Biochemistry : Identification by Structure
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Example Questions
Example Question #31 : Identification By Structure
Identify the carbohydrate class of the given molecule.
Aldopentose
Ketopentose
Aldoquintos
Ketohexose
Aldohexose
Aldopentose
The structure is an aldopentose. Aldo- refers to the aldehyde at the first carbon and pentose refers to a carbohydrate with five carbons.
Example Question #31 : Identification By Structure
Identify the carbohydrate class of the given molecule.
Ketoquintos
Aldohexose
Aldopentose
Ketohexose
Ketopentose
Ketopentose
The structure is a ketopentose. Keto- refers to the ketone at the second carbon and pentose refers to a carbohydrate with five carbons.
Example Question #33 : Identification By Structure
Identify the given structure.
L-galactose
L-glucose
D-fructose
D-glucose
D-galactose
D-glucose
This ring structure is of D-glucose. The hydroxyl group on the first carbon (the carbon to the bottom right of the oxygenin the ring) can face either down (the alpha conformation) or up (the beta conformation). Note that the beta conformer is more thermodynamically stable since all the hydroxyl groups on the ring would be in the equitorial position, thus minimizing steric hinderance and intramolecular electrostatic repulsion.
Example Question #34 : Identification By Structure
Identify the given structure.
D-mannose
D-glucose
D-ribose
D-fructose
D-galactose
D-fructose
This is the ring/cyclic structure of D-fructose.
Example Question #35 : Identification By Structure
Which of the following is the correct structure of a disaccharide?
Sucrose = glucose + glucose
Lactose = galactose + galactose
Maltose = glucose + glucose
Lactose = galactose + fructose
Maltose = sucrose + fructose
Maltose = glucose + glucose
The correct structures of the disaccharides are:
Maltose = glucose + glucose
Sucrose = glucose + fructose
Lactose = glucose + galactose
Example Question #31 : Identification By Structure
Which amino acid does this structure represent?
Arginine
Asparagine
Aspartate
Glutamine
Glutamate
Glutamate
The amino acid's R group is composed of an ethyl group, followed by a carboxylate group, and therefore represents glutamate.
Example Question #32 : Identification By Structure
Which amino acid does this structure represent?
Y
A
M
T
S
M
The amino acid's chiral carbon is connected to two methyl groups followed, by a sulfur, and finally another methyl group. Therefore, the amino acid is methionine (M).
Example Question #32 : Identification By Structure
The amino acid phenylalanine is pictured. If a hydroxyl group was added to the carbon in the red box, which amino acid would the new molecule most closely resemble?
Lysine
Alanine
Glysine
Arginine
Tyrosine
Tyrosine
The structure would most closely resembe tyrosine (pictured).
Example Question #33 : Identification By Structure
If the phenyl group in the pictured molecule were removed, what amino acid would the new structure most closely resemble?
Alanine
Tyrosine
Glycine
Phenylalanine
Valine
Alanine
Alanine is the amino acid that would be formed by removing the phenyl group from phenylalanine (the pictured molecule).
Example Question #34 : Identification By Structure
If the amide group of glutamine (pictured here) was removed and a hydroxyl group was added to the carbon bound to the alpha carbon of the resulting structure, what amino acid would be formed?
Threonine
Valine
Cysteine
Methionine
Tyrosine
Threonine
Threonine (pictured here) would be formed.
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