"couper" belongs to the 1st group of verbs ending in -er at the infinitive form (except aller):
- je coupe, tu coupes, il/elle/on coupe, nous coupons, vous coupez (polite and plural), ils/elles coupent.
Now, you should keep this link at hand: http://french.about.com/library/verb/bl-verbconjugator.htm
No, "couper" never takes the spelling of "coup" in any conjugation. It only means "to cut".
"Un coup" can be a hit, a move, it is used in many expressions:
- un coup d'oeil = a glance; un coup de pied = a kick; un coup de foudre = a lightning strike; un coup de téléphone = a phone call...
Your question has already been answered if you would kindly read through the forum. Your translation of the verb is not the problem; the problem is translating "the". « Du pain » is an undefined quantity of a mass of bread, which can be translated as "some bread" or just "bread". « Le pain » is "the bread".