Relative Clauses vs. Complement Clauses

CalifJim........................... Construction ......................... Functionof spiders ........ Prepositional phrase ... Adjective phrase complementthat a spider ......... Noun clause ............ Adjective phrase complement will bite him

Please take the following example into consideration:

John is afraid of spiders.

First of all you should determine what is "of spiders"? and then what is It's function. Better I want to say you should say The part of speech of "of spiders" and then say what the function of that is.

It is a prepositional phrase. Why? Because it starts with a preposition "of" and an object of preposition "spiders". so preposition + It's object = prepositional phrase. Right? After that we must determine It's function. And we know that because it comes after an "adjective", It is an "adjective (phrase) complement".

Now what about the next sentence:

John is afraid that spiders will bite him.

First you should determine what the kind of clause it is and then say what is it's function.

You, without any description say, It is a "noun clause" but why? Please first answer to this question and then determine it's function is "adjective phrase complement" or not.