[单项选择]As people age, their cells become less efficient and less able replace damaged components. At the same time their tissues stiffen, For example the lungs and the heart muscle expand less successfully, the blood vessels become increasingly rigid, and the ligaments and tendons tighten.
Few investigators would attribute such diverse effects to a single cause. Nevertheless, researchers have discovered that a process long known to discolor and toughen foods may also contribute to age-related impairment of both cells and tissues. That process is nonenzymatic glycosylation, whereby glucose becomes attached to proteins without the aid of enzymes. When enzymes attach glucose to proteins (enzymatic glycosylation), they do so at a specific site on a specific protein molecule for a specific purpose. In contrast, the nonenzymatic process adds glucose haphazardly to any of several sites along any available peptide chain within a protein molecule.
This nonenzymatic glyeosylation of certain p
A. It takes place more slowly than glycosylation in the human body.
B. It requires a higher ratio of glucose to protein than glycosylation requires in the human body.
C. It does not require the aid of enzymes to attach glucose to protein.
D. It proceeds more quickly when the food proteins have a molecular structure similar to that of crystallin proteins.