Previous year questions: Locomotion and Movement

These ten questions come from the NCERT Exemplar chapter on locomotion and movement, the only official previous year source available for Class 11 Biology. The set covers the skeleton, the joints, the contractile proteins, the sliding filament mechanism, the girdles and the disorders of muscles and bones. Marks follow the book convention: 1 mark MCQ, 2 marks very short answer, 3 marks short answer and 5 marks long answer. Each heading quotes the Exemplar chapter and question number.

Q1 (NCERT Exemplar, 1 mark; Chapter 20, Multiple Choice 3)

What is the type of movable joint present between the atlas and the axis?

Answer: The joint between the atlas and the axis is a pivot joint. In a pivot joint one bone turns about another, and the atlas rotates around the axis so that the head can turn from side to side. It is a synovial joint because it has a fluid filled cavity between the bones. The turning of the head from side to side is the everyday movement that this joint makes possible.

Q2 (NCERT Exemplar, 1 mark; Chapter 20, Multiple Choice 4)

The ATPase of the muscle is located where?

Answer: The ATPase activity of the muscle lies in the head of the myosin molecule, which is part of the meromyosin. The myosin head splits ATP, and the energy released is used to form and break the cross bridge with actin. The actin filament itself has binding sites for myosin but no ATPase of this kind.

Q3 (NCERT Exemplar, 1 mark; Chapter 20, Multiple Choice 8)

The knee joint and the elbow joint are examples of which kind of joint?

Answer: The knee joint and the elbow joint are hinge joints. A hinge joint allows movement in one plane only, like the opening and closing of a door. A ball and socket joint, such as the shoulder or the hip, allows movement in all planes and is a different type.

Q4 (NCERT Exemplar, 1 mark; Chapter 20, Multiple Choice 9)

Macrophages and leucocytes exhibit which kind of movement?

Answer: Macrophages and leucocytes exhibit amoeboid movement. They push out pseudopodia and crawl through the tissues, which lets them reach the site of an infection. This movement does not need bones or muscles, because it is produced by the cell itself. The same crawling movement lets a white cell leave a blood vessel and reach the tissue where it is needed.

Q5 (NCERT Exemplar, 1 mark; Chapter 20, Multiple Choice 13)

Muscles with characteristic striations and involuntary control are which type of muscle?

Answer: They are cardiac muscles. The heart muscle is striated like skeletal muscle, but it is involuntary because it works without conscious control. Skeletal muscle is striated but voluntary, while smooth muscle is involuntary but non-striated, so cardiac muscle is the only option that has both features.

Q6 (NCERT Exemplar, 2 marks; Chapter 20, Very Short Answer 9)

Give the location of a ball and socket joint in a human body.

Answer: A ball and socket joint is found at the shoulder, where the head of the humerus fits into the glenoid cavity of the pectoral girdle, and at the hip, where the head of the femur fits into the acetabulum of the pelvic girdle. In this joint the rounded head can rotate inside the cup in all planes, which gives the limb a wide range of movement.

Q7 (NCERT Exemplar, 3 marks; Chapter 20, Short Answer 7)

Write a few lines about gout.

Answer: Gout is an inflammation of the joints caused by the accumulation of crystals of uric acid in the joint. The crystals form when the uric acid level in the blood stays high, and they irritate the tissue of the joint, which becomes red, hot, swollen and extremely painful. The joint of the big toe is a commonly affected site. Treatment aims to lower the uric acid level and to reduce the inflammation, and the person is advised about diet and about drinking enough water. Repeated attacks can damage the joint, so the disorder is managed for the long term rather than only during an attack.

Q8 (NCERT Exemplar, 3 marks; Chapter 20, Short Answer 8)

What is the source of energy for muscle contraction?

Answer: The immediate source of energy for muscle contraction is ATP. The myosin head has ATPase activity, and it splits ATP into ADP and inorganic phosphate, using the released energy to pull the actin filament and then to detach and re-cock the head for the next cycle. ATP is also needed to pump calcium ions back into the sarcoplasmic reticulum during relaxation. The ATP itself is regenerated by the mitochondria of the muscle fibre, which is why a muscle that is cut off from its blood supply or oxygen runs out of energy and stops contracting.

Q9 (NCERT Exemplar, 3 marks; Chapter 20, Short Answer 9)

What are the points for articulation of the pelvic and pectoral girdles?

Answer: The pectoral girdle articulates with the axial skeleton at the sternum through the clavicle, and with the upper limb at the glenoid cavity of the scapula, which receives the head of the humerus. The pelvic girdle articulates with the axial skeleton at the sacroiliac joint between its coxal bones and the sacrum, and with the lower limb at the acetabulum, which receives the head of the femur. The two halves of the pelvic girdle also meet each other at the pubic symphysis in front.

Q10 (NCERT Exemplar, 5 marks; Chapter 20, Long Answer 3)

Explain the sliding filament theory of muscle contraction with neat sketches.

Answer: The sliding filament theory says that a muscle contracts when the thin actin filaments slide over the thick myosin filaments, so the sarcomere shortens while the filaments themselves keep their length. The sequence is as follows. The motor neuron carries a signal to the muscle fibre, and the impulse causes the sarcoplasmic reticulum to release calcium ions into the sarcoplasm. The calcium binds to troponin, which shifts the position of tropomyosin and exposes the active binding sites on the actin. The head of a myosin molecule binds an exposed actin site and a cross bridge forms. The head tilts and pulls the actin filament towards the centre of the sarcomere, which is the power stroke. The head then releases ADP and inorganic phosphate, a fresh ATP binds, and the energy of ATP breaks the cross bridge and re-cocks the head so that it can bind the next actin site. The cycle repeats many times and the thin filaments are drawn inward from both ends of the sarcomere.

In the sketch, draw a relaxed sarcomere and a contracted sarcomere side by side with the Z lines, the I band, the A band, the H zone and the M line labelled. The relaxed sarcomere has wide I bands and a wide H zone, while the contracted sarcomere has narrow I bands and a narrow H zone, and the A band keeps the same width in both. The Z lines come closer together in the contracted sarcomere. Contraction ends when calcium is pumped back into the sarcoplasmic reticulum, the troponin releases it, tropomyosin covers the actin sites again and the muscle relaxes. The pumping of calcium is itself an energy requiring step, so relaxation also depends on ATP, and a muscle that is deprived of ATP can stay locked rather than relax.

Answer habits for this set

Three habits carry the marks in this chapter. First, whenever a mechanism is asked, write it in order and name the molecule at each step: calcium from the sarcoplasmic reticulum, calcium binding to troponin, tropomyosin moving, the myosin head binding actin, the head tilting, ATP breaking the bridge and the head re-cocking. Second, whenever the skeleton is asked, give the number and the group together, for example 22 skull bones within the 80 axial bones and 126 appendicular bones. Third, whenever a disorder is asked, name the site of the problem before the symptom, because that is what separates osteoporosis from arthritis and myasthenia gravis from muscular dystrophy. A quick labelled sketch of the sarcomere or the rib cage is worth the few seconds it takes, since it lets the examiner see the structure you are describing.