BIO 251 EXAM #2 REAL EXAM QUESTIONS WITH
LATEST UPDATED CORRECT ANSWERS. GET IT 100%
ACCURATE
Thick & thin filaments, sarcomeres, myofibrils, skeletal muscle cells - answer ✔✔-How is skeletal
muscle organized?
Thick & thin filaments - answer ✔✔-What are the two types of contractile filaments?
Myosin - answer ✔✔-What are thick filaments made up of?
Actin (primary component), tropomyosin, troponin - answer ✔✔-What are thin filaments made up of?
Each thick filaments consist of many myosin molecules; half are oriented in one direction, half are
oriented in the other direction - answer ✔✔-How are thick filaments oriented?
Actin and tropomyosin arranges in a helix configuration; troponin attached to actin/tropomyosin at
regular intervals - answer ✔✔-How are thin filaments oriented?
Functional contractile unit of skeletal muscle - answer ✔✔-What are sarcomeres?
Protein disks at the ends of a sarcomere - answer ✔✔-What are Z disks?
Thin filaments attach to Z disk, thick filaments in center of sarcomere (connected to Z disk by titin) -
answer ✔✔-How are sarcomeres organized?
Sarcomeres align end to end to form myofibrils - answer ✔✔-What are myofibrils?
A T-tubule (or transverse tubule) is a deep invagination of the sarcolemma, which is the plasma
membrane of skeletal muscle and cardiac muscle cells. - answer ✔✔-What are T tubules?
These invaginations allow depolarization of the membrane to quickly penetrate to the interior of the
cell. - answer ✔✔-What is the function of T tubules?
A neuromuscular junction (or myoneural junction) is a chemical synapse formed by the contact
between a motor neuron and a muscle fiber. It is at the neuromuscular junction that a motor neuron is
able to transmit a signal to the muscle fiber, causing muscle contraction. - answer ✔✔-What is a
neuromuscular junction?
Acetylcholine - answer ✔✔-What neurotransmitter is released at the neuromuscular junction?
Cross-Bridge Cycle - answer ✔✔-What is the underlying mechanism that is common to all three types
(skeletal, smooth, and cardiac) of muscle that allows the cells to shorten?
Myosin heads of thick filaments attach to thin filaments (form cross-bridges) - answer ✔✔-What is
meant by the term cross-bridge?
Myosin heads rotate, pulling thin filaments along thick filaments toward center of the sarcomere -
answer ✔✔-What is meant by the term power stroke?
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, 1. Binding of myosin to actin, inorganic phosphate released
2. Power stroke, actin gets pulled towards middle of sarcomere, ADP is released
3. Rigor (myosin in low-energy form), New ATP binds to myosin head
4. Unbinding of myosin and actin, ATP is hydrolyzed
5. Cocking of the myosin head (myosin in high-energy form) - answer ✔✔-Describe the sequence of
events that occur during the cross-bridge cycle in skeletal muscle cells.
Calcium is the signal that ultimately leads to contraction. - answer ✔✔-What is the role of Ca2+ in
skeletal muscle contraction?
most calcium required for contraction comes from the Sarcoplasmic Reticulum; a little from
Extracellular Fluid. - answer ✔✔-Where does most of the Ca2+ required for contraction come from in
skeletal muscle cells?
SR calcium channels (ryanodine receptors) are a type of gated calcium channel
Closed until opened by DHP receptors (present on T tubule) in response to voltage change of T tubule
membrane by action potentials - answer ✔✔-How do action potentials travelling down T tubules lead to
the release of Ca2+ into the cytoplasm of skeletal muscle cells?
Ryanodine receptors are closed until opened by DHP receptors (present on T tubule) in response to
voltage change of T tubule membrane by action potentials - answer ✔✔-What is the function of DHP
receptors?
Ryanodine receptors are a type of gated calcium channel - answer ✔✔-What is the function of
ryanodine receptors?
- answer ✔✔-How does Ca2+ binding to troponin on the thin filaments trigger the formation of cross-
bridges between myosin heads and actin?
The released phosphate group then binds to the pump, causing the pump to change shape. This
shape change causes the cytosolic side of the pump to open, allowing the two Ca2+ to enter. The
cytosolic side of the pump then closes and the sarcoplasmic reticulum side opens, releasing the Ca2+
into the SR. - answer ✔✔-How is Ca2+ removed from the cytosol in skeletal muscle cells?
Slow oxidative, fast oxidative, fast glycolytic. Basis for classification: Velocity of contraction and
primary energy source - answer ✔✔-What are the three different subtypes of skeletal muscle cells and
how do they differ from one another?
Extracellular fluid - answer ✔✔-Where does most of the Ca2+ needed for smooth muscle cell
contraction come from?
Calmodulin complex activated an enzyme called myosin kinase which then adds a phosphate to
myosin, giving myosin heads the ability to bind to actin on thin filaments. - answer ✔✔-What are the
roles of calmodulin and myosin kinase in smooth muscle cell contraction?
Removes phosphate from myosin - answer ✔✔-What is the function of phosphatase in smooth muscle
cells?
Ca2+ - ATPase & Ca2+ - Na+ counter transport (Ca out, Na in) are pumped out of the cell - answer
✔✔-List the mechanisms to remove calcium from the cytoplasm of smooth muscle cells during
relaxation.
Extracellular fluid and sarcoplasmic reticulum - answer ✔✔-Where does the calcium needed for
cardiac muscle cell contraction come from?
