Macromolecules and Enzymes - GRE
Card 0 of 168
Glycogen is a polymer of glucose that is held together by
bonds. The branch points are held together by
bonds.
Glycogen is a polymer of glucose that is held together by bonds. The branch points are held together by bonds.
bonds are on the same plane, while 
bonds are not on the same plane; therefore, the 
bonds are much more useful for making branch points off of existing glycogen chains.
linkages cannot be easily broken down by eukaryotes and animals. Glycogen must be easily accessible as an energy source, and does not contain any glycosidic linkages.
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Phospholipids are comprised of
.
Phospholipids are comprised of .
The correct answer is a glycerol head containing a phosphate group and two fatty acids. Phospho refers to the phosphate group and lipid refers to the glycerol backbone attached to two fatty acid chains.
The correct answer is a glycerol head containing a phosphate group and two fatty acids. Phospho refers to the phosphate group and lipid refers to the glycerol backbone attached to two fatty acid chains.
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What qualifies a molecule to be considered an omega-3 fatty acid?
What qualifies a molecule to be considered an omega-3 fatty acid?
Omega-3 fatty acids are named after the double bond that starts on the third-to-last carbon in the fatty acid. The carboxylic acid carbon is considered the first carbon, while the last methyl group carbon is considered the "omega" carbon. As a result, the double bond will be three carbons away from the end.
Omega-3 fatty acids are named after the double bond that starts on the third-to-last carbon in the fatty acid. The carboxylic acid carbon is considered the first carbon, while the last methyl group carbon is considered the "omega" carbon. As a result, the double bond will be three carbons away from the end.
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Which type of lipid acts as a buffer for membrane fluidity?
Which type of lipid acts as a buffer for membrane fluidity?
Membrane fluidity can be buffered by cholesterol in both warm and cold environments. At high temperatures cholesterol raises the melting point, while at lower temperatures cholesterol prevents the formation of crystalline structures between phospholipids.
Membrane fluidity can be buffered by cholesterol in both warm and cold environments. At high temperatures cholesterol raises the melting point, while at lower temperatures cholesterol prevents the formation of crystalline structures between phospholipids.
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Which of the following nucleotides is present in RNA, but not DNA?
Which of the following nucleotides is present in RNA, but not DNA?
Uracil is one of the nucleotide bases that composes RNA. It is replaced by thymine in DNA.
Uracil, thymine, and cytosine are pyrimidine residues, capable of bonding and pairing with the purines adenine and guanine via hydrogen bonding. During DNA replication, thymine matches with adenine. During transcription, uracil matches with adenine.
Uracil is one of the nucleotide bases that composes RNA. It is replaced by thymine in DNA.
Uracil, thymine, and cytosine are pyrimidine residues, capable of bonding and pairing with the purines adenine and guanine via hydrogen bonding. During DNA replication, thymine matches with adenine. During transcription, uracil matches with adenine.
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Which of the following amino acids is NOT necessary for purine synthesis?
Which of the following amino acids is NOT necessary for purine synthesis?
Purines are defined by their two-ring structure. A six-member ring with two amine groups and a five-member ring with two amino groups join to form each purine molecule. Addition substituents on the rings (often ketones or other amines) determine purine identity.
Glycine, aspartate, and glutamine are necessary for purine synthesis, along with phosphoribosyl pyrophosphate (PRPP). Glycine is incorporated into the final purine product structure, while glutamine is converted to glutamate and aspartate is converted to fumarate. The final purine product is used to make useful molecules, such as adenine and guanine for nucleotide synthesis.
Purines are defined by their two-ring structure. A six-member ring with two amine groups and a five-member ring with two amino groups join to form each purine molecule. Addition substituents on the rings (often ketones or other amines) determine purine identity.
Glycine, aspartate, and glutamine are necessary for purine synthesis, along with phosphoribosyl pyrophosphate (PRPP). Glycine is incorporated into the final purine product structure, while glutamine is converted to glutamate and aspartate is converted to fumarate. The final purine product is used to make useful molecules, such as adenine and guanine for nucleotide synthesis.
