Proteins - Summary I Flashcards
______ serves as a template upon which myosin molecules form the thick filament during muscle cell differentiation and development.
Titin
Quaternary structures do not have ___________, unlike tertiary structure
NO covalent bonds (disulfide crosslinks)
The _____ are more polar than the acid forms, and hence make proteins (more/less) water-soluble
amides more
The _______ serves as an anchoring point for the protein titan
M-line
Casein is a ____________ with the phosphate attached to _______
phosphoprotein serine
Proteinases break down particular proteins of the myofibril, such as ____, ____, and _____ during postmortem conversion of muscle to meat
titin nebulin troponin-T
____-casein contains 2 cysteine residues, and is only accessible under reducing conditions
K
The a-helix is stabilized by _______ bonding due to the repetitive proximity of the peptide ___________ (electron-rich) and the _________ from the nitrogen ___ residues away
hydrogen carbonyl oxygen hydrogen 4
All the variations of ___________________ contain 8 phosphoserine residues, 7 of which are localized between 43 and 80
as1-casein
___________ binds the troponin complex to tropomyosin
Troponin-T
___________ 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
Whey protein hydrolysates
Between pH 3.1 and 5.1, at low temperatures and high concentration, B-lactoglobulin associates to form an _______
B-lactoglobulin octomer
________ make up 30% of total muscle protein, and is soluble
Sarcoplasmic proteins
The suprahelix is held together by _______ bonds supplied by ________
hydrogen glycine
Amino acids with a ____________ group can also undergo reactions with reducing sugars at high temperatures
secondary amine
Lactose can be recrystallized to yield a _________, which is used as a ________
raffinate filler in tablets
When _______-casein precipitates with Ca2+, at temperatures of < 1oC, the calcium salt is quite soluble
B
Groups of myofibers are organized into primary and secondary bundles of _______ that are segregated by another layer of connective tissue called the ________.
fascicles perimysium
10% of the total casein fraction is present in milk as _________, usually designated as _______ caseins
monomers serum
The fundamental structural unit of the myofibrils is the _________.
sarcomere
Casein and the enzyme renin are examples of _________
phosphoproteins
Upon binding to actin, _________ swivel to approximately a 45oC, pulling the _____ filaments past the _____ filaments toward the _________
myosin heads thin thick M-line
________ make up 10-20% of total muscle protein; insoluble
Stromal proteins
Soy sauce is a _____________ produced by the fermentation of soybeans
protein hydrolysate
The T-tubules are in physical contact at periodic intervals with the _____________, which is the muscle equivalent of an endoplasmic reticulum
sarcoplasmic reticulum
______ is a large skeletal protein associated with thin filaments
Nebulin
_________ contain great amounts of ______ organelles and fuels, such as mitochondria, myoglobin, and lipids
Slow-contracting (red) oxidative
The ______ consists of thin filaments only
I-band
The peptide bond is an ______ bond
amide
Decarboxylase enzymes are inhibited by ______
DMFO
However, at physiological ionic strength, G-actin monomers are polymerized “head-to-tail” in ________
F-actin
Strongly alkaline environments can lead to ___________ of amino acids
racemization
_____ contains 2 disulfide bonds, 1 free sulfhydryl group, and no phosphorus
B-lactoglobulin
In the case of casein micelles, _______________ are minimal at temperatures below 5oC
hydrophobic interactions
_________ are proteins that are soluble in 50-90% ethanol and insoluble in water
Prolamines
Gliadin from wheat is an example of ___________
prolamines
________ linkages play an important role in the 3D structure of a protein, and make it less susceptible to denaturation
Diester
All proteins are synthesized from __ amino acids
L
Whey protein concentrates are produced by ____________
ultrafiltration
At the ________ end of the myosin chain, the protein exhibits a globular structure called the ______
amino myosin head
__________ is activated by micromolar concentrations of Ca2+
u-calpain
_______ is a globular monomer
G-actin
The initial Maillard reaction forms _________
Glycosylamine
The _______ amino group is the most reactive amino group in Lysine.
epsilon
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 _______
K N C B-structures
A very high pH is needed to suppress the _____ charges on the _____ side chains (i.e. to convert _____ to ____)
positive basic NH3+ to NH2
_______ is considered to be somewhat basic, and is capable of ionizing beyond pH 10
Tryptophan
Chymosin cleaves K-casein into ___________ and a ___________
para-K-casein glycomacropeptide
filaments on opposite sides of the _____ are directed toward each other within a given sarcomere.
M-line
The _______ consists of overlapping thin and thick filaments
A-band
The AMP formed by adenylate kinase is _______ to __________, which is catalyzed by ________ (sarcoplasmic protein fraction)
deaminated IMP AMP deaminase
A very low pH is needed to suppress the _____ charges on the _____ side chains (i.e. to convert _____ to ____)
negative acidic COO- to COOH
The ____________ AA provide flavor due to their breakdown when being cooked, mainly due to the release of ______
sulfur-containing H2S
Due to the ____________ form of AA and __________, protein polymers tend to twist upon itself
L-chiral steric hindrance
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-lactalbumin lysozyme
________ has 4 disulfide linkages and no phosphate groups
a-Lactalbumin
There might be ___________ during freezing, but there is little browning due to ________________________
denaturation low temperature of sublimation
What is PER’s equation?
