Biomolecules Catalyzing The Reactions
Biomolecules - Catalyzing the Reactions
Welcome to the lecture on Biomolecules.
Today, we will discuss the role of catalysts in biochemical reactions.
Catalysts are substances that speed up chemical reactions without being consumed in the process.
They lower the activation energy required for the reaction to occur.
Enzymes are biological catalysts that play a crucial role in biochemical reactions.
Biomolecules Catalyzing The Reactions
Enzymes
Enzymes are protein molecules that act as biological catalysts.
They are highly specific in nature and catalyze specific reactions.
Enzyme names usually end with the suffix “-ase”.
For example, the enzyme that breaks down starch is called amylase.
Enzymes speed up reactions by lowering the activation energy.
Biomolecules Catalyzing The Reactions
Active Site
Enzymes have a specific region called the active site.
Substrates, the reactant molecules, bind to this active site.
The active site undergoes a conformational change to create an optimal environment for the reaction to occur.
Enzymes are not consumed in the reaction and can be reused.
Biomolecules Catalyzing The Reactions
Lock and Key Model
The lock and key model describes enzyme-substrate specificity.
According to this model, the enzyme’s active site has a specific shape that only allows substrates with a complementary shape to bind.
Only when the substrate fits perfectly into the active site, the reaction can occur.
Biomolecules Catalyzing The Reactions
Induced Fit Model
The induced fit model expands on the lock and key model.
It suggests that the active site is flexible and can change its shape slightly to accommodate the substrate.
When the substrate binds, both the enzyme and substrate undergo conformational changes, leading to an optimal fit.
Biomolecules Catalyzing The Reactions
Factors Affecting Enzyme Activity
Various factors can affect enzyme activity.
Temperature
: Enzymes have an optimal temperature at which they function best. Deviating from this temperature can denature the enzyme.
pH
: Enzymes also have an optimal pH range. Deviating from this range can affect their activity.
Substrate concentration
: Increasing substrate concentration can increase the rate of reaction until the enzyme reaches its maximum activity.
Biomolecules Catalyzing The Reactions
Competitive Inhibition
Competitive inhibition occurs when a molecule, known as a competitive inhibitor, competes with the substrate for the active site.
The competitive inhibitor has a similar shape to the substrate, allowing it to bind to the active site temporarily.
This prevents the substrate from binding and slows down the reaction.
Biomolecules Catalyzing The Reactions
Non-competitive Inhibition
Non-competitive inhibition occurs when a molecule, known as a non-competitive inhibitor, binds to a site other than the active site.
This binding changes the enzyme’s shape, making the active site less effective in catalyzing the reaction.
Unlike competitive inhibition, non-competitive inhibitors do not compete with the substrate for the active site.
Biomolecules Catalyzing The Reactions
Allosteric Regulation
Enzymes can be regulated by allosteric activators or inhibitors.
Allosteric regulation occurs when a molecule binds to a site other than the active site, causing a conformational change in the enzyme.
This conformational change can either activate or inhibit the enzyme’s activity, depending on the molecule that binds.
Biomolecules Catalyzing The Reactions
Coenzymes and Cofactors
Some enzymes require non-protein molecules called coenzymes or cofactors to function properly.
Coenzymes are organic molecules, often derived from vitamins, that assist the enzyme in catalyzing the reaction.
Cofactors are inorganic ions such as iron, zinc, or magnesium that help the enzyme’s activity.
Biomolecules Catalyzing The Reactions
Biomolecules - Catalyzing the Reactions
Welcome to the lecture on Biomolecules.
Today, we will discuss the role of catalysts in biochemical reactions.
Catalysts are substances that speed up chemical reactions without being consumed in the process.
They lower the activation energy required for the reaction to occur.
Enzymes are biological catalysts that play a crucial role in biochemical reactions.
Biomolecules Catalyzing The Reactions
Enzymes
Enzymes are protein molecules that act as biological catalysts.
They are highly specific in nature and catalyze specific reactions.
Enzyme names usually end with the suffix “-ase”.
For example, the enzyme that breaks down starch is called amylase.
Enzymes speed up reactions by lowering the activation energy.
Biomolecules Catalyzing The Reactions
Active Site
Enzymes have a specific region called the active site.
Substrates, the reactant molecules, bind to this active site.
The active site undergoes a conformational change to create an optimal environment for the reaction to occur.
Enzymes are not consumed in the reaction and can be reused.
Biomolecules Catalyzing The Reactions
Lock and Key Model
The lock and key model describes enzyme-substrate specificity.
According to this model, the enzyme’s active site has a specific shape that only allows substrates with a complementary shape to bind.
Only when the substrate fits perfectly into the active site, the reaction can occur.
Biomolecules Catalyzing The Reactions
Induced Fit Model
The induced fit model expands on the lock and key model.
It suggests that the active site is flexible and can change its shape slightly to accommodate the substrate.
When the substrate binds, both the enzyme and substrate undergo conformational changes, leading to an optimal fit.