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Which of the following processes allows DNA mismatch repair enzymes to distinguish between old and new DNA strands?
Which of the following processes allows DNA mismatch repair enzymes to distinguish between old and new DNA strands?
Template strand cytosine and adenine are methylated in DNA replication, which allows DNA mismatch repair enzymes to distinguish between old and new DNA strands.
In contrast, histone acetylation relaxes DNA coiling and allows for the DNA to be transcribed.
You can remember that methylation makes DNA mute, and acetylation makes DNA active.
Template strand cytosine and adenine are methylated in DNA replication, which allows DNA mismatch repair enzymes to distinguish between old and new DNA strands.
In contrast, histone acetylation relaxes DNA coiling and allows for the DNA to be transcribed.
You can remember that methylation makes DNA mute, and acetylation makes DNA active.
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In DNA, which of the following nucleotides forms hydrogen bonds with guanine?
In DNA, which of the following nucleotides forms hydrogen bonds with guanine?
Nucleotides (DNA monomers) and ribonucleotides (RNA monomers) are formed from a pentose sugar, phosphate group, and nitrogenous base. Each nitrogenous base has a complement that allows it to form hydrogen bonds to the template strand. This allows for the proper sequence of genetic code in DNA replication and RNA transcription.
Purine residues will always pair with pyrimidine residues. The purines are adenine and guanine. The pyrimidines are cytosine and thymine in DNA, and cytosine and uracil in RNA. Adenine will match with thymine or uracil, forming two hydrogen bonds, while cytosine will match with guanine to form three hydrogen bonds.
Nucleotides (DNA monomers) and ribonucleotides (RNA monomers) are formed from a pentose sugar, phosphate group, and nitrogenous base. Each nitrogenous base has a complement that allows it to form hydrogen bonds to the template strand. This allows for the proper sequence of genetic code in DNA replication and RNA transcription.
Purine residues will always pair with pyrimidine residues. The purines are adenine and guanine. The pyrimidines are cytosine and thymine in DNA, and cytosine and uracil in RNA. Adenine will match with thymine or uracil, forming two hydrogen bonds, while cytosine will match with guanine to form three hydrogen bonds.
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Which of the following properties is NOT a feature of the genetic code?
Which of the following properties is NOT a feature of the genetic code?
The genetic code refers to the sequence of DNA that codes for genes and proteins in the body. The genetic code is composed of three-nucleotide codons, each used to recruit an amino acid during translation and protein synthesis. Each codon codes for one and only one amino acid, making the code unambiguous; however, some amino acids have more than one codon that can be used to recruit them. This feature of the genetic code is known as degeneracy. Finally, the genetic code is universal. All living organisms use the same genetic material (DNA) in their cells and produce proteins through transcription and translation. Though the processes may change slightly between organisms, the general genetic code is universal to all cells.
The genetic code is not overlapping, meaning that the code is linear. Transcription of DNA has a fixed starting point and proceeds in a linear fashion, as does translation of mRNA. There is no overlapping or reverse reading of the genetic code.
The genetic code refers to the sequence of DNA that codes for genes and proteins in the body. The genetic code is composed of three-nucleotide codons, each used to recruit an amino acid during translation and protein synthesis. Each codon codes for one and only one amino acid, making the code unambiguous; however, some amino acids have more than one codon that can be used to recruit them. This feature of the genetic code is known as degeneracy. Finally, the genetic code is universal. All living organisms use the same genetic material (DNA) in their cells and produce proteins through transcription and translation. Though the processes may change slightly between organisms, the general genetic code is universal to all cells.
The genetic code is not overlapping, meaning that the code is linear. Transcription of DNA has a fixed starting point and proceeds in a linear fashion, as does translation of mRNA. There is no overlapping or reverse reading of the genetic code.
