Proteins IV Flashcards
Red meat does not include ______
poultry
Most of the meat consumed is from _____ animals because strengthening of the muscles is due to _______ animals
young
older
The red to reddish pink color of red meat is due to ______
myoglobin
______ is the oxygen storage protein in red meat
myoglobin
Red meat is mainly composed of _____ muscle.
skeletal
Muscle condition of the live animal is related to the animal’s __________
level of activity
Water accounts for over ____% of lean tissue by weight. The water is either ______ to _______ or free
70
bound to proteins
free (trapped within muscle cells)
While the animal was alive, the “____” water served as the medium in which nutrients and other solutes were dissolved and transported.
free
In proximate analysis of meat, protein content is typically derived from the determination of muscle ________ content by Kjeldahl analysis
nitrogen
The average ______ content is 16% of protein
nitrogen
As much as 10% of muscle nitrogen originates from __________, such as _______
non-protein sources
nucleic acids/amino acids
The true protein content of red meat is somewhat (higher/lower) than reported
lower
______ can account for 1-13% of fresh weight of separable lean tissue
Lipids
Minimal values (0.5-1%) represent the _____________ present in living cells
membrane phospholipids
Larger lipid values indicate the presence of variable amounts of __________, which are primarily ________
neutral storage lipids
triacylglycerols
The large variability in the percentage of lipid content is mostly accounted for by variability in _______ content
water
______ refers to the inorganic residue remaining after a muscle sample is incinerated at extremely high temperatures and represents the _____ component of muscle.
Ash
mineral
______, ______, and _______ make up the remaining 1% of skeletal muscle.
Carbohydrates, vitamins, and other soluble organic constituents
The main carbohydrate in muscle is ______, which is _____-term energy storage
glycogen
short
The main carbohydrate in meat is _____ because during the conversion of muscle to meat the ______ is largely converted to ______ by _________
lactate
glycogen
lactate
anaerobic glycolysis
Proteins are separated on the basis of __________
solubility
What are the three classes of proteins?
Sarcoplasmic
Myofibrillar
Stromal
________ make up 30% of total muscle protein, and is soluble
Sarcoplasmic proteins
________ make up 50-60% of total muscle protein; solubilized in concentrated salt solutions (e.g., 0.3M NaC1)
Myofibrillar proteins
________ make up 10-20% of total muscle protein; insoluble
Stromal proteins
Sarcoplasmic proteins are dissolved in the _______ inside muscle cells
cytoplasm
Sarcoplasmic proteins, such as _______ and _____ enzymes, are mainly involved in the __________________
myoglobin
glycolytic enzymes
regulation of cell and energy homeostasis
The colors of fresh, cooked, and cured meat products are due, in large part, to the content and the ________ of the ______ associated with myoglobin
oxidation state
iron
Myoglobin content tends to be in lower abundance in ______ animals, hence the pale color of ____ compared to that of ______
young
veal
adult beef
_____ constitute the largest fraction (50-60%) of muscle proteins
Myofibrillar proteins
In muscle tissue, myofibrillar proteins are assembled into complex _______ structural filaments that _____________
quaternary
regulate, support, or perform the mechanical work of contraction.
What are the three types of major myofibrillar proteins in skeletal muscle?
- Contractile
- Regulatory
- Cytoskeletal
_____ and _____ together account for about 40% of the total protein in skeletal muscle.
Myosin
actin
The behavior of _________ proteins is important in fresh meats, because the extent of contraction and rigor mortis development are critical in the successful conversion of muscle to meat, as well as in processed meats
myofibrillar
_________ proteins form the fibrous connective tissues that strengthen and protect muscles
Stromal
_______ proteins contribute to meat toughness
Stromal
_______ is the most abundant protein in the animal body
Collagen
Collagen is a ______ protein
stromal
_______ makes a small contribution to total skeletal muscle protein, but it is the most abundant protein in the animal body
Collagen
Processing and cooking methods for meat are designed to disrupt and partially solubilize ________ fibers
collagen
What are the sources of non-protein nitrogen?
