Ch 2 Life's Chemistry and the Importance of Water

Flashcards covering key vocabulary and concepts from the lecture on life's chemistry and the importance of water, including atomic structure, chemical bonding, energy transformations, chemical reactions, and the properties of water and functional groups.

Element

A fundamental substance that consists of only one kind of atom.

Atom

The basic unit of matter, composed of protons, neutrons, and electrons.

Proton

A positively charged particle clustered in the nucleus of an atom.

Electron

A negatively charged particle found outside the nucleus in electron shells, moving rapidly.

Neutron

An uncharged particle clustered in the nucleus of an atom (except for hydrogen).

Nucleus (of an atom)

The central part of an atom where protons and neutrons are clustered.

Electron Shells

Regions outside the nucleus where rapidly moving electrons are found.

Dalton (Da)

A unit for measuring the atomic mass of atoms and atomic particles.

Atomic Number

The number of protons in the nucleus, which determines the identity of an element.

Periodic Table

A table where elements are presented in order of atomic number and organized into vertical columns reflecting similar chemical properties.

Valence Shell

The outermost electron shell of an atom, whose electrons largely determine an element's chemical properties.

Isotopes

Atoms of an element that differ in the number of neutrons.

Atomic Weight

The weighted sum of the atomic masses of an element's isotopes, averaged by their frequency in nature.

Bohr Model

A simple model depicting electrons orbiting the nucleus in electron shells at different distances.

Atomic Orbital

A defined area of space within an electron shell where electrons move.

Octet Rule

States that an atom will lose, gain, or share electrons to achieve a stable configuration of eight electrons in its outermost shell (full s and p orbitals).

Noble Gases

Elements in the last column of the periodic table that have a stable configuration of eight electrons in their outermost shell and do not react with other elements.

Electronegativity

An atom's tendency to attract electrons from another atom.

Chemical Bond

An attraction between two atoms.

Covalent Bond

A strong chemical bond formed when two atoms share one or more pairs of electrons to achieve stable electron configurations in their valence shells.

Ionic Bond

A strong chemical bond formed when one atom transfers one or more electrons to another highly electronegative atom, resulting in electrostatic attraction between oppositely charged ions.

Molecule

Formed when two or more atoms join together chemically.

Compound

A molecule formed by at least two different elements.

Double Bond

A bond formed when two atoms share two pairs of electrons, resulting in two covalent bonds.

Nonpolar Covalent Bond

A covalent bond where electrons are shared equally between two atoms due to similar electronegativities.

Polar Covalent Bond

A covalent bond where electrons are unequally shared between two atoms due to differences in electronegativity, resulting in slight positive and negative charges (δ+ and δ-) on the atoms.

Ion

An electrically charged atom that has lost or gained one or more electrons.

Cation

A positively charged ion.

Anion

A negatively charged ion.

Dipole

A separation of opposite electric charges, such as those occurring in a polar covalent bond.

Dipole-Dipole Interactions

Weak electrostatic attractions between slightly charged atoms in nearby polar bonds.

Hydrogen Bond

A type of dipole-dipole interaction involving an electrostatic attraction between a slightly positively charged hydrogen atom (in -OH or -NH) and a slightly negatively charged oxygen or nitrogen atom.

Van der Waals Interactions

Very weak, transient electrostatic attractions between two atoms (even in nonpolar molecules) due to temporary dipoles caused by asymmetrical electron density.

Energy

The capacity to produce a change.

Kinetic Energy

The energy of movement, including thermal, sound, and electromagnetic energy.

Potential Energy

Stored energy, including gravitational, elastic, chemical-bond, and nuclear energy.

First Law of Thermodynamics

States that energy cannot be created or destroyed; the total amount of energy in a closed system remains constant during transformation.

Second Law of Thermodynamics

States that when an energy transformation occurs, there is an increase in entropy, meaning some energy becomes unavailable to do work.

Entropy

A measure of disorder, or how spread out energy is, or how much of the energy is unusable.

Chemical Reaction

Occurs when atoms combine or change their bonding partners, transforming substances.

Reactants

The starting substances in a chemical reaction, shown on the left side of a chemical equation.

Products

The substances formed in a chemical reaction, shown on the right side of a chemical equation.

Free Energy (ΔG)

The total energy change of a reaction, determined by differences in bond energy and change in entropy.

