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Questions and Answers
What is the primary protein structure?
What is the primary protein structure?
Amino acid monomers linked by peptide bonds; the order of amino acids is determined by genes.
What happens when two amino acids join together?
What happens when two amino acids join together?
- A molecule of oxygen is produced
- An energy molecule is released
- A water molecule is lost (correct)
- A peptide bond is created (correct)
What are the three backbone atoms in a polypeptide?
What are the three backbone atoms in a polypeptide?
Carbonyl carbon, amide nitrogen, alpha carbon
The primary structure nomenclature runs from carboxyl (C) to amine (N) of the amino acids.
The primary structure nomenclature runs from carboxyl (C) to amine (N) of the amino acids.
What is the character of a peptide bond in primary structure?
What is the character of a peptide bond in primary structure?
What do phi and psi bond rotations refer to?
What do phi and psi bond rotations refer to?
What are the two main groupings on the Ramachandran plot?
What are the two main groupings on the Ramachandran plot?
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Study Notes
Primary Protein Structure
- Comprised of amino acid monomers connected by peptide bonds.
- Sequence of amino acids is dictated by genetic information.
Peptide Bond
- Formed when two amino acids link, releasing a water molecule through condensation.
- Peptide group created; includes an amino group at the start and a carboxyl group at the end.
- Reverse reaction is known as proteolysis.
- Formation of peptide bonds is catalyzed by ribosomes.
Backbone Structure
- Consists of three backbone atoms: carbonyl carbon (C=O), amide nitrogen (N-H), and alpha carbon (with side chain R).
- Backbone linkages include:
- Peptide bond connecting the carbonyl carbon to the amino/amide.
- Amide linkage to alpha carbon.
- Alpha carbon linking back to the carbonyl carbon.
Nomenclature of Primary Structure
- Polypeptide chains have a free amino end and a free carboxyl end.
- Synthesis direction follows the amino to carboxyl orientation, designated as N-to-C.
Peptide Bond Characteristics
- Peptide bonds are polarized and can form hydrogen bonds.
- Exhibit partial double bond character, limiting rotation.
- Planar configuration allows for tighter packing, providing structural stability, with rotation only around the alpha carbon.
Phi and Psi Bond Rotation
- Phi angle refers to the N(amide)-to-alpha carbon bond.
- Psi angle relates to the alpha carbon-to-carbonyl carbon bond.
- These angles indicate the extent of rotation possible without steric hindrance.
Ramachandran Plot and Secondary Structure
- Regular phi and psi values result in distinct structural formations along the polypeptide chain.
- Main groupings on the Ramachandran plot include alpha helix and beta sheet structures, essential for secondary protein structure.
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