Biochemistry Key Terms: Hydrolysis, Enzymes, and More

Posted on Apr 1, 2025 in Biochemistry

Biochemistry Key Terms

Lesson 1, 2, and 3

• Hydrolysis reaction: The cleavage of a molecule by the addition of water.
• Amphipathic compounds: Molecules with both polar and nonpolar regions.
• Hydrophobic molecules: Molecules that are not readily dissolved in water.
• Condensation reaction: The formation of cellular polymers from their subunits by the removal of water (reversal of hydrolysis).
• Functional groups: Added groups that confer specific chemical properties on a molecule.
• pH scale: A means of designating the concentration of H+ in an aqueous solution between 1.0 M H+ and 1.0 M OH-.
• Micelles: Spherical aggregates of amphipathic molecules with their polar head groups facing toward water.
• pKa value: A measure of the tendency of a group to give up a proton.
• Clathrate structures: Highly ordered cagelike shell of water molecules around each nonpolar solute molecule.
• Osmosis: Passive diffusion characterized by the passage of water through a semipermeable membrane from a more dilute (hypotonic) to a more concentrated (hypertonic) solution.
• Hydrophilic molecules: Molecules that dissolve easily in water.
• Buffers: Aqueous systems that resist changes in pH when small amounts of acid or base are added.
• Anomeric carbon: The new chiral center formed in ring closure; the carbon is part of the hemiacetal or hemiketal group.
• Furanoses: Five-membered hemiacetals.
• Polysaccharides: Long chains of more than 20 monosaccharide units joined by glycosidic bonds.
• Ketose: A monosaccharide in which the carbonyl group is not at the end of the carbon chain.
• Glycosaminoglycan: Linear polymers composed of repeating disaccharide units.
• Pyranoses: Six-membered hemiacetals.
• Aldose: A monosaccharide in which the carbonyl group is at an end of the carbon chain.
• Monosaccharides: Simple sugars.
• Oligosaccharides: Short chains of less than 20 monosaccharide units joined by glycosidic bonds.
• Epimers: Two sugars that differ only in the configuration around one carbon atom.
• Reducing end: The end of a carbohydrate chain with a free anomeric carbon.
• Anomers: Isomeric forms of monosaccharides that differ only in their configuration about the anomeric carbon.
• Sugar derivatives: A sugar in which a hydroxyl group is replaced with another substituent.
• Hemiacetals: Monosaccharide ring structures in which the carbonyl group has formed a covalent bond with the oxygen of a hydroxyl group along the chain.
• Simple triacylglycerols: Triacylglycerols that contain three identical fatty acids.
• Cis configuration: A bond configuration in which the two hydrogen atoms adjacent to the double bond are on the same side of the chain.
• Vitamins: Essential organic compounds that an animal organism cannot produce itself, but requires in small amounts for metabolism.
• Saturated fatty acid: A fatty acid that does not contain double bonds.
• Mixed triacylglycerols: Triacylglycerols that contain two or three different fatty acids.
• Unsaturated fatty acid: A fatty acid that contains one or more double bonds.
• Trans configuration: A bond configuration in which the two hydrogen atoms adjacent to the double bond are on opposite sides of the chain.

Lesson 6

• Endergonic reactions: Thermodynamically unfavorable, energy-requiring reactions.
• Exergonic reactions: Thermodynamically favorable, energy-releasing reactions.
• Michaelis constant (Km): The substrate concentration at which V0 is one-half Vmax; a measure of the enzyme’s affinity for the substrate.
• Vmax: The maximum initial rate of a catalyzed reaction.
• Denaturation: Loss of protein structure and function.
• Oxidation reactions: Reactions in which a reduced substrate is oxidized and the produced electrons are used to reduce electron carrier molecules.
• Reduction reactions: Reactions in which an oxidized substrate is reduced with electrons aported by reduced coenzymes.
• Enzymes: Molecules (usually proteins) that accelerate chemical reactions to occur at rates fast enough to sustain life without being consumed in the process.
• Activation energy: The energy needed for the creation of a transition state between reactants and products.
• Free energy content (G): A measure of the “driving force” of a reaction of any closed system.
• Entropy (S): The randomness or disorder of the components of a chemical system.
• Enthalpy (H): The heat content of the reacting system, reflecting the number and kinds of bonds in the reactants and products.
• Catabolic reactions: Reactions that break down organic matter and harvest energy by way of cellular respiration.
• Anabolic reactions: Reactions that use energy to construct components of cells such as proteins or nucleic acids from simple molecules.

