Chapter 2: The Chemical Level of Organization

Vocabulary practice flashcards covering basic principles of chemistry, atomic structure, chemical bonds, chemical reactions, inorganic/organic compounds, and major biological macromolecules.

Matter

Anything that takes up space and has mass.

Mass

The amount of matter present in an object.

Chemical Elements

Substances that cannot be broken down into simpler substances by ordinary chemical means.

Major Elements

The four chemical elements—oxygen, carbon, hydrogen, and nitrogen—that make up about $96\%$ of total body mass.

Lesser Elements

Eight chemical elements—calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium, and iron—that make up about $3.6\%$ of total body mass.

Trace Elements

Fourteen elements present in tiny amounts that make up about $0.4\%$ of total body mass.

Goiter

An enlargement of the thyroid gland caused by a deficiency in the trace element iodine.

Atom

The smallest unit of matter that retains the unique properties and characteristics of an element.

Proton

A positively charged subatomic particle ($p^+$) located within the nucleus of an atom.

Neutron

An uncharged or neutral subatomic particle ($n^0$) located within the nucleus of an atom.

Electron

A negatively charged subatomic particle ($e^-$) that orbits the nucleus in energy levels called electron shells.

Atomic Number

The number of protons contained in the nucleus of an atom.

Mass Number

The total sum of protons and neutrons in an atom's nucleus.

Isotopes

Atoms of the same element that have identical numbers of protons but differing numbers of neutrons.

Ion

An atom or group of atoms that has a positive or negative charge due to an unequal number of protons and electrons.

Cation

A positively charged ion formed when an atom loses one or more electrons.

Anion

A negatively charged ion formed when an atom gains one or more electrons.

Molecule

A particle formed when two or more atoms share electrons.

Compound

A substance containing atoms of two or more different chemical elements combined in a fixed ratio.

Free Radical

An electrically charged atom or group of atoms with an unpaired electron in its outermost shell, making it highly reactive.

Ionic Bond

A chemical bond formed by the force of attraction holding together oppositely charged ions.

Covalent Bond

A strong chemical bond formed when two or more atoms share electrons rather than gaining or losing them.

Non-polar Covalent Bond

A covalent bond in which shared electrons are attracted and distributed equally between the bonded atoms.

Polar Covalent Bond

A covalent bond in which electrons are shared unequally between atoms, creating partial negative ($\delta^-$) and positive ($\delta^+$) charges.

Hydrogen Bond

A weak attraction between a hydrogen atom with a partial positive charge ($\delta^+$) and a neighboring electronegative atom with a partial negative charge ($\delta^-$).

Reactants

The starting materials that interact in a chemical reaction.

Products

The end substances produced as a result of a chemical reaction.

Metabolism

The sum total of all chemical reactions occurring within the human body.

Exergonic Reaction

A chemical reaction that releases more energy than it absorbs.

Endergonic Reaction

A chemical reaction that absorbs more energy than it releases.

Activation Energy

The initial collision energy required to break existing chemical bonds and initiate a chemical reaction.

Catalyst

A chemical agent that speeds up chemical reactions by lowering the required activation energy.

Anabolism

Metabolic synthesis reactions that combine smaller monomer units into complex polymers, requiring energy.

Catabolism

Metabolic decomposition reactions that break complex polymers down into simpler monomers, releasing energy.

Exchange Reaction

A chemical reaction involving both decomposition and synthesis where existing bonds break and new bonds form between exchange partners.

Reversible Reaction

A chemical reaction where the formed products can convert back into the original starting reactants.

Oxidation

The loss of electrons from a molecule, atom, or ion, releasing stored chemical energy.

Reduction

The gain of electrons by a molecule, atom, or ion, gaining chemical energy.

Inorganic Compound

A compound that usually lacks carbon, is structurally simple, and is held together by ionic or simple covalent bonds.

Organic Compound

A compound that always contains carbon, usually hydrogen, and relies on covalent bonding.

Hydrophilic

Substances containing polar covalent bonds or full charges that readily dissolve in water ("water-loving").

Hydrophobic

Substances containing mainly non-polar covalent bonds that do not dissolve easily in water ("water-fearing").

Hydrolysis

A decomposition chemical reaction that breaks larger molecules apart by adding water molecules.

Dehydration Synthesis

A chemical reaction that links two molecules together by removing a molecule of water.

Acid

A substance that dissociates into one or more hydrogen ions ($H^+$) and an anion when dissolved in water.

Base

A substance that dissociates into hydroxide ions ($OH^-$) and a cation when dissolved in water.

Salt

A compound that dissociates in water into cations and anions, neither of which is $H^+$ or $OH^-$.

pH

A scale ranging from 0 to 14 measuring the hydrogen ion concentration ($[H^+]$) in a solution.

Buffer

Chemical compounds or systems that convert strong acids or bases into weak ones to maintain pH homeostasis.

Monomer

Small building-block molecules that join together to form larger biological structures called polymers.

Polymer

A large molecule composed of repeating structural units (monomers) linked by covalent bonds.

Monosaccharides

Simple sugar monomers containing 3 to 7 carbon atoms, including glucose, fructose, galactose, deoxyribose, and ribose.

Disaccharides

Sugars formed by combining two monosaccharide monomers via dehydration synthesis, including sucrose, lactose, and maltose.

Polysaccharides

Complex carbohydrates containing tens to hundreds of monosaccharides linked by dehydration synthesis, such as glycogen, starch, and cellulose.

Glycogen

The primary storage carbohydrate in animal and human tissues.

Saturated Fatty Acid

A fatty acid chain containing only single covalent bonds between carbon atoms, fully saturated with hydrogen atoms.

Unsaturated Fatty Acid

A fatty acid chain containing one or more double covalent bonds between carbon atoms.

Triglyceride

A lipid molecule composed of a single glycerol backbone bonded to three fatty acid chains.

Phospholipid

An amphipathic lipid with a polar hydrophilic head and two non-polar hydrophobic tails, serving as a primary component of cell membranes.

Steroid

A class of lipids characterized by four fused carbon rings, including cholesterol, estradiol, testosterone, and cortisol.

Amino Acid

The building-block monomer of proteins, consisting of a central carbon, an amino group ($-NH_2$), a carboxyl group ($-COOH$), a hydrogen, and a distinct side chain (R group).

Peptide Bond

The covalent bond linking the carboxyl group of one amino acid to the amino group of another.

Denaturation

The loss of a protein's three-dimensional structure and function due to altered environmental conditions like extreme heat or pH.

Enzyme

A protein catalyst that speeds up chemical reactions with high efficiency and specificity.

Active Site

The region on an enzyme where substrate molecules bind to undergo a chemical reaction.

Nucleotide

The monomer of nucleic acids, consisting of a pentose sugar, a phosphate group, and a nitrogenous base.

DNA (Deoxyribonucleic Acid)

A double-stranded double-helix nucleic acid containing deoxyribose sugar that encodes genetic information for making proteins.

RNA (Ribonucleic Acid)

A single-stranded nucleic acid containing ribose sugar and uracil that aids in protein synthesis.

Adenosine Triphosphate (ATP)

The primary energy-transfer molecule in body cells, composed of an adenine base, a ribose sugar, and three phosphate groups.