Disaccharides (Maltose, Lactose and Sucrose)

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But isn’t lactose~ beta-d-galactose + beta-d-glucose?

amazing..... didn't need to read the Uni content at all after watching this !

Thank you very much!!

You explain very well, 🙂🙂

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Wouldn't for sucrose, you would need to specific alpha-1,-beta-2-glycosidic bond, since it's using both anomeric carbons?

I'm writing a comment here for my own reference in the future. No other places to take notes right now. '

Aldehydes can be oxidized into carboxylic acids, which are also formally called aldonic acid.

Because maltose and lactose have 1,4-glycosidic bonds (regardless of their alpha or beta conformations), this means that there is still at least one anomeric carbon capable of opening up into the open-chain aldehyde form (also known as mutarotation). Thus, it is called a reducing agent (reducing sugar).

And sucrose is not a reducing sugar because the anomeric carbons are both taken up in the alpha-1,2-glycosidic linkage, meaning that there's no chance for aldose formation....? Isn't beta-D-fructose a ketose though?

I did a bit of googling and I found that ketose sugars can tautomerize (rearranging bonds) resulting in an (enol), a double bond and -OH group. So ketoses also act as reducing sugars by becoming aldoses until a "keto-enol" shift under basic conditions...interesting.



aldoses = open chain carbohydrates with aldehyde as their oxidized functional group
ketoses = open chain carbon hydrates with ketone
hemiacetal = cyclic rings due to intramolecular reactions between an nucleophilic hydoxl group and electrophilic carbonyl carbon in an aldose

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Lactose=alpha galactose +beta glucose ???

Thank you!!! Finally, I understand this.

I have understood so much thank you

Thank you!!! Finally I understand this.

What is the full name of lactose?،🧐🤔

U are genius 😎

In fructose, hydroxyl group in C3 is in the opposite direction as others, as a result, OH resides inside the pentagon ring in C3. But when it becomes Sucrose, i noticed that hydroxyl group is inside of pentagon in C4. Can you please explain why?

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Thanks sir

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From india

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Hello sir. Is it supposedly a-D-fructose + a-D-glucose to create a-1,2-glucosidic bond?

Great lecture! Made me really understand the structure rather than basically memorizing them without any context

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Well explained ☺

very well put together lecture.

just got it now... thank you

Really helpful! Thank you!

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6. If a disaccharide is formed through a (1-> β4) glycosidic bond, it means that ______.
A. neither the first nor the second monosaccharide unit needs to be in the β-form
B. both monosaccharide units need to be in the β-form
C. only the first monosaccharide unit needs to be in the β-form
D. None of the above is correct.

Can someone help me with this qn?? )):

thank you so much !

good

The reason the maltose C1 anomeric carbon is designated alpha is that it's former hydroxyl group, which is now the glycosidic O bond linking the two monsaccharides, is cis to (on the same side of the ring) as the 4th carbon's hydoxyl group. The lecturer was wrong when he referenced it to the position of the CH2OH group attached to carbon no. 5. That group is trans to the glycosidic O bond. The alpha/beta designations refer to the positions of the anomeric hydroxyl group and the hydroxyl group oxygen which is directly bound to the highest numbered chiral carbon in the ring.

α-glucose + α-fructose = sucrose

and maltose has alpha and beta glucose
monosacharides.

Lactose has both galactose and glucose in beta anomeric conformation not in alpha glucose

Well a great video lecture.....it really built up my concepts

thank you!

Also greetings from Germany. I'm taking Biochemistry in German (not my first language) and your videos really are a life-saver for the concepts that are harder for me to translate. Much appreciated!

greetings from Germany I understood so much more in your Video than I understood in German videos or in class thank you so much🙌

Your strong pronunciation is great really learning here

isn't lactose between beta galactose and BETA glucose?

Thank you very much. I search for hours for a nice german statement. But its so much easy, when u explain it.