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Chapter 9 vocabulary - genetics
Terms in this set (16)
A peptide; the basic building block of proteins (or polypeptides).
All amino acids have two functional groups (the carboxyl and amino, shown above) bonded to the same carbon atom (called the α carbon). Also attached to the α carbon are an H atom and a side chain, or R (reactive) group.
A chain of linked amino acids; a protein
What are the four basic structures of proteins?
1. primary structure: The sequence of amino acids in the polypeptide chain that is also linear.
2. secondary structure - A spiral or zigzag arrangement of the polypeptide chain.Each shape arises from the bonding forces between amino acids that are close together in the linear sequence. These forces include several types of weak bonds, notably hydrogen bonds, electrostatic forces, and van der Waals forces. The most common secondary structures are the α helix and the β-pleated sheet.
3. tertiary structure - produce by the folding or coiling of the secondary structure to form a globular molecule.
4. Quaternary structure - The multimeric constitution of a protein. A protein is composed of two or more separate folded polypeptides, also called subunits, joined by weak bonds. The quaternary association can be between different types of polypeptides (resulting in a heterodimer if there are two subunits) or between identical polypeptides (making a homodimer).
The part of a protein that must be maintained in a specific shape if the protein is to be functional—for example, in an enzyme, the part to which the substrate binds.
-the site of protein synthesis.
-consists of one large and one small subunit.
- It is a factory containing many machines that act in concert.
-brings together tRNA and mRNA molecules
- to translate the nucleotide sequence of an mRNA into the amino acid sequence of a protein.
RNA component of the ribosome, and is essential for protein synthesis in all living organisms.
The structure of tRNA holds the secret of the specificity between an mRNA codon and the amino acid that it designates. The single-stranded tRNA molecule has a cloverleaf shape consisting of four double-helical stems and three single-stranded loops
aminoacyl-tRNA synthetase codon
An enzyme that attaches an amino acid to a tRNA before its use in translation. There are 20 different aminoacyl-tRNAs, one for each amino acid. Each aminacyl tRNA synthetase is specific for a given amino acid. Synthetases recognize tRNAs by anticodon loop and acceptor stem and other aspects of tRNA structure.
Attaches the appropriate amino acid to the tRNA acceptor stem
A nucleotide triplet in a tRNA molecule that aligns with a particular codon in mRNA under the influence of the ribosome; the amino acid carried by the tRNA is inserted into a growing protein chain. Oriented and written in the 3′ × 5′ direction.
The region in the small ribosomal subunit where the decision is made whether an aminoacyl-tRNA can bind in the A site. This decision is based on complementarity between the anticodon of the tRNA and the codon of the mRNA.
The site in the large ribosomal subunit at which the joining of two amino acids is catalyzed (cause a reaction to occur).
A short sequence in bacterial RNA that precedes the initiation AUG codon and serves to correctly position this codon in the P site of the ribosome by pairing (through base complementarity) with the 3′ end of the 16S RNA in the 30S ribosomal subunit.
pair with the 3′ end of an rRNA, called the 16S rRNA, in the 30S ribosomal subunit
The RNA sequence helps recruit the ribosome to the messenger RNA (mRNA) to initiate protein synthesis by aligning the ribosome with the start codon
What is an initiator factor and what are the difference IFs.
A protein required for the correct initiation of translation. (IF1, IF2, IF3)
F3 is necessary to keep the 30S subunit dissociated from the 50S subunit
IF1 and IF2 act to ensure that only the initiator tRNA enters the P site.
BINDS TO THE P SITE OF THE RIBOSOME
What is an initiator release factor and what are the different Release factors ?
A protein that binds to the A site of the ribosome when a stop codon is in the mRNA. (contain RF1, RF2, RF3)
RF1 recognizes UAA or UAG
RF2 recognizes UAA or UGA
both are assisted by RF3.
The ability of certain bases at the third position of an anticodon in tRNA to form hydrogen bonds in various ways, causing alignment with several different possible codons.
What are the different stages of translation?
Initiation: The first stage of transcription or translation. Its main function in transcription is to correctly position RNA polymerase before the elongation stage, and in translation it is to correctly position the first aminoacyl-tRNA in the P site.
Elongation: It is during the process of elongation that the ribosome most resembles a factory. The mRNA acts as a blueprint specifying the delivery of cognate tRNAs, each carrying as cargo an amino acid. Each amino acid is added to the growing polypeptide chain while the deacylated tRNA is recycled by the addition of another amino acid.Two protein factors called elongation factor Tu (EF-Tu) and elongation factor G (EF-G) assist the elongation process.
Termination: The last stage of transcription; it results in the release of the RNA and RNA polymerase from the DNA template. The cycle continues until the codon in the A site is one of the three stop codons: UGA, UAA, or UAG.
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