6.7.2 Protein Synthesis: An Overview Flashcards Preview

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Flashcards in 6.7.2 Protein Synthesis: An Overview Deck (10)
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1
Q

note

A
  • Review: Translation involves the synthesis of a polypeptide as dictated by a mRNA nucleotide sequence. During translation, a messenger RNA strand, tRNA molecules, and ribosomal subunits come together. Nucleotide codons on the mRNA strand specify tRNA anticodons. The tRNA molecules donate specific amino acids. The ribosomal subunits provide a physical site where translation occurs. The product of translation is a newly synthesized polypeptide strand.
    • Review: Translation takes place in three stages, initiation, elongation, and termination.
    • During translation nucleotide codons on the messenger RNA strand are converted into amino acids. The amino acids are bonded together to form a polypeptide strand. Proteins are polypeptide strands in a three-dimensional form. The events of translation, therefore, enable protein synthesis.
2
Q

The events of translation result in protein (polypeptide)

synthesis:

A
  1. A messenger RNA strand reading 5’ AUGGAUCAACGUUAA 3’ is used to translate a new polypeptide strand.
  2. A specific type of tRNA molecule possesses the anticodon 3’ UAC 5’ and the amino acid methionine. The tRNA moves into the A site of the ribosome and bonds with 5’ AUG 3’ on mRNA.
  3. With each new incoming tRNA, the complex of molecules shifts, and the result is that the ribosomal subunits move toward the 3’ end of the mRNA strand.
  4. A second tRNA molecule comes in and has the anticodon 3’ CUA 5’ and the aminoacid aspartine. It moves into the A site and binds with the mRNA codon 5’ GAU 3’. The first tRNA molecule moves into the P site. A peptide bond forms between the two amino acids.
3
Q

The events of translation result in protein (polypeptide)

synthesis, continued:

A
  1. A third tRNA molecule attaches to the A site bearing the anticodon 3’ GUU 5’ and the amino acid valine. It binds with the mRNA codon 5’ CAA 3’. The first and
    second tRNA molecules move into the E and A sites, respectively. The growing polypeptide is now three amino acids long.
  2. A fourth tRNA molecule attaches to the A site carrying the anticodon 3’ GCA 5’ and the amino acid arginine. It binds with the mRNA codon 5’ CGU 3’. The second and third tRNA molecules move into the E and
    A sites, respectively. The chain is now four amino acids longs.
  3. A fifth tRNA molecule moves to the A site. It has the anticodon 3’ AUU 5’ and does not carry an amino acid. Looking at the genetic dictionary, you can see that the
    corresponding mRNA codon, 5’ AUU 3’ is a stop codon. The tRNA’s exit via the E
4
Q

Which of the following ranks the structures in order of size from largest to smallest?

A
  • Chromosome, gene, codon, nucleotide
5
Q

In protein synthesis, __________ provides the energy necessary to form a peptide bond.

A
  • GTP
6
Q

The following section of a DNA molecule codes for a four amino acid polypeptide. Using the genetic dictionary, determine where the gene is on the molecule and what the correct amino acid sequence is.

3′ AGTTTGATCTTTGTA 5′
5′ TCAAACTAGAAACAT 3′

A
  • Methionine, phenylalanine, leucine, valine.
7
Q

Initiation of protein synthesis begins when the __________ of the mRNA binds with __________ at __________ of the ribosome.

A
  • start codon; UAC tRNA; P site
8
Q

Which of the following statements about polyribosomes is not true?

A
  • When polyribosomes occur, as soon as one copy of a polypeptide is complete, the next copy can be started.
9
Q

In the first step of protein synthesis the initiation tRNA binds to the P site of the large ribosomal subunit. Next a __________ with proper __________ comes into the __________ of the ribosome and binds with mRNA.

A
  • tRNA; anticodon; A site.
10
Q

A gene is a portion of a DNA molecule that determines the sequence of amino acids in a __________.

A
  • Polypeptide

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