BIOL 2020 Chapter Notes - Chapter 4: Beta Sheet, Alpha Helix, Alpha And Beta Carbon

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11 Feb 2013

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Bonds between r chains are tertiary structures. Multiple complex polypeptide chains are quaternary structure. 4. 1 primary structure: aa are linked by peptide bonds to form polypeptide chains. 3d structure depends on its primary structure. Formation of a dipeptide is joined by the loss of a water molecule. Peptide bonds are very stable, slow hydrolysis when catalyst absent. Polypeptide chains have polarity because both ends are different alpha amino end is the beginning and alpha carboxyl is the end. Polypeptide has a reg repeating part called the main chain or backbone, variable part is the side chain, backbone is rich in hydrogen bonding potential. Each residue contains a c=o which is a good hydrogen bond acceptor, but the amino group is a good donor or it. Disulfide bonds=oxidation of a pair of cysteine residues (cystine) The aa sequence work by sanger shows that proteins have precisely defined aa sequences. Knowing aa sequences helps with: 3d structure, knowing its mechanism, molecular pathology.

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

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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.

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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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BIOL 2020 Chapter Notes - Chapter 4: Beta Sheet, Alpha Helix, Alpha And Beta Carbon

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