AQA A LEVEL BIOLOGY MUSCLES
REVISION PAPERS 2023 WITH CORRECT
QUESTIONS AND ANSWERS
A sarcomere (Correct Answers) a part of a myofibril between two Z lines
H Zone (Correct Answers) During a contraction this section gets narrower
M line (Correct Answers) The middle point of a sarcomere, it doesn't change during
contraction
Z line (Correct Answers) The two ends of the myofibril, they get closer during
contractions.
A band (Correct Answers) The length of the myosin, does not change during
contractions as it stays in the same place and the actin filaments are pulled over it.
I band (Correct Answers) The area where there is only actin filament, gets narrower
during contraction.
Neuromuscular junction (Correct Answers) The synapse between a motor neurone and
a skeletal muscle. An action potential from here stimulates muscle
contraction/relaxation
T-tubules (Correct Answers) In the sarcolemma, they run downwards and allow an
action potential to reach the sarcoplasmic reticulum.
Sarcoplasmic reticulum (Correct Answers) A storage and release area for ca2+ ions in
muscle contraction.
Ca2+ ions (Correct Answers) Released from the sarcoplasmic reticulum. It binds to a
protein attached to tropomyosin on the actin filament and causes the protein to change
shape. This shape change moves tropomyosin out of the way of the actin-myosin
binding site so muscle contraction can occur. It also stimulates the release of ATP
hydrolase
ATP hydrolase (Correct Answers) Recocks the myosin head so it can bind to the actin-
myosin binding site forming a cross bridge.
ADP + Pi release (Correct Answers) These are released from the myosin head causing
it to pivot and bend which pulls the actin filament forwards with it. This is a power stroke.
REVISION PAPERS 2023 WITH CORRECT
QUESTIONS AND ANSWERS
A sarcomere (Correct Answers) a part of a myofibril between two Z lines
H Zone (Correct Answers) During a contraction this section gets narrower
M line (Correct Answers) The middle point of a sarcomere, it doesn't change during
contraction
Z line (Correct Answers) The two ends of the myofibril, they get closer during
contractions.
A band (Correct Answers) The length of the myosin, does not change during
contractions as it stays in the same place and the actin filaments are pulled over it.
I band (Correct Answers) The area where there is only actin filament, gets narrower
during contraction.
Neuromuscular junction (Correct Answers) The synapse between a motor neurone and
a skeletal muscle. An action potential from here stimulates muscle
contraction/relaxation
T-tubules (Correct Answers) In the sarcolemma, they run downwards and allow an
action potential to reach the sarcoplasmic reticulum.
Sarcoplasmic reticulum (Correct Answers) A storage and release area for ca2+ ions in
muscle contraction.
Ca2+ ions (Correct Answers) Released from the sarcoplasmic reticulum. It binds to a
protein attached to tropomyosin on the actin filament and causes the protein to change
shape. This shape change moves tropomyosin out of the way of the actin-myosin
binding site so muscle contraction can occur. It also stimulates the release of ATP
hydrolase
ATP hydrolase (Correct Answers) Recocks the myosin head so it can bind to the actin-
myosin binding site forming a cross bridge.
ADP + Pi release (Correct Answers) These are released from the myosin head causing
it to pivot and bend which pulls the actin filament forwards with it. This is a power stroke.
