Biological Macromolecules and Chemical Foundations of Life

Comprehensive vocabulary flashcards covering the chemical foundations of life, atomic structure, water properties, chemical bonding, and biological macromolecules (carbohydrates, lipids, proteins, and nucleic acids).

Matter

Anything that occupies space and has mass, existing on Earth in solid, liquid, or gas physical states.

Atom

The fundamental unit of matter, composed of three subatomic particles: protons, neutrons, and electrons.

Atomic Number

The number of protons present in an atom's nucleus, which defines the specific element.

Element

A basic pure substance consisting only of atoms with the same atomic number that cannot be broken down by ordinary chemical means.

Atomic Mass (Weight)

The total mass of an atom, calculated by adding the number of protons and neutrons in its nucleus.

Bohr Model

An atomic model introduced in $1913$ showing a central nucleus containing protons and neutrons surrounded by electrons in circular orbitals at defined energy shells.

Octet Rule

The principle stating that atoms are most stable when their outermost energy shell is completely filled with electrons.

Ion

An atom or group of atoms that has gained or lost one or more electrons, resulting in a net positive or negative electrical charge.

Isotopes

Different structural forms of a single element whose atoms contain the same number of protons but different numbers of neutrons.

Radioactive Isotopes

Unstable isotopes that spontaneously decay into simpler atomic forms while releasing energy.

Half-life

The amount of time required for half of the mass of a radioactive sample to decay into simpler forms.

Positron Emission Tomography (PET) Scan

A nuclear medicine imaging technique that utilizes radioactive biological tracers to produce digital images of internal organ and tissue processes.

Ionic Bond

A chemical bond formed by the complete transfer of one or more electrons from one atom to another, resulting in electrostatic attraction between oppositely charged ions.

Covalent Bond

The strongest type of chemical bond, formed when two atoms share one or more pairs of valence electrons.

Electronegativity

A measure of the attraction an atom's nucleus exerts on shared electrons within a covalent bond.

Nonpolar Covalent Bond

A covalent bond in which shared electrons are pulled equally between atoms with similar electronegativity values.

Polar Covalent Bond

A covalent bond in which electrons are shared unequally because one atom is significantly more electronegative than the other, resulting in partial electrical charges.

Hydrogen Bond

A weak electrostatic interaction between a partial positive charge on a hydrogen atom and a partial negative charge on another electronegative atom, such as oxygen or nitrogen.

Specific Heat

The amount of heat energy required to raise the temperature of a substance by $1\,^\circ\text{C}$.

Hydrophilic

Refers to polar or charged 'water-loving' molecules that interact favorably with water and dissolve readily in aqueous solutions.

Hydrophobic

Refers to nonpolar 'water-fearing' molecules that lack charges and cannot dissolve in water.

pH Scale

A logarithmic scale ranging from $0$ to $14$ that measures the relative concentration of hydrogen ions ($\text{H}^+$) in a solution.

Buffer

A chemical solution that resists rapid changes in pH when acids or bases are added, maintaining biological homeostasis.

Organic Molecules

Chemical compounds containing carbon bonded to hydrogen, serving as the basis for living organisms.

Isomers

Molecules that share the exact same chemical formula but differ in the structural arrangement or placement of their atoms and bonds.

Enantiomers

Isomeric molecules that share identical chemical formulas and bonding orders but are non-superimposable three-dimensional mirror images of each other.

Functional Group

Specific groups of atoms attached to carbon backbones that confer characteristic chemical properties and reactivity to organic molecules.

Monomer

A small molecular subunit that can bind covalently to other similar molecules to construct larger polymers.

Polymer

A large, complex organic molecule formed by repeatedly joining together smaller monomer subunits.

Condensation Reaction

A synthetic chemical process (dehydration synthesis) that links monomers via covalent bonds, producing a single molecule of water and requiring an input of energy.

Hydrolysis Reaction

A degradation chemical process that breaks covalent bonds linking monomers within polymers by adding a molecule of water, releasing energy.

Lipid

A carbon-containing biological macromolecule that is nonpolar and hydrophobic.

Fatty Acid

A hydrocarbon chain attached to a carboxylic acid ($\text{COOH}$) functional group, serving as a primary building block for most lipids.

Saturated Fat

A fatty acid whose hydrocarbon chain contains no double bonds and maximum hydrogen atoms, producing a straight shape that packs densely into solids at room temperature.

Unsaturated Fat

A fatty acid whose hydrocarbon chain contains one or more double bonds, producing kinks in cis configuration that keep the fat liquid at room temperature.

Triglyceride

A lipid composed of three fatty acid monomers joined to a glycerol backbone through ester linkages via condensation reactions.

Ester Linkage

The covalent bond formed between the hydroxyl group of glycerol and the carboxylic acid group of a fatty acid.

Phospholipid

An amphipathic lipid consisting of glycerol linked to a phosphate group ($\text{PO}_4^{3-}$) and two fatty acid tails, forming cellular membrane bilayers.

