The specific defenses of the immune system include a variety of cells that circulate in the blood and that make up organs such as the spleen and thymus. how are the cells of the immune system able to differentiate pathogens from the cells of the body?

a. the cells of pathogens are much smaller than human body cells.
b. pathogens move through the body, while human body cells are stationary.
c. pathogens contain foreign molecules, or antigens, on their outer surface.
d. pathogens release foreign molecules, or antigens, when cells of the immune system approach them.

Atypical human cell is approximately 12.00 μm in diameter and enclosed by a membrane that is 5.000 nm thick. (a) what is the volume of the cell including the membrane? (b) what is the volume of the cell membrane? (c) what percent of the total volume does its membrane occupy? to simplify the calculations, model the cell as a sphere. enter your answers using four significant figures.

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Duchenne muscular dystrophy is a serious condition caused by a recessive allele of a gene on the human x chromosome. the patients have muscles that weaken over time because they have absent or decreased dystrophin, a muscle protein. they rarely live past their twenties. how likely is it for a woman to have this condition? a) women can never have this condition.b) one-fourth of the daughters of an affected man would have this condition.c) one-half of the daughters of an affected father and a carrier mother could have this condition.d) only if a woman is xxx could she have this condition.