All Questions
Tagged with biochemistry carbohydrates
47
questions
6
votes
2
answers
161
views
What does ‘D’ in GADP (glyceraldehyde 3-phosphate) stand for?
Wikipedia says glyceraldehyde-3-phosphate can be abbreviated as G3P, GA3P, GADP, GAP, TP, GALP or PGAL, and many resources seem to use GADP as its abbreviation.
I have no idea where ‘D’ came from. ...
- 129
0
votes
0
answers
27
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Why can't the fructose monomer in sucrose be α-fructose?
In all academic sources, sucrose is identified as α−glucose (1-->2) β−fructose. However, I cannot find any explanation anywhere as to why the fructose monomer has to be in the β configuration. ...
- 11
0
votes
0
answers
24
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Bioplastic from starch
I am doing research in bioplastic from starch. I have tried many quantities and concentrations of starch, vinegar and glycerol at different temperatures. But I am unable to get a certain result of the ...
0
votes
0
answers
263
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Why does glucose react with hydroxyl amine and HCN but doesn't give Schiff's test or react with NaHSO3?
I can't understand this because if there isn't a free CHO group then it also shouldn't react with NH2OH and HCN.
On the same note can anyone also explain why pentaacetate of glucose not react with ...
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-1
votes
2
answers
2k
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Are Starch, Amylose and, Amylopectin reducing sugars?
Amylose and Amylopectin;
As per the information I've learnt, Amylose is considered a reducing sugar but Amylopectin is not because Amylose has a free "reducing end" which Amylopectin lacks, ...
1
vote
2
answers
286
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How does industry separate glucose from fructose using liquid chromatography when producing high-fructose corn syrup?
Can someone explain how the separation of glucose and fructose is achieved using liquid chromatography in the industrial production of high-fructose corn syrup?
I've seen references to ion-exchange ...
- 121
0
votes
1
answer
410
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Does changes in pH affects cyclic form of glucose in water solution?
Glucose in water solution is mainly in cyclic form. Both base and acid can catalize formation of hemiacetal, but in distinct mechanisms. I found information that monosacharides eg. glucose exist ...
10
votes
1
answer
1k
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Can sugars dissolve in liquid ammonia?
Can monosaccharides and disaccharides dissolve in liquid ammonia due to hydrogen bond formation?
My rationale is that these sugars may be able to form hydrogen bond with ammonia ($\ce{NH3}$).
- 109
0
votes
0
answers
2k
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Haworth structures of sucrose and lactose
The haworth structures of lactose and sucrose is
My question is regarding the glyosidic linkage, in lactose it is represented as a zig zag and in sucrose it is a "V". What does that mean. ...
user95393
2
votes
0
answers
212
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Do enzymes that digest ᴅ-glucose react with ʟ-glucose?
ᴅ-Glucose is common in nature and ʟ-glucose is synthesized in the lab.
I know that humans can't use ʟ-glucose in their aerobic pathways because it doesn't match the active site of the enzyme, but why ...
- 29
7
votes
2
answers
3k
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Oxidation of hydroxyl groups of glucose
In all oxidation reactions of glucose, it seems that the aldehyde group alone gets oxidised and none of the hydroxyl groups. In one reaction with nitric acid, the aldehyde group and the terminal ...
- 103
1
vote
0
answers
449
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Where does the beta notation come from in the alpha 1,2 beta glycosidic bond (in sucrose)? [duplicate]
I am confused as to where the beta is coming from (in the alpha-1,2-beta glycosidic bond in sucrose). I understand that the alpha is from the anomeric carbon of the glucose, but I don't see how the ...
8
votes
1
answer
2k
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Does cooling a potato change the nature of its carbohydrates?
A talk-show guest of Joe Rogan claimed that cooling a potato after cooking creates "resistant starch" that's better for human consumption
https://www.youtube.com/watch?v=niwqfwA2Lb8
The ...
- 519
3
votes
1
answer
3k
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How are glycosidic linkages formed?
Consider glycosidic linkages in disaccharides.
I know a condensation reaction occurs, with the loss of water.
But which OH is lost? The O in the linkage belongs to which monosaccharide?
Example: ...
- 776
5
votes
2
answers
3k
views
How does existence of alpha and beta form of glucose prove that it exists as a cyclic structure
My book says that
Glucose is found to exist in two different crystalline forms which are
named as $\alpha$ and $\beta$.
