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IB Biology B3.3: Muscle & Motility — Practice Questions & Answers
IB Biology B3.3 Muscle and motility study notes: sliding filament theory, sarcomere structure, motor units, antagonistic muscles and joint movement.
Here are 10 practice questions with full answers and explanations.
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Practice questions with answers
1
Multiple choice
What is a universal feature of living organisms related to muscle and motility?
The ability to generate movement through the interaction of contractile proteins like actin and myosin, often powered by ATP
The presence of a specialized nervous system dedicated solely to coordinating muscle contractions
The development of dedicated multicellular muscle tissues organized into antagonistic pairs
The presence of external flagella that rotate via a proton motive force to propel the organism through liquid media
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Why Movement in animals arises from ATP-powered sliding of the contractile proteins actin and myosin.
2
Multiple choice
What is the sliding filament model of muscle contraction?
Actin and myosin filaments slide past each other.
Actin filaments shorten.
Myosin filaments shorten.
Sarcomere elongates.
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Why In the sliding filament model, actin and myosin filaments slide past each other to shorten the sarcomere.
3
Multiple choice
What is the role of the protein titin in muscle relaxation?
Helps sarcomeres recoil and prevents overstretching
To bind to actin filaments and physically block myosin binding sites, preventing further contraction
To actively pump calcium ions back into the sarcoplasmic reticulum, initiating muscle relaxation
To cleave ATP molecules, directly releasing energy to power the detachment of myosin heads from actin filaments
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Why Elastic titin helps sarcomeres recoil after contraction and prevents them from being overstretched.
4
Multiple choice
Why are antagonistic muscles necessary for muscle relaxation?
Muscle tissue can only exert force when it contracts.
Muscle tissue can exert force during relaxation.
Muscle tissue requires external stimuli for relaxation.
Muscle tissue cannot relax without ATP.
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Why Muscles only pull by contracting, so an antagonistic partner is needed to move a bone back.
5
Multiple choice
What is a motor unit in skeletal muscle?
a) A motor neuron
b) A sarcomere and its associated proteins
c) A tendon and its attachment to bone
d) A ligament and its attachment to bone
e) Muscle fibers
f) Neuromuscular junctions
a) b) and c) only
a) and e) only
a) and c) only
a) e) and f)
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Why A motor unit is a single motor neuron together with all the muscle fibres it stimulates.
6
Multiple choice
What is the role of skeletons in movement?
Anchorage for muscles and levers.
Storage of calcium.
Production of blood cells.
Protection of internal organs.
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Why Skeletons anchor muscles and act as levers, converting muscle contraction into movement.
7
Multiple choice
What type of skeleton do arthropods have?
Exoskeletons.
Endoskeletons.
Hydrostatic skeletons.
Cartilaginous skeletons.
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Why Arthropods have a rigid external exoskeleton to which their muscles attach internally.
8
Multiple choice
What type of skeleton do vertebrates have?
Endoskeletons.
Exoskeletons.
Hydrostatic skeletons.
Cartilaginous skeletons.
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Why Vertebrates have an internal endoskeleton of bone and cartilage that grows with the body.
9
Multiple choice
What components are involved in movement at a synovial joint?
Bones, cartilage, synovial fluid, ligaments, muscles, and tendons
The central nervous system for motor command, the motor units for muscle innervation, and the sarcoplasmic reticulum for calcium release
Blood vessels, nerves, and adipose tissue
Epithelial tissue, connective tissue, and nervous tissue
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Why A synovial joint combines bones, cartilage, synovial fluid, ligaments, muscles and tendons to enable movement.
10
Multiple choice
What is the role of synovial fluid in a joint?
Lubrication.
Shock absorption.
Bone growth.
Muscle contraction.
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Why Synovial fluid lubricates the joint, reducing friction between the articulating surfaces.
Key terms in Muscle & Motility
Sarcomere: The contractile unit of a myofibril, the region between two Z discs; it shortens during contraction.
Myofibril: A cylindrical bundle of actin and myosin filaments running the length of a muscle fibre.
Actin: The protein of the thin filaments, anchored to the Z discs and bearing the myosin binding sites.
Myosin: The protein of the thick filaments, whose heads form cross-bridges and perform the power stroke.
Sliding filament theory: The model in which actin and myosin filaments slide past one another to shorten the sarcomere, without the filaments themselves shortening.
Cross-bridge: The temporary connection formed when a myosin head binds to an actin filament.
Tropomyosin: A protein that blocks the myosin binding sites on actin at rest, controlled by troponin and calcium.
Sarcoplasmic reticulum: The specialised internal membrane store that releases and reabsorbs Ca<sup>2+</sup> to control contraction.
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