Protein Structure

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Interacting surfaces

tertiary structure.

True or false. To take a polypeptide chain and fold it into the three dimensional structure of a protein requires elaborate machinery which behaves as a cellular erector set taking a polypeptide chain and folding it into its final state.

False. All that is required for a polypeptide chain to fold into its native three dimensional structure is its interaction with an aqueous environment

True or false. Most side chains are not compatible with an α-helix.

False. Most side chains are compatible with an α-helix because they project away from the helix-center.

True or false. Molecules of the peptide bond are free to rotate.

False. Rotation about the peptide bond does not normally occur.

True or false. The sections of the β pleated sheet are capable of running on in parallel directions.

False. Sections of the β pleated sheet are capable of running an a parallel or anti-parallel direction.

True or false. The reverse (tight, β) turns is often initiated by methionine.

False. The reverse (tight, β) turns is often initiated by proline.

True or false. The peptide group of a peptide bond have two permanent dipoles aligned in opposite directions.

False. The two permanent dipoles align in the same direction

What is the major thermodynamic driving force of protein folding?

The hydrophobic effect.

True or False. Analysis of primary structure of proteins has given insight into the molecular basis of disease.

True

True or false. An amino acid critical for the function of a protein is likely to be conserved when comparing sequences for the same protein in two evolutionarily distant organisms?

True.

True or false. Other bonds in the polypeptide backbone are free to rotate.

True.

True or false. Peptide bond has partial double bond character due to resonance stabilization.

True.

True or false. The hydrogen bonding that stabilizes the β pleated sheet is an example of tertiary structure.

True.

True or false. The α-helix is extensively stabilized by hydrogen bonds within the unit of structure

True.

How is a hydrophobic surface created on a α-helical structure?

alternate inserting hydrophobic residues every 3rd and then 4th position in the polypeptide chain.

structure of peptide bond

carbonyl and oxygen amide hydrogen are in opposite alignment in a trans configuration

What is the function of the reverse (tight, β) turn?

causes the polypeptide chain to reverse direction allowing other forms of secondary structure to fold and pack on one another

α-helix

commonly occurring secondary structure. right-handed helix wound around a central axis

tertiary structure

how segments of secondary structure fold and pack to form a complete three dimensional structure of the protein

primary structure

linear sequence of amino acids in the polypeptide chain.

quaternary structure

non-covalnet assembly of polypeptide chains

In what kind of proteins are quaternary structures found?

oligomeric proteins with more than one polypeptide chain

What does proline do to an α-helix

proline is a helix breaking or kinking amino acid.

homopolymer

quaternary structure that consists of a single protein subunit

heteropolymer

quaternary structure that consists of different protein subunits.

What are interacting surfaces a consequence of?

secondary structure allows for the segregation of side chain functional groups to different surfaces of a structure.

Reverse (tight, β) turns

secondary structure often found in globular proteins.

Random structure

secondary structure that lacks a defined repeating geometrical pattern.

β (pleated) sheet

secondary structure with extended conformation. characteristic zig-zag pattern with side chains above and below the horizontal axis.

secondary structure

short segments of the polypeptide backbone that assume distinct structures

Denaturation

the partial or complete unfolding of a protein resulting in the loss of function.

What dictates a protein's 3-D structure and function?

the primary structure


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