Biomolecules

[Wizard]

Do we have to memorise the structural formula of maltose (they give sucrose in the data booklet), and the reactions between monosaccharides to form disaccharides?

[Wizard]

Also, how is cholesterol formed? What does it do in the human body, and why can it be both good and harmful?

[shinny]

You wouldn't be expected to know the chemical formula of Maltose, but you would be expected to know how carbohydrates polymerise. Your questions about cholesterol are pretty much out of the course, but a quick Wikipedia'ing should let you find out those answers if you're interested. From what I know, the gist of it is that your body already produces all the cholesterol it needs by itself, and hence none needs to be taken through dietary means. Then supposedly there's some good cholesterols which reduce the rate at which your body uptakes the bad ones or something, but that's just what I recall off the top of my head. Like I said, just go Wikipedia it =T

[hard]

oh yay biology!

[Wizard]

Thanks shinny!
also, ive come across alpha glucose and beta glucose, which when polymerise produce different disaccharides. What is the difference between alpha and beta glucose?

[TrueTears]

the difference is that for between alpha and beta is that in beta the H-OH bond on the 1st Carbon atom is swapped around to make it a OH-H.

this might make it a bit clear:

[Wizard]

Thank you!
from the diagrams of glucose above, is the c-o-c bond an ether linkage? (the bond between the 5th and the 1st carbon) or are ether linkages only formed through condensation?

[TrueTears]

Thank you!
from the diagrams of glucose above, is the c-o-c bond an ether linkage? (the bond between the 5th and the 1st carbon) or are ether linkages only formed through condensation?

nope that is only a normal single bond, c-o-c. Ether linkages only occurs when 2 monosaccharides bond to form a disaccharide, it is the bond which holds the 2 molecules together. Examples include: glucose + glucose, glucose + fructose, glucose + galactose.

[shinny]

Think of alpha and beta as like your left and right hands. They've got the same composition, but one's a mirror image of the other. No matter how you flip them, they won't be the same. The importance of this is that when alpha and alpha bond, different products are made than if alpha and beta did.

[Mao]

Thank you!
from the diagrams of glucose above, is the c-o-c bond an ether linkage? (the bond between the 5th and the 1st carbon) or are ether linkages only formed through condensation?

nope that is only a normal single bond, c-o-c. Ether linkages only occurs when 2 monosaccharides bond to form a disaccharide, it is the bond which holds the 2 molecules together. Examples include: glucose + glucose, glucose + fructose, glucose + galactose.

[the following is not actually in the course]

that definition of ether isn't necessarily correct, as cyclic ethers can occur. Ether linkage occurs when two hydroxy groups react.

However, if you have seen diagrams of the straight chain glucose, the 1' carbon is an aldehyde, which reacts with the 5' carbon which has a hydroxy group. The double bonded O takes up the H from the hydroxy, which allows the 1' carbon to bond with the 5' 's oxygen. It's formally called a 'hemiacetal'.
http://en.wikipedia.org/wiki/Glucose
http://en.wikipedia.org/wiki/Hemiacetal