Write a correct answer to the given question based on its associated fact. Make sure that your answer is contained in the associated fact. Don't be creative and introduce any new word that is not mentioned in the associated fact! Remember that the associated fact has been rearranged to form the question. So, the correct answer words must lie within the associated fact. The correct answer can be a word, phrase, or even a sentence.

Fact: collagen is fibrous. 
Question: What texture is collagen?
fibrous.

Fact: proteins contain genes. 
Question: what do proteins contain?
genes.

Fact: Endoplasmic reticulum are membranes attached to sites where proteins are made. 
Question: What are membranes attached to sites where proteins are made?

endoplasmic reticulum.