Biomolecules Catalyzing The Reactions
Factors Affecting Enzyme Activity
Various factors can affect enzyme activity.
Temperature
: Enzymes have an optimal temperature at which they function best. Deviating from this temperature can denature the enzyme.
pH
: Enzymes also have an optimal pH range. Deviating from this range can affect their activity.
Substrate concentration
: Increasing substrate concentration can increase the rate of reaction until the enzyme reaches its maximum activity.
Biomolecules Catalyzing The Reactions
Competitive Inhibition
Competitive inhibition occurs when a molecule, known as a competitive inhibitor, competes with the substrate for the active site.
The competitive inhibitor has a similar shape to the substrate, allowing it to bind to the active site temporarily.
This prevents the substrate from binding and slows down the reaction.
Biomolecules Catalyzing The Reactions
Non-competitive Inhibition
Non-competitive inhibition occurs when a molecule, known as a non-competitive inhibitor, binds to a site other than the active site.
This binding changes the enzyme’s shape, making the active site less effective in catalyzing the reaction.
Unlike competitive inhibition, non-competitive inhibitors do not compete with the substrate for the active site.
Biomolecules Catalyzing The Reactions
Allosteric Regulation
Enzymes can be regulated by allosteric activators or inhibitors.
Allosteric regulation occurs when a molecule binds to a site other than the active site, causing a conformational change in the enzyme.
This conformational change can either activate or inhibit the enzyme’s activity, depending on the molecule that binds.
Biomolecules Catalyzing The Reactions
Coenzymes and Cofactors
Some enzymes require non-protein molecules called coenzymes or cofactors to function properly.
Coenzymes are organic molecules, often derived from vitamins, that assist the enzyme in catalyzing the reaction.
Cofactors are inorganic ions such as iron, zinc, or magnesium that help the enzyme’s activity.
Biomolecules Catalyzing The Reactions
Allosteric Activation
Allosteric activators bind to an allosteric site on the enzyme.
They induce a conformational change that enhances the enzyme’s activity.
Example
: Phosphofructokinase is an enzyme involved in glycolysis. ATP acts as an allosteric activator, increasing the enzyme’s activity when ATP levels are low.
Biomolecules Catalyzing The Reactions
Allosteric Inhibition
Allosteric inhibitors bind to an allosteric site on the enzyme.
They induce a conformational change that reduces the enzyme’s activity.
Example
: Citrate is an allosteric inhibitor of the enzyme phosphofructokinase. It inhibits glycolysis when citrate levels are high, indicating sufficient ATP production.
Biomolecules Catalyzing The Reactions
Feedback Inhibition
Feedback inhibition is a type of regulation where the product of a metabolic pathway inhibits an earlier enzyme in the pathway.
It helps maintain metabolic balance and prevents excessive product accumulation.
Example
: In the pathway for amino acid synthesis, the final product can inhibit an enzyme in the beginning of the pathway, reducing further synthesis.
Biomolecules Catalyzing The Reactions
Enzyme Kinetics
Enzyme kinetics is the study of the rates of enzyme-catalyzed reactions.
It involves the measurement of reaction rates under varying substrate concentrations.
The Michaelis-Menten equation is commonly used to describe enzyme kinetics.
Biomolecules Catalyzing The Reactions
Michaelis-Menten Equation
The Michaelis-Menten equation relates the initial reaction rate (v0) to the substrate concentration ([S]) and the enzyme’s affinity for the substrate (Km).
v0 = (Vmax * [S]) / (Km + [S])
Vmax is the maximum reaction rate that can be achieved at saturating substrate concentrations.
Biomolecules Catalyzing The Reactions
Lineweaver-Burk Plot
The Lineweaver-Burk plot is a graphical representation of the Michaelis-Menten equation.
It is a double reciprocal plot, with 1/v0 on the y-axis and 1/[S] on the x-axis.
The slope of the line represents the Km/Vmax value.
Biomolecules Catalyzing The Reactions
Enzyme Inhibition
Enzymes can be inhibited by various substances.
Reversible inhibition can be competitive, non-competitive, or uncompetitive.
Irreversible inhibition permanently inactivates the enzyme.
Biomolecules Catalyzing The Reactions
Competitive Inhibition
Competitive inhibitors compete with the substrate for the enzyme’s active site.
They bind reversibly to the active site, preventing the substrate from binding.
This type of inhibition can be overcome by increasing the substrate concentration.
Biomolecules Catalyzing The Reactions
Non-competitive Inhibition
Non-competitive inhibitors bind to a site other than the active site.
They inhibit the enzyme by changing its conformation, reducing its activity.
Increasing the substrate concentration does not overcome this type of inhibition.
Biomolecules Catalyzing The Reactions
Uncompetitive Inhibition
Uncompetitive inhibitors bind to the enzyme-substrate complex.
They inhibit the enzyme by preventing the release of the product.
This type of inhibition can only occur when the substrate is bound to the enzyme.