depends on what you mean by 'protein shake'.. protein shakes have amino acids. but you need real food if you want to bulk and you need macronutrients, not shakes. its should not count as a meal.
i drink whey protein twice a day, when i wake up and when i go to bed. neither are meals for me. the smoothie you get from the smoothie shop that is sugar, soy, and whey mixed with ice is not a meal either.
now if you were to add a lot of greens, veggies, fruits to a shake and drink it then it would be a different story.
there is a new product from mr supps called N2Bulk. its got super plasma protein, eggs, sweet potato as its main ingredients.. now that you can consider a meal, its nothing like anything you can get from a smoothie shop