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Questions and Answers
Amylase enzyme acts on α (1,4) glycosidic bond in starch, dextrins and ______.
Amylase enzyme acts on α (1,4) glycosidic bond in starch, dextrins and ______.
glycogen
Lipase enzyme acts on an ______ bond in any type of TAG (Tri Acyl Glycerol).
Lipase enzyme acts on an ______ bond in any type of TAG (Tri Acyl Glycerol).
ester
L-amino acid oxidase enzyme acts only on ______-amino acids but not D-amino acids.
L-amino acid oxidase enzyme acts only on ______-amino acids but not D-amino acids.
L
Zymogens are inactive forms of enzymes that can be activated by cleaving the ______ chain.
Zymogens are inactive forms of enzymes that can be activated by cleaving the ______ chain.
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Oxidases catalyze the removal of hydrogen from a substrate using ______ as a hydrogen acceptor.
Oxidases catalyze the removal of hydrogen from a substrate using ______ as a hydrogen acceptor.
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Dehydrogenases depend on nicotinamide coenzymes like ______ and NADP⁺.
Dehydrogenases depend on nicotinamide coenzymes like ______ and NADP⁺.
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Pathways involving isocitrate dehydrogenase include both oxidation and ______ reactions.
Pathways involving isocitrate dehydrogenase include both oxidation and ______ reactions.
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Classification of enzymes based on the reactions they catalyze results in six major ______.
Classification of enzymes based on the reactions they catalyze results in six major ______.
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Folic acid's active form is called ______.
Folic acid's active form is called ______.
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Vitamin B12 serves as a ______ group carrier.
Vitamin B12 serves as a ______ group carrier.
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Adenosinetriphosphate (ATP) acts as a ______ group donor.
Adenosinetriphosphate (ATP) acts as a ______ group donor.
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UDP-glucose is involved in the synthesis of ______.
UDP-glucose is involved in the synthesis of ______.
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UDP-galactose is important for ______ synthesis.
UDP-galactose is important for ______ synthesis.
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UDP-glucuronic acid is used in the synthesis of ______-polysaccharides.
UDP-glucuronic acid is used in the synthesis of ______-polysaccharides.
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CDP-choline is responsible for the activation of ______ base in lecithin synthesis.
CDP-choline is responsible for the activation of ______ base in lecithin synthesis.
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Active methionine is also known as ______.
Active methionine is also known as ______.
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The decline in the rate of the reaction may be due to depletion of the ______.
The decline in the rate of the reaction may be due to depletion of the ______.
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The optimum temperature for the enzyme is around ______ °C.
The optimum temperature for the enzyme is around ______ °C.
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The catalytic activity may require that an amino-group of the enzyme be in the ______ form.
The catalytic activity may require that an amino-group of the enzyme be in the ______ form.
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Extreme pH levels can lead to ______ of the enzyme.
Extreme pH levels can lead to ______ of the enzyme.
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These enzymes catalyze the linking of 2 compounds coupled to the breaking of a pyrophosphate bond in ______
These enzymes catalyze the linking of 2 compounds coupled to the breaking of a pyrophosphate bond in ______
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For pepsin, the enzyme shows maximum activity at a pH of ______.
For pepsin, the enzyme shows maximum activity at a pH of ______.
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In the presence of oxygen, L-ascorbate is converted into dehydroascorbate and water using __________.
In the presence of oxygen, L-ascorbate is converted into dehydroascorbate and water using __________.
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The rate of the reaction is directly proportional to ______ concentration.
The rate of the reaction is directly proportional to ______ concentration.
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The mechanism of enzyme action can be viewed from two perspectives: energy changes and the ______ of the active site.
The mechanism of enzyme action can be viewed from two perspectives: energy changes and the ______ of the active site.
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Enzymes like lactate dehydrogenase are categorized under __________ conditions.
Enzymes like lactate dehydrogenase are categorized under __________ conditions.
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Ascorbic acid oxidase is an example of an __________ that participates in oxidation reactions.
Ascorbic acid oxidase is an example of an __________ that participates in oxidation reactions.
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Factors affecting enzyme activity include temperature, pH, and substrate ______.
Factors affecting enzyme activity include temperature, pH, and substrate ______.
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All chemical reactions have an energy barrier called the free energy of ______.
All chemical reactions have an energy barrier called the free energy of ______.
