Module 2 – Chemical Bonds, Biomolecules & Enzymes

Vocabulary flashcards covering atomic structure, chemical bonds, molecular polarity, biomolecules, protein architecture, enzyme function, and kinetics.

Atom

The smallest unit of matter, composed of protons, neutrons, and electrons.

Proton

Positively-charged subatomic particle; its number determines an element’s identity.

Neutron

Electrically neutral subatomic particle found in an atom’s nucleus.

Electron

Negatively-charged subatomic particle that orbits the nucleus.

Ionic Bond

Chemical bond formed when one atom transfers electrons to another, creating oppositely charged ions that attract.

Covalent Bond

Chemical bond in which two atoms share pairs of electrons.

Single Covalent Bond

A covalent bond involving one shared pair (2) of electrons.

Double Covalent Bond

A covalent bond involving two shared pairs (4) of electrons.

Nonpolar Covalent Bond

Covalent bond with equal sharing of electrons between atoms.

Polar Covalent Bond

Covalent bond with unequal sharing of electrons, creating partial charges (δ+ / δ−).

Electronegativity

An atom’s tendency to attract shared electrons; higher values create polarity.

Hydrogen Bond

Weak electrostatic attraction between δ+ hydrogen and δ− electronegative atoms (e.g., O or N).

Hydrophilic

Water-loving; polar or ionic molecules that dissolve in water.

Hydrophobic

Water-fearing; non-polar molecules repelled by water.

Amphiphilic

Molecule with both hydrophilic and hydrophobic regions, e.g., phospholipids.

Phospholipid

Amphiphilic lipid forming the basic structure of cell membranes.

Cell Membrane

Phospholipid bilayer that regulates movement of substances into and out of a cell.

Polymer

Large molecule made of repeating subunits (monomers).

Monomer

Small subunit that joins with others to form a polymer.

Carbohydrate

Polymer of sugar monomers; includes glycogen in animals.

Lipid

Hydrophobic biomolecule category that includes fatty acids, triglycerides, and phospholipids.

Protein

Polymer of amino acids; performs structural, catalytic, and regulatory functions.

Nucleic Acid

Polymer of nucleotide monomers; forms DNA and RNA.

Amino Acid

Protein monomer containing amino group, α-carbon with R group, and carboxyl group.

R Group (Side Chain)

Variable group on an amino acid that determines polarity, charge, and reactivity.

Peptide Bond

Covalent bond linking amino acids between carboxyl and amino groups.

Dehydration Synthesis

Reaction that joins monomers (e.g., amino acids) by removing water; forms polymers.

Primary Structure (Protein)

Linear sequence of amino acids in a polypeptide chain.

Secondary Structure (Protein)

α-helix or β-pleated sheet formed by hydrogen bonding between backbone atoms.

Tertiary Structure (Protein)

Overall 3-D folding of a single polypeptide due to R-group interactions.

Quaternary Structure (Protein)

3-D arrangement of two or more polypeptide subunits in a protein.

Denaturation

Loss of protein’s 3-D structure (and function) due to heat, pH, etc.

Enzyme

Protein catalyst that speeds up biochemical reactions without being consumed.

Active Site

Region on an enzyme where substrate binds and reaction occurs.

Substrate

Reactant molecule that an enzyme acts upon.

Michaelis–Menten Curve

Graph showing reaction rate versus substrate concentration for an enzyme.

Vmax

Maximum reaction rate on a Michaelis–Menten curve when the enzyme is saturated.