Oral administration of amino acid mixtures have been shown to stimulate post-workout muscle anabolism hence leads to lean muscle gain. Amino acids are the basic building blocks of proteins, so do supplementation of whole protein products have the same effect as amino acid supplements?
The answer is yes. It has been found that the supplementation of protein during exercise can enhance aerobic performance in cyclists compared to the placebo (Ivy et al 2013, International Journal of Nutrition, Exercise and Metabolism); the supplementation of protein-carbohydrate drinks during resistance training can reduce muscle damage and soreness but does not improve performance (Baty et al 2007, Journal of Strength and Conditioning); protein supplementation during resistance training promotes lean body mass gain (Volek at al 2013, Journal of American College of Nutrition); and protein supplementation immediately after resistance exercise can also promote muscle protein anabolism (Reidy et al 2013, Journal of Nutrition).
The majority of the evidence to date indicates that protein supplementation is beneficial for post-exercise muscle gain. However, different types of proteins have different amino acid compositions, and thus may have different effectiveness on muscle protein anabolism. Studies compared whey and soy proteins and found that whey protein is the more effective at promoting muscle mass gain than soy protein in resistance trainers (Volek at al 2013, Journal of American College of Nutrition; Philips et al 2009, Journal of American College of Nutrition). Compared to casein/milking proteins, whey protein supplementation resulted in a higher net muscle protein balance for 1.5 hour after ingestion; however, the effect of casein protein is more prolonged (Tipton et al 2004, Medicine & Science in Sports and Exercise). Therefore, which protein product to use is really up to what works best for you.
There is a short period (generally 30-180 minutes depends on the study) where muscle protein synthesis can be stimulated after protein supplementation. After which the muscle will become refractory to elevated amino acid concentrations. By the same token, above optimal amount of amino acid intake does not stimulate additional muscle grown compared the optimal level. This is often dubbed as the "muscle full" phenomenon. Exercise and resistance training can significant modulate the level of the muscle's capacity to utilize amino acids/proteins, but there is still a limit. Excessive protein intake can add load to your kidneys and thus should be consumed wisely.