Proteins are essential biomolecules responsible for cellular functions, tissue repair, and overall physiological development in living organisms. The building blocks of proteins and amino acids are classified as either nutritionally essential or nonessential, based on their biosynthetic capabilities in the human body. Since essential amino acids cannot be synthesized endogenously, alternative sources, such as algae, which possess robust metabolic pathways for amino acid production, have been investigated. Algae, both macro- and microalgae, are photosynthetic organisms capable of producing all essential amino acids, making them valuable for nutritional and industrial applications. Their metabolic flexibility enables them to thrive under diverse environmental conditions, influencing amino acid composition and protein yield. This chapter explores the biosynthesis of essential amino acids in algae, detailing the metabolic pathways, enzymatic activity, and regulatory networks involved in amino acid metabolism. The roles of aminotransferases, synthetases, and peptidases in protein synthesis and posttranslational modifications have also been discussed. In addition, this study reveals the extraction and purification methods used for protein extraction from algae and discusses alternative biotechnological strategies for amino acid and protein production by manipulating, regulating, and studying the metabolic pathways of algae through technologies such as genetic engineering and omics approaches. This study provides insight into how algae-derived proteins can serve as sustainable and high-quality protein sources, contributing to advancements in bioengineering, food security, and biotechnological applications.