#Question id: 2337
#Unit 2. Cellular Organization
Centrioles may have originated as
#Question id: 33351
#Unit 1. Molecules and their Interaction Relevant to Biology
#Question id: 31181
#Unit 4. Cell Communication and Cell Signaling
#Question id: 2585
#Unit 1. Molecules and their Interaction Relevant to Biology
Which of the following is the correct sequence that describes the excitation and contraction of a skeletal muscle fiber?
A. Tropomyosin shifts and unblocks the cross-bridge binding sites.
B. Calcium is released and binds to the troponin complex.
C. Transverse tubules depolarize the sarcoplasmic reticulum.
D. The thin filaments are ratcheted across the thick filaments by the heads of the myosin molecules using energy from ATP.
E. An action potential in a motor neuron causes the axon to release acetylcholine, which depolarizes the muscle cell membrane.
#Question id: 3264
#Unit 11. Evolution and Behavior
Which of the following is (are) true of natural selection?