Creatine, amino acids, nucleic acids, and nucleotides
The total content of __________ only accounts for 1.6% of the wet weight of the muscle
non-protein nitrogen
________ and ________ are key components in the development of rigor mortis
Creatine
Nucleotide ATP
Parallel arrangement of elongated multinucleated cells are called ______
myofibers
Skeletal muscles are composed of _______
myofibers
T or F: Individual myofibers range from um to the entire length of the muscle
True
Each myofiber is encased in a layer of connective tissue called the
___________.
endomysium
Groups of myofibers are organized into primary and secondary bundles of _______ that are segregated by another layer of connective tissue called the ________.
fascicles
perimysium
A final layer of heavy connective tissue sheaths, called the __________, surrounds the whole muscle
epimysium
_________ merge with connective tissue tendons to link muscle to the bones
epimysium
The _______ and ________ are infiltrated in the muscle
nervous
vascular
The ___________ and the _________ combine to provide the necessary framework for maintaining the structural integrity of these tissues within the muscle.
perimysium
endomysium
____________ 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
The abundance of ________ is often used as an indicator in visual appraisal of meat quality.
marbling
Muscle contraction is triggered by increased _________ ________ concentrations
intracellular
calcium
The plasma membrane of myofibers is called the __________
sarcolemma
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)
The T-tubules are in physical contact at periodic intervals with the _____________, which is the muscle equivalent of an endoplasmic reticulum
sarcoplasmic reticulum
The sarcoplasmic reticulum is in physical content at periodic intervals with the ________
T-tubules
The muscle equivalent of the endoplasmic reticulum is the _________
sarcoplasmic reticulum
The _________ functions as a reservoir of calcium ions that serve as the trigger for muscle contraction
sarcoplasmic reticulum
The sarcoplasmic reticulum serves as a reservoir of ______
calcium
Some proteins in the interior of the SR bind _______ ions while the muscle is at rest
calcium
Other proteins in the SR open in response to electrochemical stimulus, allowing diffusion of _____ ions from the _____ to the ________
calcium
SR
sarcoplasm
What triggers muscle contraction?
Diffusion of calcium ions from within the SR to the sarcoplasm
What triggers muscle relaxation?
Protein pumps calcium back into the lumen of the SR during relaxation
___________ serve as energy transducers for the myofiber
Mitochondria
_________ serve as a major reservoir for a family of proteolytic enzymes known as _______
Lysosomes
cathepsins
_______ play a catabolic function in protein turnover
cathepsins
Myofibers are typically ____nucleated
multi
Where are the nuclei of myofibers?
Dispersed; typically found beneath the sarcolemma
The sarcoplasm may contain ______ particles and ______ droplets
glycogen
lipid
The oxygen storage, enzyme levels, metabolic intermediates are found to varying degrees within the __________
sarcoplasm
What are the 3 types of myofibers?
1) Slow-red
2A) Fast-red
2B) Fast-white
_________ contain great amounts of ______ organelles and fuels, such as mitochondria, myoglobin, and lipids
Slow-contracting (red)
oxidative
__________ are more equipped for ______ metabolism fueled by carbohydrates
Fast-contracting
anaerobic
________ are the contractile organelles of a muscle cell and constitute 80-90% of the volume of the cell.
Myofibrils
Myofibrils are composed of thin and thick protein filaments, _______, in a highly specific structural organization
myofilaments
The fundamental structural unit of the myofibrils is the _________.
sarcomere
What is observed when longitudinal sections of skeletal muscle are viewed under a microscope?
Alternating dark and light bands
A-bands are ______, and I-bands are _______
anisotropic
isotropic
The _______ consists of overlapping thin and thick filaments
A-band
The ______ consists of thin filaments only
I-band
The center of the A-band appears brighter than the distal zones (less dense), and is termed the ___-zone.
H
The ______ consists only of thick filaments with no overlapping thin filaments
H-zone
The narrow, dark, electron-dense center of the I-band is termed the __________
Z-disc
The boundaries of a sarcomere are defined by the _______ and hence a ______ represents the junction between two sarcomeres.
Z-discs
Z-disc
The ____ of proteins that constitutes the ____ serves as the anchoring structure for the proteins of the thin filaments that emanate from both sides of the _____
matrix
Z-disc
Z-disc
At the center of the _____ is a dark zone analogous to the ______.
H-zone
Z-disc
This structure, called the ______, consists of proteins that maintain the structural arrangement of the thick filament proteins
M-line
The _______ serves as an anchoring point for the protein titan
M-line
The protein _____ spans the sarcomere from the _____ to the _______
titin
M-line
Z-disc
The ______ define the boundaries of the sarcomere
Z-discs
The _________ are anchored at the Z-disc
thin filaments
The ________ in the central region of the sarcomere that partially overlap with the thin filaments
thick filaments
Sarcomere length is defined as the distance between adjacent __________
Z-disc
Sarcomere length depend on the state of contraction of the ______ or the ______ force applied to it
myofiber
stretch
The ________ theory of muscle contraction is still accepted today
sliding filament
The lengths of both _____ and ______________ remain constant, independent of whether the muscle is stretched, contracting, or in a resting state
thin
thick filaments
Electron micrographs indicate that a thick filament is surrounded by an array of ___ thin filaments
six
Huxley and Hanson proposed that ________ and ________ interdigitate, allong for the _______________
thin filaments
thick filaments
sliding of filaments past each other
When contraction takes place, the thin and thick filaments slide past each other such that the _________ at opposite ends of a sarcomere move toward each other, resulting in _________ of the sarcomere length
thin filaments
shortening
Myofibrils are made up of a smaller unit called _____________
myofilament
A myofilament is made up of two groupings of contractile proteins termed _____ and ______
myosin
actin
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
_______ sarcomeres, resulting from contraction as muscle is converted to meat, are correlated with toughness
Short
What are the four proteins that consist of the thin filaments of the sarcomere?
