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Polypeptides
Macromoecular subunits of proteins. Composed of amino acids.
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Amino acids
- 20 different building blocks of polypeptides.
- Central C bonded to a H and an Amino, Carboxyl, and R group.
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Carboxyl group
- COOH
- Bonded to central C in an amino acid.
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Amino group
- NH2
- Bonded to central C in an amino acid.
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Peptide bond
Covalent bond formed between the caboxyl of one amino acid and the amino group of an adjacent amino acid.
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Primary Strucure
The amino acid sequence.
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Secondary structure
The regular folding and twising of a peptide chain into a variety of shapes.
Product of weak electrostatic or H bonds between NH and CO.
Commonly an alpha-helix.
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Tertiay structure
3 dimensional structure created from secondary structure and often called conformation.
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Quaternary structure
Complex of polypeptide chains, more than one, in a protein.
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Genetic code
A triplet code. 3 nucleotides makes a codon in mRNA that codes for a single type of amino acid
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Frameshift mutations
A nucleotide aded or removed causes a shift in the 3 letter code causing a different amino acid to be specified.
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Reversion
The process of changing a mutant back into wild type by inserting nucleotides and returning the reading frame to the original 3 letter code.
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Degeneracy
More than one codon codes for a specific amino acid.
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Stop codons
- UAA
- UAG
- UGA
- Also called nonsense codons and do not code amino acids.
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Wobble hypothesis
- Occurs on the anticodon.
- Allows 61 sense codons to read by fewer tRNA molecules.
- 5' base or 3rd codon, can pair with more than one type of base.
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aminoacyl-tRNA synthecase
Enyzyme that attaches the correct amino acid to a tRNA molecule.
The process is called aminoacylation or charging.
Uses energy from ATP hydrolysis.
There is one for each amino acid; Total 20.
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Purines
- Nine member, double ringed structures.
- Nucleotides.
- Adenine
- Guanine
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Pyrimidines
- Six memebered, single ringed structures.
- Nucleotides.
- Cytosine
- Uracil
- Thymine
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Shine-Dalgarno sequence
- Only found in prokaryotic cells.
- A purine-rich, ribosome-binding site.
- A sequence upstream of the AUG start codon
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Peptidyl transferase
An enzyme that removes amino acid from tRNA in the P site and inds it with a peptide bond to the amino aicd located in the A site.
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Tranlocation
The ribosome moves one codon along the mRNA towards the 3' end.
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Termination factors
- Protiens that help the ribosome recognize stop codons.
- Also called release factors.
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