Chapter 2 (PART TWO)

Vocabulary flashcards covering key terms and definitions from the notes on chemical basis of life.

Matter

Anything that has weight (mass) and takes up space.

Element

The simplest substance that cannot be broken down by ordinary chemical means; living organisms rely on about 20 elements.

Atom

The smallest unit of an element that retains its properties; atoms combine to form molecules.

Chemical bond

Attraction between two or more atoms that holds them together in a molecule or compound.

Proton

Positively charged subatomic particle located in the atomic nucleus.

Neutron

Electrically neutral subatomic particle located in the atomic nucleus.

Electron

Negatively charged subatomic particle that orbits the nucleus in electron shells.

Ion

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

Atomic number

Number of protons in the nucleus of an atom; defines the element.

Mass number

Total number of protons and neutrons in the nucleus.

Isotope

Atoms of the same element with the same atomic number but different mass numbers.

Atomic weight

The average mass of the atoms of an element, based on isotope abundances.

Electron shell

Regions around the nucleus where electrons reside; first shell holds 2 electrons, second and third shells hold 8 each.

Valence shell

Outermost electron shell; its fill state determines chemical reactivity.

Ionic bond

Bond formed by the transfer of electrons, creating oppositely charged ions that attract.

Covalent bond

Bond formed by sharing electrons between atoms to fill outer shells.

Hydrogen bond

Weak attraction between a slightly positive H in one molecule and a slightly negative atom (often N or O) in another.

Polar covalent bond

A covalent bond where electrons are shared unequally, creating partial charges.

Polar molecule

Molecule with uneven distribution of electron charge, leading to partial charges.

Nonpolar molecule

Molecule where electrons are shared equally, resulting in no partial charges.

Molecule

Two or more atoms bonded together.

Compound

A molecule composed of two or more different elements.

Molecular formula

Notation showing the types and numbers of atoms in a molecule (e.g., H2O, C6H12O6).

Structural formula

Diagram showing how atoms are bonded and arranged in a molecule.

Synthesis reaction

Chemical reaction in which smaller units combine to form a larger product.

Decomposition reaction

Chemical reaction where a larger molecule is broken into smaller parts.

Exchange reaction

Reaction where parts of molecules switch places to form new substances.

Reversible reaction

A reaction that can proceed in both directions; shown with double arrows.

Enzyme

A biological catalyst that speeds up chemical reactions without being consumed.

Acid

Electrolyte that releases hydrogen ions (H+) in water.

Base

Electrolyte that releases ions which combine with hydrogen ions in water.

pH

A measure of hydrogen ion concentration in solution (0–14; 7 is neutral).

Buffer

A substance that minimizes changes in pH by neutralizing excess acids or bases.

Organic compound

Compound containing carbon and hydrogen; often non-electrolytes (e.g., carbohydrates, lipids, proteins, nucleic acids).

Inorganic substance

Compounds without carbon-hydrogen backbones; often dissolve and release ions (e.g., water, salts, oxygen, carbon dioxide).

Water (H2O)

Most abundant inorganic compound; universal solvent and major component of body fluids.

Oxygen (O2)

Gas essential for energy release from nutrients in cellular metabolism.

Carbon dioxide (CO2)

Waste product of metabolism; expelled by the lungs.

Bicarbonate ion (HCO3−)

An important buffer helping maintain acid–base balance.

Calcium ion (Ca2+)

Vital for bone structure, muscle contraction, and blood clotting.

Chloride ion (Cl−)

Major extracellular negatively charged ion; helps regulate body fluids.

Hydrogen ion (H+)

Determines acidity; higher H+ means lower pH.

Magnesium ion (Mg2+)

Important for bone structure and various metabolic processes.

Phosphate ion (PO4^3−)

Essential for ATP, nucleic acids, and cell membrane polarization.

Potassium ion (K+)

Key for polarization of cell membranes and electrical signaling.

Sodium ion (Na+)

Key for polarization of cell membranes and water balance.

Sulfate ion (SO4^2−)

Supports membrane polarization and various cellular processes.

Carbohydrate

Organic molecule providing energy and structural material; composed of C, H, O.

Monosaccharide

Simple sugar (e.g., glucose, fructose) with 5–6 carbon atoms.

Disaccharide

Two monosaccharides linked together (e.g., lactose, sucrose, maltose).

Polysaccharide

Many monosaccharides linked together (e.g., glycogen, starch).

Lipid

Organic compounds insoluble in water; include fats, phospholipids, steroids.

Triglyceride

Glycerol bound to three fatty acids; major energy source in adipose tissue.

Phospholipid

Lipid with two fatty acids and a phosphate group; forms cell membranes.

Steroid

Lipids with four fused carbon rings; cholesterol is a key example.

Cholesterol

Steroid important for membrane structure and hormone synthesis.

Protein

Organic molecules made of amino acids; roles include structure, enzymes, antibodies, and signaling.

Amino acid

Building block of proteins; contains amino, carboxyl groups and a variable R group.

Polypeptide

Long chain of amino acids forming a protein.

Primary structure

Linear sequence of amino acids in a protein.

Secondary structure

Local folding patterns (e.g., helices, sheets) stabilized by hydrogen bonds.

Tertiary structure

Three-dimensional folding of a protein due to interactions among R groups.

Quaternary structure

Arrangement of multiple polypeptide chains in a protein complex.

Conformation

Three-dimensional shape of a protein that determines its function.

Denaturation

Irreversible loss of a protein’s structure and function due to environmental changes.

Nucleic acid

Biomolecule that stores and transmits genetic information; made of nucleotides.

Nucleotide

Nucleic acid building block: a sugar, a phosphate, and a nitrogenous base.

RNA

Ribonucleic acid; single-stranded; functions in protein synthesis; uses ribose.

DNA

Deoxyribonucleic acid; double-stranded; stores genetic information; uses deoxyribose.

ATP

Adenosine triphosphate; energy-carrying molecule with three phosphate groups.