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Questions and Answers
What are enzymes?
What is the name of an enzyme that catalyzes the hydrolysis of sucrose?
Sucrase
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_.
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Enzymes show little activity at high temperatures.
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What are enzymes primarily made of?
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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.
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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.
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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.
