Essential Cell Biology Chapter 2 - Chemical Components of Cells

Vocabulary flashcards covering chemical bonds, acids and bases, cell composition, and major biological macromolecules from Chapter 2.

Ionic Bond

A chemical bond formed by the gain and loss of electrons between atoms, creating positively and negatively charged ions that attract each other.

Covalent Bond

A chemical bond formed when two atoms share one or more pairs of electrons.

Hydrogen Bond

A weak noncovalent bond formed by an electrostatic attraction between a partially positive hydrogen atom in one polar covalent bond and a partially negative atom in another.

Hydrophilic Molecules

Substances composed of ions or polar molecules that dissolve readily in water by forming electrostatic interactions or hydrogen bonds with water molecules.

Hydrophobic Molecules

Nonpolar substances, such as hydrocarbons containing many $\text{C}\text{--}\text{H}$ bonds, that are insoluble in water due to their inability to form favorable interactions with water molecules.

Acid

A substance that releases hydrogen ions ($\text{H}^+$ or protons) into solution, thereby increasing the hydronium ion concentration.

Weak Acid

An acid that does not completely dissociate in solution, such as the carboxyl group ($-\text{COOH}$).

Base

A substance that reduces the concentration of free hydrogen ions ($\text{H}^+$) in solution, either directly by accepting protons or indirectly by releasing hydroxyl ions ($\text{OH}^-$).

Weak Base

A base that only partially dissociates in solution and reversibly accepts an $\text{H}^+$ ion from water, such as compounds containing an amino group ($-\text{NH}_2$).

pH

A logarithmic measure of the acidity of a solution defined by hydronium ion concentration: $\text{pH} = -\log_{10}[\text{H}^+]$.

Dehydration Synthesis

A chemical condensation reaction that joins monomers into larger polymers through the removal of a water molecule ($\text{H}_2\text{O}$).

Hydrolysis

A chemical reaction that cleaves polymers into smaller subunits by adding a water molecule ($\text{H}_2\text{O}$).

Monosaccharide

The basic monomer subunit of carbohydrates, with the general molecular formula $(\text{CH}_2\text{O})_n$.

Glycosidic Linkage

The covalent bond formed between two monosaccharides during a condensation reaction.

Fatty Acid

An amphipathic molecule consisting of a long hydrophobic hydrocarbon tail linked to a hydrophilic carboxyl group.

Saturated Fatty Acid

A fatty acid with no double bonds in its hydrocarbon tail, forming a straight chain saturated with hydrogen atoms.

Unsaturated Fatty Acid

A fatty acid that contains one or more double bonds in its hydrocarbon tail, creating rigid kinks or bends in the chain.

Triacylglycerol

An energy storage lipid formed by connecting three fatty acid chains to a single glycerol molecule via ester linkages.

Phospholipid

A major structural lipid component of cell membranes composed of a glycerol backbone linked to two hydrophobic fatty acid tails and a hydrophilic polar phosphate head group.

Cholesterol

A steroid lipid characterized by a four-ring hydrocarbon structure that stabilizes cell membrane fluidity and serves as a precursor for steroid hormones.

Amino Acid

The monomer subunit of proteins, consisting of an $\alpha$-carbon bonded to an amino group ($-\text{NH}_2$), a carboxyl group ($-\text{COOH}$), a hydrogen atom, and a variable side group ($\text{R}$).

Peptide Bond

The rigid, planar covalent amide linkage that joins amino acids together in a polypeptide chain.

N-terminus

The end of a polypeptide chain or protein ending in a free amino group, conventionally placed on the left side of a sequence.

C-terminus

The end of a polypeptide chain or protein ending in a free carboxyl group, located at the right end of a sequence.

Primary Structure

The unique linear sequence of amino acids linked by covalent peptide bonds in a protein.

Nucleotide

The monomer subunit of nucleic acids, consisting of a nitrogenous base, a five-carbon pentose sugar, and one or more phosphate groups.

Nucleoside

A compound consisting of a nitrogenous base covalently linked to a pentose sugar without an attached phosphate group.

Pyrimidine

A class of single-ring nitrogenous bases found in nucleic acids, including cytosine ($\text{C}$), uracil ($\text{U}$), and thymine ($\text{T}$).

Purine

A class of double-ring nitrogenous bases found in nucleic acids, including adenine ($\text{A}$) and guanine ($\text{G}$).

Phosphodiester Linkage

The covalent linkage joining nucleotides together in a nucleic acid chain between the $5'$ carbon of one sugar and the $3'$ carbon of the next.

Adenosine Triphosphate (ATP)

A nucleotide derivative containing high-energy phosphoanhydride bonds used to store and transfer chemical energy within the cell.