Biochemistry 2280A Lecture Notes - Cell Membrane, Peptide, Aromatase

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scarletrabbit663

25 Aug 2013

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The second level of protein structure describes the local pattern of the backbone or linear amino acid sequence. These structural elements are stabilized by hydrogen bonds between the backbone amino and carboxyl termini. Two major types of secondary structure include the alpha helix and the beta strand (also known as the beta-pleated sheets). There are other types of secondary structures, but these two are the most common. Hydrogen bonds are bonds between a hydrogen atom and an electronegative atom, such as nitrogen or oxygen, when the hydrogen itself is covalently bonded to another electronegative atom. This form of bonding occurs very frequently in many types of protein structures. Hydrogen bonds are strongest when the three atoms involved are in a straight line. For example, amino acids in polypeptide chains are often hydrogen bonded together. Hydrogen bonding is most recognized in water molecules. The alpha helix is a coiled spring arrangement of secondary structures found in proteins.

Related Questions

The sequence of amino acids is considered to be the ________ structure of a protein.

Select one:

a. secondary

b. tertiary

c. quaternary

d. primary

The pattern the backbone folds, for example alpha-helix or beta pleated sheet, is the ________ structure of a protein.

Select one:

a. quaternary

b. secondary

c. tertiary

d. primary

Which type of forces stabilizes the primary structure of a protein?

Select one:

a. Salt bridges

b. Hydrogen bonding between the carbonyl group and amino group

c. Dipole-dipole

d. Peptide bonds

The interaction of the side chains on the amino acids, for example hydrophobic attractions, is the ________ structure of a protein.

Select one:

a. quaternary

b. secondary

c. tertiary

d. primary

violetyellowjacket662

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1. The level of protein structure that is stabilized primarilyby non-covalent interactions between the side chains within asingle polypeptide chain is refered to as its:

A) primary structure

B) secondary structure

C) tertiary structure

D) quaternary structure

E) none of the above

2. Collagen, a strong fibrous protein found in connectivetissue, bone, and the extracellular matrix, has a structure inwhich three left-handed helices wind around each other to form aright-handed triple helix. The primary structure of collagen has arepeat unit of -(Gly-X-Pro)- Which of the following bonds stabilizethe collagen triple helix? (mark all that apply)

A) Hydrogen bonds between hydroxyproline residues

B) Hydrogen bonds between N-H and C=O

C) Ionic bonds between amino acid side chains

D) Hydrogen bonds between charged amino acids

3. The non-covalent forces that stabilize the Beta-strandconformation of peptides include:

A) H-bonds between amide C=O and amide NH

B) Van der Waals packing between the peptide backbone atoms

C) Van der Waals packing due to side chain interdigitation

D) Only A and B above

E) None of the above

4. What is the approximate length difference of a 22-kDasingle-stranded ?-helical protein segment vs. a 22-kDasingle-stranded ?-strand protein segment? Assume a mean residuemass of 110 Da. Show work.

5. Circular dichroism measurements have shown that the peptidebackbone of poly-l-lysine (KKKKKKK) adopts a random coilconformation at pH 7.0, but becomes ?-helical as the pH is raisedabove 10. This observation is known as the

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Biochemistry 2280A Lecture Notes - Cell Membrane, Peptide, Aromatase

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