Why is chapter 5 a crucial moment in Frankenstein?What happens in the chapter and how does it impact the rest of the novel?

Without the inclusion of chapter five, in Mary Shelley's novel
Frankenstein, the story presented in the novel would not
exist.

Up to chapter five, Victor has told readers the tale of his
life, about his obsession with science, and his desire to reanimate life. In chapter four,
Victor's creation of the being comes to a head. He has begun gathering the parts necessary for
his creation to live--choosing them for their symmetry and proportions.

Chapter five is crucial because it is the chapter where Victor's
toils are recognized as successful. In this chapter, his creature comes to life.

I saw the dull yellow
eye of the creature open; it breathed hard, and a convulsive motion agitated its
limbs.

Victor's horror at the
appearance of his creation fuels his abandonment of the monster. No longer in love with his
creation, as he hoped, Victor is (instead) mortified by the being.

How can I describe my
emotions at this catastrophe?

Instead
of being the father his "child" would idealize, ("A new species would bless me as its creator and
source; many happy and excellent natures would owe their being to me. No father could claim the
gratitude of his child so completely as I should deserve theirs."), Victor realizes the error of
his experimentation.

Therefore, without the creature coming to life
in chapter five, the remainder of the story could not exist. Victor would not have abandoned his
"son," his "son" would not have murdered William, and Victor would not have made it his mission
to end the life of his "son." Essentially, the story would not be the tale of horror Shelley
desired it to be.