Which pair of statements best describes an essential amino acid?
it is an amino acid that contains peptide bonds. an example is proline.
it is an amino acid that contains nitrogen. an example is aspartic acid.
it is an amino acid that cannot be made by the body. it must be obtained from eating certain foods.
it is an amino acid that can be produced by the body. vitamin supplements maintain healthy levels.

Penelope studies how the structure and function of the nervous system is related to behavior. she is a psychologist

Recently, crops of vegetables such as lettuce and green onions have been contaminated, while they are still on the farm, with bacteria that cause food poisoning. how will science influence the way the government responds to prevent an increase in food-borne diseases? because science has shown that lettuce and green onions are not nutritionally valuable, the government may pass laws that ban the sale of lettuce and green onions. because science has shown that there is no way to prevent bacterial contamination, the government may pass laws that punish businesses that buy lettuce and green onions. because science has shown that the washing of hands prevent the spread of infectious diseases among people, the government may pass laws that require hand washing by everyone who handles food. because science has shown there are ways to find the source of the contamination, the government may pass laws that require farm practices that reduce the contamination of lettuce and green onions.

How are viruses different from eukaryotic cells?