Question

• What component of enzyme structure is responsible for enzyme specificity?

• How did the lactose intolerance test that pei took provide evidence that she was lactose intolerant?

Answer 1

1. Primary structure of a protein, i.e. the order that amino acids are bound together in a line, has everything it needs in order to tell the protein how to fold up into secondary and tertiary structure. Once that folding and 3D structure is formed, amino acid residues that were not close together in the primary structure, are now close together in the 3D structure. This means that they will have weak interactions among themselves. This further holds the 3D structure in place and in some cases forms Quaternary structure. The arrangement of amino acid residues determines the shape of the active site where the substrate will bind. This is what causes an enzyme to have specificity for a substrate. Think about it logically. Different confirmations of various shaped and sized amino acid residues coming together would form various shapes/sizes of clefts or crevices (active site). Therefore, only certain sized and shaped substrates could fit and bind there. The particular substrate-enzyme complex (what is formed when a substrate binds to an enzyme's active site) has a certain function or makes a certain end product. Soooooo, if that particular enzyme did not have its correct molecular architecture (3D shape), the correct substrate could not bind to the correct active site/enzyme and therefore, the correct product could not be made. This would mean that the particular enzyme with the wrong structure might bind the wrong substrate and create no product OR create a product that is not favorable in the particular reaction or environment that it is in. Does that make sense?

2. Lactose tolerance test. The lactose tolerance test gauges your body's reaction to a liquid that contains high levels of lactose. Two hours after drinking the liquid, you'll undergo blood tests to measure the amount of glucose in your bloodstream. If your glucose level doesn't rise, it means your body isn't properly digesting and absorbing the lactose-filled drink.

So, there must be no rise in blood sugar level after Lactose Intolerance test to designate a person as lactose intolerant.

Note: I have answered it generally as the case scenario wasn't really mentioned.