Chapter 2: The Chemical Level of Organization

Vocabulary flashcards covering atomic structure, chemical bonds, inorganic and organic compounds, enzymes, proteins, nucleic acids, and ATP.

Hydrogen-1

A typical hydrogen isotope whose nucleus contains $1$ proton and no neutrons, with $1$ electron orbiting the nucleus in an electron shell.

Deuterium

An isotope of hydrogen (symbolized as $\text{}^{2}\text{H}$) whose nucleus contains $1$ proton and $1$ neutron.

Tritium

An isotope of hydrogen (symbolized as $\text{}^{3}\text{H}$) whose nucleus contains $1$ proton and $2$ neutrons.

Electron Shell

The energy levels orbiting an atomic nucleus, where the first level holds up to $2$ electrons and the second and third energy levels can each contain up to $8$ electrons.

Ionic Bond

A chemical bond formed by the attraction between oppositely charged ions, created when one atom loses electrons (such as a sodium atom becoming $\text{Na}^+$) and another gains electrons (such as a chlorine atom becoming $\text{Cl}^-$).

Polar Covalent Bond

A covalent bond with unequal sharing of electrons, where one atom holds electrons more tightly, creating partial positive ($\delta^+$) and partial negative ($2\delta^-$) charges on the molecule.

Hydrogen Bond

A weak attraction between a partial positive charge ($\delta^+$) on a hydrogen atom of a polar molecule and a partial negative charge ($2\delta^-$) on an oxygen or other electronegative atom of an adjacent molecule.

Activation Energy

The minimum amount of energy required to initiate a chemical reaction, which is lowered in the presence of an enzyme catalyst.

Hydration Sphere

A sheath of oriented water molecules surrounding individual ions in solution when ionic compounds dissociate in water.

pH

A measure of relative hydrogen ion concentration ($[\text{H}^+]$), where $7.00$ is neutral, values below $7.00$ are acidic, and values above $7.00$ are basic.

Glucose

A simple monosaccharide sugar that serves as a primary energy source, existing in both straight-chain and ring structural forms.

Dehydration Synthesis

A chemical reaction that joins two molecules together through the removal of a water molecule, such as combining glucose and fructose to form sucrose.

Hydrolysis

A chemical reaction that breaks down complex molecules into simpler compounds by adding a molecule of water.

Glycogen

A branched polysaccharide composed of glucose molecules that functions as energy storage in animal cells.

Saturated Fatty Acid

A hydrocarbon chain with a carboxyl group ($-\text{COOH}$) at one end where all carbon-carbon bonds are single covalent bonds.

Unsaturated Fatty Acid

A fatty acid possessing one or more double covalent bonds between carbon atoms, creating a sharp bend in the molecular chain.

Steroids

Lipid molecules sharing a distinctive four-carbon ring framework, including cholesterol, estrogen, and testosterone.

Phospholipid

A lipid structural component of plasma membranes consisting of a diglyceride linked to a nonlipid group via a phosphate group.

Eicosanoids

Lipids such as prostaglandins and leukotrienes that serve as chemical messengers coordinating local cellular activities.

Primary Structure

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

Secondary Structure

Protein folding resulting from hydrogen bonding along the polypeptide chain, forming patterns such as an alpha helix ($\alpha$ helix) or beta sheet ($\beta$ sheet).

Tertiary Structure

The complex three-dimensional coiling and folding of a single polypeptide chain into a specific shape.

Quaternary Structure

The protein structure formed by the interaction and arrangement of multiple separate polypeptide subunits, such as the four subunits in hemoglobin.

Active Site

A specific binding region on an enzyme where substrate molecules bind to form an enzyme-substrate complex.

DNA

Deoxyribonucleic acid; a double-stranded nucleic acid coiled in a double helix containing deoxyribose sugar and bases adenine, guanine, cytosine, and thymine, which stores genetic information.

RNA

Ribonucleic acid; a single-stranded nucleic acid containing ribose sugar and bases adenine, guanine, cytosine, and uracil, which directs protein synthesis.

ATP

Adenosine triphosphate; a high-energy compound composed of adenosine and three phosphate groups that stores and transfers energy in cells.