Protein structure Flashcards
What biological functions do proteins perform?
Proteins perform the following:
Enzymes
Transport/storage
Structure/support
Cellular motion
Recognition/antibodies
Information/cell signaling
What is the basis of all protein activity?
All protein activity is based on specificity. That is, each protein is specific in its function and/or binding affinity for its substrate.
What is the hierarchy of protein structure?
Primary structure
Secondary structure
Tertiary structure
Quaternary structure
What is primary structure of a protein?
Primary structure refers to the amino acid sequence in a polypeptide chain. The sequence is read from the N-terminus (amino terminus) to the C-terminus (carboxy terminus).
What is secondary structure of a protein?
The secondary structure of a protein referes to the local conformation of the protein that gives rise to regular, repeating structures such as the alpha helix and beta pleated sheet.
What is the tertiary structure of a protein?
Tertiary structure refers to the way in which a protein folds into a characteristic three dimensional shape.
What is the quaternary structure of a protein?
Quaternary structure refers to the individual polypeptide chains in a multi-subunit protein.
How could one denature a peptide bond in a laboratory situation?
High heat and acid.
How does a peptide bon form?
Peptide bonds form via dehydration reactions. Peptides join the carboxy terminus region with the amino terminus region of amino acids.
What intramolecular forces mediate the folding of proteins?
The folding of proteins is mediated by a large number of weak, noncovalent interactions. These reactions include hydrogen bonds, electrostatic interactions, van der Waals interactions, and hydrophobic interactions.
How can polypeptide backbone conformations be described?
These can be described by their torsion angles.
What is the most stable conformation for proteins?
Most proteins adopt the trans conformation as this is the most stable conformation for a protein. Successive carbon atoms are on opposite sides of the peptide bond joining them.
True or false: The polypeptide backbone is a linked series of rigid, planar peptide groups.
True; This planar nature leads to the torsion angles that are seen in proteins.
What atoms within a polypeptide do torsion angles occur between?
Torsion angels occur between the alpha Carbon and Nitrogen bond as well as the alpha Carbon - Carbon bond.
What is the geometry of torsion angles in polypeptides?
180o when the polypeptide is in its planar, fully-extended conformation.
