36 Questions
What type of enzyme catalyzes oxidation/reduction reactions?
Oxidoreductases
What is the primary function of Trypsin?
To form two products from a substrate by hydrolysis
What type of enzyme is Aldolase?
Lyase
What is the primary function of tripeptide aminopeptidase?
To cleave amino terminal amino acid from a polypeptide
What type of enzyme is Lactate Dehydrogenase?
Oxidoreductase
What type of enzyme is Alanine Amino Transferase?
Transferase
What is the reason why an ES complex will be in an energetic minimum?
Because the enzyme is complementary to the transition state
What is the characteristic of enzymes that act on only a few related molecules?
Group specificity
What determines the specificity of an enzyme?
The groove or cleft of defined shape on the enzyme
What is the name of the classification scheme established by the I.U.B. Commission on Enzymes?
No specific name is mentioned
What is the purpose of the 4-digit number assigned to each enzyme?
To identify the enzyme uniquely
What is the characteristic of enzymes that act on only one substrate?
Absolute specificity
What is the effect of high temperatures on the structure of enzymes?
The enzyme becomes denatured and inactive.
What is the result of changes in ionization state of active site residues in an enzyme?
The Km of the enzyme changes.
What is the effect of pH on enzyme-catalysed reactions?
It can affect the rate of the reaction by changing the ionization state of the substrate.
What type of bond is formed by the action of ligases?
C-C, C-N, C-O, or C-S bonds are formed.
What type of enzyme catalyzes isomerization reactions?
Isomerases
What is the effect of unfolding of an enzyme on its activity?
The enzyme becomes inactivated.
What type of enzyme catalyzes the formation of two products from a substrate by hydrolysis?
Hydrolases
Which of the following enzymes catalyzes the transfer of functional groups from one substance to another?
Alanine aminotransferase
What type of bond is formed by Ligases during the synthesis of two molecules?
All of the above
Which enzyme catalyzes the oxidation and reduction of lactate to form pyruvate?
Lactate Dehydrogenase
What type of reaction is catalyzed by Lyases?
Non-hydrolytic addition or removal of groups
Which enzyme catalyzes the breakdown of a peptide bond?
Trypsin
What is the energy source for the synthesis of two molecules by Ligases?
ATP
What is the steady-state condition for the enzyme-substrate complex ES?
The rate of formation of ES is equal to the rate of breakdown of ES.
Which enzyme is responsible for the transfer of an amino group from glutamate to form α-ketoglutarate?
Alanine aminotransferase
What is the byproduct of the reaction catalyzed by Hydrolases?
Water
What is the Michaelis constant Km equal to?
(k-1 + k2) / k1
Which enzyme is responsible for the formation of a new C-C bond?
DNA ligase
What is the significance of Vmax in the Michaelis-Menten equation?
It is the maximal velocity of an enzyme-catalyzed reaction.
What is the relationship between Km and [S] when V0 = 0.5Vmax?
Km = [S]
What is the unit of V0 in the Michaelis-Menten equation?
M/min
What is the significance of the steady-state assumption in the Michaelis-Menten equation?
It allows for the estimation of Km and Vmax.
What is the effect of increasing the substrate concentration [S] on the initial reaction velocity V0?
V0 increases and then levels off
What is the relationship between V0 and Vmax when [S] = Km?
V0 = 0.5Vmax
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.
Learn about the specificity of enzymes, how they catalyze reactions, and their complementary nature to the transition state.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
