Biochemistry 2280A Lecture Notes - Lecture 4: Proline, Van Der Waals Force, Aromatase

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ambermink919

23 Apr 2017

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Distinguish between primary and secondary and tertiary protein structure. Describe the characteristics of an alpha helix, beta sheet. Restricts the possible folding patterns of the chain. Even proteins can be referred to as polypeptides. Proteins can fold into many different shapes. Certain structural elements are found in many proteins. General rules guiding how proteins obtain nal form. Stabilized by hydrogen bonds: between backbone n-h and c=o groups. Two major types: a-helix and b-strand: slightly <50% of the average globular protein. Other types include turns and different helices. A bond between a hydrogen bond and an electronegative atom, such as nitrogen or oxygen, when the hydrogen itself is covalently bonded to another electronegative atom. Hydrogen bonds form when a hydrogen atom is sandwiched between two electron-attracting atoms (usually o or n) Hydrogen bonds are 1/20th the strength of a covalent bond. Precise dimensions: 3. 6 residues per turn, 0. 54 nm per turn. Side chains project outwards: no interior space.

Related Questions

1. A sequence of amino acids in a certain protein is found to be â Ser â Gly â Pro â Gly â

The sequence is most probably part of a(n):

a. beta turn

b. antiparallel beta sheet

c. alpha-helix

d. parallel beta-sheet

e. alapha-sheet

2. Which statement about peptides bonds is NOT TRUE?

There is perfectly free rotation about the peptide bond.

The peptide bond has partial double-bond character.

The peptide bond is shorter than a normal carbon-nitrogen single bond.

The peptide bond usually has a trans configuration with respect to the alpha-carbons of the two amino acids involved in the peptide bond.

Peptide bonds are made via condensation of an amine and a carboxylic acid with loss of water.

3. Which of the following statements about proteins is FALSE?

	Active proteins are generally very loosely structured.
	In water-soluble proteins, hydrophobic amino acid residues are generally buried and not exposed to water.
	Primary structure determines tertiary structure.
	Secondary structure is regular, recurring arrangements in space of nearby amino acid residues in a polypeptide.
	Quaternary structure involves the interaction of subunits in a protein with more than one polypeptide chain.

maroonwallaby335

Proteins are naturally occurring polymers formed by condensation reactions of amino acids, which have the general structure

In this structure, –R represents –H, –CH₃, or another group of atoms; there are 20 different natural amino acids, and each has one of 20 different R groups. (a) Draw the general structure of a protein formed by condensation polymerization of the generic amino acid shown here. (b) When only a few amino acids react to make a chain, the product is called a “peptide” rather than a protein; only when there are 50 amino acids or more in the chain would the molecule be called a protein. For three amino acids (distinguished by having three different R groups, R1, R2, and R3), draw the peptide that results from their condensation reactions. (c) The order in which the R groups exist in a peptide or protein has a huge influence on its biological activity. To distinguish different peptides and proteins, chemists call the first amino acid the one at the “N terminus” and the last one the one at the “C terminus.” From your drawing in part (b) you should be able to figure out what “N terminus” and “C terminus” mean. How many different peptides can be made from your three different amino acids?

purpleyak702

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 - Lecture 4: Proline, Van Der Waals Force, Aromatase

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