Most sugars are embedded in complex carbohydrates

The most familiar of all sugars is sucrose—the mixed acetal formed from glucose and fructose. Sucrose is of course sweet, and is easily metabolized into fats. But if three of the OH groups in sucrose are replaced by chlorine atoms, a compound 600 times as sweet is produced: less of it is needed to get the same sweet taste and the chlorines reduce the rate of metabolism so that much less fat is made. This is the compound sucralose, discovered by chemists at Tate & Lyle and now used to sweeten soft drinks.

Sucrose is a disaccharide—two simple sugars linked by an acetal. In general, saccharides have the same relationship to sugars as peptides and proteins have to amino acids. One of the most abundant compounds in nature is a saccharide: cellulose, the structural material of plants. It is a glucose polymer and is produced in simply enormous quantities (about 1015 kg per year). Each glucose molecule is joined to the next through an acetal formed by attack of the C4 hydroxyl group of one glucose molecule on the anomeric carbon atom of the next. Here is that basic arrangement.

Notice that the anomeric bonds are all equatorial. This means that the cellulose molecule is linear in general outline. It is made rigid by extra hydrogen bonds between the 3-OH groups and the ring oxygen atoms—like this.

The polymer is also coiled to increase stability still further. All this makes cellulose very difficult to hydrolyse, and humans cannot digest cellulose as we do not have the necessary enzymes. Other mammals have evolved devices such as multiple stomachs (in ruminants, such as cattle) to enable them to degrade cellulose.

اخر الاخبار

اخبار العتبة العباسية المقدسة

معمل مياه الكفيل: عمل على مدار الساعة دون توقف لتلبية الطلب المتزايد على المياه

مركز الكفيل للصحة والسلامة: برنامج الإخلاء الطبي غطى جميع الجوانب المتعلقة بالإسعاف الطارئ

أنشطة قرآنية وعزائية للمجمع العلمي في النجف الأشرف وبغداد

أستاذ الحوزة العلمية الشيخ حسن الجواهري يطلع على الخدمات الثقافية للزائرين في مجمع أبي الفضل العباس (عليه السلام)

المزيد

الآخبار الصحية

حجم جزء محدد من الجسم يعكس الصحة العامة ومخاطر الأمراض

تفشي عدوى بكتيرية بفرنسا يحتمل ارتباطها بنوع من الجبن الطري

دراسة حديثة تكشف ما تفعله الشاشات بـ"قلوب الأطفال" !

متلازمة المبنى المريض.. هكذا يتحول تكييف الهواء إلى خطر صحي ؟؟

المزيد

الآخبار التكنلوجية

كيف تتعامل مع حرارة الطقس أثناء القيادة؟

لماذا يجب عليك إيقاف تكييف السيارة قبل إطفاء المحرك؟

دراسة تكشف سببا محتملا وراء زيادة خطر إصابة الأطفال بالتوحد

تشيلي.. العثور على متحجرة حيوان ثديي صغير من زمن الديناصورات

المزيد

مواضيع ذات صلة

Lipids

Glycosides in nature

Sugars can be fixed in one shape by acetal formation

Sugars normally exist in cyclic forms with much stereochemistry

Antiobiotics exploit the special chemistry of bacteria

Amino acids combine to form peptides and proteins

Proteins are made of amino acids

Cyclic nucleosides and stereochemistry

HIV and AIDS are treated with modifi ed nucleosides Modified nucleosides

The stimulants in tea and coffee are methylated purines

Life begins with nucleic acids

Aldol reactions catalysed by proline