Chapter 2: The Chemical Level of Organization (Principles of Anatomy and Physiology)

Vocabulary flashcards covering key terms and definitions from Chapter 2: The Chemical Level of Organization.

Matter

Anything that has mass and takes up space.

Mass

The amount of matter a substance contains; weight is the force of gravity acting on mass.

Element

A substance that cannot be broken down by chemical means; composed of one type of atom.

Atom

The smallest unit of matter that retains the properties of an element; composed of protons, neutrons in the nucleus and electrons in the electron cloud.

Proton

Positively charged subatomic particle located in the nucleus.

Neutron

Electrically neutral subatomic particle located in the nucleus.

Electron

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

Atomic number

Number of protons in an atom; defines the element.

Mass number

Total number of protons and neutrons in the nucleus of an atom.

Atomic mass

Average mass of all stable isotopes of an element; measured in daltons.

Ion

An atom that has gained or lost electrons, giving it a positive or negative charge.

Cation

Positively charged ion.

Molecule

A group of two or more atoms bonded together by sharing electrons.

Free radical

An atom or molecule with an unpaired electron in its outer shell; highly reactive.

Ionic bond

Bond formed by electrical attraction between oppositely charged ions; electrons are not shared.

Covalent bond

Bond formed when two or more atoms share electrons.

Nonpolar covalent bond

Covalent bond in which electrons are shared equally between atoms.

Polar covalent bond

Covalent bond in which electrons are shared unequally, creating partial charges.

Hydrogen bond

Weak bond between oppositely charged parts of polar molecules; important for structure and properties of water and macromolecules.

Octet rule

Principle that atoms are most stable with eight electrons in their valence shell.

Water

Polar solvent essential for life; dissolves many substances, provides cohesion, high heat capacity, and participates in hydrolysis and dehydration synthesis.

Hydrolysis

Chemical reaction that uses water to break bonds and split molecules.

Dehydration synthesis

Chemical reaction that removes water to form a new bond between monomers.

Acid

Substance that dissociates to release hydrogen ions (H+); proton donor.

Base

Substance that dissociates to release hydroxide ions (OH−) or accepts protons; proton acceptor.

Salt

Substance that dissociates into cations and anions other than H+ or OH−; product of acid-base neutralization.

pH

Measure of hydrogen ion concentration in a solution; scale from 0 to 14 with 7 as neutral.

Buffer

System that resists changes in pH by converting strong acids or bases into weak acids or bases.

Inorganic compound

Compounds usually lacking carbon; water is the most important inorganic compound in living systems.

Organic compound

Compounds that contain carbon (often hydrogen); covalent bonds; typically large molecules.

Carbon

Element that forms four covalent bonds; foundational to all organic chemistry.

Functional group

Specific group of atoms that impart characteristic properties and reactions to organic molecules.

Hydroxyl

-OH group; polar and hydrophilic; common in alcohols and carbohydrates.

Carboxyl

-COOH group; acidic and hydrophilic; common in amino acids.

Phosphate

Phosphate group (-PO4^3−) that is highly hydrophilic and energy-related (e.g., in ATP).

Amine

-NH2 group; basic; can accept a proton; common in amino acids.

Monosaccharide

Simple sugar; examples include glucose, fructose, galactose, ribose, and deoxyribose.

Lipid

Hydrophobic organic molecules including fatty acids, triglycerides, phospholipids, and steroids.

Fatty acid

Carboxylic acid chain that can be saturated or unsaturated.

Triglyceride

A lipid composed of glycerol bound to three fatty acids; major energy storage form.

Phospholipid

Lipid with a hydrophilic phosphate head and hydrophobic tails; major component of cell membranes.

Steroid

Lipid with four fused carbon rings (cholesterol, hormones, bile salts, vitamin D).

Protein

Large nitrogen-containing molecules that provide structure, regulate processes, transport, and act as enzymes.

Amino acid

Building blocks of proteins; central carbon attached to amino group, carboxyl group, hydrogen, and a variable side chain.

Peptide bond

Covalent bond linking amino acids in a protein.

Primary structure

Unique sequence of amino acids in a protein.

Enzyme

Biological catalyst that speeds up chemical reactions; typically proteins ending in -ase.

Active site

Region of an enzyme where the substrate binds.

DNA

Deoxyribonucleic acid; double helix; stores genetic information in cells; composed of nucleotides with sugar (deoxyribose), phosphate, and bases.

RNA

Ribonucleic acid; single-stranded; guides protein synthesis; bases include A, C, G, U.

Nucleotide

Monomer of nucleic acids; consists of sugar, phosphate, and a nitrogenous base.

ATP

Adenosine triphosphate; primary energy-storing molecule in cells; energy stored in high-energy phosphate bonds.

Cellular respiration

Process by which cells convert glucose into ATP; includes anaerobic and aerobic pathways.

Anaerobic

Processes that occur without oxygen; yield limited ATP (e.g., 2 ATP per glucose during glycolysis).

Aerobic

Process that requires oxygen; yields a large amount of ATP (about 30–32 ATP per glucose in oxidative phosphorylation).