Weight gained/Weight of protein consumed
_____________ is one of the best methods of drying in terms of maintaining protein functionality, nutritional quality, and enzyme activity (expensive)
Freeze drying
_______ is the most abundant muscle protein, constituting 43% of the muscle myofibril.
Myosin
Arginine, Tryptophan, Histidine, Glutamine, and Asparagine all have a ___________ group
secondary amine
___________ contains 5 phosphoserine residues that are localized between 1 and 40, which contains practically all the __________ sites of the molecule
B-casein ionizable
The C-CO-NH-C unit is planar with the ___________ and ___________ of the peptide bond always trans to each other
carboxyl oxygen amino hydrogen
The center of the A-band appears brighter than the distal zones (less dense), and is termed the ___-zone.
H
The _________ trigger the release of Ca2+ from the lumen of the __________, which rises at least ____-fold
T-tubules sarcoplasm 100
Which milk protein has a dynamic disulfide bond?
B-lactoglobulin
This structure, called the ______, consists of proteins that maintain the structural arrangement of the thick filament proteins
M-line
Below pH 3.0 and above pH 8.0, __________exists as a ______
B-lactoglobulin monomer
At the pH of milk, _________ tends to form a ______
B-lactoglobulin dimer
________ 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.
Caseins caseinates
What are the 3 types of myofibers?
1) Slow-red 2A) Fast-red 2B) Fast-white
_____-casein is a monomer
K
The side chains of the amides of _____________ and _____________ play a role in non-enzymatic browning reactions
aspartic acid glutamic acid
__________ modifies the activity of galactosyl transferase
a-lactalbumin
________ are proteins that are soluble in water and precipitated by ammonia
Histones
The _________ are anchored at the Z-disc
thin filaments
Proteins are separated on the basis of __________
solubility
Classify the troponin subunits from largest to smallest.
Troponin-C < Troponin-I < Troponin-T
_____ is the largest single polypeptide chain known
Titin
_________ are basic proteins, which contain large amounts lysines and arginines
Histones
____________ causes extensive denaturation and browning if sugars are present
Drum drying
Each myofiber is encased in a layer of connective tissue called the _______________
endomysium
________ contains a portion with 12 carboxyl groups from _____________ and _____________ residues, making it extremely ______
as1-casein glutamic acid aspartic acid polar
In ___-casein, varying amounts of carbohydrate are bound to the peptide chain through Threonine residues at positions 131, 133, 135, or 136 (A variant)
K
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
water alkali
The electrostatic interactions in casein micelles are mostly between ________ and ________ that form bridges between __________ and ________ residues
calcium calcium phosphate phosphoserine glutamic acid
_________ serve as a major reservoir for a family of proteolytic enzymes known as _______
Lysosomes cathepsins
When myosin heads form cross-bridges between the thick and thin filaments, they are placed ________ to the thick filament axis
perpendicular
The narrow, dark, electron-dense center of the I-band is termed the __________
Z-disc
The plasma membrane of myofibers is called the __________
sarcolemma
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
as1-casein apolar phosphate cysteine
________ precipitates with Ca2+ more easily than as1-casein
as2-casein
What are the three classes of proteins?
Sarcoplasmic Myofibrillar Stromal
B-lactoglobulin is effective at binding __________
retinol
__________ is found both in the sarcoplasm and as a component of the ______ of the myofibril
Creatine kinase M-line
________ binds Ca2+ ions
Troponin-C
The protein _____ spans the sarcomere from the _____ to the _______
titin M-line Z-disc
Unlike _____-casein, ______-casein does not self-associate spontaneously
as1 B
________________ adds UDP-galactose to glucose and produces _______ and UDP, which is faster when __________ is attached
galactosyl transferase lactose a-lactalbumin
a-lactalbumin uses calcium to form _________________ bonds that tend to make the molecule resistant to thermal unfolding
intramolecular ionic
At very low ionic strength, actin exists primarily as __________
G-actin
________ make up 50-60% of total muscle protein; solubilized in concentrated salt solutions (e.g., 0.3M NaC1)
Myofibrillar proteins
The ___ variant of B-lactoglobulin forms more readily than the ___ variant since it has an extra ______ group
A B carboxyl
_________ runs the entire length of the thin filament, spanning seven actin monomers
Tropomyosin
Certain proteins can reduce surface tension, resulting in the formation of a ____
foam
__________ are proteins that are soluble in neutral, dilute salt solution, but not in distilled water
Globulins
The ___________ and the _________ combine to provide the necessary framework for maintaining the structural integrity of these tissues within the muscle.
