L4. Protein Synthesis and Sorting; Collagen Flashcards
What is the 1st stage of protein synthesis?
Activation of amino acids
–> tRNA aminoacylated
What is the 2nd stage of protein synthesis?
Initiation of translation
- mRNA and aminoacylated tRNA bind to ribosome
What is the 3rd stage of protein synthesis?
Elongation
- cycles of animoacyl-tRNA binding and peptide bond formation until STOP codon
What is the 4th stage of protein synthesis?
Termination and ribosome recycling
- mRNA and protein dissociate, ribosome recycled
What is the 5th stage of protein synthesis?
Folding and posttranslational processing
- Catalysed by a variety of enzymes
Which stage involves the synthesis of mRNA using a DNA template?
a) Initiation
b) Elongation
c) Transcription
d) Translation
Answer: c) Transcription
In which stage does the ribosome read the mRNA codons and assemble amino acids into a polypeptide chain?
a) Transcription
b) Translation
c) Initiation
d) Termination
Answer: b) Translation
During which stage does the mRNA move from the nucleus to the cytoplasm?
a) Termination
b) Elongation
c) Transcription
d) Initiation
Answer: c) Transcription
What is the function of tRNA in protein synthesis?
a) Synthesizing mRNA
b) Carrying amino acids to the ribosome
c) Reading mRNA codons
d) Translating DNA to RNA
Answer: b) Carrying amino acids to the ribosome
Which stage involves the formation of a peptide bond between amino acids?
a) Elongation
b) Initiation
c) Termination
d) Transcription
Answer: a) Elongation
Match the correct stage of protein synthesis to its description:
Initiation
A. Synthesis of mRNA using DNA template
Elongation
B. Assembly of amino acids into a polypeptide chain
Termination
C. Movement of mRNA from nucleus to cytoplasm
Transcription
D. Formation of a peptide bond between amino acids
Translation
E. Start of protein synthesis; ribosome attaches to mRNA
Answers for Mix and Match:
E. Start of protein synthesis; ribosome attaches to mRNA
D. Formation of a peptide bond between amino acids
C. Movement of mRNA from nucleus to cytoplasm
A. Synthesis of mRNA using DNA template
B. Assembly of amino acids into a polypeptide chain
During transcription, RNA polymerase reads the DNA template and synthesizes mRNA.
True / False
Answer: True
The start codon AUG codes for the amino acid methionine.
True / False
Answer: True
Aminoacylated tRNA molecules carry amino acids to the ribosome during translation.
True / False
Answer: True
Termination is the stage where the ribosome reads the mRNA codons and assembles amino acids.
True / False
Answer: False
Translation occurs in the nucleus of the cell.
True / False
Answer: False
Which are the following is/are true for protein synthesis in eukaryotes?
a) All proteins are initially synthesised with methionine at their C-terminus.
b) All proteins are initially synthesised with methionine at their N-terminus.
c) All proteins are initially synthesised with tryptophan at their C-ternimus.
d) All proteins are initially synthesised with a multiple of 3 amino acids in their sequence.
e) None of the above
b) All proteins are initially synthesised with methionine at their N-terminus.
Which of the following is true about the stages in protein synthesis?
a) Binding of SRP to the signal peptide and the ribosome temporarily accelerates protein synthesis.
b) The newly synthesised polypeptides include a signal peptide at their carboxyl termini.
c) Amino acids are incorporated in a random manner during elongation.
d) During termination, mRNA and protein dissociate from ribosome.
e) Proteins folding happens during protein synthesis, inside the ribosome.
d) During termination, mRNA and protein dissociate from robosome.
Which of the following statements is false?
a) Collagen is a protein in which the polypeptides are mainly folded into alpha helix conformation.
b) Disulfide linkages are important for keratin structure.
c) Gly residues are particularly abundant in collagen.
d) Collagen undergoes multiple post-translational modifications and processing before it assembles into its fibril.
e) 5-hydroxylysyl is important to crosslink Collagen Fibrils.
a) Collagen is a protein in which the polypeptides are mainly folded into alpha helix confirmation.
