Podcast
Questions and Answers
What is the purpose of Benedict’s test in biochemistry?
What is the purpose of Benedict’s test in biochemistry?
- To detect the presence of proteins
- To detect the presence of monosaccharides and some disaccharides (correct)
- To detect the presence of lipids
- To detect the presence of polysaccharides
Which types of saccharides have an aldehyde group?
Which types of saccharides have an aldehyde group?
- Only monosaccharides with aldehyde or ketone groups (correct)
- Both monosaccharides and polysaccharides
- Only polysaccharides
- Only monosaccharides with ketone groups
What type of saccharides can open into aldoses?
What type of saccharides can open into aldoses?
- Only di-saccharides
- Only mono-saccharides
- Mono and some di-saccharides with a hemiacetal group (correct)
- Polysaccharides
What is the characteristic feature of all monosaccharides?
What is the characteristic feature of all monosaccharides?
Why can some di-saccharides not open into aldoses?
Why can some di-saccharides not open into aldoses?
Which reagent is used to detect the presence of monosaccharides and some disaccharides directly in a urine sample?
Which reagent is used to detect the presence of monosaccharides and some disaccharides directly in a urine sample?
Which type of saccharides can be isomerized in an alkaline medium to give an aldehyde?
Which type of saccharides can be isomerized in an alkaline medium to give an aldehyde?
Which group of saccharides has a characteristic feature that allows them to open into aldoses?
Which group of saccharides has a characteristic feature that allows them to open into aldoses?
Why do some di-saccharides test negative with Benedict’s reagent?
Why do some di-saccharides test negative with Benedict’s reagent?
What characteristic feature do all monosaccharides have that allows them to be isomerized to aldehydes?
What characteristic feature do all monosaccharides have that allows them to be isomerized to aldehydes?
Which monosaccharide will give a positive result in Seliwanoff's test after more than 7 minutes?
Which monosaccharide will give a positive result in Seliwanoff's test after more than 7 minutes?
What is the characteristic feature of the monosaccharide that allows it to be isomerized to fructose and then dehydrated to give a positive Seliwanoff's test result?
What is the characteristic feature of the monosaccharide that allows it to be isomerized to fructose and then dehydrated to give a positive Seliwanoff's test result?
Which disaccharide should be digested to monosaccharides of fructose before it can give a positive Seliwanoff's test result?
Which disaccharide should be digested to monosaccharides of fructose before it can give a positive Seliwanoff's test result?
What is the minimum time it takes for fructose to dehydrate and give a positive result in Seliwanoff's test?
What is the minimum time it takes for fructose to dehydrate and give a positive result in Seliwanoff's test?
What is the minimum concentration of fructose (ketose) that the Seliwanoff's test is sensitive to, in the absence of glucose (aldose)?
What is the minimum concentration of fructose (ketose) that the Seliwanoff's test is sensitive to, in the absence of glucose (aldose)?
Study Notes
Seliwanoff's Test
- Used to differentiate between ketoses and aldoses in mono and disaccharides
- Uses HCl as a dehydrating agent and resorcinol as a condensing agent
Reaction Principle
- Involves a dehydration reaction due to the hydroxyl groups of the sugar
- Seliwanoff's reagent consists of resorcinol in dilute hydrochloric acid
- Ketoses (e.g. fructose) are more readily dehydrated by HCl than aldoses
Test Results
- Produces a clear colored solution with intensity proportional to the amount of ketoses
- Can be coupled with spectrophotometric measurement to quantify the amount of ketoses in solution
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Description
Test your knowledge about the reactions of carbohydrates, including Benedict’s test and the types of saccharides based on their functional groups.
