Frequently asked questions
Questions about the different types of proteins and amino acids
- What is a protein?
- What is an amino acid?
- What is an alpha-amino acid?
- What are my protein requirements?
- What happens to the proteins I eat?
- What are branched-chain amino acids? What are they good for?
- What does the L in L-Lysine, L-methionine ... mean?
Questions about the website and its functions
- Tetramino - why this name?
- Why is a food not present on the website?
- What is this about vectors and angles?
Proteins and amino acids
What is a protein?
A protein is a large molecule consisting of long sequences of amino acids. Proteins are essential to living organisms, as they perform a variety of vital functions, notably as enzymes (to catalyze chemical reactions) or as structural proteins (to provide stiffness or generate mechanical forces).
What is an amino acid?
This website looks at amino acids as the building blocks used by the body to form proteins. More generally, an amino acid is an organic molecule characteristized by an amine group (NH2) and a carboxyl group (COOH). The molecule consists of these two groups along with another group (called side chain) which is characteristic of each amino acid. Several hundreds of amino acids are known, but only 23 of them may be combined into proteins. This website focuses on these 23 proteinogenic amino acids.
What is an alpha-amino acid?
An alpha-amino acid (α-amino acid ) is an amino acid in which the alpha carbon (the carbon atom next to the carboxyl group -COOH) is directly bonded to an amino group (-NH2). Alpha amino acids are the most commonly found amino acids in nature. The twenty standard amino acids are alpha-amino acids.
What are my protein requirements?
This question is related to that of amino acid requirements. Generally, protein requirements are the combination of total nitrogen requirements (for the synthesis of nonessential amino acids, among other things) and of requirements for essential amino acids. The most important determinant for protein requirements is age, along with pregnancy and lactation. For young adults, 0.75 g.kg-1.day-1 is considered to be a safe protein intake (FAO/WHO/UNU 1985).Further reading:
- Campbell, W. W., Crim, M. C., Dallal, G. E., Young, V. R., & Evans, W. J. (1994). Increased protein requirements in elderly people: new data and retrospective reassessments. The American Journal of clinical nutrition, 60(4), 501-509.
What happens to the proteins I eat?
After their ingestion, proteins undergo a digestion process: they are broken down into amino acids (protein catabolism). These amino acids may be polymerized into new proteins (using information encoded in genes), converted into other amino acids, or undergo a further breakdown (amino acid catabolism). The new proteins do not remain idle: breakdown and new synthesis keep happening at various rates, depending on the kind of protein.
What are branched-chain amino acids? What are they good for?
Chemically, branched-chained amino acids (BCAA) are characterized by an aliphatic side-chain with a branch. Branched-chained amino acids usually refer to leucine, isoleucine and valine, the three proteinogenic BCAAs. Among other roles, BCAAs are supposed to promote anabolism (protein synthesis).Further reading:
- Blomstrand, E., Eliasson, J., Karlsson, H. K., & Köhnke, R. (2006). Branched-chain amino acids activate key enzymes in protein synthesis after physical exercise. The Journal of nutrition, 136(1), 269S-273S.
What does the L in L-Lysine, L-methionine ... mean?
Enantiomers The 20 standard proteinogenic amino acids are alpha-amino acids. Most alpha-amino acids (apart from glycine) can exist in two forms which are non-superposable mirror images of each other, also called enantiomers: an L-form and a D-form. However, the standard amino acids found in nature are all of the L-form. In contrast, synthetic amino acids are often mixtures of L- and D- molecules (racemic mixtures). When we write lysine on this website, we mean L-Lysine, the naturally-occurring form.
Tetramino - the website
Tetramino - why this name?
Because we thought balancing amino acids might look like the old game of Tetris. In reality, achieving some balance in amino acids is easier and more natural than to stack up Tetris bricks perfectly. Still, the game is worth considering. Also, 'tetramino' sounds like 'season' in greek, and we think seasons are an important aspect of food.
Why is a food not present on the website?
The food nutritional data stem from the USDA nutrient database. However, we chose to use only a small subset of these foods, concentrating on vegetarian foods and avoiding processed foods. Also, some foods could not be included because of missing data on their amino acid content. Still, if you would really like to have some food added, do write us an email, and we will see if this is possible.
What is this about vectors and angles?
A way of telling quantitatively 'how different' two amino acid patterns (or foods or proteins) are is to represent each amino acid pattern as a vector in some N-dimensional vectorial space, with one dimension for every essential amino acid, and to compute the angle between these vectors. A lower (or more negative) angle value means the two foods are more different in their amino acid profile.