population growth described by exponential and logistic models with carrying capacity; nutrient cycles include carbon, nitrogen and phosphorus.