BC 351: 3-D STRUCTURE OF PROTEINS
13 Cards in this Set
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X-ray diffraction and nuclear magnetic resonance, two techniques used to solve the three-dimensional structure of molecules, differ in that...
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...only molecules to be analyzed by NMR need to be labeled with isotopes
Only certain isotopes, such as 1H, 13C, 15N, 19F, and 31P, possess the kind of nuclear spin needed to produce a detectable NMR signal.
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Tertiary structures such as the twisted β sheet and the β barrel form because of...
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...the natural tendency of parallel β strands to twist in a right-handed direction
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Two or more proteins that have little sequence similarity, but share the same major structural motif and have functional similarities, belong to the same...
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...superfamily
Proteins and protein families belong to the same superfamily if they share little sequence similarity, but have the same major structural motif and are functionally similar.
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The Hsp70 molecular chaperone proteins are more abundant in cells stressed by elevated temperatures because...
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...Hsp70 is needed to protect proteins that have been denatured by heat
Hsp70 protects denatured proteins by binding to regions of unfolded polypeptides rich in hydrophobic residues, preventing inappropriate aggregation.
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A protein is in its native conformation when...
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...it is in any of its functional, folded states
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Hydrogen bonds between amino acids in a polypeptide occur between which chemical groups?
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the C=O and N-H groups
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Protein disulfide isomerase aids in the folding of proteins by...
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...shuffling disulfide bonds between amino acids
Protein disulfide isomerase catalyzes the interchange or shuffling of disulfide bonds until the bonds of the native conformation are formed.
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Proline residues are most likely to occur in which secondary structure?
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a β turn
Proline residues often occur in β turns because the peptide bond involving the imino nitrogen of proline assumes a configuration that is amenable to a tight turn.
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Fibrous proteins differ from globular proteins in that...
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...fibrous proteins tend to serve structural functions, and globular proteins are more likely to be enzymes
Fibrous proteins, which have polypeptide chains arranged in long strands or sheets, are ideal for providing support and shape. Globular proteins, which are compact and varied in…
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Why is the α-helix conformation in polypeptides such a stable form?
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The α helix structure is stabilized by hydrogen bonds.
The α helix structure is stabilized by internal hydrogen bonds between the hydrogen atom attached to the electronegative nitrogen atom of a peptide linkage and the electronegative carbonyl oxygen atom of the fourth amino acid on t…
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In what way do the Hsp70 class and the chaperonin class of proteins differ from each other?
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Only the chaperonin class forms elaborate protein complexes that contain a pocket into which unfolded proteins bind.
The GroEL chaperonin forms a complex with pockets, in which unfolded proteins are bound and properly folded before release.
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A protein in solution is more likely to maintain its native conformation when...
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...its hydrophobic residues are largely buried in the protein interior
A protein in solution will have its hydrophobic residues largely buried in the protein interior, away from water.
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Which bonds are planar (cannot rotate) in a polypeptide backbone?
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C-N bonds
C-N peptide bonds are planar and are unable to rotate. Rotation is permitted about the N-Cα and the Cα-C bonds.
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BC 351: THE FOUNDATIONS OF BIOCHEMISTRY