Exergonic Reaction

A chemical reaction that releases energy, having a negative free energy (ΔG < 0).

Endergonic Reaction

A chemical reaction that requires an input of energy to occur, having a positive free energy (ΔG > 0).

Hydrolysis

A chemical reaction in which a molecule interacts with water, resulting in its breakdown into simpler molecules (typically exergonic).

Condensation Reaction

A chemical reaction in which two molecules combine to form a larger molecule, producing water as a by-product (typically endergonic).

Activation Energy (Ea)

The total amount of energy that must be supplied for a chemical reaction to begin.

Reaction Rate

A measure of how fast products are made per unit of time in a chemical reaction.

Reversible Reaction

A reaction in which both the forward and reverse reactions occur simultaneously.

Equilibrium (chemical reaction)

The point in a reversible reaction where the rates of the forward and reverse reactions are equal and the relative concentrations of reactants and products no longer change.

Specific Heat (of water)

The amount of heat that must be absorbed or lost to change the temperature of 1 gram of water by 1 degree Celsius.

Heat of Vaporization (of water)

The great deal of energy required to vaporize water.

Cohesion (of water)

The attraction of identical water molecules for one another, largely due to hydrogen bonds.

Surface Tension

The force generated by cohesion between water molecules, allowing the surface to resist external force.

Adhesion (of water)

The attraction of water molecules to different molecules or surfaces.

Solvent

A substance in which other substances can dissolve; water is often called the 'universal solvent'.

Hydrophilic

Describes 'water-loving' substances that dissolve easily in water, typically because they are polar or charged.

Hydrophobic

Describes 'water-fearing' substances that do not dissolve in water, typically because they are nonpolar.

Hydration Shell

A layer of water molecules surrounding an ion in solution.

Amphipathic

Describes molecules that have both hydrophobic (water-fearing) and hydrophilic (water-loving) regions.

Self-ionization (of water)

The process where a very small fraction of water molecules spontaneously ionize to form H₃O⁺ and OH⁻ ions.

Hydroxide Ion (OH⁻)

A negatively charged molecular ion formed from the self-ionization of water.

Hydronium Ion (H₃O⁺)

A positively charged cation formed when an H⁺ from water self-ionization adds to another water molecule; often used interchangeably with H⁺.

Neutral Solution

An aqueous solution where the concentrations of H₃O⁺ and OH⁻ ions are equal, with a pH of 7.

Acid (Arrhenius definition)

A compound that raises the concentration of H⁺ (or H₃O⁺) ions when dissolved in water.

Base (Arrhenius definition)

A compound that produces proton acceptors such as OH⁻ ions when dissolved in water, reducing the H₃O⁺ concentration.

pH

The negative logarithm of the concentration of H₃O⁺ ions, used to measure the acidity or basicity of an aqueous solution.

Buffer (chemical)

A solution that stabilizes pH changes, causing only very small pH changes when acids or bases are added.

Functional Groups

Small clusters of atoms attached to larger organic molecules that confer specific chemical properties and reactivity.

Organic Chemistry

The study of carbon-based molecules.

Structural Isomers

Molecules with the same chemical formula but differing in how their atoms and functional groups are joined to one another.

Stereoisomers

Molecules with the same atoms and functional groups but differing in their three-dimensional geometry.

Methyl Group

A nonpolar functional group (-CH₃), important for protein modification and in cytosine nucleotide.

Hydroxyl Group

A polar functional group (-OH), involved in hydrogen bonding and often participates in condensation reactions.

Sulfhydryl Group

A polar functional group (-SH), capable of forming disulfide bridges to stabilize protein structure.

Aldehyde Group

A polar and very reactive functional group (R-CHO), important in energy-releasing reactions.

Keto Group

A polar functional group (R-CO-R'), important in carbohydrates and energy reactions.

Carboxyl Group

A charged, acidic functional group (-COOH) that ionizes to -COO⁻ and H⁺ in living tissues and reacts with amino groups to form peptide bonds.

Amino Group

A charged, basic functional group (-NH₂) that accepts H⁺ to form -NH₃⁺ in living tissues and reacts with carboxyl groups to form peptide bonds.

Phosphate Group

A charged, acidic functional group (-OPO₃²⁻) that ionizes to -O-P-O₂⁻ and 2 H⁺ in living tissues, entering into condensation reactions and releasing significant energy upon hydrolysis when bonded to another phosphate.