Chapter 4

Question 1

α helix only

Answer 1

1. Cylinder Structure

2. One full turn every 3.6 amino acids

Question 2

β sheet only

Answer 2

1. Consists of antiparallel or parallel strands

2. Side Chains alternating above and below the structure

Question 3

Both α helix & β sheet

Answer 3

1. Can be formed by many sequences

2. Formed by hydrogen-bonding between backbone atoms

Question 4

The antibody is composed by __ polypeptide chains

Answer 4

4

Question 5

If SDS-PAGE were used for a pure sample of this protein that was preincubated with mercaptoethanol, then there would be __ bands expected.

Answer 5

2

Question 6

How do most motor proteins ensure their movements are unidirectional?

Answer 6

They couple a conformational change to the hydrolysis of an ATP molecule.

Question 7

A disulfide bond is a ___ interaction within the protein.

Answer 7

covalent

Question 8

Protein molecules that have a quaternary structure must have two or more of which of the following?

Answer 8

polypeptide chains

Question 9

What is the definition of a protein-binding site?

Answer 9

any region on a protein’s surface that interacts with another molecule through “noncovalent” bonding.

Question 10

What are protein families?

Answer 10

Evolutionary related proteins that are similar in amino acid sequence and three-dimensional conformation.

Question 11

In a globular protein, where would the amino acid tryptophan most likely be found?

Answer 11

buried in the protein’s interior

Question 12

What does the primary structure of a protein refer to?

Answer 12

The linear amino acid sequence of the protein.

Question 13

What do the segments of a transmembrane protein that cross the lipid bilayer usually consist of?

Answer 13

an α helix with mostly nonpolar side chains

Question 14

For which reason are α helices and β sheets common folding patterns in polypeptides?

Answer 14

The amino acid side chains are not directly involved in their formation.

Question 15

The protein can be unfolded by a process called ____

Answer 15

Denaturation

Question 16

Generally speaking, what determines the biological activity of a protein?

Answer 16

amino acid sequence.

Question 17

What provides the information necessary to specify the three-dimensional shape of a protein? Choose the best answer in the context of which generally applies to most proteins.

Answer 17

protein’s amino acid sequence.

Question 18

Which part of an amino acid gives it its unique properties?

Answer 18

side chain.

Question 19

Which part of amino acids are involved in a peptide bond?

Answer 19

amino group of one amino acid and carboxyl group of the other.

Question 20

Hydrogen bonding between N-H and C=O groups of every fourth amino acid within a polypeptide chain results in which type of folding pattern?

Answer 20

a helix

Question 21

A stretch of amino acids in a polypeptide chain that is capable of independently folding into a defined sturcture is called a ____

Answer 21

domain

Question 22

A binding site on the surface of a protein interacts specifically with another protein through___

Answer 22

many weak noncovalent interactions.

Question 23

How does phosphorylation of a protein affect its activity?

Answer 23

It could increase or decrease activity.

Question 24

How many amino acids are commonly used in making proteins?

Answer 24

20

Question 25

Which parts of amino acids are involved in a peptide bond?

Answer 25

amino group of one amino acid and carboxyl group of the other

Question 26

Which part of an amino acid gives it its unique properties?

Answer 26

side chain (R group in protein)

Question 27

What is the best type of model for visualizing the surface of a protein?

Answer 27

space-filling

Question 28

What are the two types of β sheets?

Answer 28

parallel and antiparallel

Question 29

What does the primary structure of a protein refer to?

Answer 29

The linear amino acid sequences of the protein.

Question 30

Consider the thermodynamic properties of chemical reactions. Even though enzymes do not affect the overall energy of the reactants or the products (i.e., the thermodynamics), they alter the speed of the reaction. Enzymes accomplish this by doing which of the following?

Answer 30

reducing the activation energy of a reaction

Question 31

For a given protein, hydrogen bonds can form between which of the following?

Answer 31

1. atoms in the polypeptide bacbone 2. atoms of two peptide bonds 3. atoms in two side chains 4. a side chain and water.

Question 32

How does an allosteric inhibitor work?

Answer 32

It binds to a site other than the active site, causing a conformational change in the enzyme that makes the active site less accommodating to the substrate.

Question 33

How does phosphorylation control protein activity?

Answer 33

The phosphate group induces a change in the protein's conformation.

Question 34

What kind of enzyme adds a phosphate group to another protein?

Answer 34

kinase

Question 35

What kind of enzyme removes a phosphate group from a protein?

Answer 35

phosphatase

Question 36

In an α helix, hydrogen bonds form between which of the following?

Answer 36

every fourth amino acid.