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2) Food Chemistry I > Proteins II > Flashcards

Proteins II Flashcards

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1
Q

Proteins that are made up of only amino acids are termed _________

A

simple proteins

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2
Q

Proteins of most interest from a food science perspective are _______ and ________

A

albumins and globulins

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3
Q

_________ are proteins that are soluble in neutral distilled water

A

Albumins

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4
Q

__________ are proteins that are soluble in neutral, dilute salt solution, but not in distilled water

A

Globulins

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5
Q

B-lactoglobulin from milk and myosin/actin from meat are examples of ________

A

globulins

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6
Q

_________ are proteins that are soluble in dilute acid or base, but not in neutral solutions

A

Glutelins

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7
Q

Gliadin from wheat is an example of ___________

A

prolamines

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8
Q

_________ are proteins that are soluble in 50-90% ethanol and insoluble in water

A

Prolamines

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9
Q

__________ are proteins that are insoluble in water and neutral salts

A

Scleroproteins

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10
Q

_________ are proteins that are resistant to enzymatic hydrolysis

A

Scleroproteins

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11
Q

________ are generally structural proteins (keratin, collagen)

A

Scleroproteins

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12
Q

_________ are basic proteins, which contain large amounts lysines and arginines

A

Histones

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13
Q

Histones contain large amounts _______ and _______

A

lysines

arginines

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14
Q

________ are proteins that are soluble in water and precipitated by ammonia

A

Histones

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15
Q

_________ proteins contain additional chemical moieties other than amino acids

A

Conjugated

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16
Q

The non-amino acid component of conjugated proteins is termed the _________ group, and it can drastically modify the properties

A

prosthetic group

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17
Q

How are simple proteins classified?

A

Based on their solubility

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18
Q

How are complex proteins classified?

A

Based on their prosthetic groups

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19
Q

________ are proteins that are complexed with lipids; generally, with triglycerides and phospholipids

A

Lipoproteins

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20
Q

_______ are abundant in nature and have good emulsifying properties (ex: egg yolk proteins)

A

Lipoproteins

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21
Q

_______ are proteins that are complexed with carbohydrate

A

Glycoproteins

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22
Q

In glycoproteins, the carbohydrate is generally attached to the _____ group of ______ or _____ by an __-glycosidic bond

A

OH
serine
threonine
O

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23
Q

In glycoproteins, the carbohydrate is generally attached to the _____ group of _______ by an __-glycosidic bond

A

amide
asparagine
N

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24
Q

________ are proteins that are complex with a metal ion, which is generally loosely chelated

A

Metalloproteins

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25
Q

Fe2+ in myoglobin and hemoglobin, where Fe2+ is chelated by a porphyrin ring structure is an example of a ____________

A

metalloprotein

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26
Q

Numerous _______ have metal ions as prosthetic groups

A

enzymes

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27
Q

_________ are proteins that are conjugated to inorganic phosphates

A

Phosphoproteins

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28
Q

Casein and the enzyme renin are examples of _________

A

phosphoproteins

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29
Q

In phosphoproteins, the phosphate is generally linked to proteins by the ___ group of _______ or _________

A

OH
serine
threonine

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30
Q

The more (simple/complex) a protein is, the more susceptible it is to its environment

A

complex

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31
Q

Proteins are much (less/more) sensitive to their environment than lipids and carbohydrates

A

more

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32
Q

Proteins can undergo drastic changes in structure (_________) under relatively mild conditions

A

Denaturation

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33
Q

Does denaturation break peptide bonds?

