12 Questions
What is the primary purpose of conformational changes in enzymes upon substrate binding?
To optimize binding and orientation of the substrate
What type of interactions are involved in enzyme-substrate binding?
Hydrogen bonds, ionic interactions, and van der Waals forces
What is the significance of substrate orientation in enzyme-catalyzed reactions?
It ensures that the substrate is in close proximity to the catalytic residues
What is the characteristic of the active site in an enzyme?
It is a highly conserved region on the enzyme surface
What is the primary reason for the high substrate specificity of enzymes?
The combination of binding interactions and active site geometry
What is the role of the serine residue in the active site of serine proteases?
It participates in a nucleophilic attack on the peptide bond
The active site of an enzyme is typically 20-25 Å in diameter.
False
The Michaelis-Menten constant (Km) is a measure of the enzyme's catalytic efficiency.
False
The enzyme-substrate complex is a permanent complex formed between the enzyme and substrate.
False
Enzymes destabilize the transition state, increasing the energy barrier and reducing the reaction rate.
False
Allosteric regulation is a mechanism by which the enzyme's activity is modulated by binding of effectors to the active site.
False
The catalytic step of chymotrypsin involves the formation of a pentahedral intermediate.
False
Study Notes
Enzyme Catalytic Mechanism
Conformational Change
- Enzymes undergo conformational changes upon substrate binding to optimize binding and orientation
- These changes can be induced fit or lock-and-key models
- Conformational changes allow for precise substrate binding and positioning for catalysis
Binding
- Enzymes bind substrates through weak interactions (e.g., hydrogen bonds, ionic interactions, van der Waals forces)
- Binding energy is used to overcome the energy barrier for the reaction
- Optimal binding is crucial for efficient catalysis
Orientation
- Enzymes orient substrates in a specific manner to facilitate catalysis
- Orientation is critical for positioning the substrate for nucleophilic attack or other chemical reactions
- Correct orientation ensures that the substrate is in close proximity to the catalytic residues
Active Site
- The active site is the region on the enzyme where substrate binding and catalysis occur
- The active site is typically a pocket or cleft on the enzyme surface
- The active site is highly conserved and contains specific amino acid residues that participate in catalysis
Substrate Specificity
- Enzymes are highly specific for their substrates due to the precise binding and orientation requirements
- Substrate specificity is achieved through a combination of binding interactions and active site geometry
- Substrate specificity ensures that enzymes only catalyze specific reactions and maintain cellular homeostasis
Serine Proteases
- Serine proteases are a family of enzymes that use a serine residue in the active site for nucleophilic attack
- Examples of serine proteases include chymotrypsin, trypsin, and elastase
- Serine proteases are involved in various physiological processes, including digestion and blood clotting
Catalytic Step of Chymotrypsin
- Chymotrypsin is a serine protease that hydrolyzes peptide bonds
- The catalytic step involves a nucleophilic attack by the serine residue on the carbonyl carbon of the peptide bond
- The reaction proceeds through a tetrahedral intermediate, which is stabilized by the active site residues
- The catalytic step is facilitated by the precise binding and orientation of the substrate in the active site
Learn about the enzyme catalytic mechanism, including conformational changes, binding, orientation, and substrate specificity. Understand the role of the active site and serine proteases in enzyme catalysis.
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