- Actin
- Tropomyosin and troponin
- Nebulin
The thin contractile filament of the sarcomere is _______
actin
The thin regulatory filaments of the sarcomere are _______ and ______
tropomyosin
troponin
The thin cytoskeletal filament of the sarcomere is ________
nebulin
The thick filaments of the sarcomere are primarily composed of ________, and _____ is also associated with thick filaments
myosin
titin
______ is the second most abundant protein in muscle, constituting 20% of the myofibrillar protein content.
Actin
At very low ionic strength, actin exists primarily as __________
G-actin
However, at physiological ionic strength, G-actin monomers are polymerized “head-to-tail” in ________
F-actin
________ is a two-stranded, double-helical assembly that constitutes the backbone of the thin filament
F-actin
_______ is a globular monomer
G-actin
filaments on opposite sides of the _____ are directed toward each other within a given sarcomere.
M-line
One end of each thin filament is attached to the _______
Z-line
_____ binds to _______ during muscle contraction, forming cross-bridges between the ______ and ______ filaments
Actin
myosin
thin
thick
Actin binds to the regulatory proteins _______ and _______
tropomyosine
troponin
_____________ exists in the myofiber as a head-to-tail polymer
Tropomyosin
_________ runs the entire length of the thin filament, spanning seven actin monomers
Tropomyosin
Troponin consists of 3 subunits: _______, _______, and ______
Troponin-T
Troponin-C
Troponin-I
Classify the troponin subunits from largest to smallest.
Troponin-C < Troponin-I < Troponin-T
___________ binds the troponin complex to tropomyosin
Troponin-T
________ binds Ca2+ ions
Troponin-C
________ inhibits the actomyosin ATPase
Troponin-I
Troponin binds near the head-tail junctions of _______ molecules
tropomyosin
There is/are _____ troponin complex per tropomyosin molecule
one
________ and _______ act in concert to permit the sliding of myosin along the thin filaments
Tropomyosin
troponin
Upon neural stimulation at the neuromuscular junction, ____ ions are released inside the cell
Ca2+
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 a large skeletal protein associated with thin filaments
Nebulin
One _______ molecule extends from the Z-line to the distal end of a thin filament
nebulin
_______ is the most abundant muscle protein, constituting 43% of the muscle myofibril.
Myosin
________ is an extremely large protein that consists of six polypeptide chains
Myosin
At the ________ end of the myosin chain, the protein exhibits a globular structure called the ______
amino
myosin head
The helical tails of two myosin heavy chains intertwine to form a helical ________
coiled-coil
Under physiological conditions, side-by-side myosin molecules coalesce via their _____ portions to form _____ filaments
tail
thick
The ________ project radially from the thick filament shaft and are directed toward the thin filaments
myosin heads
Like the thin filaments, the thick filaments are arranged in _______ fashion; myosin molecules on opposite sides of the M-line point in the ________ direction
bipolar
opposite
_______ acts as an ATPase enzyme, splitting ATP and liberating energy
Myosin
The active site of the myosin ATPase and the force transduction are localized in the _________
myosin head
During contraction, ___________ are able to link to ______ of the ____ filament and form cross-bridges
myosin heads
actin molecules
thin
_____ is the largest single polypeptide chain known
Titin
Titin spans ______ a sarcomere, running from the_____ to the ______
1/2
Z-line
M-line
______ appears to act as a cytoskeletal structure that maintains thick filament integrity.
Titin
______ serves as a template upon which myosin molecules form the thick filament during muscle cell differentiation and development.
Titin
The portion of ______ located in the gap between the ______ filament and the ______ is elastic
titin
thick filament
Z-line
_____ may be involved in restoring resting sarcomere length when the muscle relaxes
Titin
When the muscle cell is at rest, _________ sterically blocks __________ from the binding sites of the _____ filament.
tropomyosin
myosin heads
actin
Upon stimulation of a muscle fiber by the nerve, the neurochemical impulse is transmitted into the fiber by the _______.