A

No, the primary structure remains intact

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34
Q

Denaturation influences the ______ and _______ structures

A

secondary and tertiary structures

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35
Q

Casein has little _________ structure, and hence does not denature readily even when boiled

A

secondary

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36
Q

Unfolding of the tertiary structure/unraveling of the secondary structure makes the peptide bonds more accessible to ____________

A

proteolytic enzymes

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37
Q

Denaturation of a protein generally results in a reduction in _________

A

solubility

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38
Q

Denaturation results in generally ________ viscosity, and gelation may occur

A

increased

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39
Q

_________ is no longer possible following denaturation

A

Crystallization

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40
Q

____________ may be decreased or lost following denaturation

A

Enzymatic activity

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41
Q

If denaturation is extensive, the __________ form can be completely unraveled and its ________ structure badly disrupted

A

globular

secondary

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42
Q

When the globular form is unraveled due to denaturation, ___________ groups are exposed, which can react with each other so that _______ or ________ takes place

A

reactive groups
polymerization
aggregation

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43
Q

Some proteins form _____ when denatured, while others _______

A

gels

precipitate

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44
Q

In denaturation, milk and acid produces a _____, while heating collagen produces a ______

A

curd

gel

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45
Q

______ causes denaturation because an increase in kinetic energy of molecules results in the disruption of _____________, which are relatively weak

A

Heat

hydrogen bonds

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46
Q

A shift in pH affects the overall charge of the molecule, which influences the ______________________ to the _______________, and can cause denaturation

A

electrostatic bond contribution

tertiary structure

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47
Q

Proteins with significant quantities of ___________, ___________, and ___________ are especially susceptible to changes in pH

A

aspartic acid, glutamic acid, and lysine

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48
Q

Many soluble proteins ________ when they are subjected to environmental conditions close to their isoelectric point

A

precipitate

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49
Q

___________ are compounds that can effectively compete with the peptide linkage for hydrogen bonds can readily disrupt both tertiary and secondary structure

A

Hydrogen bond breakers

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50
Q

Urea is an example of a ___________

A

hydrogen bond breakers

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51
Q

Hydrogen bond breakers disrupt ____________ and ____________ structures

A

secondary

tertiary

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52
Q

Urea is commonly used to denature proteins for analysis by __________

A

electrophoresis

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53
Q

_______ and _______ can disrupt H-bonds by _______________ of a protein

A

Alcohol
acetone
partial dehydration

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54
Q

The degree of structure modification of alcohol/acetone is (less/more) severe than urea

A

less

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55
Q

_____________ and _____________ are commonly used to precipitate enzymes from solution for isolation with minimal denaturation

A

Alcohol

acetone

56
Q

___________ have both hydrophilic and hydrophobic moieties

A

Detergents

57
Q

__________ can bridge the hydrophobic and hydrophilic regions of a protein and result in the opening of the structure of the protein

A

Detergents

58
Q

SDS is a ____________ and is often used for analysis by ___________

A

detergent

electrophoresis

59
Q

_________________ make the environment hydrophobic, which can turn the protein macromolecule inside out and denature

A

Organic solvents

60
Q

_______________ can make enzymes work in opposite ways

A

Organic solvents

61
Q

Certain proteins can reduce surface tension, resulting in the formation of a ____

A

foam

62
Q

Each air bubble in a foam has a thin __________ that separates the two environments: _________ water and __________ air

A

membrane
hydrophilic
hydrophobic

63
Q

At the interface in a foam, protein molecules rearrange themselves to _______________

A

reduce their free energy

64
Q

Foods that contain appreciable amounts of protein generally undergo browning when they are heated under _________________________, which is known as the _________ Reaction or ______________

A

low-moisture conditions
Maillard
Non-Enzymatic Browning

65
Q

Non-Enzymatic Browning involves the reaction of an ___________ group of a reducing sugar and a _____________ group of an amino acid or peptide or protein

A

aldehyde

free amino

66
Q

The initial Maillard reaction forms _________

A

Glycosylamine

67
Q

Glycosylamine undergoes a series of reactions called _____________

A

Amadori rearrangement

68
Q

Amadori rearrangements involves the loss of _______ from within the sugar portion of the molecule

A

water

69
Q

In the Maillard reaction, after the loss of water, the sugar portion undergoes _______ and breaks up ____________ (produces aroma/flavor) that readily polymerize into ___________

