AP Biology : Understanding Ribosomes, tRNA, and Anti-codons
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Example Questions
Example Question #11 : Understanding Ribosomes, T Rna, And Anti Codons
Which of the following choices will most likely be found in the aminoacyl site of the large ribosomal unit?
The tRNA molecule with the next amino acid to be added to the polypeptide chain
The amino-acid free tRNA
Initiation factors
The growing polypeptide chain
The tRNA molecule with the next amino acid to be added to the polypeptide chain
The large ribosomal subunit has three sites that interact with tRNA molecules—the peptidyl “P” site, the aminoacyl “A” site, and the exit “E” site. The P-site holds the tRNA corresponding to the most recently added amino acid, which is attached to the growing polypeptide chain by a peptide bond. The A-site holds the tRNA with the next amino acid to be added to the chain. Finally, the E-site holds the free tRNA without an amino acid that was previously in the P-site.
Example Question #12 : Understanding Ribosomes, T Rna, And Anti Codons
If the codon in the mRNA strand is 5' CAG, what is the anticodon strand sequence?
5' GUC
3' GUC
3' GTC
3' CUG
5' GTC
3' GUC
The mRNA strand is synthesized 5' to 3' and contains the codons. tRNA contains the anticodons needed for the corresponding amino acid, and is paired to the codon 3' to 5'.
Example Question #12 : Understanding Ribosomes, T Rna, And Anti Codons
The mRNA codon for methionine is 5' AUG 3'. What is the corresponding anticodon found on the methionine tRNA?
5' UAG 3'
3' AUG 5'
5' ATG 3'
3' UAC 5'
3' TAC 5'
3' UAC 5'
The anticodon of any codon will be the RNA nucleotides that complement the codon sequence. In RNA, adenine (A) complements uracil (U) while cytosine (C) complements guanine (G). Hence, for the codon 5' AUG 3', the complements will be 3' UAC 5'. Note that many of the incorrect answers contain thymine (T), a nucleotide not found in RNA.
Example Question #11 : Understanding Ribosomes, T Rna, And Anti Codons
Which of the following amino acids is responsible for the initiation of the translation of a polypeptide?
Valine
Asparagine
Leucine
Methionine
Alanine
Methionine
The start codon for any strand of RNA begins with the codon that codes for the amino acid methionine. This is the first amino acid in a polypeptide chain. The abbreviation for methionine is: Met.
Example Question #12 : Understanding Ribosomes, T Rna, And Anti Codons
Proteins that will be secreted outside of the plasma membrane of the cell are translated from ribosomes found __________.
on the smooth endoplasmic reticulum
on the plasma membrane
on the rough endoplasmic reticulum
in the nucleus
in the cytosol
on the rough endoplasmic reticulum
When translated from a ribosome on the rough endoplasmic reticulum (RER), the protein is moved through the RER until it is released in a lipid vesicle that can transport the protein to the plasma membrane, where the lipid vesicle fuses with the lipid membrane and the protein is secreted outside the cell. Smooth endoplasmic reticulum does not have ribosomes on it and is used for the production and transport of lipids and in detoxification. No ribosomes are found in the nucleus or directly on the plasma membrane. Ribosomes in the cytosol translate proteins that stay inside the cell.
Example Question #113 : Dna, Rna, And Proteins
In messenger RNA, each codon specifies a particular __________.
amino acid
nucleotide
pyrimidine
purine
amino acid
In messenger RNA, each codon is three nucleotides that codes for a particular amino acid during translation. Purines and pyrimidines are types of nucleotides on DNA and RNA. The genetic code is redundant, but each codon only codes for one amino acid.
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