Animal bioenergetics can be defined as the conversion chemical energy from food into forms that can be used in vivo for maintenance, development and growth as well as reproduction. Thus, metabolic strategies that maximize the efficiency of energy assimilation may be beneficial to animals, especially under changing environmental conditions like elevated temperatures. Protein metabolism is a major contributor to resting energetic costs in ectotherms and protein accretion is a central component of growth. Proteins are responsible as cellular catalysts, essential structural elements and are core to defense against heat damages. Hence, a thorough understanding of protein turnover can provide insights to how energy metabolism interacts with growth dynamics under temperature change. In this thesis, two developed methods are used to assess protein metabolism in adult as well as embryonic stages of the freshwater snail Planorbella duryi. Using a novel D5-phenylalanine tracer approach to protein metabolism to flood endogenous phenylalanine pools we measure protein metabolism in the adult snails and test the effect of temperature acclimation on both the kinetics of protein synthesis and degradation. A novel open-chambered respirometer was utilized for the estimation of protein metabolism cost during embryonic development. While biochemical processes are often associated with a 2-fold to 3-fold change per 10°C change in temperature, protein metabolism following acclimation suggests marked compensation for temperature effects in the adults. Embryonic snails showed a higher commitment of energy metabolism to protein synthesis, as may be expected given the rapid cellular turnover and growth during this life-stage.