Lesson 7 & 8

• Glucagon: A peptide hormone that regulates carbohydrate metabolism by increasing the breakdown of glycogen from hepatocytes due to a decrease in blood glucose.
• Glucose transporters: Proteins that transport glucose by facilitative diffusion down concentration gradients.
• Sugar nucleotides: Compounds in which the anomeric carbon of a sugar is activated by attachment to a nucleotide through a phosphate ester linkage.
• Glycogenesis: The process of glycogen synthesis, in which glucose molecules are added to chains of glycogen for storage.
• Glycosome: A complex composed of the glycogen molecule, the enzymes involved in its synthesis and lysis, and the regulatory enzymes.
• Glycogenolysis: The process of glycogen breakdown, in which glucose molecules are released.
• Insulin: A peptide hormone that regulates carbohydrate metabolism by increasing the uptake of glucose to be stored as glycogen when glucose is in high concentrations in the blood.
• Substrate-level phosphorylations: Reactions that involve soluble enzymes and chemical intermediates to produce ATP by ADP phosphorylation.
• Respiration-linked phosphorylations: Reactions that involve membrane-bound enzymes and transmembrane gradients of protons to produce ATP by ADP phosphorylation.
• Protein phosphatases: Enzymes that catalyze dephosphorylation.
• Glycogenin: A protein that is both the primer and the enzyme that catalyzes the assembly of the glycogen molecule.
• Isozymes: Enzymes that catalyze the same reaction but are encoded by different genes and differ in their kinetic and regulatory properties.
• Protein kinases: Enzymes that catalyze phosphorylation.

Lesson 4

• Isoelectric point: The characteristic pH at which the net electric charge of a molecule is zero.
• Peptides: Molecules formed by less than fifty amino acids joined by peptide bonds.
• Coenzyme: A complex organic or metallo-organic cofactor.
• Zwitterion: A dipolar ion of an amino acid.
• Apoenzyme: The protein part of a holoenzyme.
• Proteins: Molecules formed by more than 50 amino acids joined by peptide bonds.
• Cystine: Two cysteines bound by a disulfide bond.
• Protomers: Each of the identical units of an oligomeric protein.
• Residue: An amino acid unit in a peptide or protein.
• Proteinogenic amino acid: Amino acids which are incorporated biosynthetically into proteins during translation.
• Holoenzyme: A complete, catalytically active enzyme together with its bound coenzyme and/or metal ions.
• Homologous proteins: Members of protein families.
• R groups: Side chains of an amino acid.
• Cofactor: A chemical component that is required for the enzyme’s biological activity.
• Carboxyl-terminal: The amino acid residue at the end of a peptide or protein with a free carboxyl group.
• Orthologs: Homologs that are present in different species.
• Oligopeptide: Molecules formed by less than 15 amino acids joined by peptide bonds.
• Stereochemistry: The fixed spatial arrangement of atoms.
• Polypeptide: Molecules formed by 15-50 amino acids joined by peptide bonds.
• Paralogs: Homologs that are present in the same species.
• Amino-terminal: The amino acid residue at the end of a peptide or protein with a free α-amino group.
• Prosthetic groups: Chemical components permanently associated with proteins in addition to amino acids.
• Enantiomers: Stereoisomers that are nonsuperimposable mirror images of each other.
• Multisubunit proteins: Proteins with two or more polypeptides associated noncovalently.
• Allosteric protein: A protein in which the binding of a ligand to one site affects the binding properties of another site on the same protein.