Answer
A. molecules
Explanation
When atoms or elements combine, they are called molecules. When molecules combine they form compounds.
I thinks it's C although I'm not 100% positive.
Answer:
Endoplasmic reticulum.
Explanation:
Second messengers are known as intracellular signaling molecules released from the cell in response to exposure to extracellular signaling molecules. Second messenger activate physiological changes at a cellular level, for example proliferation, migration, differentiation, survival, and apoptosis.
Calcium ions are hydrophilic, water-soluble molecules. They are present in intracellular component know as endoplasmic reticulum and quickly released when needed. They are necessary for many important functions including fertilization, muscle contractions, and neurotransmitter release.
