Proteins VI Flashcards
<p>\_\_\_\_\_\_ are digestible substantially faster than muscle proteins</p>
<p>Fish proteins</p>
<p>Fish proteins are composed of:
- 65-75% \_\_\_\_\_\_\_\_ proteins
- 20-30% \_\_\_\_\_\_\_\_ proteins
- 3-10% \_\_\_\_\_\_\_\_\_\_ proteins</p>
<p>myofibrillar
sarcoplasmic
connective tissue</p>
<p>The proportion of myofibrillar proteins in fish total protein is \_\_\_\_\_ than in mammalian total protein, and the relative proportions of the individual proteins are \_\_\_\_\_\_</p>
<p>higher
| similar</p>
<p>The heat stability of the fish myofibrillar proteins is \_\_\_\_ than that of their mammalian counterparts, and protein hydrolysis by trypsin is \_\_\_\_\_\_.</p>
<p>lower
| faster</p>
<p>Which two properties account for the good digestibility of fish proteins?</p>
<p>- The heat stability is low
| - The protein hydrolysis by trypsin is fast</p>
<p>Fish sarcoplasmic proteins are mostly \_\_\_\_\_\_\_</p>
<p>enzymes</p>
<p>When \_\_\_\_\_\_ proteins are separated electrophorically, patterns are discerned, which is helpful in fish taxonomy</p>
<p>sarcoplasmic </p>
<p>The amino acid composition of fish myoglobin is \_\_\_\_\_\_\_\_ to that of mammalian myoglobin.</p>
<p>different</p>
<p>Fish myoglobin contains a \_\_\_\_\_ residue that is absent in mammalian myoglobin. Myoglobin and other pigments are concentrated in the \_\_\_\_\_ muscle.</p>
<p>cysteine
| dark</p>
<p>\_\_\_\_\_\_\_\_\_ is absent in some mollusks and in Antarctic fish with colorless blood.</p>
<p>Hemoglobin</p>
<p>In strongly pigmented fish, pigment degradation reactions can inducse \_\_\_\_\_\_\_\_\_</p>
<p>meat discoloration</p>
<p>The content of connective tissue protein in fish muscle is \_\_\_\_\_ than in mammalian muscle.</p>
<p>lower</p>
<p>\_\_\_\_\_\_ is the main component of connective tissue in fish, and the remainder is \_\_\_\_\_\_</p>
<p>Collagen
| elastin</p>
<p>The shrinkage temperature of \_\_\_\_\_ collagen is 45oC as compared to 60-65 °C for \_\_\_\_\_\_\_ collagen.</p>
<p>fish
| mammalian</p>
<p>What are the two factors that render fish more tender than mammalian meat?</p>
<p>- Lower content of connective tissue protein
| - Lower shrinkage temperature</p>
<p>The \_\_\_\_\_\_\_\_\_ account for the low congealing temperature of polar fish of Arctic regions</p>
<p>antifreeze serum glycoproteins</p>
<p>The amino acid sequence of antifreeze glycoproteins is characterized by a high degree of \_\_\_\_\_\_</p>
<p>periodicity</p>
<p>The molecular weight of \_\_\_\_\_\_\_\_ is in the range of 10.5-27 kilodaltons, and the conformation is generally stretched, with several -helical regions.</p>
<p>antifreeze serum glycoproteins</p>
<p>The antifreeze effects of serum glycoproteins are attributed to the \_\_\_\_\_\_ residues as well as the \_\_\_\_\_ side chains of the peptide moiety</p>
<p>disaccharide
| methyl</p>
<p>\_\_\_\_\_\_\_\_ is the predominant free amino acid in fish with dark-colored flesh (tuna, mackerel).</p>
<p>Histidine</p>
<p>\_\_\_\_\_\_'s content in the flesh is typically 0.6-1.3% of the fresh weight and can even exceed 2%. </p>
<p>Histidine</p>
<p>During bacterial decay of the flesh, a large amount of \_\_\_\_\_\_\_\_\_ is formed from \_\_\_\_\_\_\_.</p>
<p>histamine
| histidine</p>
<p>Fish with dark-colored flesh have more free \_\_\_\_\_\_ than fish with light-colored flesh</p>
<p>histidine</p>
<p>Fish muscle tissue has a high content of \_\_\_\_\_\_, which is derived from \_\_\_\_\_, but lacks a \_\_\_\_\_\_ group</p>
<p>taurine
cysteine
carboxyl</p>
______ is a concentrate of insoluble fish muscle proteins that forms a solid cohesive gel when warmed.
Surimi
______ production is a highly mechanized process that starts with mechanical filleting and deboning of fresh, lean (_____-muscle) fish (most commonly ___________ followed by comminution at 5-10 °C.
