Which cell organelles are well-developed in secretory cells?

On which organelle of the cell structure does intracellular digestion depends? What is the chemical content of those organelles?

What is the endosymbiotic hypothesis about the origin of mitochondria? What are the molecular facts that support the hypothesis? To which other cellular organelles the hypothesis can also be applied?

Which are the cell organelles that participate in the cell division and in the formation of cillia and flagella of some eukaryotic cells?

What are mitochondria? What is the basic morphology of these organelles and in which cells can they be found?

What are the molecular facts that support the hypothesis? To which other cellular organelles the hypothesis can also be applied?