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2) Food Chemistry I > Proteins - Summary I > Flashcards

Proteins - Summary I Flashcards

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1
Q

______ serves as a template upon which myosin molecules form the thick filament during muscle cell differentiation and development.

A

Titin

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2
Q

Quaternary structures do not have ___________, unlike tertiary structure

A

NO covalent bonds (disulfide crosslinks)

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3
Q

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

A

amides more

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4
Q

The _______ serves as an anchoring point for the protein titan

A

M-line

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5
Q

Casein is a ____________ with the phosphate attached to _______

A

phosphoprotein serine

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6
Q

Proteinases break down particular proteins of the myofibril, such as ____, ____, and _____ during postmortem conversion of muscle to meat

A

titin nebulin troponin-T

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7
Q

____-casein contains 2 cysteine residues, and is only accessible under reducing conditions

A

K

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8
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

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9
Q

All the variations of ___________________ contain 8 phosphoserine residues, 7 of which are localized between 43 and 80

A

as1-casein

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10
Q

___________ binds the troponin complex to tropomyosin

A

Troponin-T

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11
Q

___________ are produced by the enzymatic treatment of WPI to break the proteins into peptides that are more easily digested, while the nutritional quality of the protein remains high

A

Whey protein hydrolysates

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12
Q

Between pH 3.1 and 5.1, at low temperatures and high concentration, B-lactoglobulin associates to form an _______

A

B-lactoglobulin octomer

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13
Q

________ make up 30% of total muscle protein, and is soluble

A

Sarcoplasmic proteins

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14
Q

The suprahelix is held together by _______ bonds supplied by ________

A

hydrogen glycine

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15
Q

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

A

secondary amine

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16
Q

Lactose can be recrystallized to yield a _________, which is used as a ________

A

raffinate filler in tablets

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17
Q

When _______-casein precipitates with Ca2+, at temperatures of < 1oC, the calcium salt is quite soluble

A

B

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18
Q

Groups of myofibers are organized into primary and secondary bundles of _______ that are segregated by another layer of connective tissue called the ________.

A

fascicles perimysium

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19
Q

10% of the total casein fraction is present in milk as _________, usually designated as _______ caseins

A

monomers serum

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20
Q

The fundamental structural unit of the myofibrils is the _________.

A

sarcomere

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21
Q

Casein and the enzyme renin are examples of _________

A

phosphoproteins

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22
Q

Upon binding to actin, _________ swivel to approximately a 45oC, pulling the _____ filaments past the _____ filaments toward the _________

A

myosin heads thin thick M-line

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23
Q

________ make up 10-20% of total muscle protein; insoluble

A

Stromal proteins

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24
Q

Soy sauce is a _____________ produced by the fermentation of soybeans

A

protein hydrolysate

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25
Q

The T-tubules are in physical contact at periodic intervals with the _____________, which is the muscle equivalent of an endoplasmic reticulum

A

sarcoplasmic reticulum

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26
Q

______ is a large skeletal protein associated with thin filaments

A

Nebulin

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27
Q

_________ contain great amounts of ______ organelles and fuels, such as mitochondria, myoglobin, and lipids

A

Slow-contracting (red) oxidative

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28
Q

The ______ consists of thin filaments only

A

I-band

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29
Q

The peptide bond is an ______ bond

A

amide

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30
Q

Decarboxylase enzymes are inhibited by ______

A

DMFO

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31
Q

However, at physiological ionic strength, G-actin monomers are polymerized “head-to-tail” in ________

A

F-actin

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32
Q

Strongly alkaline environments can lead to ___________ of amino acids

A

racemization

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33
Q

_____ contains 2 disulfide bonds, 1 free sulfhydryl group, and no phosphorus

A

B-lactoglobulin

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34
Q

In the case of casein micelles, _______________ are minimal at temperatures below 5oC

A

hydrophobic interactions

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35
Q

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

A

Prolamines

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36
Q

Gliadin from wheat is an example of ___________

A

prolamines

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37
Q

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

A

Diester

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38
Q

All proteins are synthesized from __ amino acids

A

L

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39
Q

Whey protein concentrates are produced by ____________

A

ultrafiltration

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40
Q

At the ________ end of the myosin chain, the protein exhibits a globular structure called the ______

