Why does a knowledge of grammar improve reading comprehension?

How can a knowledge of sentence structure help to improve your reading comprehension?
The link between reading comprehension and sentence analysis is clear: Every word or group of words-- every part of the sentence-- is telling us something. The question is: What is that word, or group of words, or sentence part saying? What is it telling us that we need to know? 
Each word or group of words plays a key role in giving us information. In order to find out what information each part or group of words is giving to us, we need to ask the verbs and nouns questions. Answers to those questions will allow us to see what each word or group of words is saying, or helping the sentence to say, or rather how each word or group of words is helping the writer to communicate her meaning to us. So in order to improve both your reading comprehension and writing, you must first master your sentence comprehension skills.