As people age, their cells become less efficient and
less able to replace damaged components. At the same
time their tissues stiffen. For example, the lungs and the
heart muscle expand less successfully, the blood vessels
(5) become increasingly rigid, and the ligaments and tendons
tighten.
Few investigators would attribute such diverse effects
to a single cause. Nevertheless, researchers have discov-
ered that a process long known to discolor and toughen
(10)foods may also contribute to age- related impairment of
both cells and tissues. That process is nonenzymatic
glycosylation, whereby glucose becomes attached to pro-
teins without the aid of enzymes. When enzymes attach
glucose to proteins (enzymatic glycosylation), they do so
(15)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 glycosylation of certain proteins
(20)has been understood by food chemists for decades,
although few biologists recognized until recently that the
same steps could take place in the body. Nonenzymatic
glycosylation begins when an aldehyde group (CHO) of
glucose and an amino group (NH2) of a protein are
(25)attracted to each other. The molecules combine, forming
what is called a Schiff base within the protein. This com-
bination is unstable and quickly rearranges itself into a
stabler, but still reversible, substance known as an
Amadori product.
參考答案:随着人们年龄,其效率较差细胞变得较少损坏零件更换. 在此同时他们组织变硬. 例如,肺部扩及心脏肌肉较少成功的血脉(5)日益僵化 和韧带和肌腱收紧. 调查人员将这种属性数多样效果单一原因. 尽管如此, 科学家发现与煤炭的过程,并锻炼皆知变色(10)食品可能有助于老年性受损细胞和组织都. 这个过程是酶促糖,即成为糖附在亲thuringiensis没有借助酶. 当以葡萄糖酶蛋白高度(酶法糖化) 他们这样做(15)在一个特定的地点特定蛋白质分子为特定目的. 相比之下, 酶促过程的任何补充葡萄糖胡乱攀附有几种可供蛋白质分子肽链内. 这某些酶糖化蛋白质(20)食品化学家已明白十年 虽然直到最近几个生物学家公认的步骤可以发生在同一部位. 酶促糖醛集团开始时(草)和氨基葡萄糖(氨基)是一种蛋白质(25)相互吸引. 分子结合,形成了所谓的内夫碱蛋白质. 这个组件Bination不稳定,迅速重新组合成一个稳定的,但仍可逆, 阿马物质称为产物.
