Chapter 2: The Chemical Basis of Life

Vocabulary flashcards covering key concepts from Chapter 2: The Chemical Basis of Life, including atomic structure, chemical bonds, water properties, pH, and basic biochemistry concepts.

Atom

The smallest unit of an element that retains the properties of that element.

Element

A chemical substance that cannot be broken down into a different substance.

Proton

Positively charged particle in the nucleus.

Neutron

Electrically neutral particle in the nucleus.

Electron

Negatively charged particle orbiting the nucleus.

Nucleus

Dense center of an atom containing protons and neutrons.

Electron cloud

Region around the nucleus where electrons are found.

Atomic number

The number of protons in the nucleus; identifies the element (e.g., 6 for carbon).

Atomic mass

Total number of protons and neutrons in the nucleus.

Isotope

Variants of the same element with different numbers of neutrons.

Carbon-12

Isotope with 6 protons and 6 neutrons; common and stable.

Carbon-13

Isotope with 6 protons and 7 neutrons; stable.

Carbon-14

Isotope with 6 protons and 8 neutrons; rare and radioactive.

Radioactivity

The process by which unstable atomic nuclei decay, emitting radiation.

Radiation

Energy released by radioactive decay; can be dangerous and come in several types.

Neutron radiation

Radiation consisting of neutrons.

Radiocarbon dating

Dating method using carbon-14 decay to estimate age of organic remains (limit ~60,000 years).

Bond

Attractive force that holds atoms together in molecules.

Molecule

A group of two or more atoms held together by chemical bonds.

Covalent bond

Bond formed when atoms share electrons; tends to be strong.

Ionic bond

Bond formed by transfer of electrons; atoms become ions that attract.

Hydrogen bond

Weak attraction between polar molecules, crucial in biology (e.g., between water molecules and in DNA/protein structures).

Van der Waals forces

Weak intermolecular forces due to transient charges between molecules.

Electronegativity

A measure of an atom’s ability to attract electrons in a bond.

Nonpolar covalent bond

Covalent bond where electrons are shared equally (small electronegativity difference).

Polar covalent bond

Covalent bond where electrons are shared unequally (moderate electronegativity difference).

Octet rule

Atoms are most stable when their valence shell has eight electrons.

Valence shell

Outermost electron shell involved in bonding.

Valence (bonding capacity)

The number of bonds an atom can form (e.g., O=2, C=4, N=3).

Carbon’s versatility

Carbon can form four covalent bonds, enabling diverse organic structures (rings and long chains).

Water

Polar molecule (H2O) with unequal electron sharing due to oxygen’s electronegativity.

Polarity

Having an uneven distribution of electron density, creating partial charges.

Cohesion

Attraction between like molecules (water to water).

Adhesion

Attraction between unlike molecules (water to other surfaces).

Surface tension

Cohesive forces at the water surface that enable certain organisms to float or walk on water.

High specific heat

Water’s capacity to store a lot of heat with only a small change in temperature.

Heat of vaporization

Energy required to convert liquid water to water vapor.

Universal solvent

Water’s ability to dissolve many substances.

Solvent

The dissolving agent in a solution.

Solute

The substance dissolved in a solvent.

Solution

A homogeneous mixture of a solute dissolved in a solvent.

pH

Measure of hydrogen ion concentration in a solution; logarithmic scale; lower pH = more acidic, higher pH = more basic.

Acid

Substance that increases H+ concentration, lowering pH.

Base

Substance that increases OH- concentration, raising pH.

Buffer

Molecule that helps resist pH changes by releasing or absorbing H+.

Bicarbonate

Buffer in blood produced by kidneys to maintain pH.

pH 7.4

Normal blood pH; close to neutral.

Metabolic acidosis

Condition where buffering capacity is exceeded, lowering blood pH (e.g., lactic acid buildup).

Stomach acid

Low pH digestive environment that denatures proteins and kills pathogens.

Ice floats

Solid water is less dense than liquid water, allowing ice to insulate bodies of water.

DNA

Deoxyribonucleic acid; double helix stabilized by hydrogen bonds between bases.

Adenine

DNA base that pairs with thymine via hydrogen bonds.

Thymine

DNA base that pairs with adenine via hydrogen bonds.

α-helix

A common protein secondary structure stabilized by hydrogen bonds.

β-pleated sheet

Another protein secondary structure stabilized by hydrogen bonds.

Macromolecule

A large molecule such as protein, nucleic acid, or carbohydrate.