Surimi white Alaskan pollock
The minced Alaskan pollack is extracted with water until basically only ______, ______, _____, and small amounts of _____
myosin actin actomyosin collagen
The purpose of the process of surimi is to remove strong _______ compounds and pigments as well as ________ proteins that can interfere with the gelation of the myofibrillar proteins
flavor | water-soluble
The resulting odorless and flavorless high-protein fish flesh, termed “raw surimi”, has enhanced ___-forming, ____-holding, and ____-binding properties by comparison with the original minced fish.
gel water fat
Paramyosin is a protein that is similar to ______ that is present in the ____ filaments of all invertebrates
myosin | thick
The addition of _______ in surimi further enhances the gel-forming abilities
paramyosin
After elimination of excess water, _______ (such as sugars or sugar alcohols) are added and the surimi is then frozen
cryoprotectants
The further processing of surimi involves gelation induced by addition of ____ + ______.
salt | heating
The role of the added salt in surimi is to ______ the _______ proteins.
solubilize | myofibrillar
In surimi, in addition to salt, ____ and ____ may be added
starch | egg white
The first step in the gelation of surimi is the setting of the gel, characterized by the formation of a loose 3D network by partially denatured _____ and ____
actin | myosin
The second step in the gelation of surimi is the formation of __________, characterized by the conversion of the loose network to an ordered, non-transparent gel that is more cohesive and elastic
The protein content of ______ is 9.7-10.6%, depending on the age of the hen.
albumen
In eggs, ____ content is about 0.03%, while ____ can reach a level of almost 1%.
lipid | carbohydrates
The carbohydrates in albumen are either ____ (mostly glucose) or combined with ____
free | protein
Ovalbumin, ovotransferrin, ovomucoid, and lysozyme are the major _______ proteins.
egg-white
The major globular protein in albumen is _______
ovalbumin
________ is a phosphoglycoprotein, with a molecular weight of about 44.5 kDa.
Ovalbumin
_______ is the only egg-white protein to contain a free sulfhydryl group
Ovalbumin
________ readily coagulates, a process which is observed when egg white sets on heating
Ovalbumin
_______ is also easily denatured when exposed to a new surface and is important in conferring stability to foams.
Ovalbumin
During storage of eggs, ________ converts to S- a more stable form with increased resistance to denaturation.
ovalbumin
Separation and purification of _______ is commonly performed by half-saturating the egg white with _______, followed by the addition of ________ to ____ the pH to its isoelectric point
ovalbumin ammonium sulfate sulfuric acid lower
Three to six _______ procedures are necessary to produce pure ovalbumin.
recrystallization
__________methods based on __________ have also been reported for the high-yield purification of ovalbumin.
Liquid chromatography | ion exchange
From a functional standpoint, ______ proteins such as ______ are known to have good gelling ability.
globular | ovalbumin
________ forms a transparent gel or a turbid gel upon heating, depending on the ________ and the ___ of the solution.
Ovalbumin ionic strength pH
Ovotransferrin is also known as ________
conalbumin
_________ accounts for 12% of the egg- white protein content and has a molecular weight of about 77-80 kDa.
Ovotransferrin
The _______ family is a group of iron-binding proteins widely distributed in biological fluids
transferrin
The _____-sequestering properties of transferrin are responsible for its bacteriostatic and bactericidal activities.
iron
During the separation of ovalbumin from albumen, _________ is transported with ovalbumin into the filtrate resulting from half- saturation with ammonium sulfate.
ovotransferrin
Further fractional precipitation with ________ or ____ fractionation produces pure ovotransferrin. Ovotransferrin may also be purified by ________ chromatography.
ammonium sulfate alcohol ion-exchange
_________ is the most easily heat-denatured egg protein but it is less susceptible to surface denaturation than ovalbumin.
Ovotransferrin
_______ is less susceptible to surface denaturation than ________
Ovotranferrin | ovalbumin
________ is also present as a component of the egg-yolk proteins, differing only by its carbohydrate prosthetic group.
Ovotransferrin
_________ is a glycoprotein consisting of three tandem homologous domains, each cross-linked by three disulfide bonds, with a total molecular weight of 28 kDa.
Ovomucoid
The carbohydrate in ________ is present as three polysaccharide chains, each attached to the polypeptide through an asparaginyl residue.
ovomucoid
Ovomucoid can be precipitated from albumen after the removal of ______ and ______ by complete saturation with _______ or by the addition of excess _____.
ovalbumin ovotransferrin ammonium sulfate alcohol
Among the egg-white proteins, ______ is unique in its resistance to heat coagulation.
ovalbumin
________ can be heated at 100 °C under acidic conditions for long periods without any apparent changes in its physical or chemical properties.
Ovalbumin
________ represents about 3.4% of egg white. It has a total of 129 amino acid residues and contains four disulfide bridges.
Lysozyme
_______ is a _______ enzyme commonly found in nature that catalyzes the hydrolysis of the glycosidic linkage between NAM acid and NAG in the polysaccharides of certain bacterial cell walls.