A

amino myosin head

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41
Q

__________ is activated by micromolar concentrations of Ca2+

A

u-calpain

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42
Q

_______ is a globular monomer

A

G-actin

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43
Q

The initial Maillard reaction forms _________

A

Glycosylamine

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44
Q

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

A

epsilon

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45
Q

In the horse and rider model of __-casein, the ___-terminal makes up the horse, the ____-terminal makes up the rider, and the two legs of the horse are made of _______

A

K N C B-structures

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46
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

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47
Q

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

A

Tryptophan

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48
Q

Chymosin cleaves K-casein into ___________ and a ___________

A

para-K-casein glycomacropeptide

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49
Q

filaments on opposite sides of the _____ are directed toward each other within a given sarcomere.

A

M-line

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50
Q

The _______ consists of overlapping thin and thick filaments

A

A-band

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51
Q

The AMP formed by adenylate kinase is _______ to __________, which is catalyzed by ________ (sarcoplasmic protein fraction)

A

deaminated IMP AMP deaminase

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52
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

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53
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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54
Q

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

A

L-chiral steric hindrance

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55
Q

40% of the residues of the AA sequences of _____________and _____________ are the same, including the cysteine residues, and 20% of the residues are similar

A

a-lactalbumin lysozyme

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56
Q

________ has 4 disulfide linkages and no phosphate groups

A

a-Lactalbumin

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57
Q

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

A

denaturation low temperature of sublimation

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58
Q

What is PER’s equation?

A

Weight gained/Weight of protein consumed

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59
Q

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

A

Freeze drying

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60
Q

_______ is the most abundant muscle protein, constituting 43% of the muscle myofibril.

A

Myosin

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61
Q

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

A

secondary amine

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62
Q

___________ contains 5 phosphoserine residues that are localized between 1 and 40, which contains practically all the __________ sites of the molecule

A

B-casein ionizable

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63
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

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64
Q

The center of the A-band appears brighter than the distal zones (less dense), and is termed the ___-zone.

A

H

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65
Q

The _________ trigger the release of Ca2+ from the lumen of the __________, which rises at least ____-fold

A

T-tubules sarcoplasm 100

66
Q

Which milk protein has a dynamic disulfide bond?

A

B-lactoglobulin

67
Q

This structure, called the ______, consists of proteins that maintain the structural arrangement of the thick filament proteins

A

M-line

68
Q

Below pH 3.0 and above pH 8.0, __________exists as a ______

A

B-lactoglobulin monomer

69
Q

At the pH of milk, _________ tends to form a ______

A

B-lactoglobulin dimer

70
Q

________ and ________ are used in the manufacture of paper for coating to improve the adhesion of ink to the surface, in waterproof glue, to make fabrics water-repellent, etc.

A

Caseins caseinates

71
Q

What are the 3 types of myofibers?

A

1) Slow-red 2A) Fast-red 2B) Fast-white

72
Q

_____-casein is a monomer

A

K

73
Q

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

A

aspartic acid glutamic acid

74
Q

__________ modifies the activity of galactosyl transferase

A

a-lactalbumin

75
Q

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

A

Histones

76
Q

The _________ are anchored at the Z-disc

A

thin filaments

77
Q

Proteins are separated on the basis of __________

A

solubility

78
Q

Classify the troponin subunits from largest to smallest.

A

Troponin-C < Troponin-I < Troponin-T

79
Q

_____ is the largest single polypeptide chain known

A

Titin

80
Q

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

A

Histones

81
Q

____________ causes extensive denaturation and browning if sugars are present

A

Drum drying

82
Q

Each myofiber is encased in a layer of connective tissue called the _______________

A

endomysium

83
Q

________ contains a portion with 12 carboxyl groups from _____________ and _____________ residues, making it extremely ______

A

as1-casein glutamic acid aspartic acid polar

84
Q

In ___-casein, varying amounts of carbohydrate are bound to the peptide chain through Threonine residues at positions 131, 133, 135, or 136 (A variant)

