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Questions and Answers
What are enzymes?
What are enzymes?
What is the name of an enzyme that catalyzes the hydrolysis of sucrose?
What is the name of an enzyme that catalyzes the hydrolysis of sucrose?
Sucrase
Match the enzyme group with the type of reaction catalyzed:
Match the enzyme group with the type of reaction catalyzed:
Oxidoreductases = Transfer of O & H atoms between substances Transferases = Transfer of a chemical group from 1 substance to another Hydrolases = Hydrolysis reactions Lyases = Addition or removal of a chemical group other than by hydrolysis Isomerases = The rearrangement of groups within a molecule Ligases = Formation of bonds between 2 molecules using energy derived from the breakdown of ATP
Most enzymes work best at a pH close to neutral, around pH_.
Most enzymes work best at a pH close to neutral, around pH_.
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Enzymes show little activity at high temperatures.
Enzymes show little activity at high temperatures.
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What are enzymes primarily made of?
What are enzymes primarily made of?
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What are the molecules at the beginning of an enzymatic process called?
What are the molecules at the beginning of an enzymatic process called?
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Enzymes catalyze almost all chemical reactions taking place in the cells.
Enzymes catalyze almost all chemical reactions taking place in the cells.
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Match the following enzyme groups with the type of reaction they catalyze:
Match the following enzyme groups with the type of reaction they catalyze:
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Enzymes increase the rate of chemical reactions by lowering the ______ of activation.
Enzymes increase the rate of chemical reactions by lowering the ______ of activation.
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Study Notes
Enzymes as Biological Catalysts
- Enzymes are biomolecules that catalyze chemical reactions, increasing their rates
- They are proteins, except for a few RNA molecules
- Enzymes convert substrates into products, remaining unchanged by the chemical reaction
- They are present in all living cells and are biological catalysts
Naming Enzymes
- Enzyme names typically end in "-ase"
- The name identifies the reacting substance and describes the function of the enzyme
- Examples: sucrase (catalyzes hydrolysis of sucrose), oxidases (catalyze oxidation reactions), pepsin and trypsin (digestion enzymes)
Classification of Enzymes
- Oxidoreductases: transfer of O & H atoms between substances (e.g., dehydrogenases, oxidases)
- Transferases: transfer of a chemical group from one substance to another (e.g., transaminases, phosphorylases)
- Hydrolases: hydrolysis reactions (e.g., peptidases, lipases, phosphatases)
- Lyases: addition or removal of a chemical group other than by hydrolysis (e.g., decarboxylases)
- Isomerases: rearrangement of groups within a molecule (e.g., isomerases, mutases)
- Ligases: formation of bonds between two molecules using energy from ATP breakdown (e.g., synthetases)
Active Site of an Enzyme
- The active site is a region within an enzyme that fits the shape of substrate molecules
- Amino acid side-chains align to bind the substrate through H-bonding, salt-bridges, hydrophobic interactions, etc.
- Products are released when the reaction is complete, no longer fitting well in the active site
Enzyme Specificity
- Enzymes have varying degrees of specificity for substrates
- They may recognize and catalyze a single substrate, a group of similar substrates, or a particular type of bond
Lock-and-Key Model
- The active site has a rigid shape, and only substrates with the matching shape can fit
- The substrate is a key that fits the lock of the active site
- (Note: This is an older model and does not work for all enzymes)
Enzyme-Catalyzed Reactions
- Enzymes increase the rates of chemical reactions by lowering the energy of activation
- They catalyze nearly all chemical reactions in the cells of the body
- The overall reaction for the conversion of substrate to product can be written as: E + S ES → E + P
Factors Affecting Enzyme Function
- Temperature: optimum temperature for human enzymes is usually 37°C
- pH: changes in pH can disrupt bonds and 3D shape, affecting enzyme activity
- Enzyme concentration: increasing enzyme concentration increases the rate of reaction
- Substrate concentration: increasing substrate concentration increases the rate of reaction, but eventually levels off when the enzyme is saturated
Inhibitors and Regulation
- Inhibitors: molecules that reduce enzyme activity
- Competitive inhibition: inhibitor and substrate compete for the active site
- Non-competitive inhibition: inhibitor binds to an allosteric site, changing the enzyme's shape
- Irreversible inhibition: inhibitor destroys enzyme activity, usually by bonding with side-chain groups in the active site
- Feedback inhibition: the final product of a pathway inhibits an earlier step in the pathway, regulating production
Enzymes as Biological Catalysts
- Enzymes are biomolecules that catalyze chemical reactions, increasing their rates
- They are proteins, except for a few RNA molecules
- Enzymes convert substrates into products, remaining unchanged by the chemical reaction
- They are present in all living cells and are biological catalysts
Naming Enzymes
- Enzyme names typically end in "-ase"
- The name identifies the reacting substance and describes the function of the enzyme
- Examples: sucrase (catalyzes hydrolysis of sucrose), oxidases (catalyze oxidation reactions), pepsin and trypsin (digestion enzymes)
Classification of Enzymes
- Oxidoreductases: transfer of O & H atoms between substances (e.g., dehydrogenases, oxidases)
- Transferases: transfer of a chemical group from one substance to another (e.g., transaminases, phosphorylases)
- Hydrolases: hydrolysis reactions (e.g., peptidases, lipases, phosphatases)
- Lyases: addition or removal of a chemical group other than by hydrolysis (e.g., decarboxylases)
- Isomerases: rearrangement of groups within a molecule (e.g., isomerases, mutases)
- Ligases: formation of bonds between two molecules using energy from ATP breakdown (e.g., synthetases)
Active Site of an Enzyme
- The active site is a region within an enzyme that fits the shape of substrate molecules
- Amino acid side-chains align to bind the substrate through H-bonding, salt-bridges, hydrophobic interactions, etc.
- Products are released when the reaction is complete, no longer fitting well in the active site
Enzyme Specificity
- Enzymes have varying degrees of specificity for substrates
- They may recognize and catalyze a single substrate, a group of similar substrates, or a particular type of bond
Lock-and-Key Model
- The active site has a rigid shape, and only substrates with the matching shape can fit
- The substrate is a key that fits the lock of the active site
- (Note: This is an older model and does not work for all enzymes)
Enzyme-Catalyzed Reactions
- Enzymes increase the rates of chemical reactions by lowering the energy of activation
- They catalyze nearly all chemical reactions in the cells of the body
- The overall reaction for the conversion of substrate to product can be written as: E + S ES → E + P
Factors Affecting Enzyme Function
- Temperature: optimum temperature for human enzymes is usually 37°C
- pH: changes in pH can disrupt bonds and 3D shape, affecting enzyme activity
- Enzyme concentration: increasing enzyme concentration increases the rate of reaction
- Substrate concentration: increasing substrate concentration increases the rate of reaction, but eventually levels off when the enzyme is saturated
Inhibitors and Regulation
- Inhibitors: molecules that reduce enzyme activity
- Competitive inhibition: inhibitor and substrate compete for the active site
- Non-competitive inhibition: inhibitor binds to an allosteric site, changing the enzyme's shape
- Irreversible inhibition: inhibitor destroys enzyme activity, usually by bonding with side-chain groups in the active site
- Feedback inhibition: the final product of a pathway inhibits an earlier step in the pathway, regulating production
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Description
Learn about enzymes, biomolecules that catalyze chemical reactions, and their roles in cells. Understand how enzymes convert substrates into products and their importance in living cells.