A

scission
low-molecular weight compounds
brown pigments

70
Q

The brown pigments in the Maillard reaction are called __________

A

melanoidins

71
Q

In terms of the protein, the net result of the Maillard reaction is that ______ will be “_______”

A

Lysine

bound

72
Q

The “bound” Lysine from the Maillard reaction causes _________ that limits _______________ of the protein

A

steric hindrance

enzymatic digestion

73
Q

Enzymatic action will stop ___ amino acid on either side of the bound Lysine, leaving an indigestible ______, which is poorly absorbed and used by the body

A

one

tripeptide

74
Q

Non-enzymatic browning can adversely affect the ___________ value of proteins

A

nutritional

75
Q

What is PER?

A

Protein Efficiency Ratio

76
Q

PER (increases/decreases) due to the Maillard reaction

A

decreases

77
Q

What is PER’s equation?

A

Weight gained/Weight of protein consumed

78
Q

Amino acids with a ____________ group can also undergo reactions with reducing sugars at high temperatures

A

secondary amine

79
Q

Argine, Tryptophan, Histidine, Glutamine, and Asparagine all have a ___________ group

A

secondary amine

80
Q

If reducing sugars are mainly absent, the cross-linking of proteins can occur at higher temperatures by the formation of _____ bonds between ____ and _____ groups on side chains of AA

A

amide
COOH
NH2

81
Q

Do cross-linking reactions form peptide bonds?

A

No, since they do not involve an alpha-carbon

82
Q

Can amide bonds formed from cross-linking reactions be hydrolyzed by digestive proteolytic enzymes?

A

No, since they do not have peptide bonds

83
Q

Enzymatic action of cross-linked amide bonds will stop at ___ amino acid on either side of the cross-linked amino acids, leaving an indigestible ___________

A

one

hexapeptide

84
Q

The preparation of protein concentrates and isolates often calls for the treatment of proteins with _____ in the presence of ____ to modify their properties

A

alkali

heat

85
Q

In harsh conditions, “new” ___________ can form if free AAs are present or produced

A

amino acids

86
Q

Is the formation of Lysinoalanine beneficial?

A

No, since it is unnatural and poorly absorbed; may be toxic (renal failure)

87
Q

Lysinoalanine is produced under ____________

A

very harsh conditions

88
Q

Strongly alkaline environments can lead to ___________ of amino acids

A

racemization

89
Q

Racemization converts _________ to _____ mixtures

A

L-amino acids

D-L

90
Q

____________ results in the loss of effectiveness of amino acids as building blocks for protein synthesis

A

Racemization

91
Q

__________ are abundant in living tissue and are secreted by microorganisms

A

Proteolytic enzymes

92
Q

__________ results in a reduction in molecular weight and loss of functionality

A

Proteolysis

93
Q

________ may lead to bitter hydrophobic peptides

A

Proteolysis

94
Q

__________ causes the tenderization of meat by papain

A

Proteolysis

95
Q

_________ is associated with microbial spoilage of high-protein foods

A

Putrefaction

96
Q

_________ involves degradation of free amino acids, produced by _______ enzymes secreted by _________

A

Putrefaction
proteolytic
spoilage microorganisms

97
Q

The free amino acids are attacked by ___________ and ___________ in putrefaction

A

microbial deaminases

decarboxylases

98
Q

________ remove amine groups and _________ remove carboxyl groups from free amino acids in ___________

A

Deaminases
decarboxylases
putrefaction

99
Q

The products of _________ are volatile and rather repulsive odiferous compounds

A

Putrefaction

100
Q

In putrefaction, at lower pHs, ________ are the most active, while at higher pHs, the _________ are the most active

A

decarboxylases

deaminases

101
Q

The deaminase and decarboxylase reactions in putrefaction reduce ________ and increase________