A

K

85
Q

To produce a casein product that is soluble or readily dispersible, the casein is dispersed in ______ and treated with ______ at 90oC and pH 6.2-6.7

A

water alkali

86
Q

The electrostatic interactions in casein micelles are mostly between ________ and ________ that form bridges between __________ and ________ residues

A

calcium calcium phosphate phosphoserine glutamic acid

87
Q

_________ serve as a major reservoir for a family of proteolytic enzymes known as _______

A

Lysosomes cathepsins

88
Q

When myosin heads form cross-bridges between the thick and thin filaments, they are placed ________ to the thick filament axis

A

perpendicular

89
Q

The narrow, dark, electron-dense center of the I-band is termed the __________

A

Z-disc

90
Q

The plasma membrane of myofibers is called the __________

A

sarcolemma

91
Q

In _______, AA 100-199 are _______ and responsible for the self-association tendencies of the protein despite the repulsive forces between the _________ groups, and the lack of ___________ residues

A

as1-casein apolar phosphate cysteine

92
Q

________ precipitates with Ca2+ more easily than as1-casein

A

as2-casein

93
Q

What are the three classes of proteins?

A

Sarcoplasmic Myofibrillar Stromal

94
Q

B-lactoglobulin is effective at binding __________

A

retinol

95
Q

__________ is found both in the sarcoplasm and as a component of the ______ of the myofibril

A

Creatine kinase M-line

96
Q

________ binds Ca2+ ions

A

Troponin-C

97
Q

The protein _____ spans the sarcomere from the _____ to the _______

A

titin M-line Z-disc

98
Q

Unlike _____-casein, ______-casein does not self-associate spontaneously

A

as1 B

99
Q

________________ adds UDP-galactose to glucose and produces _______ and UDP, which is faster when __________ is attached

A

galactosyl transferase lactose a-lactalbumin

100
Q

a-lactalbumin uses calcium to form _________________ bonds that tend to make the molecule resistant to thermal unfolding

A

intramolecular ionic

101
Q

At very low ionic strength, actin exists primarily as __________

A

G-actin

102
Q

________ make up 50-60% of total muscle protein; solubilized in concentrated salt solutions (e.g., 0.3M NaC1)

A

Myofibrillar proteins

103
Q

The ___ variant of B-lactoglobulin forms more readily than the ___ variant since it has an extra ______ group

A

A B carboxyl

104
Q

_________ runs the entire length of the thin filament, spanning seven actin monomers

A

Tropomyosin

105
Q

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

A

foam

106
Q

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

A

Globulins

107
Q

The ___________ and the _________ combine to provide the necessary framework for maintaining the structural integrity of these tissues within the muscle.

A

perimysium endomysium

108
Q

____________ are less likely to trigger allergic reactions than _________________; they are used often in infant formulas

A

Whey protein hydrolysates non-hydrolyzed whey protein

109
Q

Stretching results from an increase in _____ separation, accomplished by sliding of thin filaments of a sarcomere from each other as they move along the ________

A

Z-disc A-band

110
Q

_________ proteins form the fibrous connective tissues that strengthen and protect muscles

A

Stromal

111
Q

The _________ functions as a reservoir of calcium ions that serve as the trigger for muscle contraction

A

sarcoplasmic reticulum

112
Q

The _______ penetrate into the myofiber, and form a network of ____________, distributed along the length of the myofiber, and conduct the stimulus for contraction into the interior of the myofiber

A

sarcolemma transverse tubules (T-tubules)

113
Q

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

A

Tyrosine ester

114
Q

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

A

aspartic acid, glutamic acid, and lysine

115
Q

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

A

Glutelins

116
Q

One _______ molecule extends from the Z-line to the distal end of a thin filament

A

nebulin

117
Q

________ inhibits the actomyosin ATPase

A

Troponin-I

118
Q

The ______ consists only of thick filaments with no overlapping thin filaments

A

H-zone

119
Q

At the center of the _____ is a dark zone analogous to the ______.

A

H-zone Z-disc

120
Q

Which milk protein associates to form a barrel with _______ and a lid with _______?

