translation, transcrption and cell signalling

Transcription

Process of copying genetic information from DNA into mRNA.

RNA Polymerase

Enzyme that builds an RNA strand using DNA as a template.

Promoter

Specific DNA sequence where RNA polymerase binds to begin transcription.

Template Strand

DNA strand that RNA polymerase reads to create complementary RNA.

Initiation

First stage of transcription when RNA polymerase binds to the promoter and DNA unwinds.

Elongation

Stage of transcription when RNA polymerase adds complementary RNA nucleotides.

Termination

Final stage of transcription when RNA polymerase stops and releases the RNA strand.

mRNA (Messenger RNA)

Carries genetic instructions from DNA to the ribosome.

Uracil (U)

RNA nitrogenous base that replaces thymine (T).

RNA Processing

Modification of pre-mRNA to produce mature mRNA in eukaryotic cells.

5' Cap

Modified nucleotide added to the beginning of mRNA that protects it and helps ribosome recognition.

Poly-A Tail

Chain of adenine nucleotides added to the end of mRNA that increases stability and helps nuclear export.

Introns

Non-coding sections of pre-mRNA removed during RNA splicing.

Exons

Sections of pre-mRNA that remain after splicing and are joined together.

Splicing

Process of removing introns and joining exons together.

Spliceosome

Complex of proteins and RNA that removes introns from pre-mRNA.

Translation

Process of using mRNA instructions to build a protein.

Ribosome

Cellular structure that reads mRNA and joins amino acids to form a protein.

tRNA (Transfer RNA)

Molecule that carries specific amino acids to the ribosome.

Codon

Group of three nucleotides on mRNA that specifies an amino acid or stop signal.

Anticodon

Three-nucleotide sequence on tRNA that pairs with a complementary mRNA codon.

Amino Acids

Building blocks of proteins.

Polypeptide

Chain of amino acids connected by peptide bonds.

Peptide Bond

Chemical bond that connects two amino acids.

Start Codon (AUG)

Codon that signals the beginning of translation and codes for methionine.

Stop Codons

UAA, UAG and UGA; signal the end of translation.

Initiation (Translation)

Stage when the ribosome assembles on mRNA and the initiator tRNA binds to the start codon.

Elongation (Translation)

Stage when tRNAs bring amino acids and the ribosome forms peptide bonds to grow the polypeptide.

Termination (Translation)

Stage when a stop codon is reached and the completed polypeptide is released.

A Site (Aminoacyl Site)

Ribosome site where incoming tRNA carrying an amino acid binds.

P Site (Peptidyl Site)

Ribosome site that holds the tRNA carrying the growing polypeptide chain.

E Site (Exit Site)

Ribosome site where empty tRNA leaves.

Translocation

Movement of the ribosome along mRNA by one codon during translation.

Release Factor

Protein that recognizes a stop codon and causes the polypeptide to be released.

Central Dogma

Flow of genetic information from DNA to RNA to protein.

Cell Signaling

Process by which cells communicate using chemical or physical signals.

Ligand

Signaling molecule that binds to a specific receptor.

Receptor

Protein that recognizes and binds a signaling molecule to initiate a cellular response.

Reception

First stage of cell signaling when a ligand binds to a receptor.

Transduction

Second stage of cell signaling when the signal is transmitted through a series of molecules inside the cell.

Response

Final stage of cell signaling when the cell performs a specific action.

Signal Amplification

Process where one signaling molecule activates many downstream molecules, increasing the strength of a signal.

Autocrine Signaling

Cell communicates with itself by releasing signals that bind to its own receptors.

Paracrine Signaling

Cell sends signals to nearby cells.

Endocrine Signaling

Cells release hormones into the bloodstream to communicate with distant cells.

Synaptic Signaling

Neurons communicate with target cells by releasing neurotransmitters across a synapse.

Contact-Dependent Signaling

Communication that requires direct physical contact between cells.

Cell-Surface Receptor

Receptor located on the plasma membrane that binds signaling molecules outside the cell.

Intracellular Receptor

Receptor located inside the cell that binds signaling molecules able to cross the plasma membrane.

GPCR (G-Protein-Coupled Receptor)

Cell-surface receptor that activates a G protein when a ligand binds.

G Protein

Protein that relays signals from an activated GPCR to other molecules inside the cell.

GDP

Molecule bound to an inactive G protein.

GTP

Molecule that binds to and activates a G protein.

GTP Hydrolysis

Process where GTP is converted into GDP, turning the G protein off.

Effector Protein

Protein activated by a G protein that helps produce a cellular response.

Second Messenger

Small intracellular molecule or ion that carries signals within the cell.

cAMP

Second messenger that activates protein kinase A (PKA).

Adenylyl Cyclase

Enzyme that converts ATP into cAMP.

PKA (Protein Kinase A)

Enzyme activated by cAMP that phosphorylates target proteins.

Phosphorylation

Addition of a phosphate group to a protein or other molecule.

Protein Kinase

Enzyme that adds phosphate groups to target proteins.

Protein Phosphatase

Enzyme that removes phosphate groups from proteins.

Desensitization

Process that reduces a cell's response to a signal despite continued exposure to a ligand.

Arrestin

Protein that binds certain activated, phosphorylated GPCRs and helps prevent further G-protein activation.

RTK (Receptor Tyrosine Kinase)

Cell-surface receptor that activates signaling pathways through phosphorylation of tyrosine residues.

Dimerization

Process where two receptor molecules join together.

Autophosphorylation

Process where an activated receptor adds phosphate groups to itself or its partner receptor.

Tyrosine

Amino acid residue on proteins that can receive a phosphate group during RTK activation.

Calcium Ions (Ca²⁺)

Second messenger that activates various proteins and cellular processes.

IP₃ (Inositol Triphosphate)

Second messenger that triggers calcium release from the endoplasmic reticulum.

DAG (Diacylglycerol)

Second messenger that helps activate protein kinase C (PKC).

PKC (Protein Kinase C)

Enzyme activated by signaling molecules such as DAG that phosphorylates target proteins.