Question

In Lewis Carroll's tale "Through the Looking Glass," Alice wonders whether "looking-glass milk" on the other side of the mirror would be fit to drink. Based on your knowledge of chirality and enzyme action, comment on the validity of Alice's concern.

Short answer

Alice's concern about the drinkability of the 'looking-glass milk' is valid since the 'looking-glass milk' would be a mirror image of real milk and thus have different chirality. The enzymes in our body are highly stereospecific and would not be able to process and digest the milk's nutrients effectively because their shape wouldn’t match the shape of the enzymes, making it unfit for consumption.

Step-by-step solution

Concept of Chirality

Chirality is a property of a molecule that is not superimposable on its mirror image. These different forms are known as enantiomers and have the same physical and chemical properties except for their interaction with plane polarized light and their reaction with other chiral molecules. For example, a particular molecule will have a 'left handed' and a 'right handed' version, much like our own hands are mirror images but not superimposable on each other.

Enzyme Action and Chirality

Enzymes are biological catalysts that speed up chemical reactions by providing a specific binding site where the reaction can occur, reducing the required energy. Enzymes are highly specific in their action, meaning they will bind to specific molecules (known as substrates) to perform a specific reaction. This is because the shape of the enzyme's active site is complementary to the substrate's shape. Now, this specificity extends to the chirality of the substrate molecule as well. If the substrate molecule is chiral, then the enzyme will be specific to either one of its enantiomers.

Commenting on Alice's Concern

If 'looking-glass milk' is a mirror image of real milk, then the molecules in looking-glass milk would be enantiomers of the original molecules. Given the specificity of our body's enzymes to particular enantiomers, the looking-glass milk likely wouldn't be digestible. In other words, our body's enzymes might not recognize or be able to interact effectively with the mirror image molecules, so the milk might not be fit to drink. Therefore, Alice's concern is indeed valid.