Amphipathic Molecule

A molecule possessing both hydrophilic (polar) and hydrophobic (nonpolar) chemical regions.

Steroid

A class of lipids distinguished by a characteristic four-ring carbon structure synthesized from the precursor hydrocarbon squalene.

Wax

A protective lipid made of long fatty acid chains esterified to long-chain alcohols, providing a strongly hydrophobic surface coating on plants and animals.

Carbohydrate

A biological macromolecule composed of carbon, hydrogen, and oxygen in an approximate ratio of $1:2:1$ ($\text{C:H:O}$), functioning in energy storage, cell identity, and structural support.

Aldose Sugar

A monosaccharide featuring a carbonyl group located at the end of its carbon chain, forming an aldehyde.

Ketose Sugar

A monosaccharide featuring a carbonyl group located in the middle of its carbon chain, forming a ketone.

Glycosidic Linkage

A covalent bond formed between two hydroxyl groups of monosaccharides during a condensation reaction.

Glycoprotein

A cell-surface marker consisting of carbohydrate sugar chains covalently bonded to a protein, functioning in cell-cell recognition.

Starch

The primary energy storage polysaccharide in plant roots and seeds, composed of $\alpha\text{-glucose}$ monomers joined by $\alpha\text{-1,4-glycosidic}$ linkages in helical structures.

Glycogen

The primary energy storage polysaccharide in animals, stored in liver and muscle cells as highly branched helices of $\alpha\text{-glucose}$ monomers.

Cellulose

A major structural polysaccharide in plant cell walls made of $\beta\text{-1,4-glycosidic}$ linkages that form parallel, hydrogen-bonded fibers resistant to enzymatic hydrolysis.

Chitin

A structural polysaccharide with $\beta\text{-1,4-glycosidic}$ linkages and $\text{NHCOCH}_3$ groups that provides support in fungal cell walls and arthropod exoskeletons.

Protein

A diverse biological macromolecule composed of aminated hydrocarbons (carbon, hydrogen, oxygen, nitrogen) folded into complex functional shapes.

Amino Acid

The monomer building block of proteins, consisting of an $\alpha\text{-carbon}$ linked to an amine group ($\text{NH}_2$), carboxyl group ($\text{COOH}$), hydrogen ($\text{H}$), and a variable side chain ($\text{R}$).

Zwitterion

A dipolar ion containing equal numbers of positively and negatively charged functional groups, resulting in a net electrical charge of zero.

Peptide Bond

An unusually strong single covalent bond that links the carboxyl group of one amino acid to the amino group of another with partial double-bond character.

Primary Structure

The linear sequence of amino acids within a polypeptide chain, written by convention from N-terminus to C-terminus.

Secondary Structure

Regular localized folding patterns within a polypeptide—specifically $\alpha\text{-helices}$ and $\beta\text{-pleated sheets}$—formed by hydrogen bonds along the peptide backbone.

Tertiary Structure

The overall three-dimensional shape of a single folded polypeptide chain resulting from interactions among R-group side chains and the backbone.

Quaternary Structure

The overall protein structure formed when two or more individual polypeptide chain subunits assemble into a functional complex.

Denaturation

The loss of a protein's folded three-dimensional shape and biological function caused by extreme changes in temperature or pH.

Nucleic Acid

An organic macromolecule composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus that stores and transmits heritable genetic information.

Nucleotide

The monomer subunit of nucleic acids, consisting of a phosphate group, a pentose sugar (ribose or deoxyribose), and a nitrogenous base.

Phosphodiester Bond

The covalent linkage connecting the $5'$ phosphate group of one nucleotide to the $3'$ hydroxyl group of another in a nucleic acid chain.

ATP (Adenosine Triphosphate)

A specialized ribonucleotide containing three phosphate groups that serves as the primary intracellular energy currency in living cells.

Condensation Reaction

A chemical process (also known as a dehydration synthesis reaction) that iteratively synthesizes organic polymers by linking monomers with covalent bonds, yielding a single molecule of water ($\text{H}_2\text{O}$) per reaction and requiring energy input.

Hydrolysis Reaction

A chemical process that degrades organic polymers into monomeric subunits by severing covalent bonds using a single molecule of water ($\text{H}_2\text{O}$) per reaction, typically releasing energy.

Fatty Acid

A biological lipid building block consisting of a hydrocarbon chain bonded to a carboxylic acid ($\text{-COOH}$) functional group.

Saturated Fat

A lipid with no double bonds in its carbon-hydrogen chains, containing the maximum number of hydrogen atoms and taking a linear shape that allows tight packing into solids at room temperature.

Unsaturated Fat

A lipid containing one or more carbon-carbon double bonds that produce kinks in the cis configuration, preventing tight molecule packing and keeping it liquid at room temperature.

