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2) Food Chemistry I > Proteins I > Flashcards

Proteins I Flashcards

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1
Q

______ flavors can arise in proteinaceous systems due to low molecular weight ________________

A

Bitter

hydrophobic peptides

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2
Q

Aromatic amino acids are largely (hydrophilic/hydrophobic)

A

hydrophobic

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3
Q

What does the following sequence favour?

-P-N-P-P-N-N-P-

A

a-helix formation

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4
Q

Proline and hydroxyproline are found extensively in __________ proteins

A

structural

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5
Q

________ can serve as an attack point for reducing sugars

A

Amides

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6
Q

The hydrophobicity of ________ AA increases as their chain lengthens

A

aliphatic

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7
Q

The amino acids linked by peptide bonds represent the _______ level of structure of proteins

A

primary

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8
Q

_______ is 50% ionized at pH 10.5

A

Lysine

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9
Q

Glycine, Alanine, Valine, Leucine, and Isoleucine are _______ AA.

A

aliphatic

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10
Q

______________ AA are readily hydrolyzed to their corresponding acids under conditions of heat and/or acidic conditions

A

Carboxylic

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11
Q

OH-group on hydroxyl AA serve as a _________ bonding site and is a generally reactive moiety.

A

hydrogen

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12
Q

____________ AA are found extensively in structural proteins

A

Imino acids

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13
Q

The D configuration has an OH group on the _______

A

right

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14
Q

Gamma-COOH group of ___________ are 50% ionized at pH 4.2

A

glutamic acids

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15
Q

Quaternary structures do not have ___________, unlike tertiary structure

A

NO covalent bonds (disulfide crosslinks)

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16
Q

What are nonpolar AA?

A

Glycine, Alanine, Valine, Leucine, Isoleucine, Methionine, Phenylalanine or Tryptophan

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17
Q

Serine, Threonine, and Tyrosine are __________ AA.

A

hydroxyl

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18
Q

A protein’s lowest point of solubility is at its ____________

A

isoelectric point

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19
Q

___ separate macromolecules, of which __ are identical, are intertwined to form a suprahelix

A

3 2

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20
Q

_______ aromatic AA is reactive due to its OH group; forms _____ linkages with phosphate

A

Tyrosine ester

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21
Q

At low pH, the amino acid is _______

A

protonated (NH3+)

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22
Q

The ____________ AA provide flavor due to their breakdown when being cooked, mainly due to the release of ______

A

sulfur-containing H2S

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23
Q

_______ speed up the flavor development in cheese

A

Lipases

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24
Q

The R group in Histidine is the _________ group

A

imidazole

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25
Q

What determines whether a helical structure forms?

A

AA composition

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26
Q

The ability to leaven dough is specifically due to __________

A

Gluten

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27
Q

The peptide bond is an ______ bond

A

amide

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28
Q

Surimi makes use of __________ to make analogs of crab meat and scallops

A

pollock

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29
Q

Monosodium glutamate is the _____________ salt of glutamic acid

A

monosodium

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30
Q

The _______ amino group is the most reactive amino group in Lysine.

A

epsilon

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31
Q

Synthetic production of amino acids generally leads to _________ mixtures of D and L isomers

A

racemic

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32
Q

In carboxylic AA, at pH 7 and above, most of the free carboxyl groups would be _________ charged.

A

negatively

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33
Q

Why aren’t proline and hydroxyproline considered to be amino acids?

A
  • They do not contain a true amino group (NH2) - Instead they contain an imino group (NH)
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34
Q

________ readily undergoes rapid reaction with reducing sugars (Maillard reaction), which reduces the availability of this essential amino acid

A

Lysine

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35
Q

What structure does the following sequence favour?

-N-P-N-P-N-P-N-

A

B-sheet formation

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36
Q

Due to the ____________ form of AA and __________, protein polymers tend to twist upon itself

A

L-chiral steric hindrance

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37
Q

What are exogenous enzymes supplied by?

