Deck 10: Overview of Proteins

Question 1

The backbone chain of a protein is composed of :

A) -C-C-N-C-C-N-
B) -N-C-N-N-C-N-N-C-
C) -C-O-N-C-C-N-C-N-C-
D) _C-N-C-N-C-N-,
E) None of these

Answer 1

A

Question 2

Mucoproteins are comprised of:

A) Protein and a sugar
B) Lipid and a sugar
C) Lipid and a protein
D) Iron and protein
E) None of these

Answer 2

A

Question 3

If the pH of a colloidal dispersion nears its isoelectric point, it may:

A) Be toxic and should not be eaten
B) Explode
C) have to be shaken before it can be eaten
D) Precipitate
E) Separate into two layers upon standing

Answer 3

D

Question 4

Two or more peptide chains held tightly together in a quaternary structure.

A) Methionine
B) Tryptophan
C) Hemoglobin
D) Leucine
E) Hydroxyproline

Question 5

Compounds that can act as an acid or a base, depending on conditions, are said to be:

A) Ambidextrous
B) Conjugated
C) Amphoteric
D) Esoteric
E) none of these

Question 6

Enzymes are ineffective after heating because they are:

A) Proteins, and heat changes their physical shape
B) Carbohydrates and heat dissolves them
C) Too acidic
D) Bound to an acid
E) None of these

Question 7

Denaturation of proteins by heat occurs as protein molecules;

A) Repel each other
B) Relax from their tertiary structure and form secondary bonds between molecules
C) Change to their tertiary structure and repel each other
D) Take up iron
E) Form fibrous strands and become more soluble

Question 8

The covalent bond between the nitrogen of one amino acid and the carbon of the carboxyl group of another amino acid is called:

A) Actomyosin
B) Myoglobin
C) Nitric linkage
D) Peptide linkage
E) Tertiary structure

Question 9

The α-helical configuration describes the following level of protein structure:

A) Primary
B) Secondary
C) Tertiary
D) Quaternary
E) None of the above

Question 10

A peptide bond is formed by linking the carbon of one amino acid with the:

A) Carboxyl group on the next amino acid
B) Nitrogen atom on the original amino acid
C) Nitrogen on the next amino acid
D) Hydrogen on the next amino acid
E) None of these

Question 11

Myoglobin and hemoglobin are classified as:

A) Globular proteins
B) Metalloproteins
C) Fibrous proteins
D) Lipoproteins
E) None of these

Question 12

At the isoelectric point, the neutral nature of the molecule makes a protein have:

A) Minimum solubility
B) Maximum solubility
C) No pH
D) The ability to form very stable emulsions
E) A very strong attraction for oil.

Question 13

Proteins are large molecules containing 100 or more amino acid residues, which are linked together covalently by:

A) Water
B) Oxygen
C) Peptide bonds
D) Proline bonds
E) Lipids

Question 14

Fibrous proteins of particular interest from the standpoint of food:

A) Collagen and elastin
B) Leucine and isoleucine
C) Metalloproteins
D) Lipoprotein
E) Globular proteins

Question 15

Protein molecule s it occurs naturally without external influences such as heat or changes in pH.

A) Native protein
B) Peptide bond
C) Lipids
D) Hydrogen bond
E) Secondary bond

Question 16

When a dipeptide is formed, the other compound formed is:

A) Hydrogen gas
B) Oxygen
C) Carbon dioxide
D) Water
E) None of these

Question 17

A β-pleated sheet is an example of the following level of protein structure:

A) Primary
B) Secondary
C) Tertiary
D) Quaternary
E) None of the above

Question 18

The fibrous nature of collagen is due to the comparatively large amounts of:

A) Methionine and tryptophan
B) Leucine and isoleucine
C) Methionine and phenylalanine
D) Proline and hydroxyproline
E) None of these

Question 19

The isoelectric point is the:

A) Ability of an amino acid to carry a positive or negative charge
B) pH at which proteins are least soluble and most easily precipitated
C) pH at which proteins are most soluble and combine easily in foods
D) Point at which cross linkages are the strongest
E) Structure of a protein where the polar chains fold to the outside and the non-polar chains fold to the inside

Question 20

Protein coagulation occurs most readily at:

A) pH 2.5
B) pH 7.0
C) pH 6.6
D) A protein's isoelectric point
E) None of these

Question 21

Beating denatures some of the proteins in egg whites.

Question 22

Some enzymes catalyze hydrolysis of specific proteins.

Question 23

The change in the native state of a protein caused by heat is called

A) Hydrolysis
B) Curdling
C) Denaturation
D) Precipitation
E) All of the above

Question 24

Edible films can be made from starch, but not from proteins.

Question 25

Distinguish between/among:
e.g., collagen and elastin. Conjugated proteins are proteins combined with another compound, such as carbohydrates or lipids. Examples are lipoproteins and phosphoproteins.

Question 26

When proteins coagulate, they are more soluble.

Question 27

Denaturation is the unfolding of the native state of a protein caused by heat, salts, pH, and/or mechanical shear.

Question 28

Denaturation, coagulation, and hydrolysis are physical changes

Question 29

Differentiate among the primary, secondary, and tertiary structure of a protein.

Question 30

What substance hydrolyzes gelatin, resulting in a loss of gel strength?

A) Substrate
B) Proteolytic enzyme
C) Trypsin inhibitor
D) Amphoteric
E) Nitric linkage

Question 31

Amino acids may coil in an alpha helix stabilized by hydrogen bonds.

Question 32

Globular proteins have a pleated sheet configuration that is held in place by secondary bonding forces.

Question 33

The isoelectric point of most proteins is the same pH.

Question 34

Define the following terms (be specific) and give an example of where each occurs.