Triglyceride

A lipid polymer functioning in energy storage composed of three fatty acid monomers joined to a single glycerol molecule via ester linkages.

Ester Linkage

A covalent bond formed during condensation reactions between the carboxylic acid group of a fatty acid and a hydroxyl group of glycerol.

Phospholipid

An amphipathic lipid consisting of a glycerol molecule linked to a phosphate group ($\text{PO}_4^{3-}$) and two fatty acid chains, forming cell and organelle membranes.

Amphipathic Molecule

A molecule that contains both hydrophilic (polar) and hydrophobic (nonpolar) regions.

Steroid

A unique family of lipids distinguished by a four-ring structure, synthesized by cyclizing the triterpenoid hydrocarbon squalene.

Wax

A lipid composed of long fatty acid chains esterified to long-chain alcohols that forms a hydrophobic protective coating on plant leaves and animal surfaces.

Vernix

A white, creamy, waxy lipid substance on newborn babies' skin that protects against pruny and wrinkly skin during nine months floating in amniotic fluid.

Monosaccharide

A simple sugar building block of carbohydrates composed of carbon, hydrogen, and oxygen in a ratio of $\approx 1:2:1$ ($\text{(CH}_2\text{O)}_n$).

Aldose Sugar

A monosaccharide containing a carbonyl group located at the end of its carbon chain, forming a highly reactive aldehyde.

Ketose Sugar

A monosaccharide containing a carbonyl group located in the middle of its carbon chain, forming a reactive ketone.

Glycosidic Linkage

A covalent bond joining separate monosaccharides through a condensation reaction between hydroxyl groups.

Starch

The primary energy storage carbohydrate in plants, composed of $\alpha$-glucose monomers connected by $\alpha$-1,4-glycosidic linkages with $\alpha$-1,6 branching every ~20 units.

Glycogen

The primary energy storage carbohydrate in animals (stored in liver and muscles), composed of $\alpha$-glucose monomers connected by $\alpha$-1,4-glycosidic linkages with $\alpha$-1,6 branching every ~10 units.

Cellulose

A structural polysaccharide in plant cell walls made of $\beta$-glucose monomers joined by $\beta$-1,4-glycosidic linkages that are resistant to enzymatic hydrolysis.

Glycoprotein

A molecule formed by joining carbohydrates to proteins via covalent bonds, functioning on outer cell surfaces as identification badges for recognition and signaling.

Amino Acid

The monomer building block of proteins consisting of a central $\alpha$-carbon bonded to an amine group ($\text{-NH}_2$), a carboxylic acid group ($\text{-COOH}$), a hydrogen atom ($\text{-H}$), and a variable side chain ($\text{-R}$).

Zwitterion

A dipolar molecule containing functional groups with positive and negative electrical charges while maintaining a net charge of zero.

Peptide Bond

An unusually strong single covalent bond formed between a carboxyl carbon of one amino acid and an amine nitrogen of another, possessing double-bond characteristics from electrons in the carbonyl group.

Primary Protein Structure

The linear sequence of amino acids in a polypeptide chain, conventionally written from the N-terminus to the C-terminus.

Secondary Protein Structure

Localized structural folding of a polypeptide chain into $\alpha$-helices or $\beta$-pleated sheets stabilized by hydrogen bonds between backbone carbonyl oxygens and amino hydrogens.

Tertiary Protein Structure

The overall functional three-dimensional folded shape of a polypeptide resulting from interactions between R-groups and the backbone (hydrogen bonds, van der Waals forces, ionic bonds, and disulfide bonds).

Quaternary Protein Structure

The overall macromolecular organization resulting from intermolecular interactions between two or more separate polypeptide subunits.

Denaturation

The unfolding of a protein structure in response to changes in temperature or pH, rendering the protein nonfunctional.

Nucleotide

The monomer subunit of nucleic acids composed of a phosphate group, a pentose sugar (ribose or deoxyribose), and a nitrogenous base.

Phosphodiester Bond

A covalent bond formed via condensation between the 5' phosphate group of one nucleotide and the 3' hydroxyl group of another nucleotide.

Purines

A class of double-ring nitrogenous bases found in nucleic acids, consisting of Adenine [A] and Guanine [G].

Pyrimidines

A class of single-ring nitrogenous bases found in nucleic acids, consisting of Cytosine [C], Uracil [U] (RNA only), and Thymine [T] (DNA only).

ATP (Adenosine Triphosphate)

A specialized nucleotide containing three phosphate groups that serves as the primary energy currency of the cell.

Atomic Number

The specific number of protons present in the nucleus of an atom, defining its chemical identity as an element.

Isotope

A variant form of an element containing the same number of protons but a different number of neutrons in its atomic nucleus.

Half-Life

The time required for half the mass of a radioactive isotope to decay into simpler forms.

Ionic Bond

A chemical bond formed by electrostatic attraction between oppositely charged ions following the complete transfer of electrons between atoms.