In chemistry PO4 is non polar, but in biology the phosphate functional group PO4 is polar? How so?

In Biology, it is connected to a carbon, and the carbons are usually connected to other carbons or hydrogens. So, it is essentially polar when compared to carbon or hydrocarbons.

The phosphate (PO4) functional group can exhibit different properties depending on the context in which it is found, whether it is in chemistry or biology.

In the field of chemistry, when we refer to PO4 as nonpolar, it is mainly in the context of simple, isolated phosphate ions. In this case, the four oxygen atoms surrounding the central phosphorus atom are arranged symmetrically, resulting in a linear structure. Since each oxygen atom has the same electronegativity as phosphorus, there is an equal sharing of electrons among them. Due to this balanced arrangement of charge, the PO4 ion is considered nonpolar.

However, in biological systems, the phosphate group is often attached to organic molecules (such as sugars or amino acids) to form esters or phosphoester bonds. In these cases, the phosphate group can exhibit polarity because the organic molecules to which it is attached may have functional groups that are polar or charged. For example, in nucleotides, which are the building blocks of DNA and RNA, the phosphate group is esterified to a sugar (ribose or deoxyribose) and a nitrogenous base. The sugar and the base can have polar functional groups, making the overall molecule polar.

Therefore, the properties of the phosphate group can vary depending on its interactions with other atoms or molecules in a biological context. In isolation, it may be considered nonpolar, but when present in complex biomolecules, it can contribute to the overall polarity of the molecule.

The reason for the discrepancy in polarity between chemistry and biology when it comes to the phosphate functional group (PO4) is due to the different contexts in which the concept of polarity is used.

In chemistry, polarity is often discussed in the context of individual molecules. Molecules are considered polar if there is an uneven distribution of electron density, leading to the presence of a positive and a negative pole within the molecule. This can result from differences in electronegativity between the atoms involved.

In the case of PO4 as a standalone molecule, it is considered nonpolar because the phosphate atom (P) and the four oxygen atoms (O) are symmetrical around the central phosphorus atom. This symmetry leads to an even distribution of electron density and no separation of charges, resulting in a nonpolar molecule.

However, in biology, the concept of polarity is often used in the context of biological macromolecules such as proteins, nucleic acids, and phospholipids. In this context, polarity refers to the presence of charged or polar chemical groups (polar functional groups) within the macromolecule.

The phosphate functional group (PO4) in biology is considered polar because it contains negatively charged oxygen atoms that can form strong ionic or hydrogen bonds with other molecules. These interactions play important roles in biological processes, such as DNA replication, signaling pathways, and energy storage.

Therefore, even though the PO4 molecule itself is nonpolar, the phosphate functional group is considered polar in biology due to its ability to interact with other molecules in a polar or charged manner.