perimysium endomysium
____________ are less likely to trigger allergic reactions than _________________; they are used often in infant formulas
Whey protein hydrolysates non-hydrolyzed whey protein
Stretching results from an increase in _____ separation, accomplished by sliding of thin filaments of a sarcomere from each other as they move along the ________
Z-disc A-band
_________ proteins form the fibrous connective tissues that strengthen and protect muscles
Stromal
The _________ functions as a reservoir of calcium ions that serve as the trigger for muscle contraction
sarcoplasmic reticulum
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
sarcolemma transverse tubules (T-tubules)
_______ aromatic AA is reactive due to its OH group; forms _____ linkages with phosphate
Tyrosine ester
Proteins with significant quantities of ___________, ___________, and ___________ are especially susceptible to changes in pH
aspartic acid, glutamic acid, and lysine
_________ are proteins that are soluble in dilute acid or base, but not in neutral solutions
Glutelins
One _______ molecule extends from the Z-line to the distal end of a thin filament
nebulin
________ inhibits the actomyosin ATPase
Troponin-I
The ______ consists only of thick filaments with no overlapping thin filaments
H-zone
At the center of the _____ is a dark zone analogous to the ______.
H-zone Z-disc
Which milk protein associates to form a barrel with _______ and a lid with _______?
B-lactoglobulin B-structures a-helix
_______ is used to remove headspace oxygen from food packages
Glucose oxidase
_________ are proteins that are soluble in neutral distilled water
Albumins
The red to reddish pink color of red meat is due to ______
myoglobin
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
water-binding capacity
____________ is unusual since the molecule is more stable to heat in the presence of calcium
a-lactalbumin
_______ and _______ can disrupt H-bonds by _______________ of a protein
Alcohol acetone partial dehydration
__________ are proteins that are insoluble in water and neutral salts
Scleroproteins
Upon stimulation of a muscle fiber by the nerve, the neurochemical impulse is transmitted into the fiber by the _______.
T-tubules
Myoglobin is present in greater abundance in _______ myofibers because they derive a greater share of their energy from ____________
slow-red oxidative metabolism
IMP is further degraded to ________, which imparts a _____ flavor to meat
hypoxanthine bitter
Sugars and carbohydrate are often attached to the amide group of asparagine by an ___-glycosidic linkage
N
____________ 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.
Adipose tissue perimysium
In putrefaction, at lower pHs, ________ are the most active, while at higher pHs, the _________ are the most active
decarboxylases deaminases
Which method is highly detrimental to whey?
- Steam injection - Precipitation of the denatured proteins - Sedimentation centrifuge - Drying
A final layer of heavy connective tissue sheaths, called the __________, surrounds the whole muscle
epimysium
Putrefactive odors and flavors are due to compounds produced by the _____________________________ by _________
enzymatic deamination or decarboxylation of free AA microbial enzymes
The portion of ______ located in the gap between the ______ filament and the ______ is elastic
titin thick filament Z-line
______ contains 11 phosphoserine and 2 cysteine residues
as2-casein
Enzymatic action of cross-linked amide bonds will stop at ___ amino acid on either side of the cross-linked amino acids, leaving an indigestible ___________
one hexapeptide
Denaturation of a protein generally results in a reduction in _________
solubility
_____ may be involved in restoring resting sarcomere length when the muscle relaxes
Titin
_____________ are used to make meaty flavours
Protein hydrolysates
How is whey usually dried? What is a technique that can reduce the cost?
- Spray drying - Reverse osmosis
The thick filaments of the sarcomere are primarily composed of ________, and _____ is also associated with thick filaments
myosin titin
_________ AA are very reactive and play an important role in protein structure
Carboxylic
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 _____
Troponin-C Troponin-T tropomyosin tropomyosin actin actin myosin
_________ is associated with microbial spoilage of high-protein foods
Putrefaction
Electron micrographs indicate that a thick filament is surrounded by an array of ___ thin filaments
six
______ is the most hydrophobic casein
B-casein
____________ converts ADP to ATP and AMP, and is an enzyme present in the sarcoplasmic protein fraction
Adenylate kinase
Which casein acts like soap?
B-casein Polar head and an apolar tail
Like _______-casein, _______-casein contains no cysteine residues
as1 B
_______________ can make enzymes work in opposite ways
Organic solvents
Why aren’t proline and hydroxyproline considered to be amino acids?
They do not contain a true amino group (NH2) - Instead they contain an imino group (NH)
The R group in Histidine is the _________ group
imidazole
Phosphorylase B is more abundant in _______ myofibers because these myofibers rely heavily on ______ for energy requirements
fast-white glycolysis
Classify the types of casein in order of most present to least present.
as1 > B > K > as2 > γ
What are the four proteins that consist of the thin filaments of the sarcomere?
- Actin - Tropomyosin and troponin - Nebulin
Normally, __-casein occurs as a trimer or as higher oligomers by the formation of ________bonds
K disulfide
_________ are degradation products of B-casein formed by milk proteases
gamma-casein
