Which cell structure is referred to as the gatekeeper because it directs substances to move into and out of the cell? a cell wall b nucleus c vacuole d cell membrane?

White blood cells that attack foreign particles. 1) antigen 2) immunity 3) antibiotic 4) leukocytes 5) fever 6) germicide

Bohr hypothesized what about the atom?

Temperature, pH, and ionic concentrations each play an important role in the proper functioning of enzymes.

What is the path of totality during a solar eclipse? O A. The sun is behind the moon, which casts its shadow on Earth. O B. The sun is between Earth and the moon, which casts its shadow on Earth. LOC.

What is chlorosis and what does it affect

Why don't absorptive surfaces of the small intestine get damaged by the acids from the stomach?

For any gene, when there are two alleles, and the frequency of one of the alleles is 0.5, then the frequency of the other one is:

Suppose a large number of dead fish are found floating in a lake. how would you determine whether they died from cultural eutrophication or from exposure to toxic chemicals?

Which best explains how gravity contributes to the formation of layers in protoplanets? Gravity attracts materials and causes compaction, which produces heat and leads to the melting, sinking, and rising of materials.

1. As an object moves towards another object the sound waves bunch up. True Or False 2. As an object moves toward another object the sound waves have lower frequency. True or False. 3.