Biochemistry : Identifying Biochemical Molecules
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Example Questions
Example Question #66 : Identification By Structure
Primary protein structure is primarily held together by what type of bond?
Hydrogen bond
Phosphodiester bond
Peptide bond
Ionic bond
Van der waals interactions
Peptide bond
Primary protein structures are composed of amino acids linked together by peptide bonds. Secondary protein structures are held together by hydrogen bonds. Phosphodiester bonds can be found between sugar and phosphate groups in the backbone of DNA.
Example Question #121 : Identifying Biochemical Molecules
Why is the tertiary structure of a protein always conserved, even more so than the primary structure?
Tertiary structure is more closely associated with the protein's function
The primary structure is more conserved than the tertiary structure
The primary and tertiary structure of a protein are equally conserved
The bonds holding the tertiary structure are stronger than those of the primary structure
Tertiary structure is more closely associated with the sequence of the protein
Tertiary structure is more closely associated with the protein's function
The primary structure of a protein deals with its sequence while the tertiary structure deals with the folding of the protein. The folding of the protein is what determines its function, and because this is important in maintaining the life of organisms, the tertiary structure must be heavily conserved.
Example Question #68 : Identification By Structure
Which of these are negatively charged amino acids at pH 7?
I. Aspartic acid
II. Glutamic acid
III. Lysine
IV. Arginine
IV only
I and II
I, II, and III
III and IV
I, III, and IV
I and II
Amino acids are classified based on their charged (polar groups) at neutral pH (pH=7).Lysine (Lys, K), arginine (Arg, R) and histidine (His, H) are positively charged at neutral ph (pH=7), while aspartate and glutamate are negatively charged.
Example Question #1 : Identifying Specific Nucleic Acid Structures
Identify the nucleobase.
Guanine
Cytosine
Thymine
Adenine
Uracil
Guanine
The structure represents guanine because of the characteristic carbonyl group at carbon 6 and amine group and carbon 2.
Example Question #2 : Identifying Specific Nucleic Acid Structures
Identify the nucleobase.
Uracil
Cytosine
Thymine
Guanine
Adenine
Adenine
The structure is adenine because of the characteristic amine group on carbon 6 and lack of any other substituents.
Example Question #2 : Identifying Specific Nucleic Acid Structures
Identify the nucleobase.
Thymine
Guanine
Adenine
Uracil
Cytosine
Thymine
The structure represent thymine because of the characteristic carbonyl groups at both carbons 2 and 4 and the methyl group at carbon 5.
Example Question #3 : Identifying Specific Nucleic Acid Structures
Identify the nucleobase.
Cytosine
Uracil
Guanine
Adenine
Thymine
Uracil
The structure represents uracil because of the carbonyl groups attached to both carbons 2 and 4 and the lack of any other substituents.
Example Question #4 : Identifying Specific Nucleic Acid Structures
Identify the nucleobase.
Cytosine
Adenine
Guanine
Uracil
Thymine
Cytosine
The structure represents cytosine because of the characteristic amine group on carbon 4, instead of the carbonyl group that is present on carbon 4 of both thymine and uracil.
Example Question #5 : Identifying Specific Nucleic Acid Structures
Which of the following are considered pyrimidines?
I: adenine
II: thymine
III: cytosine
IV: guanine
III and IV
I and III
I and II
I and IV
II and III
II and III
Pyrimidines are nitrogenous bases with 1 ring structure, whereas purines are nitrogenous bases with 2 ring structures. Cytosine and thymine are pyrimidines since they both have one ring structure, whereas adenine and guanine are purines with two connected ring structures. (Note: in RNA, uracil would be considered a pyrimidine in the place of thymine.) One way to help you remember which bases belong to which chemical groups, remember that pyrimidines, like pyramids are sharp, and sharp things CUT - Cytosine, Uracil, and Thymine.
Example Question #3 : Identifying Specific Nucleic Acid Structures
Name the given ring systems and determine whether they are soluble or insoluble.
Amine ring; insoluble
Pyrimidine ring; purine ring; insoluble
Purine ring; pyrimidine ring; insoluble
Cytosine; adenine,; soluble
Pyrimidine ring; purine ring; soluble
Pyrimidine ring; purine ring; insoluble
The six-membered ring is a pyrimidine. The purine ring system has two rings: a six-membered and a five-membered ring. These aromatic rings are hydrophobic, making them relatively insoluble. The pyrimidine bases in nucleotides are cytosine, uracil, and thymine; the purine bases in nucleotides are adenine and guanine.
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