Next it says that
This behaviour could not be explained by the open ...
- 305
3
votes
1
answer
228
views
Production of ʟ-glucose
What chain(s) of reactions are used to produce ʟ-glucose? I did a search on Google Scholar, but to my surprise nothing came up. My guess would be that the synthesis starts from ᴅ-glucose for which ...
- 133
3
votes
1
answer
89
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Can Molisch test be used to separate monosaccharides from polysaccharides?
Do the results of Molisch test on monosaccharides have any differences with when it's done to disaccharides or polysaccharides?
- 55
3
votes
1
answer
12k
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Why can't amylase digest glycogen?
Amylase is an enzyme that breaks down starch in the form of amylopectin and amylose. Both amylose and amylopectin are formed by alpha glucose joined together by (1-4) and (1-6) glycosidic bonds. ...
- 131
3
votes
1
answer
12k
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Monosaccharides configurations (alpha beta, D L) identification
I am really finding it difficult to identify the correct configuration(s) of a given monosaccharide, in fact my friends and I have been trying to solve this, much to our annoyance.
In one of our ...
- 167
6
votes
4
answers
4k
views
Why is fermentation of cellulose to produce biofuel and nutrients so difficult?
The formula for glucose is $\ce{C6H12O6}$ and that of cellulose is very similar $\ce{C6H10O5}$. Glucose can be readily fermented by yeast and other micro-organisms to produce carbon dioxide and ...
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10
votes
1
answer
432
views
What is the correct way to notate conformation preferences of polysaccharides?
In some webpages (1 or 2) are found the way to notate the conformational preferences of monosaccharides such as furanose and pyranose.
But, it lacks to give a brief description on how to do it with ...
- 2,600
0
votes
1
answer
705
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Glycoside Formation Reaction
Whenever we add $\ce{H+}$/ Ethanol to glucose in its hemiacetal form, why doesn't pinacone/pinacolone rearrangement take place in place of nucleophillic substitution. The product would lead to ...
- 1,132
0
votes
1
answer
178
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Asking about definitions of word "sugar" in biochemistry
In a lecture about anabolic pathways of sugar, the lecturer was not clear when stating the name of a multiple sugar carrier & it sounded like "dolichol"so is it correct?
9
votes
3
answers
27k
views
How do you recognize a carbohydrate molecule?
I am studying carbohydrates in organic chemistry and I am confused a bit on what they are and how you recognize whether a molecule is a carbohydrate or not. For example, will a carbohydrate always ...
- 1,096
3
votes
2
answers
7k
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If α-glucose is less stable than β-glucose, why is glucose almost always α in its compounds?
Maltose, saccharose, turanose, trehalose, trehalulose, amylopectin, amylose - they are all α. Why? Also, why is cellulose β?
- 1,651
-4
votes
2
answers
17k
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In Glucose, how will you prove the presence of the following? [closed]
One carbonyl group
5 hydroxyl groups
One primary alcholic group
- 99
-2
votes
1
answer
746
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Why isn't sucrose a reducing sugar but maltose is? [duplicate]
I read one of the answers for a similar question, According to that it is due to the hemiacetale group converting into a carbonyl group. I don't get why the same thing can't be applied to sucrose ...
0
votes
1
answer
212
views
Why does the AraC arabinose sensing system only respond to the presence of L-arabinose?
I understand that when arabinose is present it interacts with araC and changes it shape, promoting the binding of RNA polymerase with the promoter and GFP is produced. However, I don't understand why ...
- 397
5
votes
1
answer
213
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Polysaccharides from non-cyclic sugars?
I have only come across polysaccharides from monosaccharides that has undergone intramolecular cyclization reaction. I was wondering if it is possible for polysaccharides to form from linear sugars? ...
- 1,697
1
vote
0
answers
148
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If Substance A is more soluble in water than Substance B, will Substance A be more easily absorbed by the body?
I am comparing the solubilities of artificial vs natural sweeteners for my Chemistry IB Internal Assessment. I must demonstrate personal engagement, so I am relating my topic to weight management in ...
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3
votes
1
answer
187
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Gel filtration separation of cellulose, starch, oxytocin and palmitic acid
I am studying biochemistry and I have been asked by my teacher to find a procedure for separating cellulose, starch, the peptide oxytocin (9 a.a) and palmitic acid ($\ce{C16}$) using gel filtration ...
