The Chemical Context of Life Flashcards

These vocabulary flashcards cover the fundamental principles of chemistry as applied to biology, including atomic structure, chemical bonding, properties of water, and pH balance.

Matter

Anything that has mass and occupies space.

Protons

Positively charged particles located in the nucleus of an atom.

Neutrons

Neutral particles located in the nucleus of an atom.

Electrons

Negatively charged particles found in orbitals surrounding the nucleus.

Element

The simplest form of matter; each contains only one type of atom.

Elements of Life

The four most abundant elements in living organisms: Hydrogen ($63.5\%$), Oxygen ($25.6\%$), Carbon ($9.1\%$), and Nitrogen ($1.06\%$).

Atomic Number

The number of protons in the nucleus, which is equal to the number of electrons in an electrically neutral atom.

Atomic Mass

The sum of protons and neutrons in an atom, measured in daltons (or amu).

Ion

A charged particle resulting from an unbalanced number of protons and electrons.

Cation

A particle with a net positive charge because it has more protons than electrons.

Anion

A particle with a net negative charge because it has fewer protons than electrons.

Orbital

The area around a nucleus where an electron is most likely to be found; it can contain no more than two electrons.

Oxidation

The loss of an electron during a chemical reaction.

Reduction

The gain of an electron during a chemical reaction.

Isotope

Atoms of a single element that possess different numbers of neutrons.

Half-life

The time it takes for one-half of the atoms in a sample of a radioactive isotope to decay.

Valence Electrons

The number of electrons in an atom's outermost energy level.

Octet Rule

The tendency of atoms to establish completely full outer energy levels, consisting of $8$ electrons ($2$ in the first level).

Ionic Bond

A bond formed by the attraction of oppositely charged ions, such as in salt ($NaCl$).

Salt

A compound that releases ions other than $H^+$ and $OH^-$ when dissolved in water.

Covalent Bond

A chemical bond formed when atoms share one or more pairs of electrons to fill their outermost shell.

Electronegativity

An atom's affinity for electrons.

Nonpolar Covalent Bond

A bond where atoms share electrons equally because they have similar electronegativity.

Polar Covalent Bond

A bond where atoms share electrons unequally due to different electronegativities, creating partial charges.

Hydrogen Bond

A weak, transitory attraction between polar molecules, such as the polarity-based attraction between water molecules.

Cohesion

The tendency of water molecules to stick to other water molecules via hydrogen bonding.

Adhesion

The tendency of water molecules to stick to other polar molecules via hydrogen bonding.

Specific Heat

The amount of heat water must absorb before its temperature increases measurably, providing a stabilizing effect.

Heat of Vaporization

The energy required to convert liquid water into gas; the resulting evaporation lowers surface temperature.

Hydrophilic

"Water-loving" molecules that are polar or ionic and readily interact with water.

Hydrophobic

"Water-fearing" molecules that are nonpolar and aggregate in water.

pH Scale

A measure of the number of hydrogen ions ($H^+$) in a solution; a change of $1$ on the scale represents a $10\times$ change in concentration.

Acid

Any substance that dissociates in water to increase the $[H^+]$ and lower the pH.

Base

A substance that combines with $H^+$ dissolved in water, thereby lowering the $[H^+]$ of the solution.

Buffer

A substance that resists changes in pH by releasing or absorbing hydrogen ions to keep $[H^+]$ relatively constant.

Carbonic Acid-Bicarbonate Buffer System

A system where $H_2CO_3 \rightarrow HCO_3^- + H^+$ when blood pH rises, and $HCO_3^- + H^+ \rightarrow H_2CO_3$ when blood pH drops.