PHGY 215 – FINAL 2026 EXAM PREP
QUESTIONS AND ANSWERS VIEW AHEAD
PRACTICE SOLUTION
◉ Striated.
Answer: Marked with a linear ridge or groove, often as one of a
number of similar parallel features
◉ Muscle.
Answer: A whole skeletal muscle is made up of individual muscle
fibres, each of which runs the entire length of the muscle
◉ Muscle Fibre.
Answer: - The muscle fibres run parallel to each other and are
surrounded by connective tissues
- A muscle fibre is actually a single muscle cell
- These cells are multinucleated and have a very large number of
mitochondria
◉ Myofibrils.
Answer: - Along the length of a muscle fibre, the cell is divided into
discrete contractile elements called myofibrils
,- A myofibril displays a pattern of light and dark bands that give the
muscle fibre a striated pattern
- There is a highly organized cytoskeletal pattern of thick and thin
filaments, which are myosin and actin, respectively
- Myofibrils are the contractile elements in muscle fibres
- They display a pattern of light and dark bands, which we call I
bands and A bands, respectively
◉ A Band.
Answer: - The A bands, also called the dark bands, are made up of
stacked thick and thin filaments that are aligned parallel to each
other and its borders are defined by the length of the thick filaments
- The middle of the A band is slightly lighter as the thin filament do
not reach this far from the ends
- This lighter portion is also called the H zone
◉ I Band.
Answer: - The I bands, also called the light bands, are made up of the
portion of the thin filaments that do not extend into the A band
- In the middle of the I band is a vertical line called the Z line
◉ H Zone.
Answer: - The slightly lighter portion of the A band is called the H
zone
,- It only contains proteins that hold the thick filaments, myosin,
together in a stack
- Myosin is composed of 2 heavy chains and 2 light chains
- The H zone only contains the heavy chains
- These proteins are seen as the M line running down the centre of
the H zone
◉ M Line.
Answer: - The proteins that hold the thick filaments together in a
stack are seen as the M line
- The M line runs down the centre of the H zone
◉ Z Line.
Answer: - In the middle of the I band is a vertical line called the Z
line
- The distance from one Z line to the next Z line is called a sarcomere
and is what we consider to be the functional unit of skeletal muscle
◉ Sarcomere.
Answer: - When relaxed, a sarcomere is about 2.5 x 10^-6 m in
width
- When muscles are growing, they extend the length of the muscle
fibre by adding new sarcomeres onto the ends
, - The area in the A band where the thick and thin filaments overlap
contains cross-bridges, that extend from the thick filaments and
from when thin filaments bind
◉ Cross-bridges.
Answer: Connection formed when mobile myosin heads bind to
actin molecules in muscles
◉ Thick Filament.
Answer: - The thick filament is composed of the protein myosin
- Myosin is a motor protein, in that it uses ATP to mov along actin
filaments
- Each molecule of myosin is a dimer of two subunits
- Each subunit looks like a golf club, in that it has a long shaft with a
globular head
- When the dimers come together, the "shaft" or tail portions wrap
around each other
- Within a thick filament, two dimers come together in a tail-to-tail
formation and then these stack up with other myosin molecules
- The heads stick out and contain two important sites, an actin
binding site, and a myosin ATPase site
◉ Thin Filament.
QUESTIONS AND ANSWERS VIEW AHEAD
PRACTICE SOLUTION
◉ Striated.
Answer: Marked with a linear ridge or groove, often as one of a
number of similar parallel features
◉ Muscle.
Answer: A whole skeletal muscle is made up of individual muscle
fibres, each of which runs the entire length of the muscle
◉ Muscle Fibre.
Answer: - The muscle fibres run parallel to each other and are
surrounded by connective tissues
- A muscle fibre is actually a single muscle cell
- These cells are multinucleated and have a very large number of
mitochondria
◉ Myofibrils.
Answer: - Along the length of a muscle fibre, the cell is divided into
discrete contractile elements called myofibrils
,- A myofibril displays a pattern of light and dark bands that give the
muscle fibre a striated pattern
- There is a highly organized cytoskeletal pattern of thick and thin
filaments, which are myosin and actin, respectively
- Myofibrils are the contractile elements in muscle fibres
- They display a pattern of light and dark bands, which we call I
bands and A bands, respectively
◉ A Band.
Answer: - The A bands, also called the dark bands, are made up of
stacked thick and thin filaments that are aligned parallel to each
other and its borders are defined by the length of the thick filaments
- The middle of the A band is slightly lighter as the thin filament do
not reach this far from the ends
- This lighter portion is also called the H zone
◉ I Band.
Answer: - The I bands, also called the light bands, are made up of the
portion of the thin filaments that do not extend into the A band
- In the middle of the I band is a vertical line called the Z line
◉ H Zone.
Answer: - The slightly lighter portion of the A band is called the H
zone
,- It only contains proteins that hold the thick filaments, myosin,
together in a stack
- Myosin is composed of 2 heavy chains and 2 light chains
- The H zone only contains the heavy chains
- These proteins are seen as the M line running down the centre of
the H zone
◉ M Line.
Answer: - The proteins that hold the thick filaments together in a
stack are seen as the M line
- The M line runs down the centre of the H zone
◉ Z Line.
Answer: - In the middle of the I band is a vertical line called the Z
line
- The distance from one Z line to the next Z line is called a sarcomere
and is what we consider to be the functional unit of skeletal muscle
◉ Sarcomere.
Answer: - When relaxed, a sarcomere is about 2.5 x 10^-6 m in
width
- When muscles are growing, they extend the length of the muscle
fibre by adding new sarcomeres onto the ends
, - The area in the A band where the thick and thin filaments overlap
contains cross-bridges, that extend from the thick filaments and
from when thin filaments bind
◉ Cross-bridges.
Answer: Connection formed when mobile myosin heads bind to
actin molecules in muscles
◉ Thick Filament.
Answer: - The thick filament is composed of the protein myosin
- Myosin is a motor protein, in that it uses ATP to mov along actin
filaments
- Each molecule of myosin is a dimer of two subunits
- Each subunit looks like a golf club, in that it has a long shaft with a
globular head
- When the dimers come together, the "shaft" or tail portions wrap
around each other
- Within a thick filament, two dimers come together in a tail-to-tail
formation and then these stack up with other myosin molecules
- The heads stick out and contain two important sites, an actin
binding site, and a myosin ATPase site
◉ Thin Filament.
