Theme 2C Flashcards
what is translation
the assembly of amino acids into polypeptides
what do amino acids contain
amino and carboxyl groups, bonded to a central C with a hydrogen and R group
how are two amino acids joined together
by a covalent peptide bond between the carboxyl and amino groups by a dehydration reaction
what are polypeptides
linear chains of amino acids linked by peptide bonds
what are proteins
structures that are folded and may contain multiple polypeptides
how many common amino acids are there
20
what are the 4 main groups of amino acids
non-polar amino acids, uncharged polar amino acids, charged amino acids, and aromatic amino acids
what is notable about non-polar amino acids
R groups usually contain -CH2 or CH3
what is notable about uncharged polar amino acids
R groups usually contain oxygen or OH
what is notable about charged amino acids
R groups usually contain acids or bases that can ionize
what is notable about aromatic amino acids
r groups contain a carbon ring with alternating single/double bonds
what are the three special functional amino acids
methionine, proline, and cysteine
what does methionine do
what does proline do
causes bend in polypeptide chains
what does cysteine do
its disulfide bridge contributes to structure of polypeptides
primary protein structure
amino acid sequence determines folding and 3D structure which is critical for proper function
secondary protein structure
depends on H bonding in the polypeptide backbone
tertiary structure
the 3D structure of a single polypeptide, is composed of interactions between amino acid side chains
quatronary structure
interactions between more than one polypeptide to form a multi subunit protein (like hemoglobin)
what do chaperones do
protect slow folding or denatured proteins by preventing their aggregation
UAA, UAG, and UGA
stop codons
AUG
methionine, start codon
how is degeneracy shown in the genetic code
most amino acids are specified by more than one codon
what are the three rules of the genetic code
- codons on mRNA are read 5’-3’
- codons do not overlap and there are no gaps
- message in translated in a fixed reading frame set by the start codon
what is the acceptor stem
where the amino acid is attached and contains the sequence 5’ - CCA -3’ at the 3’ end of the tRNA
why are there less tRNAs and mRNA codons
some tRNAs can read more than one codon
why can tRNAs read more than one mRNA codon
wobble pairing, the base at the 5’ end of the anticodon can form H bonds with more than one base type
what is “charging”
adding the amino acids to the tRNA to create an aminoacyl-tRNA
what does aminoacyl tRNA synthetase do
adds the amino acid to the receptor stem of the correct tRNA
how many different versions of aminoacyl tRNA synthesases are there
20, one for each of the 20 amino acids
what is the large subunit (50S)
contains the peptidyl-transferase center for formation of peptide bonds
what is the small subunit (30S)
contains decoding center where charged tRNAs read and decode the codon of mRNA
what are the three binding sites of ribosomes
aminoacyl, peptidal, and exit
what does the aminoacyl binding site bind to
the tRNA carrying the next amino acid to be added
what does the peptidal tRNA binding site bind to
the tRNA attached to the growing peptide chain
what does the exit binding site bind to
the tRNA that carried the previous amino acid added
what is the initiation complex made of in eukaryotes
ribosome, mRNA, and the initiator bound to methionine e
which direction does tRNA can the mRNA
5’ -3’ (staring at the 5’ cap)
what are stop codons recognized by
proteins called release factors
how does termination release a completed polypeptide
release factor binds to A site and stimulates peptidyl transferase to cleave polypeptide from P site tRNA
what are the two ways of post-transcriptional regulation of proteins
- phosphorylation
- ubiquination
what is phosphorylation
the addition of a phosphate group to a protein by kinase enzymes, which can activate or inhibit the protein’s activity
what is uniquination
addition of ubiquitin molecules to proteins to target them for destruction by the proteasome
what is epigenetics
changes in gene transcription that occur without changes in DNA sequence
the removal of a mRNA stop codon
1. translation or post translation
2. impact on protein expression (abundance)
3. molecular process affected
translation, no increase/decrease, longer polypeptide
increase ubiquitination of proteins:
- translation or post translation
- impact on protein expression (abundance)
- molecular process affected
post translation, decrease, enhanced degredation by the proteasome
complete inhibition of animpacylation (charging)
- translation or post translation
- impact on protein expression (abundance)
- molecular process affected
translation, decreased, no translation occurring (no amino acid attached to tRNAs)
decrease in histone acetylation in promoter
- translation or post translation
- impact on protein expression (abundance)
- molecular process affected
post translation, no impact on histone protein expression, DNA wound more tightly around histone preventing access to transcriptional initiation complex
change amino acid attached to tRNA from serine to lysine
- translation or post translation
- impact on protein expression (abundance)
- molecular process affected
translation, no increase/decrease, change amino acid sequence of polypeptide