A

Microorgniams contaminating food

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38
Q

Amino acids can act as acids or bases and are said to be __________

A

amphoteric

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39
Q

The ___ structure wants to reduce its free energy

A

3rd

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40
Q

__________ are mirror images of a compound, which are not superimposable. ________ are an example

A

Enantiomers Amino acids

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41
Q

For all amino acids (except _______), the alpha-carbon is an asymmetric carbon

A

Glycine

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42
Q

The __________ group of cysteine is very basic, and ionized at pH 8.2

A

sulfhydral (-SH)

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43
Q

Meat contains an appreciable amount of ___________, which provide flavor as well as being a source of ____________ products

A

free amino acids Maillard reaction

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44
Q

_______ is considered to be somewhat basic, and is capable of ionizing beyond pH 10

A

Tryptophan

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45
Q

_______ are used to tenderize meat.

A

Proteases

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46
Q

Proteins that have a significant amount of _______ and _______ tend to have high isoelectric points

A

lysines arginines

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47
Q

All proteins are synthesized from __ amino acids

A

L

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48
Q

Proteins are composed of ___ amino acids

A

20

49
Q

_________ AA are relatively unreactive

A

aliphatic

50
Q

The L configuration has an OH group on the _______

A

left

51
Q

Disrupted _______ is extensively used in the food industry as a gelling agent

A

collagen

52
Q

When an asymmetric carbon is present, molecules can rotate ___________ light in _______ directions

A

plane-polarized opposite

53
Q

The suprahelix is held together by _______ bonds supplied by ________

A

hydrogen glycine

54
Q

Lysine contains ___ amino groups

A

2

55
Q

Lysine, Histidine, and Arginine are _______ AA.

A

basic

56
Q

The side chains of the amides of _____________ and _____________ play a role in non-enzymatic browning reactions

A

aspartic acid glutamic acid

57
Q

_____________ are used to make meaty flavours

A

Protein hydrolysates

58
Q

A very low pH is needed to suppress the _____ charges on the _____ side chains (i.e. to convert _____ to ____)

A

negative acidic COO- to COOH

59
Q

_____________ and _____________ do not contribute to a-helix formation

A

Proline hydroxyproline

60
Q

A very high pH is needed to suppress the _____ charges on the _____ side chains (i.e. to convert _____ to ____)

A

positive basic NH3+ to NH2

61
Q

_______ is used to remove headspace oxygen from food packages

A

Glucose oxidase

62
Q

The _______________ of proteins is important in stabilizing protein conformation through ________________

A

charge distribution electrostatic force

63
Q

The _____ are more polar than the acid forms, and hence make proteins (more/less) water-soluble

A

amides more

64
Q

The breakdown products of proteins , ________ and _______, are major contributors to flavor

A

amino acids peptides

65
Q

__________ is a breakdown product of proteins that contributes to flavor in Chinese cuisine

A

MSG

66
Q

__ amino acids cannot be used by the body for protein synthesis

A

D

67
Q

Amino acids decompose at relatively ___ temperatures due to their attributes as a _____

A

high salt

68
Q

In a diester linkage, one ________ group is linked to two ________ AA via ester linkages

A

phosphate hydroxyl

69
Q

Sugars and carbohydrate are often attached to the amide group of asparagine by an ___-glycosidic linkage

A

N

70
Q

What is autolytically?

A

Using endogenous enzymes

71
Q

Soy sauce is a _____________ produced by the fermentation of soybeans

A

protein hydrolysate

72
Q

The quaternary structure of proteins represents ___ or more tertiary globular proteins associating as a group to form _______, ______, or________

A

2 dimers, tetramers, or octamers

73
Q

When _________________ AA are incorporated into a protein side chain, they interrupt the natural tendency to form an _______ since they cannot form intramolecular ________ bonds

A

imino a-helix hydrogen

74
Q

________ is weakly basic; ionized at pH 6

A

Histidine

75
Q

_______ is a protein with elastic properties not found in other grains

A

Gluten

76
Q

The peptide bond has a ____________ character

A

partial double bond

77
Q

_________ AA play an important role in stabilizing protein conformation through hydrophobic interactions

A

Aromatic

78
Q

What is attached to the alpha carbon in an amino acid?

