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Draft:Biological affinity

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Biological affinity is the level of attraction between two molecules in the field of biology, such as between plant root cells and nutrients, enzymes and substrates, or ligands and receptors[1]. Biological affinity can be further categorized when discussing certain applications, such as binding affinity (when discussing ligand and receptors) or enzyme affinity (when discussing enzymes and their substrates). Substances are characterized as having either high or low affinity. Molecules with high affinity can take up or bind to substances more readily than those with lower affinity.

Certain molecules' affinities can be quantified. For example, enzyme affinity can be quantified by the Michaelis constant, Km. A higher Michaelis constant is indicative of lower affinity, and vice versa.[2] Nutrient uptake, which is a function of affinity and nutrient concentration, can be quantified mathematically.[3] The Monod equation can be used to calculate the actual uptake rate, while the Michaelis-Menten curve is used to visualize these rates. The Monod equation and Michaelis-Menten curve were originally developed based on studies of cell growth and enzymatic reactions, however they can both be modified and applied to calculating nutrient uptake[2]. Each quantity is specific to the affinity of the molecules being studied, so it's important to distinguish between them and not refer to biological affinity as one singular value.

MM-curve
Figure 1: Michaelis-Menten curve demonstrating the reaction rate of an enzyme at a given concentration with a given amount of substrate.

Figure 1: Michaelis-Menten curve demonstrating the reaction rate of an enzyme at a given concentration with a given amount of substrate.

References

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  1. ^ Gohlke, Holger; Klebe, Gerhard (2002-08-02). "Approaches to the Description and Prediction of the Binding Affinity of Small-Molecule Ligands to Macromolecular Receptors". Angewandte Chemie International Edition. 41 (15). Wiley: 2644–2676. doi:10.1002/1521-3773(20020802)41:15<2644::aid-anie2644>3.0.co;2-o. ISSN 1433-7851. PMID 12203463.
  2. ^ Charles B. Miller and Patricia A. Wheeler. Biological Oceanography (second edition). Wiley-Blackwell, West Sussex (2012).
  3. ^ Lindemann, Christian; Fiksen, Øyvind; Andersen, Ken H.; Aksnes, Dag L. (2016-03-11). "Scaling Laws in Phytoplankton Nutrient Uptake Affinity". Frontiers in Marine Science. 3. Frontiers Media SA. doi:10.3389/fmars.2016.00026. ISSN 2296-7745.