Translation & Post-Translational Modifications CHAPTER 9.5

Vocabulary flashcards covering key terms from translation, genetic code, and post-translational modification topics.

Proteome

The complete set of proteins expressed by a genome in a cell/organism, including products from genes and post-translational modifications.

Post-translational modification (PTM)

Chemical modifications that occur to a polypeptide after translation, affecting activity, localization, stability, or interactions.

Methylation

Addition of methyl groups to amino acids or nucleic acids; often regulates activity or interactions; SAM is a common methyl donor.

S-adenosyl methionine (SAM)

A common methyl group donor used by methyltransferases in methylation reactions.

Acetylation

Addition of acetyl groups to proteins (often on lysine); can modulate charge and function, frequently linked to transcriptional regulation.

Histone acetyltransferases (HATs)

Enzymes that acetylate histones, generally promoting transcription by loosening chromatin structure.

Glycosylation

Attachment of carbohydrate groups to proteins, forming glycoproteins; includes N-linked and O-linked types.

N-linked glycosylation

Attachment of sugars to asparagine residues; common in the endoplasmic reticulum and Golgi.

O-linked glycosylation

Attachment of sugars to serine or threonine residues; occurs after N-linked glycosylation.

Lipidation

Attachment of lipid groups to proteins, increasing hydrophobicity and membrane association.

Protein folding

Process by which a polypeptide assumes its functional three-dimensional structure.

Protein localization

Targeting and distribution of a protein to its cellular or extracellular destination.

Endoplasmic reticulum (ER)

Organelle where secretory and membrane proteins enter, begin folding, and are sorted; signal peptides direct entry.

Nucleus

Organelle housing DNA and transcription machinery; site of transcription.

Mitochondrion

Organelle producing ATP; site of some PTMs and protein import; contains its own genome.

Reading frame

Division of nucleotide sequence into consecutive codons that determine amino acid sequence.

Codon

A three-nucleotide sequence in mRNA that encodes an amino acid or a stop signal.

Start codon

AUG; initiates translation and codes for methionine at the start.

Stop codon

UAA, UAG, or UGA; terminates translation and does not encode an amino acid.

Coding strand

DNA strand whose sequence corresponds to the mRNA (with T instead of U); also called the sense strand.

Template strand

DNA strand used as the template for RNA synthesis; complementary to the mRNA.

mRNA

Messenger RNA; carries the protein-coding sequence from DNA to the ribosome for translation.

tRNA

Transfer RNA; adaptor molecule that brings specific amino acids to the ribosome in accordance with codons.

Aminoacyl-tRNA synthetase

Enzyme that charges tRNA with its correct amino acid, ensuring translation fidelity.

Frameshift mutation

Insertion or deletion of nucleotides that shifts the reading frame, altering downstream amino acids.

Reversion mutation

A second mutation that restores reading frame or function after a frameshift.

Universal genetic code

The nearly universal mapping of codons to amino acids used across most organisms.

Mitochondrial genetic code

Variant genetic code used by mitochondria; some codons differ from the universal code.

Introns

Noncoding sequences removed during RNA processing (splicing) from the primary transcript.

Exons

Coding sequences retained in mature mRNA and translated into protein.

Central dogma

Concept that genetic information flows from DNA to RNA to protein.

Transcription

Synthesis of RNA from a DNA template, occurring in the nucleus.

Translation

Synthesis of a polypeptide from mRNA at the ribosome.

Post-translational processing

Modifications and processing after translation, including folding, cleavage, and chemical modifications.

Signal sequence

N-terminal motif that directs a protein to the ER and the secretory pathway.

Signal hypothesis

Model proposing that signal sequences direct polypeptides to the ER for sorting.

Protein sorting

Directing proteins to their correct cellular compartments (ER, Golgi, membrane, etc.).

Rough endoplasmic reticulum (RER)

ER studded with ribosomes; site of synthesis and entry for secretory/membrane proteins.

Golgi apparatus

Organelle where proteins are modified (e.g., glycosylation), sorted, and dispatched.

Secreted protein

Protein that is released outside the cell after processing through ER and Golgi.

Chaperone

Molecules that assist proper protein folding and prevent misfolding or aggregation.

Phosphorylation

Addition of a phosphate group to a protein, often regulating activity.

Kinase

Enzyme that catalyzes phosphorylation.

Glycoprotein

Protein with covalently attached carbohydrate chains.

tRNA fidelity

Accuracy with which aminoacyl-tRNA synthetases charge tRNAs to match codons.