Understanding Protein and Enzyme Function - GRE Subject Test: Biology
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How do enzymes speed up reactions?
How do enzymes speed up reactions?
Enzymes speed up reactions by lowering the energy required to begin the reaction (the activation energy). They do not have any direct effect on the change in free energy, nor do they provide extra energy to the system. Enzymes also cannot alter the substrate concentration. Catalytic action will never be able to influence the equilibrium constant or equilibrium concentrations of a reaction.
Enzymes speed up reactions by lowering the energy required to begin the reaction (the activation energy). They do not have any direct effect on the change in free energy, nor do they provide extra energy to the system. Enzymes also cannot alter the substrate concentration. Catalytic action will never be able to influence the equilibrium constant or equilibrium concentrations of a reaction.
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Which of the following is not typical of an enzyme?
Which of the following is not typical of an enzyme?
Enzymes are used to increase the rate of a reaction. This is accomplished by lowering the activation energy required for substrates to react, often by altering the transition state. Enzymes do not, however, increase the amount of products formed; they simply help the equilibrium be reached more quickly. In other words, enzymes change the rate of a reaction, but not the equilibrium.
Enzymes are used to increase the rate of a reaction. This is accomplished by lowering the activation energy required for substrates to react, often by altering the transition state. Enzymes do not, however, increase the amount of products formed; they simply help the equilibrium be reached more quickly. In other words, enzymes change the rate of a reaction, but not the equilibrium.
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Which of the following will not result from enzymatic activity in a cell?
Which of the following will not result from enzymatic activity in a cell?
Although it may seem counterintuitive, both the forward and reverse reaction rates are sped up by an enzyme. Without this happening, more product would be created by the enzyme than normal, and enzymes DO NOT increase the amount of products created in a system. Enzymes also do not affect the enthalpy of a reaction, so making a reaction more exothermic is not an acceptable answer.
Although it may seem counterintuitive, both the forward and reverse reaction rates are sped up by an enzyme. Without this happening, more product would be created by the enzyme than normal, and enzymes DO NOT increase the amount of products created in a system. Enzymes also do not affect the enthalpy of a reaction, so making a reaction more exothermic is not an acceptable answer.
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What is the group of proteins needed for cell synthesis in bacteria called?
What is the group of proteins needed for cell synthesis in bacteria called?
The replisome is coded for by essential genes passed between bacteria. Without these proteins, a bacterial cell cannot form more cells. "-some" stands for a collection of proteins that function together, and "repli-" for replication. The TATA box is a DNA sequence involved in the indication of the start of a gene, chromosomes are collected strands of genetic material, the spliceosome removes introns from pre-mRNA, but this, along with all post translational modification, only occurs in eukaryotes. The cytosome is the part of the cell that is specialized for phagocytosis.
The replisome is coded for by essential genes passed between bacteria. Without these proteins, a bacterial cell cannot form more cells. "-some" stands for a collection of proteins that function together, and "repli-" for replication. The TATA box is a DNA sequence involved in the indication of the start of a gene, chromosomes are collected strands of genetic material, the spliceosome removes introns from pre-mRNA, but this, along with all post translational modification, only occurs in eukaryotes. The cytosome is the part of the cell that is specialized for phagocytosis.
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After an unknown compound is added to an enzyme-mediated reaction mixture, the enzyme rate is reduced but 
remains constant. Which of the following best explains this situation?
After an unknown compound is added to an enzyme-mediated reaction mixture, the enzyme rate is reduced but
The Michaelis-Menten constant 
is temperature and pH dependent. It is the substrate concentration at which the rate is half of 
. Noncompetitive inhibitors alter the shape of an enzyme, slowing down the reaction rate without affecting 
. Competitive inhibitor bind to enzyme active sites, increasing the 
.
The Michaelis-Menten constant
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The Gila monster, H. suspectum, produces a neurotoxic venom containing helothermine, which causes lethargy and partial paralysis of the limbs. Considering that this toxin partially inhibits voluntary muscle contraction, which of the following is the most likely mechanism?
The Gila monster, H. suspectum, produces a neurotoxic venom containing helothermine, which causes lethargy and partial paralysis of the limbs. Considering that this toxin partially inhibits voluntary muscle contraction, which of the following is the most likely mechanism?
Helothermine is a peptide toxin that inhibits calcium channels in the cerebellar granule cells. The cerebellum is the part of the brain that controls voluntary muscle movements such as those in the limbs, and the toxin must be inhibiting very specifically to cause those two symptoms and not total paralysis or other problems.
Helothermine is a peptide toxin that inhibits calcium channels in the cerebellar granule cells. The cerebellum is the part of the brain that controls voluntary muscle movements such as those in the limbs, and the toxin must be inhibiting very specifically to cause those two symptoms and not total paralysis or other problems.
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Proteins have many functions. Which of the following can be functions of proteins?
I. Enzymes
II. Transcriptional regulators
III. Structural proteins
IV. Hormones
Proteins have many functions. Which of the following can be functions of proteins?
I. Enzymes
II. Transcriptional regulators
III. Structural proteins
IV. Hormones
Proteins serve all of these functions and many more. Most enzymes are proteins, which help to catalyze spontaneous reactions. Ribozymes can also serve this function but are instead made out of RNA. Proteins can act as transcriptional regulators which can turn on or off gene transcription. Structural proteins, such as actin, can help to maintain the shape of a cell. Other small proteins, such as insulin, can act as hormones which can diffuse throughout the body relaying important messages.
Proteins serve all of these functions and many more. Most enzymes are proteins, which help to catalyze spontaneous reactions. Ribozymes can also serve this function but are instead made out of RNA. Proteins can act as transcriptional regulators which can turn on or off gene transcription. Structural proteins, such as actin, can help to maintain the shape of a cell. Other small proteins, such as insulin, can act as hormones which can diffuse throughout the body relaying important messages.
