Bio 201 Study guide PDF

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study guide for cell Biology...

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Which of the following statements about the "heads" of the myosin molecules is TRUE? A) they form permanent links with actin filaments B) they can attach to different sites on the actin filament C) they straighten the myosin filaments D) they allow the myosin filaments to wrap around each other E) none of the above True or False: Unflexing of the myosin head requires ATP. Muscle contraction is caused by A) actin filaments sliding past each other. B) myelin filaments sliding past each other. C) myosin filaments sliding past each other. D) actin filaments sliding past myelin filaments. E) actin filaments sliding past myosin filaments. E) actin filaments sliding past myosin filaments. Which of the following statements about H zones and I bands is TRUE? A) the H zones contain only myosin, while the I bands contain only actin B) the H zones contain only actin, while the I bands contain only myosin C) the H zones contain only myosin, while the I bands contain both actin and myosin D) the H zones contain both actin and myosin, while the I bands contain only actin

E) the H zones and the I bands each contain both actin and myosin Each actin filament is composed of A) a single strand of actin molecules. B) two strands of actin molecules wrapped together. C) three strands of actin molecules wrapped together. D) four strands of actin molecules wrapped together. E) hundreds of strands of actin molecules wrapped together. During muscle contraction A) the A band remains the same and the I band narrows. B) the I band remains the same and the A band narrows. C) both the A band and I band remain the same. D) both the A band and I band narrow. E) both the A band and I band become wider. True or False: In a contracting muscle the Z lines come closer together. True or False: In a relaxed muscle, the H zone is at its narrowest width. As actin and myosin filaments slide past each other during muscle contraction, A) actin filaments shorten, while myosin filaments do not. B) myosin filaments shorten, while actin filaments do not. C) either actin or myosin filaments shorten, but not both at the same time.

D) both actin and myosin filaments shorten. E) neither actin nor myosin filaments shorten. During contraction of a muscle, calcium ions bind to... A) the actin myofilament. B) the troponin molecule. C) the tropomyosin molecule. D) the sarcoplasmic reticulum. E) the sarcolemma. The bond between the actin and myosin head is broken when... A) an ATP molecule binds to the myosin head. B) an ATP molecule binds to the actin molecule. C) an ATP molecule breaks down on the myosin head. D) an ATP molecule breaks down on the actin molecule. E) ADP and phosphate bind to the myosin head. Energy is released when... A) ADP is broken down into ATP and phosphate. B) ATP is broken down into ADP and phosphate. C) ADP and phosphate combine to form ATP. D) ATP and phosphate combine to form ADP. E) AMP and two phosphates combine to form ATP. True or False: When cross bridges form and the muscle fibers contract, the actin myofilament slides past the myosin myofilament. Where does the calcium for the cross-bridge formation come from?

A) Extracellular Ca B) Intracellular Ca C) Intraorganelle (SR) Ca D) All of the above C) Intraorganelle Ca - the source of calcium in skeletal muscle comes exclusively from the sarcoplasmic reticulum (SR)

An action potential enters a neuron... A) by diffusion. B) by the T-tubules. C) by the sarcolemma. D) by the sarcoplasmic reticulum. E) by the actin myofilament. What structures do the calcium ions bind to when muscle contraction is initiated? A) the actin myofilament. B) the troponin molecule. C) the tropomyosin molecule. D) the sarcoplasmic reticulum. E) the sarcolemma. Cross bridges form between... A) troponin and tropomyosin. B) calcium and sodium. C) the sarcolemma and the sarcoplasmic reticulum. D) the T-tubules and the sarcolemma

An action potential arriving at the presynaptic terminal causes... A) voltage-gated sodium ion channels to open, and sodium ions to diffuse into the cell. B) voltage-gated calcium ion channels to open, and calcium ions to diffuse out of the cell. C) voltage-gated calcium ion channels to open, and calcium ions to diffuse into the cell. D) acetylcholine to diffuse into the cell. E) ligand-gated sodium channels to open, and sodium ions to diffuse out of the cell. The functional unit of muscular contraction is the ____ ____.

Motor Unit *defined as the motor neuron and all of the muscle fibers that it innevates What are the three differences between motor units?

Speed of contraction, Strength of contraction, and Endurance of contraction...