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For amino acids, the phi (
) angle refers to the bond between
and the alpha carbon while the psi (
) angle refers to the bond between the alpha carbon and
.
For amino acids, the phi (
These bonds are specifically referring to the invariable portions of the amino acid and, thus, do not involve the R group (functional group).
This is more of a definition-based answer. The phi angle refers to the bond between the amine nitrogen and the alpha carbon, while the psi angle refers to the bond between the alpha carbon and the carbonyl carbon of the carboxylic acid. These bonds play important roles in determining possible protein structures.
These bonds are specifically referring to the invariable portions of the amino acid and, thus, do not involve the R group (functional group).
This is more of a definition-based answer. The phi angle refers to the bond between the amine nitrogen and the alpha carbon, while the psi angle refers to the bond between the alpha carbon and the carbonyl carbon of the carboxylic acid. These bonds play important roles in determining possible protein structures.
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Which of the following amino acid sequences is most likely to form an alpha-helix?
Which of the following amino acid sequences is most likely to form an alpha-helix?
Amino acid sequences with a lot of alanine (A) residues are higly likely to form alpha-helices. Glycine (G) and proline (P) residues often cap alpha-helices, though glycine can sometimes be found inside alpha-helices as well.
Proline is never found inside an alpha-helix due to the conformational hindrance caused by the hydrogen bonding within the residue. Proline is usually found in bends in a protein structure.
Amino acid sequences with a lot of alanine (A) residues are higly likely to form alpha-helices. Glycine (G) and proline (P) residues often cap alpha-helices, though glycine can sometimes be found inside alpha-helices as well.
Proline is never found inside an alpha-helix due to the conformational hindrance caused by the hydrogen bonding within the residue. Proline is usually found in bends in a protein structure.
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Which of the following is true regarding the protonation of histidine at a pH of 7?
Which of the following is true regarding the protonation of histidine at a pH of 7?
Histidine has the following pKa values:
COOH - 1.82
R-group - 6.00
NH3 - 9.17
Any pH below the pKa will cause the molecule to be protonated, while any pH above the pKa will cause the molecule to deprotonate. At a pH of 7, the COOH group to deprotonate, but the NH3 and R-group will remain protonated.
Histidine has the following pKa values:
COOH - 1.82
R-group - 6.00
NH3 - 9.17
Any pH below the pKa will cause the molecule to be protonated, while any pH above the pKa will cause the molecule to deprotonate. At a pH of 7, the COOH group to deprotonate, but the NH3 and R-group will remain protonated.
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Which part of its amino acid mediates the interactions that form the tertiary structure of a protein?
Which part of its amino acid mediates the interactions that form the tertiary structure of a protein?
Tertiary structure of a protein is determined by interactions between the R-groups of the amino acids that make up that protein. The secondary structure of a protein is mediated by the backbone atoms of the polypeptide chain which includes the carboxyl and amine groups. The alpha carbon are what the R-groups are attached to an do not directly contribute to any level of protein structure.
Tertiary structure of a protein is determined by interactions between the R-groups of the amino acids that make up that protein. The secondary structure of a protein is mediated by the backbone atoms of the polypeptide chain which includes the carboxyl and amine groups. The alpha carbon are what the R-groups are attached to an do not directly contribute to any level of protein structure.
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Interactions between which of these mediates the secondary structure of a protein?
Interactions between which of these mediates the secondary structure of a protein?
Hydrogen bonds between repeating units of the polypeptide backbone (namely the amino groups and carboxyl groups) mediate secondary structure in proteins.
Hydrogen bonds between repeating units of the polypeptide backbone (namely the amino groups and carboxyl groups) mediate secondary structure in proteins.
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Protein molecular structure can be described as a hierarchy. Which level of protein structure consists of spatial arrangements, such as alpha helices or beta sheets, that occur due to local folding in a polypeptide chain?