Lysozyme | bacteriolytic
______ is used as a natural food preservative and is extracted by a combination of ______ and _____ precipitation
Lysozyme chromatography salting-out
_______ is a heat-stable enzyme
Lysozyme
_______ exhibits enzymatic activity over a broad range of temperatures, and can withstand boiling water for 1-2 minutes
Lysozyme
______ is stable in freeze-drying and thermal drying processes and maintains its activity when redissolved in water
Lysozyme
Lysozyme has optimum activity for ______ foods
low-acid
______ is a strongly basic minor albumen protein
Avidin
_______ is employed in biomedical research by taking advantage of its high affinity for biotin in immunoassays, affinity chromatography, and molecular labelling
Avidin
________ appear to be important in the foaming properties of albumin
Ovoglobulins
________ is a multi-type serine protease inhibitor with a molecular weight of 50 kDa, and comprises seven domains conferring trypsin,chymotrypsin,and elastase inhibitory activity.
Ovoinhibitor
_________ is made of an apoprotein that also binds riboflavin, a B group vitamin
Flavoprotein
Avidin, ovoglobulin, ovoinhibitor, and flavoprotein are _____
minor albumen proteins
Egg yolk consists of 48.7% ____, 16.4% _____, and 32.9% _____
water protein fat
What are the three reasons that explain why egg yolks are good emulsifiers?
- High lipid content - High proportion of phospholipids - More than 90% of lipids present in the yolk are associated with proteins to form lipoproteins
What are the four classes of proteins found in egg yolk?
- Lipoproteins - Livetins - Phosphoproteins - Minor proteins, including enzymes
Lipoproteins from egg-yolk are separated by ________ into ______ (68%), and ______ (14%)
ultracentrifugation LDLP HDLP
_______ lipoprotein has a density of 0.98
LDLP
_______ forms the lipovitellenin fraction
LDLP
__________ accounts for one-third of the yolk and contains large amounts of lipids
LDLP
The lipid composition of LDLP is mostly composed of _____ and _______
Triglycerides | phospholipids
The LDLP fraction is primarily present in the form of ______ suspended in the ______ fraction
tiny micelles | plasma
LDLP micelles have a core of ______ with ______ and proteins radiating toward the surface of the micelle and interacting with water, making a stable _______ emulsion
triglycerides phospholipids oil-in-water
_______ form the lipovitellin fraction
HDLP
_______ has a density of > 1.0
HDLP
______ makes up the insoluble granules in egg yolk
HDLP
The lipid portion of HDLP is primarily composed of _______ (60%) and ______ (40%)
phospholipids | triglycerides
Lipovitallin can be separated into two components, that differ by their ______ content
phosphorus
___-lipovitellin (0.48% phosphorus), and ____-lipovitellin (0.27 phosphorus)
a | f
_______ also contains phosvitin
HDLP
_______ is a phosphorus-rich, lipid-free protein that is strongly associated with lipovitellin
Phosvitin
________ are lipid-free globular glycoproteins represent about 10% of egg-yolk total solids.
Livetins
________ are water soluble and correspond to blood serum proteins of the chicken.
Livetins
________, which makes up ~10% of total yolk protein, is the most highly phosphorylated protein known to date.
Phosvitin
Almost 50% of _______'s amino acids are serine, of which 90% are phosphorylated.
phosvitin
The isoelectric point of ______ is 4.0. At neutral pH, it is highly _______ charged owing to ionization of the ______ groups.
phosvitin negatively phosphate
Phosvitin has a high affinity for ______, particularly ____ ions
metal | ferric
______ is soluble in weak salt solutions and to some extent in water
Phosvitin
______ is associated with the granules due to strong ionic bonding to _______ proteins and is not found in the ______ fraction of the egg yolk
Phosvitin lipovitellin plasma
________ causes an increase in the time period required to whip egg whites.
Pasteurization
Pasteurization denatures the __________ network, thus resulting in the longer whip time.
ovomucin-lysozyme
The ____ is another important factor that affects performance and stability of egg white foams.
pH
Adjustment of _____ to pH 8.75 results in _____ in whip time and volume of cake.
albumen | increases
Egg white is more _____ to heat treatment when the pH is adjusted to 7.6 using lactic acid, hydrochloric acid or potassium acid tartrate.
stable
__________________performs more favourably than acetic or citric acid at pH 6.0, but __________ is important in that it sequesters the iron and prevents a red discoloration of the meringue due to conalbumin-iron complex.
Potassium acid tartrate | citric acid
__________ sequesters the iron and prevents a red discoloration of the meringue due to conalbumin-iron complex.
Citric acid
The pH of albumen should be adjusted to ____ before pasteurization, thereby protecting the ovalbumin, lysozyme and ovomucoid against damage by heat.
7.0
Define heat coagulation of eggs.
Designates the process of thermal denaturation and aggregation of proteins in albumen and in yolk.
Denaturation of proteins involves the breaking of _______ bonds, the uncoiling of ______ chains, and the exposure of ______ groups.
hydrogen polypeptide reactive
Aggregation of denatured albumen proteins occurs by the formation of ______, ______, and ______ linkages.
hydrophobic electrostatic disulfide
The denaturation temperature of albumen proteins is highest in ________, and lowest in ________
ovalbumin | ovotransferrin
