What is the primary function of the transverse tubules?
A. They conduct action potentials from the surface of the muscle fiber to internal regions near myofibrils.
B. They act as a channel for Ca2+ ions during excitation-contraction coupling.
C. They form cross-bridges between actin and myosin during muscle contraction.
D. They attach troponin to tropomyosin.
E. They attach muscle fibers to skeletal elements to exert force.
A. They conduct action potentials from the surface of the muscle fiber to internal regions near myofibrils.
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Which of the following are examples of molecular homologies? Select all that apply.
_____ Use of DNA as an information storage molecule. _____ The lack of an IGF-1 gene in prokaryotes. _____ Similarities among in the metabolic process for the break down of glucose. _____ The biochemical pathways for cellular respiration in plants and animals. _____ The biochemical pathways for photosynthesis in plants and cellular respiration in animals.
Which of the following occurs during recombination?
a. Homologous chromosomes exchange linear segments of genetic material. b. One gene interferes with the expression of another gene. c. Identical alleles are expressed simultaneously in a heterozygote. d. The gene order of homologous chromosomes is significantly altered.
Approximately what percentage of the immune system is located in the intestinal tract?
a) 1% b) 10% c) 100% d) 70%
When looking at plant and animal cells with an electron microscope, you notice that the plant cells have more Golgi membranes than the animal cells. This is most likely because unlike in animal cells, in plant cells the Golgi apparatus is involved in the production of
A. cytoplasm. B. mitochondria. C. chloroplasts. D. cell walls.