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1
vote
1
answer
650
views
Why do we have glycogen in the muscles and not glucose? [closed]
Why do we have glycogen in the muscles and not glucose?
I know this is in contrast to liver cells, which, on demand, readily do break down their stored glycogen into glucose and send it through the ...
- 11
4
votes
1
answer
3k
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Phosphoglucose isomerase mechanism
The mechanism for phosphoglucose isomerase changing glucose 6 phosphate to fructose 6 phosphate shows histidine protonating the c5 oxygen and lysine deprotonation the c1 oxygen to form an open chain ...
- 105
9
votes
1
answer
3k
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Why do polysaccharides consisting of alpha-glucose have helical structures?
Why do the polysaccharides consisting of alpha-glucose such as starch and glycogen have helical structure, while the one such as cellulose consisting of beta glucose don't display such structures?
The ...
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4
votes
1
answer
1k
views
l- versus d-glucose
I recently purchased Dextrose from a local bulkfood store. I want to use it instead of table sugar. My concern is that it may be l-glucose instead of d-glucose. According to Wikipedia l-glucose is too ...
- 43
3
votes
1
answer
2k
views
Find the number of water molecules "embedded" in sucrose
Recently I got a question as follows:
How many molecules of water are joined with 12 atoms of carbon in a molecule of sucrose ?
(A) 12
(B) 11
(C) 6
(D) 10
I am unable to ...
- 482
1
vote
1
answer
326
views
Fermentation of different types of sugar
I'm searching for the difference in the fermentation of muscovado sugar, honey and sugar cane. I have used a specific microbiota to to ferment these three types of sugar and have to explain why I've ...
29
votes
2
answers
82k
views
Why does fructose reduce Tollen's reagent and Fehling's solution?
Even though fructose is a ketohexose (ketone-containing hexose, a six-carbon monosaccharide), it reduces Tollen's reagent and Fehling's solution. Generally, a ketone does not reduces Tollen's reagent ...
- 26.3k
2
votes
1
answer
89
views
Tensile properties of cellulose fibres
In cellulose fibres, such as cotton or hemp, I've noticed different percentages of lignin and cellulose. How does this affect their tensile strength and toughness? Are there any other important ...
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3
votes
1
answer
298
views
Creating small amounts of cellulosic ethanol from bamboo
I own a medium-sized farm and commercial aquaponics business in Pennsylvania. I try to make my business as green, sustainable, carbon-neutral and self-sufficient as possible.
As a way to cut out the ...
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14
votes
2
answers
5k
views
Why starch (amylose) and cotton (cellulose) are so different?
Both amylose and cellulose have the same "monomer" structure (glucose), so what makes them look/form so differently?
- 4,265
6
votes
1
answer
564
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How is it that fructose has a different metabolic pathway than glucose but yet glucose is converted to fructose?
Fructose is described to have a different metabolic pathway (a more fat-inducing one) than glucose (see: http://healthyeating.sfgate.com/difference-between-sucrose-glucose-fructose-8704.html) as it ...
- 703
14
votes
1
answer
61k
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How do you identify reducing / non-reducing sugar by looking at structure?
Identifying reducing / non-reducing sugar been confusing me for a while now , I know that reducing sugar contain aldehyde or ketone group . It's easy to identify them in monosaccharides but this ...
- 685
7
votes
2
answers
4k
views
Can I break starch down into glucose units?
I was wondering if starch can be broken up into individual glucose units. Because on a site I saw, it said that through acid hydrolysis starch can be broken up into amylose and amylopectin. However, ...
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2
votes
1
answer
6k
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In water, will sucrose be hydrolysed by water to form glucose and fructose molecules? [duplicate]
If I dissolve sucrose sugar ($\ce{C_12H_22O_11}$) in water, would the water readily hydrolyse the sucrose sugar to form glucose and fructose sugars?
- 483
4
votes
1
answer
237
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Fermentation in beer (reaction schemes)?
I've been struggling with this for a while, and I can't seem to solve the problem. Alcohol is made in the fermentation process in beer:
Sugars formed during mashing (maltose and maltotriose) will ...
- 173
10
votes
2
answers
5k
views
Is formaldehyde a carbohydrate?
Formaldehyde has the formula $\ce{CH2O}$, and the ratio of atoms in a simple carb is $\ce{1C:2H:1O}$. This fits the formula of carbohydrates. When I researched this, I found some sources saying that ...
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