1. Current speeds through gap junctions to contractile cell
2. Action potentials travel along plasma membrane and T tubules
GRADESMORE.COM
LATEST UPDATED CORRECT ANSWERS. GET IT 100%
ACCURATE
Thick & thin filaments, sarcomeres, myofibrils, skeletal muscle cells - answer ✔✔-How is skeletal
muscle organized?
Thick & thin filaments - answer ✔✔-What are the two types of contractile filaments?
Myosin - answer ✔✔-What are thick filaments made up of?
Actin (primary component), tropomyosin, troponin - answer ✔✔-What are thin filaments made up of?
Each thick filaments consist of many myosin molecules; half are oriented in one direction, half are
oriented in the other direction - answer ✔✔-How are thick filaments oriented?
Actin and tropomyosin arranges in a helix configuration; troponin attached to actin/tropomyosin at
regular intervals - answer ✔✔-How are thin filaments oriented?
Functional contractile unit of skeletal muscle - answer ✔✔-What are sarcomeres?
Protein disks at the ends of a sarcomere - answer ✔✔-What are Z disks?
Thin filaments attach to Z disk, thick filaments in center of sarcomere (connected to Z disk by titin) -
answer ✔✔-How are sarcomeres organized?
Sarcomeres align end to end to form myofibrils - answer ✔✔-What are myofibrils?
A T-tubule (or transverse tubule) is a deep invagination of the sarcolemma, which is the plasma
membrane of skeletal muscle and cardiac muscle cells. - answer ✔✔-What are T tubules?
These invaginations allow depolarization of the membrane to quickly penetrate to the interior of the
cell. - answer ✔✔-What is the function of T tubules?
A neuromuscular junction (or myoneural junction) is a chemical synapse formed by the contact
between a motor neuron and a muscle fiber. It is at the neuromuscular junction that a motor neuron is
able to transmit a signal to the muscle fiber, causing muscle contraction. - answer ✔✔-What is a
neuromuscular junction?
Acetylcholine - answer ✔✔-What neurotransmitter is released at the neuromuscular junction?
Cross-Bridge Cycle - answer ✔✔-What is the underlying mechanism that is common to all three types
(skeletal, smooth, and cardiac) of muscle that allows the cells to shorten?
Myosin heads of thick filaments attach to thin filaments (form cross-bridges) - answer ✔✔-What is
meant by the term cross-bridge?
Myosin heads rotate, pulling thin filaments along thick filaments toward center of the sarcomere -
answer ✔✔-What is meant by the term power stroke?
GRADESMORE.COM
, 1. Binding of myosin to actin, inorganic phosphate released
2. Power stroke, actin gets pulled towards middle of sarcomere, ADP is released
3. Rigor (myosin in low-energy form), New ATP binds to myosin head
4. Unbinding of myosin and actin, ATP is hydrolyzed
5. Cocking of the myosin head (myosin in high-energy form) - answer ✔✔-Describe the sequence of
events that occur during the cross-bridge cycle in skeletal muscle cells.
Calcium is the signal that ultimately leads to contraction. - answer ✔✔-What is the role of Ca2+ in
skeletal muscle contraction?
most calcium required for contraction comes from the Sarcoplasmic Reticulum; a little from
Extracellular Fluid. - answer ✔✔-Where does most of the Ca2+ required for contraction come from in
skeletal muscle cells?
SR calcium channels (ryanodine receptors) are a type of gated calcium channel
Closed until opened by DHP receptors (present on T tubule) in response to voltage change of T tubule
membrane by action potentials - answer ✔✔-How do action potentials travelling down T tubules lead to
the release of Ca2+ into the cytoplasm of skeletal muscle cells?
Ryanodine receptors are closed until opened by DHP receptors (present on T tubule) in response to
voltage change of T tubule membrane by action potentials - answer ✔✔-What is the function of DHP
receptors?
Ryanodine receptors are a type of gated calcium channel - answer ✔✔-What is the function of
ryanodine receptors?
- answer ✔✔-How does Ca2+ binding to troponin on the thin filaments trigger the formation of cross-
bridges between myosin heads and actin?
The released phosphate group then binds to the pump, causing the pump to change shape. This
shape change causes the cytosolic side of the pump to open, allowing the two Ca2+ to enter. The
cytosolic side of the pump then closes and the sarcoplasmic reticulum side opens, releasing the Ca2+
into the SR. - answer ✔✔-How is Ca2+ removed from the cytosol in skeletal muscle cells?
Slow oxidative, fast oxidative, fast glycolytic. Basis for classification: Velocity of contraction and
primary energy source - answer ✔✔-What are the three different subtypes of skeletal muscle cells and
how do they differ from one another?
Extracellular fluid - answer ✔✔-Where does most of the Ca2+ needed for smooth muscle cell
contraction come from?
Calmodulin complex activated an enzyme called myosin kinase which then adds a phosphate to
myosin, giving myosin heads the ability to bind to actin on thin filaments. - answer ✔✔-What are the
roles of calmodulin and myosin kinase in smooth muscle cell contraction?
Removes phosphate from myosin - answer ✔✔-What is the function of phosphatase in smooth muscle
cells?
Ca2+ - ATPase & Ca2+ - Na+ counter transport (Ca out, Na in) are pumped out of the cell - answer
✔✔-List the mechanisms to remove calcium from the cytoplasm of smooth muscle cells during
relaxation.
Extracellular fluid and sarcoplasmic reticulum - answer ✔✔-Where does the calcium needed for
cardiac muscle cell contraction come from?
1. Current speeds through gap junctions to contractile cell
2. Action potentials travel along plasma membrane and T tubules
GRADESMORE.COM
