Module 10: Biomolecules

Vocabulary practice flashcards covering enzyme classification, kinetics, mechanisms, and inhibition, alongside nucleic acid structures, replication, transcription, and translation.

Enzyme

A protein that acts as a biological catalyst to increase reaction rates by up to $10^{20}$ times and lower activation energy without being consumed.

Carbonic anhydrase

An enzyme that catalyses the reaction $CO_2 + H_2O \rightarrow H_2CO_3$ to remove carbon dioxide from cells, forming up to 36 million molecules per minute.

Absolute specificity

The catalytic property where an enzyme will catalyse only one specific reaction of only one substance, such as urease hydrolysing urea.

Relative specificity

The catalytic property where an enzyme catalyses the reactions of any structurally related substances, such as proteases hydrolysing various proteins.

Stereochemical specificity

The catalytic property where an enzyme only catalyses reactions of a single 3D stereochemical isomer, such as D-amino acid oxidase reacting only with D-amino acids.

International Enzyme Commission (IEC) system

A systematic nomenclature scheme that categorises enzymes into six classes based on the reaction catalysed, systematically naming the substrate, the functional group acted on, and the reaction type.

Active site

The specific 3D region of an enzyme determined by its polypeptide conformation where substrate binding and catalytic reactions occur.

Enzyme-substrate (E-S) complex

The temporary molecular association formed when a substrate binds to the active site of an enzyme prior to chemical conversion into products.

Lock-and-key model

A mechanism of enzyme action stating that the active site has a rigid, pre-formed 3D shape that fits only a substrate of the exact corresponding shape.

Induced-fit model

A mechanism of enzyme action stating that the enzyme has a flexible active site that modifies and adapts its conformation to match the shape of the incoming substrate.

Co-factor

A small non-protein molecule or inorganic ion that an enzyme requires in order to function properly.

Co-enzyme

An organic non-protein molecule that functions as a co-factor to aid enzyme catalytic activity.

Apoenzyme

The inactive protein component that remains after all co-factors or co-enzymes have been removed from an enzyme.

Irreversible inhibition

Permanent inhibition in which an inhibitor forms a permanent bond to a specific functional group of an enzyme, permanently stopping its catalytic activity.

Competitive inhibition

A form of reversible inhibition where an inhibitor with a molecular structure similar to the substrate directly competes with the substrate for binding at the active site.

Non-competitive inhibition

A form of reversible inhibition where an inhibitor binds to a site other than the active site, altering the 3D shape of the enzyme and active site so the substrate can no longer bind.

Assay

A medical procedure used to quantify the concentration or activity of a specific substance, such as an enzyme, in body fluids for disease diagnosis.

Nucleotide

The basic monomer unit of nucleic acids, consisting of a heterocyclic nitrogenous base, a monosaccharide, and a phosphate group.

Pyrimidines

Single-ring heterocyclic amine bases occurring in nucleic acids, specifically cytosine (C), thymine (T), and uracil (U).

Purines

Two-ring heterocyclic amine bases occurring in nucleic acids, specifically adenine (A) and guanine (G).

Primary structure of DNA

The specific linear sequence of heterocyclic bases attached to an alternating sugar-phosphate backbone.

Secondary structure of DNA

The double helix conformation consisting of two anti-parallel nucleotide strands coiled in a right-hand spiral held together by hydrogen bonds between complementary bases.

Complementary base pairing

The specific hydrogen bonding arrangement in DNA where adenine pairs with thymine via two hydrogen bonds and guanine pairs with cytosine via three hydrogen bonds.

DNA replication

The process of unwinding the DNA double helix and synthesising two identical daughter DNA molecules using complementary deoxyribonucleotides.

Replication fork

The Y-shaped active point where the DNA double helix strands begin separating and unwinding, catalysed by helicase.

Leading strand

The newly synthesized DNA strand formed continuously in the $5'$ to $3'$ direction toward the advancing replication fork.

Lagging strand

The newly synthesized DNA strand formed discontinuously away from the replication fork as short Okazaki fragments.

Semiconservative replication

The mechanism of DNA duplication that yields two daughter DNA molecules, each containing one intact parental template strand and one newly formed strand.

Transcription

The process by which RNA polymerase unwinds DNA and links complementary ribonucleotides to synthesize a strand of messenger RNA (mRNA) from a DNA template.

Messenger RNA (mRNA)

A single-stranded RNA molecule that carries genetic coding information from nuclear DNA to ribosomes in the cytoplasm for protein synthesis.

Ribosomal RNA (rRNA)

The structural RNA that constitutes approximately $65\%$ of a ribosome's mass.

Transfer RNA (tRNA)

An RNA molecule responsible for delivering specific amino acids from the cytoplasm to the ribosome to assemble growing polypeptide chains.

Codon

A sequence of three consecutive nucleotide bases on mRNA that specifies a particular amino acid or serves as a translational stop signal.

Stop codon

One of three specific mRNA base triplets (UAG, UAA, or UGA) that do not code for any amino acid and signal the termination of translation.

Translation

The cellular process wherein the genetic code transcribed onto mRNA is decoded at ribosomes to assemble amino acids into a polypeptide chain.

Peptidyl site (P-site)

The binding site on a ribosome that holds the tRNA attached to the growing peptide chain during translation.

Aminoacyl site (A-site)

The binding site on a ribosome where an incoming tRNA carrying the next required amino acid enters and aligns with its codon.

Mutation

A permanent change in the DNA base sequence that occurs at an approximate natural rate of one in every $10^{10}$ replicated bases.