Page 157 - The Manga Guide to Biochemistry
P. 157
They are, but let’s get back to cellulose, okay? There’s an enzyme contained in our
saliva called α-amylase, which can break down starches, like rice, into pieces, but
α-amylase cannot break down cellulose.
Why not?
Well, look at the β(1→4) glycosidic bond shown in the following figure.
O OO
m jOm jOm j O
→β(1 4) glycosidic bond
Hey, the parts that are connected are different, aren’t they? They have a strange
shape, almost like the letter N.
The β(1→4) glycosidic bond differs from the α(1→4) glycosidic bond in that the
positions of the hydrogen atom (H) and the hydroxyl group (OH) are flipped around
their carbon. This creates a bond that is N-shaped rather than U-shaped, like the
α(1→4) glycosidic bond.
Yeah, no offense to the β type, but its connection seems twisted and totally weird!
OH Carbon at O OH
j position 1 j
OH H
α type β type
The Greek letters α and β represent the position of the hydroxyl group (OH) on carbon
1. When OH is on the bottom, as shown on the left in the above figure, it is the α type.
When it’s at the top, it is the β type.
Biochemistry in Our Everyday Lives 143
