Macronutrients

• The need of protein was demonstrated in the early nineteenth century:

  animals that were only fed fats, CHO and minerals were unable to maintain their body weight and showed severe wasting of muscle and other tissues.
• In a non-growing adult, protein is needed to replace proteins lost by ‘wear and tear’.
• In a growing individual, protein is needed to make up new tissue.
• Protein performs vital functions in the body, there are ~30 000 50 000 different proteins.
• Proteins are made of aminoacids (aa), which all have the same basic structure: an amino group (NH3+) and a carboxilic acid group (COO-)
• 21 aa are involved in the synthesis of proteins
• Differents proteins and their functions : enzymes = they perform metabolic reactions, Transport proteins : They carry other substances around the body or across cell membranes, Contractile proteins : They are responsible for muscle contraction (heart, smooth muscle) and Structural proteins : They ‘hold up’ the body and provide a barrier, ex. bone and skin
• Proteins : they all contain C H O and N, and in some cases also S. The most useful feature for us is the N content.