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At alkaline pH, an amino-group of the enzyme may become ______.
At alkaline pH, an amino-group of the enzyme may become ______.
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The effect of an enzyme is to decrease the energy of activation by providing an alternate reaction pathway with a lower free energy of ______.
The effect of an enzyme is to decrease the energy of activation by providing an alternate reaction pathway with a lower free energy of ______.
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Glutathione __________ helps detoxify peroxides in the cell.
Glutathione __________ helps detoxify peroxides in the cell.
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A temporary combination between the enzyme and its substrate forms the enzyme-______ complex.
A temporary combination between the enzyme and its substrate forms the enzyme-______ complex.
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Kinases are a type of transferase that specifically transfer __________ groups.
Kinases are a type of transferase that specifically transfer __________ groups.
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Emil Fischer proposed the Lock and ______ theory to explain enzyme specificity.
Emil Fischer proposed the Lock and ______ theory to explain enzyme specificity.
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Hydrolases, such as amylase, are responsible for the __________ of glycosidic bonds.
Hydrolases, such as amylase, are responsible for the __________ of glycosidic bonds.
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Enzymes that create double bonds by removing groups from substrates without hydrolysis are classified as __________.
Enzymes that create double bonds by removing groups from substrates without hydrolysis are classified as __________.
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The induced fit theory postulated by Daniel Koshland suggests that the enzyme changes its ______ upon binding the substrate.
The induced fit theory postulated by Daniel Koshland suggests that the enzyme changes its ______ upon binding the substrate.
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Enzyme kinetics is the study of rates of chemical reactions that involve ______.
Enzyme kinetics is the study of rates of chemical reactions that involve ______.
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Isomerases are enzymes that catalyze the interconversion of optical, geometric, or positional __________.
Isomerases are enzymes that catalyze the interconversion of optical, geometric, or positional __________.
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The type of inhibition that cannot be reversed by increasing substrate concentration is called ______ inhibition.
The type of inhibition that cannot be reversed by increasing substrate concentration is called ______ inhibition.
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Examples of non-specific irreversible inhibitors include heat, X-rays, and heavy metals such as ______.
Examples of non-specific irreversible inhibitors include heat, X-rays, and heavy metals such as ______.
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Organophosphorus compounds like Malathion inhibit the enzyme ______.
Organophosphorus compounds like Malathion inhibit the enzyme ______.
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Toxic gases such as lewisite bind to the ______ group of enzymes, causing inhibition.
Toxic gases such as lewisite bind to the ______ group of enzymes, causing inhibition.
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Fluoride ion (F⁻) can inhibit enzymes by precipitating ______, which is necessary for activation.
Fluoride ion (F⁻) can inhibit enzymes by precipitating ______, which is necessary for activation.
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Cyanide ion (CN⁻) can bind to ______ ions required for the activity of cytochrome oxidase.
Cyanide ion (CN⁻) can bind to ______ ions required for the activity of cytochrome oxidase.
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Isoniazid (INH) combines with ______ phosphate coenzyme, which is required for transaminases enzymes.
Isoniazid (INH) combines with ______ phosphate coenzyme, which is required for transaminases enzymes.
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EDTA forms a chelate with ______ and calcium, inhibiting certain enzymes like enolase.
EDTA forms a chelate with ______ and calcium, inhibiting certain enzymes like enolase.
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Study Notes
Enzymes
- Enzymes are protein catalysts that speed up chemical reactions in biological systems without being changed themselves.
- All enzymes are proteins, except some types of RNA molecules, called ribozymes, which act catalytically, primarily in the cleavage and synthesis of phosphodiester bonds.
- The substrate is the substance upon which an enzyme acts.
- Enzymes can be intracellular, acting within cells (e.g., metabolic enzymes ALT & AST), or extracellular, acting outside the cell (e.g., digestive enzymes pepsin & amylase).
- Enzymes are mainly synthesized in the cytosol or endoplasmic reticulum (ER), although some are synthesized and function in mitochondria.
- Enzymes are found in all body cells and are located in extracellular fluids (e.g., plasma, CSF) and intracellular compartments (e.g., cell membrane, cytosol, mitochondria, lysosomes, microsomes, nucleus).
Enzyme Activity Measurement
- International unit (IU): The amount of enzyme that converts one micromole (µmol) of substrate to product per minute. (1 IU = 1 µmol/min)
- Katal (kat): The amount of enzyme that converts one mole (mol) of substrate to product per second (1 kat = 1 mol/s).
