L6 3D Structure of Proteins Part 2 of 2

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Question #1

The α helix and beta sheet are examples of ___________structures

A Secondary

B Quaternary

C Primary

D Tertiary

Question #2

Within the α helix, the atoms of peptide bonds participates in hydrogen bonding.

A TRUE

B FALSE

Question #3

A beta-sheet is formed by hydrogen bonding between the hydrogen of an amine group and the backbone carbonyl group.

A TRUE

B FALSE

Question #4

The only amino acid that can form disulfide bonds is methionine

A FALSE

B TRUE

Question #5

2-mercaptoethanol is a chemical agent used in denaturing proteins. Its primary method of denaturing involves separating disulfide bonds. Based on this method of denaturation, what is the lowest level of protein structure affected by 2-mercaptoethanol?

A Tertiary structure

B Primary structure

C Secondary structure

D Quaternary structure

Question #6

Which of the following is not a component of tertiary structure?

A Hydrophobic interactions

B Disulfide bonds

C Ionic bonds

D Interactions between two or more sub-units

E Hydrogen bonds

Question #7

When a protein has two or more polypeptide subunits, their arrangement in space is referred to as quaternary structure.

A TRUE

B FALSE

Question #8

In an alpha helix, all of the H bonds lie parallel to the helix axis and all of the carbonyl groups are pointing in one direction along the helix axis while the N-H groups are pointing in the opposite direction.

A TRUE

B FALSE

Question #9

Fibrous proteins are typically soluble in water.

A FALSE

B TRUE

Question #10

Tertiary structure arises from the interaction of amino acids that are close by in the primary structure.

A FALSE

B TRUE

Question #11

The pitch of a helix contains 3.6 amino acids.

A FALSE

B TRUE

Question #12

A protein with a quaternary structure has multiple subunits.

A FALSE

B TRUE

Question #13

A disulfide bond, also called an S-S bond, or disulfide bridge, is a covalent bond derived from two thiol groups.

A TRUE

B FALSE

Question #14

The analysis of a protein for its amino acid content is valuable in determining the protein’s

A primary structure

B tertiary structure

C main structure

D secondary structure

E quaternary structure

Question #15

The attractive forces that are important in the secondary structure of a protein are ________.

A disulfide bonds

B salt bridges

C peptide bonds

D hydrogen bonds

E hydrophobic interactions

Question #16

Since denaturation reactions are not strong enough to break the peptide bonds, the primary structure (sequence of amino acids) remains the same after a denaturation process.

A TRUE

B FALSE

Question #17

Heat increases the kinetic energy and causes the molecules to vibrate so rapidly and violently that the covalent interactions are disrupted.

A TRUE

B FALSE

Question #18

Reducing agents disrupt the hydrogen bonds.

A TRUE

B FALSE

Question #19

Detergents denature proteins by interfering with the hydrophobic interactions in the proteins structure

A FALSE

B TRUE

Question #20

Heavy metals denature proteins by ________.

A releasing amino acids

B disrupting hydrophobic interactions

C changing the temperature of the protein solution

D disrupting salt bridges

E disrupting disulfide bonds

Question #21

An acid can denature a protein by ________.

A breaking disulfide bridges

B disrupting hydrophobic interactions within a protein chain

C agitating the protein chains

D removing helping molecules such as heme

E disrupting salt bridges between side chains

Question #22

The primary structure of a protein chain is

A determined by the types of bonds it contains

B the order of amino acids

C the arrangement of the chain in the long molecule

D the overall shape of the protein

E determined by the side chains

Question #23

Disulfide bonds exist only in tertiary and quaternary structures.

A FALSE

B TRUE

Question #24

In the β-pleated sheet secondary structure of a protein, two or more amino acid sequences in separate parts of the protein are held together ________.

A in random order, due to hydrophobic interactions

B in a triple helix

C in a double helix

D by hydrogen bonding between different sections of the polypeptide chain

E in a coil, by hydrogen bonding

Question #25

Disulfide bonds in a protein chain connect ________.

A an alcohol and a carboxylic acid group

B an amine and a carboxylic acid group

C tryptophan and alanine residues

D two asparagine residues

E two cysteine residues

Question #26

The term “denaturation,” when used in conjunction with proteins or nucleic acids, refers to a change in structural characteristics primarily due to __________.

A the disruption of covalent bonds

B changes in primary structure

C the binding of toxic compounds

D the disruption of non-covalent bonds

Question #27

A structure that has hydrogen bonds between polypeptide chains arranged side by side is

A tertiary structure

B alpha helix

C primary structure

D beta sheet

Question #28

Which of the following properties of a protein is least likely to be affected by changes in pH?

A Primary structure

B Net charge

C Tertiary structure

D Secondary structure

Question #29

What kinds of interactions do NOT contribute to the tertiary protein structure?

A Van der Waals interactions

B disulfide bridges

C hydrogen bonds

D salt bridges

E peptide bonds

Question #30

What does the quaternary structure of a protein involve?

A random coil alternating with a-helix

B the complete three-dimensional conformation

C the association of two or more peptide chains

D partial denaturation

Question #31

Which of the following is an example of the secondary structure of a protein?

A Hydrophobic interactions

B Disulfide bonds between cysteine residues

C Hydrogen bonding between R groups

D Hydrogen bonding between an amine and carbonyl group

E Peptide bonding between amino acids

Question #32

β turns connect the ends of two adjacent segments of a parallel β sheet.

A TRUE

B FALSE

Question #33

Collagen, the most abundant protein in the body, is an example of what type of protein?

A Peripheral

B Integral

C Fibrous

D Globular

Question #34

The side chains of a beta sheet are oriented parallel to the plane of the sheet.

A FALSE

B TRUE

Question #35

Antiparallel beta sheets are more stable than parallel beta sheets.

A FALSE

B TRUE

Question #36

Ala and Leu are strong a-helix formers.

A TRUE

B FALSE

Question #37

Because of the geometry of the individual amino acids, the hydrogen bonds of an antiparallel beta sheet occur at an angle.

A FALSE

B TRUE

Question #38

The stability of an alpha-helix is affected by the side and the identity of the side chains.

A TRUE

B FALSE

Question #39

Each hydrogen bond in a alpha helix closes a loop containing 3.6 atoms.

A TRUE

B FALSE

Question #40

Within an α helix, each carbonyl oxygen (residue n) of the polypeptide backbone is hydrogen-bonded to the backbone amide hydrogen of the fifth residue further toward the C-terminus.

A FALSE

B TRUE

Question #41

The pitch of a helix is 3.6 angstroms.

A FALSE

B TRUE

Question #42

In the α-helix structure, the protein backbone is wound around an imaginary axis, and the R groups of the amino acid residues run parallel the axis.

A FALSE

B TRUE

Question #43

Glycine is often found in the middle of an alpha-helix.

A TRUE

B FALSE

Question #44

Ala and Leu are strong alpha-helix breakers.

A TRUE

B FALSE

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L6 3D Structure of Proteins Part 2 of 2

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