A

molecular weight

volatility

102
Q

________ are generally responsible for high-protein systems becoming putrefactive

A

Microorganisms

103
Q

_____ are especially susceptible to putrefaction

A

Fish

104
Q

Fish undergo an enzymatic reaction that produces putrefactive-like compounds: conversion of ________ to ______ by the enzyme ______________________

A

TMAO (no smell)
TMA (volatile and putrefactive)
Trymethylamine-N-oxide reductase

105
Q

Production of ____ in fish correlates well with the rise in the microbial population and the overall rise in putrefactive compounds

A

TMA

106
Q

Measuring ____ provides an indication of freshness of fish

A

TMA

107
Q

Decarboxylase enzymes are inhibited by ______

A

DMFO

108
Q

Most proteins are ____________ and can bind water

A

hygroscopic

109
Q

______ proteins play an important role in absorbing and retaining moisture in bread; maintaining a soft texture

A

Milk

110
Q

Addition of _____ protein to hamburger helps retain moisture, making the burger juicier

A

soy

111
Q

The water-binding capacity is strongly associated with the ____ species present (NH3+ and COO-) and _______ bonding sites (C=O, N-H) that are readily hydrated

A

ionic

hydrogen

112
Q

The water-binding capacity may also be associated with the presence of a ___________ in the protein as a _______ group

A

polysaccharide

prosthetic

113
Q

Water, having a strong _________________, can form a hydration shell around polar groups

A

dipole moment

114
Q

A ______________________illustrates the equilibrium moisture associated with a material as a function of relative humidity at a constant temperature

A

moisture sorption isotherm

115
Q

What are the three types of water-binding?

A
  • Bound-water
  • Water-associated with bound water
  • Free-water
116
Q

_______________ is hydrogen bonded to the protein or a hydrate of an ionic species, and is an integral part of the molecular structure that cannot be removed

A

Bound water

117
Q

________________ is more mobile, yet still somewhat structure

A

Water-associated with bound water

118
Q

_______________ is unstructured, quite mobile, and can be removed relatively easily

A

Free water

119
Q

________ is the region where proteins show their water absorption capacity

A

Free water

120
Q

A protein’s ability to bind water is a function of its __________composition, overall structure (including ______ groups), and ______

A

amino acid
prosthetic groups
charge

121
Q

_____________ processes may involve substantial changes in factors that clearly affect protein structure (temperature, pH, ionic strength)

A

Water-removal

122
Q

_________ has very little effect on the nutritional quality of proteins because no heat is involved

A

Freezing

123
Q

_______ can cause major structural changes in proteins

A

Freezing

124
Q

In tissue systems (meat, fish), _________ can cause extensive denaturation due to changes in ionic strength and pH caused by local concentration effects and the removal of water from the microenvironment of the protein molecule

A

freezing

125
Q

The extent of __________ is often dependent on the _____ of freezing

A

denaturation

rate

126
Q

The changes from freezing are exemplified by the loss of __________________ (manifested by the development of freezer drip) and often result in a loss of desirable texture

A

water-binding capacity

127
Q

Deteriorative effects of dehydration processes may be due to _________ and/or _________

A

denaturation

browning

128
Q

_____________ is one of the best methods of drying in terms of maintaining protein functionality, nutritional quality, and enzyme activity (expensive)

A

Freeze drying

129
Q

What are the two types of water-removal processes?

A
  • Freezing

- Dehydration

130
Q

There might be ___________ during freezing, but there is little browning due to ________________________

A

denaturation

low temperature of sublimation

131
Q

In the case of ______, freeze drying is optimal in terms of retaining water-binding capacity of the proteins

A

meat

132
Q

____________ is used extensively for protein solutions (milk, egg whites)

A

Spray drying

133
Q

In __________, some denaturation may take place due to higher temperatures and shear at the nozzle

A

spray drying

134
Q

In ______________, some browning in the case of egg whites and milk take place due to the presence of glucose and lactose (Maillard reaction)

A

spray drying

135
Q

____________ causes extensive denaturation and browning if sugars are present

A

Drum drying

2) Food Chemistry I (31 decks)

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