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Enzymes come in many shapes and sizes and serve various functions. Which of the following are characteristics of enzymes?
I. Allow non-spontaneous reactions to occur
II. Bring substrates together in the proper orientation for catalysis
III. Reduce the activation energy of the reaction
IV. Reduce the free energy change of reaction
Enzymes come in many shapes and sizes and serve various functions. Which of the following are characteristics of enzymes?
I. Allow non-spontaneous reactions to occur
II. Bring substrates together in the proper orientation for catalysis
III. Reduce the activation energy of the reaction
IV. Reduce the free energy change of reaction
Enzymes are capable of many things but they are not able to help facilitate non-spontaneous reactions. An enzyme can however help spontaneous reactions occur much faster. Enzymes help catalyze reactions by orienting substrates in the necessary positions for reaction. Without enzymes, substrates would have to bump into each other with the exact necessary orientation and energy, which is very rare. Enzymes are capable of lowering the activation energy of a reaction but have no effect on the overall free energy change of a reaction; recall the distinction between kinetics and thermodynamics.
Enzymes are capable of many things but they are not able to help facilitate non-spontaneous reactions. An enzyme can however help spontaneous reactions occur much faster. Enzymes help catalyze reactions by orienting substrates in the necessary positions for reaction. Without enzymes, substrates would have to bump into each other with the exact necessary orientation and energy, which is very rare. Enzymes are capable of lowering the activation energy of a reaction but have no effect on the overall free energy change of a reaction; recall the distinction between kinetics and thermodynamics.
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Which of the following are true about enzyme inhibition?
I. Enzymes can be inhibited by end-products of that enzymatic pathway
II. Competitive inhibitors can lower an enzymes 
III. Non-competitive inhibitors inhibit enzyme action by binding to a site other than the active site
IV. Non-competitive inhibitors can lower an enzymes 
Which of the following are true about enzyme inhibition?
I. Enzymes can be inhibited by end-products of that enzymatic pathway
II. Competitive inhibitors can lower an enzymes
III. Non-competitive inhibitors inhibit enzyme action by binding to a site other than the active site
IV. Non-competitive inhibitors can lower an enzymes
Enzymes can be inhibited by end products of an enzymatic pathway. This is illustrated in the case of ATP acting as an inhibitor of enzymes found within the pathway for ATP production. This prevents the overabundance of a certain end-product. Competitive inhibitors do not lower an enzymes 
. Maximal velocity can still be achieved in the presence of a competitive inhibitor, but it requires a higher concentration of substrate to do so. Non-competitive inhibitors can lower an enzymes . This is because non-competitive inhibitors bind to sites other than the active site, known as allosteric binding sites.
Enzymes can be inhibited by end products of an enzymatic pathway. This is illustrated in the case of ATP acting as an inhibitor of enzymes found within the pathway for ATP production. This prevents the overabundance of a certain end-product. Competitive inhibitors do not lower an enzymes
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Which of the following statements about the general roles and properties of biological enzymes is not true?
Which of the following statements about the general roles and properties of biological enzymes is not true?
Enzymes are not consumed or used up during a reaction, rather they simply increase the rate of reaction by making it "easier" for the reaction to occur, i.e. lowering the activation energy. Equilibrium is not altered by the presence of an enzyme. There are examples of catalytic RNA molecules (ribosomes) and therefore biological catalysts are not always proteins.
Enzymes are not consumed or used up during a reaction, rather they simply increase the rate of reaction by making it "easier" for the reaction to occur, i.e. lowering the activation energy. Equilibrium is not altered by the presence of an enzyme. There are examples of catalytic RNA molecules (ribosomes) and therefore biological catalysts are not always proteins.
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The activity of certain enzymes can be modulated via effector binding to __________ sites; regulation at these sites often results in a conformational changes that alters the activity level of the enzyme either positively or negatively without the effector binding to the active site.
The activity of certain enzymes can be modulated via effector binding to __________ sites; regulation at these sites often results in a conformational changes that alters the activity level of the enzyme either positively or negatively without the effector binding to the active site.
The definition of allosteric enzyme regulation is that a cofactor or molecule binds and interacts with a site on the enzyme other than the active site. This often changes something about the shape of the enzyme which changes something about its interaction with its substrate, thus modulating how active the enzyme is.
The definition of allosteric enzyme regulation is that a cofactor or molecule binds and interacts with a site on the enzyme other than the active site. This often changes something about the shape of the enzyme which changes something about its interaction with its substrate, thus modulating how active the enzyme is.
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I. Cytochrome c oxidase, an important enzyme in the electron transport chain, uses copper ions as cofactors.
II. Cofactors are always metal ions, such as iron and copper.
III. An enzyme will have a binding site specific for one type of cofactor.
IV. Some cofactors can be formed from vitamins C, B12, and K, and these cofactors then serve to facilitate electron transport in many biological processes.
I. Cytochrome c oxidase, an important enzyme in the electron transport chain, uses copper ions as cofactors.
II. Cofactors are always metal ions, such as iron and copper.
III. An enzyme will have a binding site specific for one type of cofactor.
IV. Some cofactors can be formed from vitamins C, B12, and K, and these cofactors then serve to facilitate electron transport in many biological processes.
Cofactors are not always metal ions, nor are enzymes limited to interactions with a single cofactor. Cofactors can be metal ions, but they can also be organic molecules, and an enzyme may be able to bind and be altered by many of them. The other two statements are true.
Cofactors are not always metal ions, nor are enzymes limited to interactions with a single cofactor. Cofactors can be metal ions, but they can also be organic molecules, and an enzyme may be able to bind and be altered by many of them. The other two statements are true.
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