The question "what amino acid is the same" appears to ask for an identification of an amino acid that has identical forms. However, all standard amino acids have unique structures and properties. If we interpret this question as seeking an amino acid with no distinct isomers among its common forms, then glycine is the most fitting answer. Unlike other amino acids, glycine does not have a chiral center because its side chain (R group) is a hydrogen atom. This means it cannot exist in different stereoisomeric forms (like L- and D-forms) and is the simplest of the amino acids. Glycine's unique structure makes it essential in the formation of proteins, contributing flexibility due to its small size and lack of a specific side chain. It also plays key roles in the synthesis of other biological molecules such as purines, pyrimidines, and heme. Given its simplicity and unique features, glycine stands out as the amino acid without distinct isomeric forms.

Low-density polyethylene (LDPE) is a thermoplastic made from the polymerization of ethylene. Its chemical formula is (C2H4)n, which represents the polymer made up of repeating units of ethylene (C2H4). LDPE is distinguished from other polyethylene variants by its lower density, a result of its highly branched polymer chain. This branching gives LDPE its characteristic lightweight and flexibility, making it ideal for applications such as plastic bags, containers, and tubing. LDPE's unique properties stem from the specific conditions under which it is synthesized, including high pressure and temperature, which favor the formation of its branched structure. As a highly versatile material, LDPE is an essential polymer in the packaging industry and various consumer products.

Titanium dioxide is generally considered a safe ingredient in many products like sunscreens or food additives. However, it could pose potential health risks when inhaled in excessive amounts, potentially leading to respiratory tract irritation and damage. It's also classified by the International Agency for Research on Cancer as potentially carcinogenic to humans when inhaled. Long-term exposure can potentially increase the risk of chronic respiratory disease. Despite these risks, the Food and Drug Administration (FDA) considers it safe when used in appropriate amounts. It is advised to use products containing titanium dioxide responsibly and cautiously.