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Questions and Answers
What type of enzyme catalyzes oxidation/reduction reactions?
What type of enzyme catalyzes oxidation/reduction reactions?
- Hydrolases
- Oxidoreductases (correct)
- Isomerases
- Transferases
What is the primary function of Trypsin?
What is the primary function of Trypsin?
- To form two products from a substrate by hydrolysis (correct)
- To isomerize a single molecule
- To transfer a functional group from one substance to another
- To catalyze oxidation/reduction reactions
What type of enzyme is Aldolase?
What type of enzyme is Aldolase?
- Transferase
- Oxidoreductase
- Lyase (correct)
- Hydrolase
What is the primary function of tripeptide aminopeptidase?
What is the primary function of tripeptide aminopeptidase?
What type of enzyme is Lactate Dehydrogenase?
What type of enzyme is Lactate Dehydrogenase?
What type of enzyme is Alanine Amino Transferase?
What type of enzyme is Alanine Amino Transferase?
What is the reason why an ES complex will be in an energetic minimum?
What is the reason why an ES complex will be in an energetic minimum?
What is the characteristic of enzymes that act on only a few related molecules?
What is the characteristic of enzymes that act on only a few related molecules?
What determines the specificity of an enzyme?
What determines the specificity of an enzyme?
What is the name of the classification scheme established by the I.U.B. Commission on Enzymes?
What is the name of the classification scheme established by the I.U.B. Commission on Enzymes?
What is the purpose of the 4-digit number assigned to each enzyme?
What is the purpose of the 4-digit number assigned to each enzyme?
What is the characteristic of enzymes that act on only one substrate?
What is the characteristic of enzymes that act on only one substrate?
What is the effect of high temperatures on the structure of enzymes?
What is the effect of high temperatures on the structure of enzymes?
What is the result of changes in ionization state of active site residues in an enzyme?
What is the result of changes in ionization state of active site residues in an enzyme?
What is the effect of pH on enzyme-catalysed reactions?
What is the effect of pH on enzyme-catalysed reactions?
What type of bond is formed by the action of ligases?
What type of bond is formed by the action of ligases?
What type of enzyme catalyzes isomerization reactions?
What type of enzyme catalyzes isomerization reactions?
What is the effect of unfolding of an enzyme on its activity?
What is the effect of unfolding of an enzyme on its activity?
What type of enzyme catalyzes the formation of two products from a substrate by hydrolysis?
What type of enzyme catalyzes the formation of two products from a substrate by hydrolysis?
Which of the following enzymes catalyzes the transfer of functional groups from one substance to another?
Which of the following enzymes catalyzes the transfer of functional groups from one substance to another?
What type of bond is formed by Ligases during the synthesis of two molecules?
What type of bond is formed by Ligases during the synthesis of two molecules?
Which enzyme catalyzes the oxidation and reduction of lactate to form pyruvate?
Which enzyme catalyzes the oxidation and reduction of lactate to form pyruvate?
What type of reaction is catalyzed by Lyases?
What type of reaction is catalyzed by Lyases?
Which enzyme catalyzes the breakdown of a peptide bond?
Which enzyme catalyzes the breakdown of a peptide bond?
What is the energy source for the synthesis of two molecules by Ligases?
What is the energy source for the synthesis of two molecules by Ligases?
What is the steady-state condition for the enzyme-substrate complex ES?
What is the steady-state condition for the enzyme-substrate complex ES?
Which enzyme is responsible for the transfer of an amino group from glutamate to form α-ketoglutarate?
Which enzyme is responsible for the transfer of an amino group from glutamate to form α-ketoglutarate?
What is the byproduct of the reaction catalyzed by Hydrolases?
What is the byproduct of the reaction catalyzed by Hydrolases?
What is the Michaelis constant Km equal to?
What is the Michaelis constant Km equal to?
Which enzyme is responsible for the formation of a new C-C bond?
Which enzyme is responsible for the formation of a new C-C bond?
What is the significance of Vmax in the Michaelis-Menten equation?
What is the significance of Vmax in the Michaelis-Menten equation?
What is the relationship between Km and [S] when V0 = 0.5Vmax?
What is the relationship between Km and [S] when V0 = 0.5Vmax?
What is the unit of V0 in the Michaelis-Menten equation?
What is the unit of V0 in the Michaelis-Menten equation?
What is the significance of the steady-state assumption in the Michaelis-Menten equation?
What is the significance of the steady-state assumption in the Michaelis-Menten equation?
What is the effect of increasing the substrate concentration [S] on the initial reaction velocity V0?
What is the effect of increasing the substrate concentration [S] on the initial reaction velocity V0?
What is the relationship between V0 and Vmax when [S] = Km?
What is the relationship between V0 and Vmax when [S] = Km?
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Study Notes
Enzyme Specificity
- Enzymes usually catalyze only one type of reaction and act on only a few related molecules.
- Substrate specificity is determined by the shape and charge of the active site, which allows only the correct substrate to fit.
- Enzymes can be highly specific, acting on only one substrate or one isomer of a compound.
Classification of Enzymes
- Enzymes are classified into six main classes based on the type of reaction they catalyze.
- Each class is further divided into subgroups according to their substrate or source.
- Each enzyme is identified by a unique 4-digit number.
Types of Enzymes
Oxidoreductases
- Catalyze oxidation/reduction reactions, transferring H and O atoms or electrons from one substance to another.
- Example: Lactate Dehydrogenase.
Transferases
- Catalyze the transfer of functional groups from one substance to another.
- Example: Alanine Aminotransferase.
Hydrolases
- Catalyze the formation of two products from a substrate by hydrolysis (splitting using water).
- Example: Trypsin.
Lyases
- Catalyze non-hydrolytic addition or removal of groups from substrates, cleaving C-C, C-N, C-O, or C-S bonds.
- Example: Aldolase.
Isomerases
- Catalyze isomerization changes within a single molecule.
- Example: Phosphoglucose Isomerase (Phosphohexose Isomerase).
Ligases
- Join together two molecules by synthesizing new C-O, C-S, C-N, or C-C bonds with simultaneous breakdown of ATP.
- Example: DNA Ligase.
Properties of Enzymes
Effects of Temperature
- Enzyme structure is stabilized by many weak bonds, which can be easily broken by heat, leading to a disorganized or tangled structure and loss of catalytic activity.
Effects of pH
- Changes in pH can have direct effects on the rate of enzyme-catalyzed reactions, affecting substrate binding, active site residues, and enzyme unfolding.
- pH changes can lead to changes in ionization states, additional acid/base catalysis, and altered substrate binding.
Enzyme Kinetics
- The Michaelis-Menten equation describes the kinetics of enzyme-catalyzed reactions.
- The equation relates the initial reaction velocity (V0) to the substrate concentration ([S]), the maximal velocity (Vmax), and the Michaelis constant (Km).
- When V0 = 0.5Vmax, the substrate concentration [S] is equal to the Michaelis constant Km.
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