Enzymes MDCAT Quiz: Enzymes are biological catalysts that speed up chemical reactions in living organisms. They play a vital role in nearly all physiological processes, such as digestion, metabolism, and cellular signaling. Enzymes are proteins, though some RNA molecules also have catalytic activity. The concept of enzymes is very essential for MDCAT students in the subject areas of biochemistry and physiology.
Structure of Enzymes:
Enzymes are usually large proteins, consisting of amino acid chains folded into specific three-dimensional shapes. The active site is the region of the enzyme that binds to the substrate, which is the molecule upon which the enzyme acts. The structure of the enzyme is highly specific to the substrate, and this specificity is important for the proper functioning of the enzyme. Activity of the enzyme may be influenced by temperature, pH, and the presence of inhibitors or activators.
Examples:
The enzyme amylase has an active site that specifically binds to the starch molecules, helping in their breakdown to simpler sugars.
Mechanism of Action:
Enzymes catalyze reactions by reducing the activation energy required for the reaction to take place. They form an enzyme-substrate complex, wherein the enzyme temporarily binds to the substrate, and this facilitates the conversion of the substrate into products. There exist two major models to explain enzyme action: the lock and key model and the induced fit model. In the lock and key model, the enzyme’s active site perfectly fits the substrate just like a key fitting into a lock. In the induced fit model, the enzyme’s active site undergoes a slight conformational change upon substrate binding.
Example:
Zinc is a cofactor for the enzyme carbonic anhydrase, which participates in the regulation of blood pH.
Enzyme Kinetics:
Enzyme kinetics is the study of the rates of enzyme-catalysed reactions. The Michaelis-Menten equation relates the rate of the reaction with the concentration of the substrate. The Km value, or Michaelis constant, is a substrate concentration when the rate of reaction reaches half of its maximal value (Vmax). Lower Km values indicate higher affinity between the enzyme and substrate.
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Free Flashcard: Key Insights on Enzymes
The free Flashcard set on enzymes covers important aspects, including structure, classification, and kinetics. Use these flashcards to better prepare and be confident in dealing with questions related to the topic during the MDCAT exam.
Enzymes act as __________ in biochemical reactions.
Catalysts
The specific region where the substrate binds to the enzyme is called __________.
Active site
Enzymes __________ the activation energy of a chemical reaction.
Lower
Enzyme activity can be affected by __________.
Temperature
The substance upon which an enzyme acts is known as the __________.
Substrate
Enzymes are typically composed of __________.
Proteins
The "lock and key" model describes the __________ of enzyme-substrate interaction.
Specificity
Enzymes can be denatured by __________.
High temperature
The enzyme that breaks down hydrogen peroxide is __________.
Catalase
The pH level can affect the __________ of enzymes.
Activity
The enzyme involved in the breakdown of starch is __________.
Amylase
The enzyme responsible for breaking down proteins in the stomach is __________.
Pepsin
The process by which enzymes speed up reactions is called __________.
Catalysis
Enzyme inhibitors can be __________ or __________.
Reversible, irreversible
The region on the enzyme that changes shape upon substrate binding is the __________.
Active site
Enzymes are __________ at the end of the reaction.
Unchanged
The process of forming a complex between an enzyme and its substrate is known as __________.
Enzyme-substrate complex
Enzymes work best at their __________ temperature.
Optimal
Enzyme activity can be increased by __________.
Substrate concentration
The reaction rate of enzymes typically follows a __________ curve.
Michaelis-Menten
Enzyme activity can be influenced by __________.
Concentration of coenzymes
__________ are non-protein molecules that assist in enzyme function.
Coenzymes
The enzyme that helps in the digestion of fats is __________.
Lipase
The maximum rate at which an enzyme can catalyze a reaction is called __________.
Vmax
__________ enzymes have more than one polypeptide chain.
Multimeric
Enzyme specificity is determined by the __________.
Shape of the active site
Enzyme inhibitors can reduce enzyme activity by __________.
Blocking the active site
__________ enzymes are involved in the breakdown of biological molecules.
Catabolic
The process by which an enzyme loses its activity is called __________.
Denaturation
__________ is a cofactor that helps in the functioning of enzymes.
Metal ions
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