T-tubules
The _________ trigger the release of Ca2+ from the lumen of the __________, which rises at least ____-fold
T-tubules
sarcoplasm
100
Some of the Ca2+ ions bind to _____, causing a conformational change in _______, the tropomyosin-binding subunit
troponin-C
troponin-T
Following the conformational change in troponin-T, the position of _______ is shifter to a location deeper in the ______ filament, which exposes _____ binding sites on the ______ monomers
tropomyosin
actin
myosin
actin
Using energy provided by the ATPase activity of _____, the ________ are now able to bind to _______ molecules of the ____ filament, forming cross-bridges between the thick and thin filaments
myosin
myosin heads
actin
thin
When myosin heads form cross-bridges between the thick and thin filaments, they are placed ________ to the thick filament axis
perpendicular
Upon binding to actin, _________ swivel to approximately a 45oC, pulling the _____ filaments past the _____ filaments toward the _________
myosin heads
thin
thick
M-line
With myosin heads on opposite sides of the _____ pulling the ____ filaments toward the middle, the sarcomere shortens.
M-line
thin
When the sarcomere is shortened, a molecule of ____ binds to the ________, causing its detachment from ______
ATP
myosin head
actin
When the myosin head detaches from actin, the ____ molecule is hydrolyzed to provide energy for the structural rearrangement of the _______ back to the 90oC
ATP
myosin head
_____ provides the chemical energy needed for transport of Ca2+ from the ___ Ca2+ concentration in the sarcoplasm to the ____ concentration in the lumen of the SR.
ATP
low
high
With the pumping of Ca2+ back into storage, ______ resumes its original conformation and thus _______ returns to its original position on the ____ filament, thereby blocking the myosin binding sites and causes the muscle to relax
troponin
tropomyosin
actin
_________ proteins comprise 25-30% of the total muscle protein content
Sarcoplasmic
Sarcoplasmic proteins are located in the __________
sarcoplasm
Because of packing constraints imposed by the organization of the myofibrillar proteins, the __________ proteins are largely restricted to the cellular fluid bathing the myofibrils.
sarcoplasmic
_________ proteins include enzymes associated with glycolysis and glycogenolysis, ancillary enzymes such as creatine kinase and AMP deaminase, proteinases, and the oxygen storage protein myoglobin.
Sarcoplasmic
Glyceraldehyde phosphate dehydrogenase, accounts for over 20% of the total _________ protein fraction
sarcoplasmic
Phosphorylase B is more abundant in _______ myofibers because these myofibers rely heavily on ______ for energy requirements
fast-white
glycolysis
Myoglobin is present in greater abundance in _______ myofibers because they derive a greater share of their energy from ____________
slow-red
oxidative metabolism
The greatest quantities of _______ (up to 70% of the total sarcoplasmic protein fraction) are found in whale muscle because a large supply of oxygen is required during prolonged deep-sea dives.
myoglobin
Another enzyme of significance in both living muscle tissue and in postmortem conversion of muscle to meat is _______________
creatine kinase
__________ is found both in the sarcoplasm and as a component of the ______ of the myofibril
Creatine kinase
M-line
Creatine kinase acts on _____________ when intensive work demands are placed on the muscle to do
creatine phosphate
As ATP is consumed, _________ quickly replaces the loss by catalyzing the addition of _________ from creatine phosphate to ADP
creatine kinase
phosphate
In resting muscle, _____ and __________ restore ATP, and some of the excess high-energy capacity that is in the form of ATP is stored in __________
glycolytic
oxidative metabolism
creatine-phosphate
What are the 4 ways to convert ADP to ATP?
- Oxidative phosphorylation
- Glycolysis
- Creatine kinase
- Adenylate kinase
____________ converts ADP to ATP and AMP, and is an enzyme present in the sarcoplasmic protein fraction
Adenylate kinase
The reaction catalyzed by _______ becomes especially significant postmortem as cellular stores of oxygen, glycogen, and creatine phosphate are exhausted
adenylate kinase
The AMP formed by adenylate kinase is _______ to __________, which is catalyzed by ________ (sarcoplasmic protein fraction)
deaminated
IMP
AMP deaminase
IMP is further degraded to ________, which imparts a _____ flavor to meat
hypoxanthine
bitter
The calcium-dependent proteinases in muscle sarcoplasm are called ______
calpains
__________ is activated by micromolar concentrations of Ca2+
u-calpain
________ is activated by milimolar concentrations of Ca2+
m-calpain
_________ is activated by submicromolar concentrations of Ca2+
calpain 3
Proteinases break down particular proteins of the myofibril, such as ____, ____, and _____ during postmortem conversion of muscle to meat
titin
nebulin
troponin-T