Protein molecular structure can be described as a hierarchy. Which level of protein structure consists of spatial arrangements, such as alpha helices or beta sheets, that occur due to local folding in a polypeptide chain?
Primary structure simply describes the order of amino acids in a polypeptide chain. Tertiary structures describe global folding of the entire chain, which may be made up of a multitude of secondary structures like alpha helices or beta sheets. Quaternary structure describes the position of numerous subunits in a protein complex comprised of two or more smaller protein. Huge multiunit proteins are ordered by supramolecular structure.
Primary structure simply describes the order of amino acids in a polypeptide chain. Tertiary structures describe global folding of the entire chain, which may be made up of a multitude of secondary structures like alpha helices or beta sheets. Quaternary structure describes the position of numerous subunits in a protein complex comprised of two or more smaller protein. Huge multiunit proteins are ordered by supramolecular structure.
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Sucrose is a polysaccharide made up of
and
.
Sucrose is a polysaccharide made up of and .
Sucrose is one of the more common sugars, and is composed of glucose and fructose. Sucrose is also known as table sugar.
Galactose and glucose are the components of lactose. Maltose is made up of two glucose molecules.
Sucrose is one of the more common sugars, and is composed of glucose and fructose. Sucrose is also known as table sugar.
Galactose and glucose are the components of lactose. Maltose is made up of two glucose molecules.
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Which of the following is the primary reason that starch can be digested by humans, but cellulose cannot?
Which of the following is the primary reason that starch can be digested by humans, but cellulose cannot?
Both starch and cellulose are polysaccharides composed of glucose monosaccharides, but only starch can be digested by humans. The reason for this lies in the type of glycosidic linkages between glucose monomers. Starch has alpha (1-4) linkages which can be broken down, but cellulose has beta (1-4) linkages. Humans do not have the necessary enzyme to digest this type of glycosidic linkage.
Both starch and cellulose are polysaccharides composed of glucose monosaccharides, but only starch can be digested by humans. The reason for this lies in the type of glycosidic linkages between glucose monomers. Starch has alpha (1-4) linkages which can be broken down, but cellulose has beta (1-4) linkages. Humans do not have the necessary enzyme to digest this type of glycosidic linkage.
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Which of the following sugars is a ketose?
Which of the following sugars is a ketose?
A ketose is defined as any monsaccharide that has a ketone functional group while in its linear form. Fructose is a ketose, while the other three options are all aldoses.
A ketose is defined as any monsaccharide that has a ketone functional group while in its linear form. Fructose is a ketose, while the other three options are all aldoses.
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Which of the following changes cannot be accomplished by an enzyme in a chemical reaction?
Which of the following changes cannot be accomplished by an enzyme in a chemical reaction?
An enzme is a biological catalyst that increases the rate of a reaction. This is accomplished by lowering the activation energy necessary to start the reaction. The equilibrium of the reaction, however, is not affected. This means that enthalpy and entropy are not affected by an enzyme's presence.
An enzme is a biological catalyst that increases the rate of a reaction. This is accomplished by lowering the activation energy necessary to start the reaction. The equilibrium of the reaction, however, is not affected. This means that enthalpy and entropy are not affected by an enzyme's presence.
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The class of enzymes that break bonds by forming a new double bond or ring structure (rather than by hydrolysis or oxidation) is best characterized as which of the following?
The class of enzymes that break bonds by forming a new double bond or ring structure (rather than by hydrolysis or oxidation) is best characterized as which of the following?
The correct answer is lyases. This class of enzymes only requires one substrate for the forward reaction.
Ligases catalyze the formation of a bond between two molecules, isomerases rearrange the atoms of a molecule, kinases phosphorylate molecules, and transferases transfer or join functional groups from one molecule to another.
The correct answer is lyases. This class of enzymes only requires one substrate for the forward reaction.
Ligases catalyze the formation of a bond between two molecules, isomerases rearrange the atoms of a molecule, kinases phosphorylate molecules, and transferases transfer or join functional groups from one molecule to another.
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