Water DP IB Biology HL Notes

Crucial for dissolving solutes, cohesion/adhesion of water, DNA base-pairing, protein structures, mRNA/tRNA interactions, and membrane surface effects.
Essential to water's role as a medium for metabolic reactions, making up 70-95% of cell mass.

Cohesion and adhesion facilitate water transport in plants and surface tension.
Hydrophilic molecules dissolve in water; hydrophobic molecules group together.
Water is a universal solvent for biological molecules. Solutes vary in solubility, affecting transport.
Enzymes need water for shape/stability; water aids enzyme-substrate binding.
High specific heat stabilizes temperatures in aquatic habitats and organisms.
Ice is less dense, providing habitats and insulation.
Water has high thermal conductivity and viscosity, benefiting aquatic life.

Water likely came from asteroids and meteorites, releasing vapor that condensed on early Earth.
Extraterrestrial life requires liquid water in the Goldilocks zone.
Transit spectroscopy identifies water signatures on exoplanets, which must also be large enough to maintain an atmosphere.