A
  • NH2 - COOH - R-group
79
Q

Amino acids have a crystalline structure, and are soluble in water since they have the attributes of a _______

A

salt

80
Q

The a-helix is stabilized by _______ bonding due to the repetitive proximity of the peptide ___________ (electron-rich) and the _________ from the nitrogen ___ residues away

A

hydrogen carbonyl oxygen hydrogen 4

81
Q

Proline and hydroxyproline are _______ acids

A

imino

82
Q

________ are usually 5-15 AA in length

A

B-strands

83
Q

_____ has been linked to Chinese Restaurant Syndrome

A

MSG

84
Q

Carbohydrates are often attached to the OH group of _________ or _________ by an __-glycosidic bond

A

serine threonine O

85
Q

When the overall charge on the protein averages out to neutral, the protein is said to be at its ____________

A

isoelectric point

86
Q

The suprahelix is found in _________

A

collagen

87
Q

_________ AA are very reactive and play an important role in protein structure

A

Carboxylic

88
Q

At its isoelectric point, the amino acid is a ___________

A

zwitterion

89
Q

_______ proteins can form a curd

A

Milk and soybean

90
Q

________ contains a very basic guanidino group, which has a pKa of 12.5

A

Arginine

91
Q

The structure of an enantiomer is _______

A

tetrahedral

92
Q

Phenylalanine, Tyrosine, and Tryptophan are _______ AA.

A

aromatic

93
Q

In a peptide bond, the ________ is linked to the __________

A

a-amino group a-carboxyl group

94
Q

Does glutamic acid or glutamine dissolve better in water?

A

Glutamine

95
Q

Collagen is a major structural animal protein composed of large amounts of _______ and _______

A

glycine proline

96
Q

The polypeptide chain starts at the __-terminus with the ____ group, and ends at the ___-terminus with the ____ group

A

N amino C carboxyl

97
Q

The C-CO-NH-C unit is planar with the ___________ and ___________ of the peptide bond always trans to each other

A

carboxyl oxygen amino hydrogen

98
Q

Aspartic and glutamic acids are found in nature as their corresponding _______: ____________ and ____________

A

amides asparagine glutamine

99
Q

Proteins that contain significant amounts of aspartic and glutamic acid tend to have _____ isoelectric points.

A

low

100
Q

Rotation of the _________ is restricted to 6o

A

peptide bond

101
Q

As the pH of an amino acid is increased, ___ protons are stripped away

A

Two

102
Q

________ is very reactive and can undergo oxidation/reduction reactions to form the _____ cystine

A

Cysteine

dimer

103
Q

The major feature of ________ AA is their ability to form an ester linkage with a phosphate group

A

hydroxyl

104
Q

________ linkages play an important role in the 3D structure of a protein, and make it less susceptible to denaturation

A

Diester

105
Q

__________ is a synonym for optical isomer

A

Enantiomers

106
Q

AA are generally considered to be precursors of _____________ odors and flavors in meat and fish

A

putrefactive

107
Q

Putrefactive odors and flavors are due to compounds produced by the _____________________________ by _________

A

enzymatic deamination or decarboxylation of free AA microbial enzymes

108
Q

Meat analogs from soy protein via ___________ using __________ technology

A

texturization extrusion

109
Q

B-carboxyl group of __________ are 50% ionized at pH 3.8

A

aspartic acids

110
Q

What is the issue with racemic mixtures?

A

Only half have AA activity

111
Q

Cysteine, Cystine, and Methionine are _______ AA.

A

sulfur-containing

112
Q

If a _____ forms between ___ cysteine residues, it forms a _______________

A

dimer 2 disulfide crosslink

113
Q

__ AA are considered essential

A

9

114
Q

Each turn of the a-helix involves ___ AA residues

A

3.6

115
Q

_______ are used to manufacture corn syrups/sugars

A

Amylases

116
Q

What are the 5 types of interactions/bonds found in the tertiary structure of proteins?

A
  • Hydrophobic interactions - Electrostatic interactions - Hydrogen bonding - Disulfide crosslinks - Van der Waals interactions
117
Q

_______ amino acids are responsible for UV absorbance of most proteins at 280

A

Aromatic

118
Q

The basic subunit for the suprahelix is ___________

A

tropocollagen

2) Food Chemistry I (31 decks)

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