Chapter 2: The Chemical Level of Organization

Vocabulary practice flashcards covering fundamental chemistry, chemical reactions, enzymes, inorganic compounds, and organic macromolecules from Chapter 2.

Chemistry

The science that deals with the structure of matter.

Matter

Anything that takes up space and has mass.

Atom

The smallest stable unit of matter.

Protons

Positively charged subatomic particles found in the nucleus of an atom.

Neutrons

Neutral subatomic particles found in the nucleus of an atom.

Electrons

Negatively charged subatomic particles that orbit around the nucleus of an atom.

Atomic number

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

Electron cloud

The three-dimensional area surrounding the nucleus of an atom that contains orbiting electrons.

Electron shell

A two-dimensional representation of an electron cloud surrounding the nucleus.

Element

A pure substance composed of atoms of one kind, which cannot be broken down into simpler substances by ordinary physical means.

Isotopes

Versions of an element that have different numbers of neutrons in their nuclei.

Mass number

The total number of protons plus neutrons in the nucleus of an atom.

Radioisotopes

Isotopes with unstable or radioactive nuclei that undergo radioactive decay.

Half-life

The time required for half of a given amount of a radioactive isotope to decay.

Atomic weight

An average of the different atomic masses and proportions of an element's isotopes.

Mole

A specific quantity of an element that has a weight in grams equal to its atomic weight.

Avogadro's number

The constant number of atoms contained in $1\,\text{mol}$ of any given element, equal to $6.023 \times 10^{23}$.

Valence shell

The outermost electron shell of an atom, whose number of electrons determines the element's chemical properties.

Inert elements

Elements that have a full valence shell and are chemically nonreactive.

Molecule

A chemical structure consisting of two or more atoms joined by shared electrons.

Compound

A chemical substance composed of two or more atoms of different elements.

Ionic bonds

Chemical bonds created by the attractions between positively charged cations and negatively charged anions.

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.

Covalent bonds

Strong chemical bonds created when atoms share electrons.

Nonpolar covalent bonds

Covalent bonds involving equal sharing of electrons between atoms that have an equal pull on electrons.

Polar covalent bonds

Covalent bonds involving unequal sharing of electrons between atoms.

Hydrogen bonds

Weak electrical attractions between the partial positive charge of a hydrogen atom in a polar covalent bond and the partial negative charge of an oxygen, nitrogen, or fluorine atom in another polar covalent bond.

Metabolism

All the chemical reactions occurring in the cells and tissues of the body at any given time.

Work

The movement of an object or a change in the physical structure of matter.

Energy

The capacity to do work.

Kinetic energy

The energy of motion.

Potential energy

Stored energy an object possesses because of its position or its physical or chemical structure.

Decomposition reactions

Chemical reactions that break molecules into smaller fragments.

Hydrolysis

A decomposition reaction that involves water to break complex molecules down into smaller fragments.

Catabolism

Decomposition reactions in cells that release energy to power cellular processes.

Synthesis reactions

Chemical reactions that assemble larger molecules from smaller molecules.

Dehydration synthesis

A synthesis reaction that joins molecules together while releasing a molecule of water.

Anabolism

Synthesis reactions in cells that use energy to create chemical bonds.

Exchange reactions

Chemical reactions that rearrange existing components of molecules into new products.

Activation energy

The amount of energy required to start a chemical reaction.

Enzymes

Biological catalysts that lower activation energy to speed up chemical reactions without being consumed.

Exergonic reactions

Reactions in which the amount of energy released is greater than the activation energy, yielding a net release of energy.

Endergonic reactions

Reactions in which the activation energy is greater than the energy produced, absorbing energy overall.

Nutrients

Essential substances obtained from food that are necessary for normal physiological function.

Metabolites

Substances that are directly involved in metabolism.

Inorganic compounds

Compounds that do not contain carbon in bonds to hydrogen as their primary structural component.

Organic compounds

Compounds that contain carbon held in covalent bonds with hydrogen.

Solution

A uniform mixture of two or more substances.

Solute

The dissolved substance in a solution.

Solvent

The liquid medium in which solutes are distributed.

Hydration spheres

Structures formed when polar water molecules surround individual ions or polar molecules to keep them in solution.

Electrolytes

Soluble inorganic substances whose dissociated ions conduct electrical current in solution.

Hydrophilic

Molecules or ions that interact readily with water molecules.

Hydrophobic

Molecules, such as nonpolar fats and oils, that do not interact readily with water.

Colloid

A liquid mixture containing dispersed proteins or other large molecules that remain suspended.

Suspension

A liquid mixture containing large particles that will settle out of solution if left undisturbed.

pH

The negative logarithm of the hydrogen ion concentration of a solution in moles per liter.

Acid

A solute that adds hydrogen ions (proton donor) to a solution.

Base

A solute that removes hydrogen ions (proton acceptor) from a solution.

Salt

An ionic compound that dissociates in water into cations and anions other than hydrogen ions and hydroxide ions.

Buffers

Compounds that stabilize the pH of solutions by neutralizing added acids or bases.

Monomers

Identical or similar organic subunits that join together to form a polymer.

Polymers

Large organic macromolecules formed by joining repeating monomer subunits.

Functional groups

Specific groupings of atoms in organic compounds that influence the chemical properties of those compounds.

Carbohydrates

Organic macromolecules containing carbon, hydrogen, and oxygen in a ratio near $1:2:1$.

Isomers

Molecules that have the exact same molecular formula but different structural arrangements.

Lipids

Organic macromolecules containing carbon and hydrogen in a ratio near $1:2$ with relatively little oxygen, mostly hydrophobic.

Fatty acids

Long chains of carbon and hydrogen atoms with a carboxyl group ($-\text{COOH}$) at one end.

Eicosanoids

Lipids derived from arachidonic acid that function in immunity and local intercellular signaling.

Triglycerides

Glycerides composed of a single glycerol molecule bound to three fatty acid chains.

Steroids

Large lipid molecules characterized by a distinct four-ringed carbon structure.

Phospholipids

Structural lipids consisting of a diglyceride attached to a phosphate group and a nonlipid group.

Micelles

Spherical structures formed by phospholipids and glycolipids in water, with hydrophilic heads facing outward and hydrophobic tails on the inside.

Peptide bond

A covalent bond formed via dehydration synthesis linking the carboxyl group of one amino acid to the amino group of another.

Primary structure

The specific sequence of amino acids along the length of a polypeptide chain.

Secondary structure

The protein shape resulting from hydrogen bonding along the polypeptide chain, forming alpha helices or beta sheets.

Tertiary structure

The complex three-dimensional coiling and folding of a polypeptide chain resulting from interactions between R groups.

Quaternary structure

The protein structure resulting from interactions between two or more individual polypeptide chains.

Denaturation

A change in the three-dimensional structure of a protein that leads to a loss of function.

Glycoproteins

Large functional proteins containing small attached carbohydrate groups.

Proteoglycans

Large polysaccharide chains linked together by polypeptide chains.

Nucleic acids

Large organic macromolecules composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus that store and process genetic information.

Nucleotides

The structural monomer units of nucleic acids, each composed of a pentose sugar, a phosphate group, and a nitrogenous base.

ATP (Adenosine triphosphate)

A high-energy nucleotide compound composed of adenosine and three phosphate groups, serving as the principal cellular energy storage molecule.