Impulses conducted along the muscle fiber's transverse tubules stimulate the release of calcium ions into the cytoplasm
A. from the sarcoplasmic reticulum.
B. from the actin and myosin subunits.
C. from the troponin.
D. from the extracellular fluid in the neuromuscular junction.
E. from the Z line.
Answer: A
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Polycistronic transcription units are common in
A) Archaea. B) Bacteria. C) Eukarya. D) both Archaea and Bacteria.
All of the membranes of the eukaryotic cell are in dynamic continuity except for the:
A. mitochondria and chloroplasts. B. endoplasmic reticulum. C. golgi apparatus. D. nuclear membrane.
Which of the following events occurs directly after a DNA molecule is unzipped?
A.) Mismatched nucleotide bases are identified and replaced. B.) Free-floating nucleotides pair up with exposed bases. C.) Identical double-stranded DNA molecules are formed. D.) Enzymes break hydrogen bonds between base pairs.
What might happen if a functional copy of the TP53 gene is not present in a cell?
a) the cell may make no p21 inhibitory protein, preventing the cell from passing the G1 checkpoint and no Bax protein, which would prevent the cell from initiation apoptosis b) all of the choices are correct c) the cell proceeds to S phase before it is ready and before DNA repairs are completed d) abnormal cells with the potential to become malignant are produced