A

B-lactoglobulin B-structures a-helix

121
Q

_______ is used to remove headspace oxygen from food packages

A

Glucose oxidase

122
Q

_________ are proteins that are soluble in neutral distilled water

A

Albumins

123
Q

The red to reddish pink color of red meat is due to ______

A

myoglobin

124
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

125
Q

____________ is unusual since the molecule is more stable to heat in the presence of calcium

A

a-lactalbumin

126
Q

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

A

Alcohol acetone partial dehydration

127
Q

__________ are proteins that are insoluble in water and neutral salts

A

Scleroproteins

128
Q

Upon stimulation of a muscle fiber by the nerve, the neurochemical impulse is transmitted into the fiber by the _______.

A

T-tubules

129
Q

Myoglobin is present in greater abundance in _______ myofibers because they derive a greater share of their energy from ____________

A

slow-red oxidative metabolism

130
Q

IMP is further degraded to ________, which imparts a _____ flavor to meat

A

hypoxanthine bitter

131
Q

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

A

N

132
Q

____________ may also be found embedded in the __________ and is visible in red meats as while flecks of fat (marbling) in contrast to the red background of myofibers.

A

Adipose tissue perimysium

133
Q

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

A

decarboxylases deaminases

134
Q

Which method is highly detrimental to whey?

A
  • Steam injection - Precipitation of the denatured proteins - Sedimentation centrifuge - Drying
135
Q

A final layer of heavy connective tissue sheaths, called the __________, surrounds the whole muscle

A

epimysium

136
Q

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

A

enzymatic deamination or decarboxylation of free AA microbial enzymes

137
Q

The portion of ______ located in the gap between the ______ filament and the ______ is elastic

A

titin thick filament Z-line

138
Q

______ contains 11 phosphoserine and 2 cysteine residues

A

as2-casein

139
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

140
Q

Denaturation of a protein generally results in a reduction in _________

A

solubility

141
Q

_____ may be involved in restoring resting sarcomere length when the muscle relaxes

A

Titin

142
Q

_____________ are used to make meaty flavours

A

Protein hydrolysates

143
Q

How is whey usually dried? What is a technique that can reduce the cost?

A
  • Spray drying - Reverse osmosis
144
Q

The thick filaments of the sarcomere are primarily composed of ________, and _____ is also associated with thick filaments

A

myosin titin

145
Q

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

A

Carboxylic

146
Q

When ____ binds to Ca2+, this causes a change in the binding of ____ to ____, which in turns alters the binding between _______ and _______ in the thin filaments, which allows _____ to bind to _____

A

Troponin-C Troponin-T tropomyosin tropomyosin actin actin myosin

147
Q

_________ is associated with microbial spoilage of high-protein foods

A

Putrefaction

148
Q

Electron micrographs indicate that a thick filament is surrounded by an array of ___ thin filaments

A

six

149
Q

______ is the most hydrophobic casein

A

B-casein

150
Q

____________ converts ADP to ATP and AMP, and is an enzyme present in the sarcoplasmic protein fraction

A

Adenylate kinase

151
Q

Which casein acts like soap?

A

B-casein Polar head and an apolar tail

152
Q

Like _______-casein, _______-casein contains no cysteine residues

A

as1 B

153
Q

_______________ can make enzymes work in opposite ways

A

Organic solvents

154
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)

155
Q

The R group in Histidine is the _________ group

A

imidazole

156
Q

Phosphorylase B is more abundant in _______ myofibers because these myofibers rely heavily on ______ for energy requirements

A

fast-white glycolysis

157
Q

Classify the types of casein in order of most present to least present.

A

as1 > B > K > as2 > γ

158
Q

What are the four proteins that consist of the thin filaments of the sarcomere?

A
  • Actin - Tropomyosin and troponin - Nebulin
159
Q

Normally, __-casein occurs as a trimer or as higher oligomers by the formation of ________bonds

A

K disulfide

160
Q

_________ are degradation products of B-casein formed by milk proteases

A

gamma-casein

2) Food Chemistry I (31 decks)

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