The answers are;
The muscular contractions are wave-like
The muscular contractions are entirely involuntary
This action is called peristalsis.
It is powered by the expansion and contraction of the smooth muscles present in the esophagus. It is controlled by the sympathetic activity of the autonomic nervous system hence
the movements are involuntary.
The statement "When levels of the amino acid are high, it binds to the repressor, allowing synthesis of this amino acid to proceed" (A).
E. coli needs amino acids to survive. It can ingest the amino acid, Tryptophan from the environment. When the levels of Tryptophan are low, it can synthesize Tryptophan by using enzymes that are encoded in five genes. These genes lie next to each other in the tryptophan operon. If tryptophan is available in the environment, E. coli will not synthesize it.
During photosynthesis, plants use carbon dioxide and water to make sugar and oxygen. Some of this sugar, which is found in a variety of hydrocarbons, is recycled within the chloryphll.