Nature of Enzymes
- Most enzymes are proteins, existing either as simple or holoenzymes.
- Simple enzymes consist solely of a protein molecule.
- Holoenzymes are composed of a protein part (apoenzyme) and a non-protein part (cofactor).
- Cofactors can be organic molecules (like vitamins) or inorganic metal ions (e.g., Fe²⁺, Zn²⁺, Mg²⁺).
Organic Molecules in Enzymes
- Prosthetic groups are small organic molecules covalently bonded to the apoenzyme.
- Coenzymes are small organic molecules noncovalently bound to the apoenzyme.
- Coenzymes are often derivatives of vitamins and can accept or donate specific groups during a reaction.
Enzyme Classification
- Enzymes are divided into classes based on the type of reaction they catalyze.
- Codehydrogenases, group-transferring coenzymes (e.g., NAD+, NADP+, FAD, FMN), and other coenzymes are important enzyme components.
Enzyme Specificity
- Enzymes are highly specific for their substrates.
- Absolute specificity: An enzyme acts upon a single substrate or very closely related substrates.
- Group specificity: An enzyme acts on molecules with specific functional groups (e.g. amino, phosphate).
Enzyme Action
- Active sites: Specialized pockets or clefts on enzymes where substrates bind and reactions occur. The binding site is specific for a given substrate. The catalytic site is where the actual reaction occurs.
- Binding site: Portion of the active site where the substrate binds.
- Catalytic site: Portion of the active site where the reaction with the substrate is catalyzed.
- Enzyme-substrate complex: A temporary complex formed when the enzyme interacts with its substrate at the active site.
- Catalytic efficiency: The enzyme significantly increases the rate of a reaction compared to similar uncatalyzed reactions
- Turnover number: Measures the number of substrate molecules one enzyme molecule converts into product per unit time.
Enzyme Kinetics
- Initial velocity (V0): The rate of a reaction at the start of the process, when little product has been formed.
- Michaelis-Menten equation: Describes the relationship between substrate concentration ([S]) and reaction velocity.
- Km (Michaelis constant): This constant relates to the substrate concentration [S] when the initial velocity (V0) half of Vmax. It reflects the affinity between the enzyme and the substrate.
Enzyme Regulation
- Enzyme activity can be regulated through various mechanisms, such as changes in enzyme amount, allosteric regulation, covalent modification, and presence of inhibitors.
- Covalent modification: Reversible activation/inactivation of enzymes by the addition or removal of chemical groups (e.g., phosphorylation).
- Allosteric control: Binding of molecules to sites other than the active site affects enzyme activity.
- Feedback inhibition: The end product of a metabolic pathway inhibits an enzyme earlier in the pathway.
Inhibitors
- Inhibitors are substances that decrease enzyme activity.
- Competitive inhibition: Inhibitor and substrate compete for the same binding site on the enzyme.
- Non-competitive inhibition: Inhibitor and substrate bind to separate, distinct sites on the enzyme, altering its conformation and reducing catalytic ability.
- Irreversible inhibition: Inhibitor permanently binds to the enzyme, rendering it inactive.
Enzyme Nomenclature and Classification
- Trivial names: Provide little insight into the enzyme’s function, source, or reaction.
- Recommended names: Include the substrate and the type of reaction catalyzed (e.g., sucrase, carbohydrase).
- Enzyme commission numbers: Systematic numerical codes assigning enzymes to specific classes of reactions they catalyze.
Isoenzymes
- Isoenzymes: Multiple forms of an enzyme that catalyze the same reaction but have different amino acid sequences, physical properties, or organ distribution.
- Isoenzymes are useful for diagnostic purposes; changes in levels can indicate particular diseases or tissue damage.
Factors Affecting Enzyme Activity
- Temperature, pH, substrate concentration, enzyme concentration, enzyme inhibitors, coenzymes, and activators are factors influencing enzyme activity rates and optimum conditions.
Plasma Enzymes
- Functional and non-functional plasma enzymes are important indicators for tissue and organ damage.
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Description
Test your knowledge on the functions and mechanisms of various enzymes in biochemistry, including amylase, lipase, and dehydrogenases. This quiz covers aspects like enzyme activation, coenzymes, and important metabolic pathways. Perfect for students studying biochemistry or related fields.
