Essential Chemistry for Biology - Water and pH

Flashcards covering the essential chemical properties of water, the distinction between hydrophilic and hydrophobic molecules, the pH scale, and the function of buffers in biological systems.

Hydrogen bonding

The attraction caused by the polarization of water molecules that causes them to clump together.

Cohesive

The characteristic of water where it sticks to itself.

Adhesive

The characteristic of water where it sticks to other things, such as rain sticking to a person.

Capillary action

The process that brings water from tree roots to leaves many feet above by utilizing cohesion and adhesion.

Temperature

A measure of the vibrational energy of molecules.

Temperature homeostasis

The maintenance of a stable internal state, which water helps protect by resisting sudden temperature changes.

Density

Defined as $\text{mass/volume}$ or $\text{weight/space it takes up}$; for water, the solid form is uniquely less dense than the liquid form.

Lattice

The crystal structure water molecules form as they freeze and move apart because hydrogen bonds become more permanent.

Solvent

The substance in a solution that dissolves the solute; water's polar nature makes it a 'universal' example.

Solute

The substance that is dissolved by a solvent within a solution.

Hydrolytic enzymes

Enzymes that more easily break down food particles when they are dissolved in water and dispersed.

Hydrophilic

Molecules that interact with or 'like' water, often containing lots of electronegative oxygens.

Hydrophobic

Molecules that do not interact with or 'hate' water molecules.

Hydrogen ion ($H^+$)

A positively charged ion formed when water molecules fall apart; they are extremely reactive and can break down organic molecules.

Hydroxide ion ($OH^-$)

A negatively charged ion produced when a water molecule dissociates.

pH scale

A scale measuring the concentration of $H^+$ ions ($[H^+]$), where each unit change represents a factor of 10.

Acid

A compound that releases $H^+$ into water, lowering the pH and creating a state where $[H^+] > [OH^-]$.

Base

A compound that releases $OH^-$ or combines with $H^+$, increasing the pH and creating a state where $[H^+] < [OH^-]$.

Neutral

A state, such as in pure water, where the concentrations of hydrogen ions and hydroxide ions are equal ($[H^+] = [OH^-]$), represented by pH 7.

Buffers

Substances that prevent major changes in pH by absorbing excess $H^+$ or $OH^-$ to maintain an organism's optimum pH range.