Chapter 15 Flashcards
(33 cards)
Draw the structure of an amino acid and state how many common amino acids there are
* You only need to know the basic structure—you do not need to know the structures of the
different R groups shown in the large box of this figure
central carbon atom bonded to NH 2, COOH, and H, 20
O
||
NH2/\OH
- Draw the linkage of two amino acids that have been joined by a peptide bond
Bond between H and OH of R group
- Describe primary, secondary, tertiary, and quaternary protein structures
Primary- AA chain
Secondary- Alpha helix and beta sheet
Tertiary- Helixes and sheets interact in a complex
Quaternary- Multiple AA chains
Define codon
A codon is a sequence of three adjacent nucleotides in DNA or RNA coding for an Amino acid
- Know what is meant by the degeneracy of the genetic code
- Degeneracy: 1 amino acid may be specified by more than one codon, some amino acids are carried by more than one tRNA
- Codons are written
5’ to 3’
- Know what is meant by wobble in the code
- Wobble (nonstandard base pairing at 3rd position (3’) of codon) allows 1 anticodon to pair with > 1
codon
- Start (initiation) codon =
AUG
Out of 64 codons, 61 codons encode proteins because
3 codons are termination codons
- Define translation
genetic code from mRNA used to create a sequence of AA
- Know where translation occurs within the cell
Ribosomes
- Describe tRNA charging as detailed below
tRNA becomes charged with AA via aminoacyl-tRNA synthetase enzymes
First step of translation initiation in prokaryotes: as detailed below
- IF-3 binds to small ribosomal subunit, and both bind Shine-Dalgarno sequence in mRNA
First step of translation elongation as detailed below
- After initiation, the fMet-tRNA is in the P site of the ribosome
Explain the process of translation termination as detailed below
- When stop codon is in the A site, a release factor comes to the A site
- Another release factor joins the ribosome and all components are released
Differentiate between translation initiation in prokaryotes and that of eukaryotes
- In eukaryotes, small ribosomal subunit binds to 5’ cap and poly(A) tail assists with this binding
- Small subunit then moves along mRNA searching for the start codon (scanning)
- Once start codon is found, the rest of initiation is similar to prokaryotes but [[[there are more
initiation factors involved in the process]]]
Explain simultaneous transcription and translation and state whether this occurs in prokaryotic or
eukaryotic cells.
Archaea lack nuclear membranes, *** Prokaryotic
- Explain polyribosomes and state whether these occur in prokaryotic or eukaryotic cells.
Groups of ribosomes on mRNA like beads on a thread to create polypeptides. both
- Define posttranslational modifications and explain its importance
Modifications after translation which can be critical to make a functional protein
o Prokaryotes: AUG codes for
n-formyl methionine
o Eukaryotes: AUG codes for
methionine
- Stop codons:
UAA, UAG, UGA
o_________ corresponds to stop codons, thus ____________ is encoded by them
o Also called nonsense codons or termination codons
No tRNA, no amino acid
Isoaccepting tRNAs are tRNAs with _______________. Wobble allows the anticodon on one type of tRNA to pair with more than one type of codon on mRNA.
different anticodons that accept the same amino acid
