It  -- This is from the third-person, singular form of the verb.

is -- (WT) This helping verb indicates passive form and the present tense of the verb. Though "it is written," is translated in the present tense in the KJV, the Greek is in a tense that indicates an action completed in the past.

written, -- "Written" is the Greek verb that  means "to mark," "to express by written characters," "to write a letter," "to write down [a law]," and so on.

missing "the"  -- (MW) The untranslated word is the Greek definite article, which usually precedes a noun and, without a noun, takes the meaning of "the one." The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those"). See this article for more. 

Man -- The word translated as "man" more generally means "humanity" as well as "a man."

shall -- This helping verb "shall" indicates that the verb is the future tense. Helping or auxiliary verbs are needed to translate the Greek verb forms into English.

not -- The Greek word translated as "not" is the Greek negative used to deny objective facts, not opinions. It makes a negative statement of fact. Adding "really" to the sentence captures the same idea.

live -- The verb means "live," "to be alive,” “to be full of life," "to be strong," and "to be fresh." So it is life in the sense of a vital life, strong and growing. Perhaps in English, “thrive” would be more precise. It is in the future tense, which we cannot tell by the “shall live” because the KJV and other Bibles translated both the future tense and the subjective mood in the same way, so “he going to thrive.” But again, the form is the middle voice, so “by himself.” So this verb, with the negatives means “he is not going to thrive by himself.” This is a pretty interesting statement even without the “bread” part. Christ also uses it in the sense of "making a living." There are several other words in the Gospels translated as "life" discussed in this article. The differences are important.- The term translated as "live" is in the future tense. The Greek term means not only to have  life and breath but to the enjoyment of living as well, specifically, to be "full of life." This verb is in the middle voice, indicating an act on, for, or by himself. 

missing "himself" -- (MV)  The middle voice of the verb indicates that the subject does something to, for, or by themselves. 

by -- The word translated as "by" means "on," "over," "upon," "against," "before," "after," "during," "by" or "on." The primary meaning of this word is "upon," which works well for the idea of "living on bread."

bread -- The Greek word for "bread" or more precisely, "loaf," but is was used generically to mean "food." The original Hebrew (Deu 8:3) from which this quote is taken referred to mana in the desert. Moses describes the hunger and suffering of the Jews in the desert and how God sent them mana. 

alone, -- "Alone" is an adjective modifying "bread" that means "alone," "solitary," "only," "single," "unique," "made in one piece," "without [someone]," "only [something]," "unique," "one above all others," and "on one condition only."

but -- The Greek phrase starts with the conjunction meaning "but" and a preposition that means "by" or, more generally, "through." These do not appear in the Hebrew.

by - The word translated as "by" means "on," "over," "upon," "against," "before," "after," "during," "by" or "on." The primary meaning of this word is "upon," which works well for the idea of "living on bread."

every -- The next word, "every" is the from the Greek word that is usually translated as "all" but here it is used as an adjective modifying the singular noun translated as "word" so "every" works well. Again, no such word appears in the Hebrew.

word -- (WW) It is interesting that this is the first use of the English word "word" in the NT. However, it is not the Greek word usually translated as "word" but another word that comes closer to "remark" or "saying" that our idea of a word. See this article for details. In Hebrew, there is no word for "word" in the quote.

that -- (IW) There is nothing that can be translated as "that" in the Greek source. It is added because the form of the following word is changed.

proceedeth -- (WF) The Greek word translated as "proceedeth"  means "going out" or “departing out”. This is not a verb but a participle, "departing out" modifying the word translated as "word." The form is passive so "being poured out." In Hebrew, the word is mowtsa that means simultaneously the source of something going forth, the thing that goes forth, and the way of going forth. In English, we might say “outpouring” to capture it because the form isn’t an active verb, but an adjective. “Outpouring” works because we also use it describing speech, which is what this adjective modifies.

out  -- This is from the prefix of the verb that means "out of" and "from."

missing "through"-- (MW) The untranslated word "through" means "through," in the midst of," or "by (a cause)." This is the word Jesus typically uses to mean "by" a cause.  This word more clearly means "by" than the preposition above.

of -- This word "of"  comes from the genitive case of the following word that required the addition of a preposition in English.  The most common is the "of" of possession.

the -- (WW) There is no Greek article "the" here in the source, but when a word doesn't have a definite article, the indefinite article can be added in English translation.

mouth  -- The Greek word translated as "mouth" means "mouth" but it also means "speech," "utterance," "any outlet or entrance," and "the foremost part" of something. For example, the blade or point of a weapon.The Greek term translated as "mouth" also means the foremost part, such as the point of a spear or the blade of a sword. While God doesn't have a mouth or even parts, he does have a foremost in Christ.

of -- This word "of"  comes from the genitive case of the following word that required the addition of a preposition in English.  The most common is the "of" of possession.

God. -- Finally, the Greek word for "God" means simply "God" or "divine." The Greek is unusual here because there is no "the" before the Greek word, which is usually how Jesus uses this word to refer to the Divine. The missing article may be due to the fact that this is a quote for the Greek Old Testament. See this article.