Enzymes Overview Quiz
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Questions and Answers

What type of reactions are involved in catabolism?

  • Redox reactions
  • Dehydration synthesis reactions
  • Endergonic reactions
  • Hydrolytic reactions (correct)

Which of the following describes the energy characteristics of catabolic reactions?

  • They produce energy without the use of water.
  • They consume more energy than they produce.
  • They are always active at ambient temperature.
  • They produce more energy than they consume. (correct)

What role do enzymes play in metabolic reactions?

  • They substitute for reactants in metabolic pathways.
  • They do not influence the rate of reactions.
  • They help lower the activation energy required. (correct)
  • They increase the activation energy needed for reactions.

Which process is primarily associated with anabolic reactions?

<p>Dehydration synthesis (A)</p> Signup and view all the answers

What is the primary reason that metabolic reactions typically require enzymes?

<p>To lower the activation energy needed to initiate the reactions. (C)</p> Signup and view all the answers

What is the term for the complete, catalytically active enzyme along with its bound coenzyme or metal ion?

<p>Holoenzyme (B)</p> Signup and view all the answers

Which of the following statements about enzymes is true?

<p>Enzymes lower the activation energy for reactions. (D)</p> Signup and view all the answers

What type of reactions do anabolic enzymes catalyse?

<p>Formation of bonds between molecules (B)</p> Signup and view all the answers

Which characteristic of catalysts is described as recoverable, allowing only small amounts to be used in reactions?

<p>Recoverability (D)</p> Signup and view all the answers

What characterizes endergonic reactions?

<p>High input energy with lower energy release after product formation (A)</p> Signup and view all the answers

What drives anabolic reactions according to the provided content?

<p>Utilization of energy from ATP (C)</p> Signup and view all the answers

How do enzymes affect the activation energy of a reaction?

<p>They provide an alternative pathway and lower the activation energy (D)</p> Signup and view all the answers

Which of the following describes a feature of enzymes in biochemical reactions?

<p>They can reach the reaction equilibrium faster. (C)</p> Signup and view all the answers

What is the primary purpose of enzymes in metabolic reactions?

<p>To catalyze reactions without being altered (D)</p> Signup and view all the answers

Which model suggests that an enzyme's active site changes shape to fit the substrate?

<p>Induced Fit Model (C)</p> Signup and view all the answers

Which type of metabolic reaction is characterized by the consumption of more energy than it produces?

<p>Endergonic reactions (C)</p> Signup and view all the answers

What is the role of a catalyst in a biochemical reaction?

<p>It lowers the activation energy and increases reaction rate. (C)</p> Signup and view all the answers

What governs the binding specificity of enzymes to their substrates?

<p>The 3D arrangement of atoms on the active binding site (B)</p> Signup and view all the answers

What happens to the equilibrium of a reaction when an enzyme is present?

<p>The equilibrium is reached faster but remains unchanged (C)</p> Signup and view all the answers

In the 'Lock and Key' model of enzyme action, what is emphasized?

<p>The rigid structure of the enzyme's active site (B)</p> Signup and view all the answers

What is formed when an enzyme binds to its substrate?

<p>A stable enzyme-substrate intermediate (D)</p> Signup and view all the answers

What is the main class of the enzyme with the commission number 2.7.1.1?

<p>Transferase (C)</p> Signup and view all the answers

Which of the following statements accurately describes the function of cofactors?

<p>Cofactors can be non-protein molecules that assist enzymes. (D)</p> Signup and view all the answers

What distinguishes coenzymes from prosthetic groups?

<p>Coenzymes act as temporary carriers, while prosthetic groups remain attached. (A)</p> Signup and view all the answers

Which metal ion is commonly known as a cofactor for enzymatic reactions?

<p>Iron (Fe) (D)</p> Signup and view all the answers

How does the 'active site' of an enzyme influence its function?

<p>It determines which substrate(s) can bind to the enzyme. (B)</p> Signup and view all the answers

What type of cofactor is NAD (Nicotinamide adenine dinucleotide)?

<p>Coenzyme (A)</p> Signup and view all the answers

What is the role of magnesium ions (Mg^2+) in enzymatic reactions?

<p>They help activate the enzyme for catalysis. (D)</p> Signup and view all the answers

Which of the following statements about vitamins as cofactors is correct?

<p>Vitamins can be precursors for organic cofactors. (A)</p> Signup and view all the answers

What does a lower K_M value indicate about an enzyme's affinity for its substrate?

<p>The enzyme has a higher affinity for the substrate. (B)</p> Signup and view all the answers

In a non-competitive inhibition scenario, how does the V_max value change?

<p>Decreases. (A)</p> Signup and view all the answers

What is the effect of uncompetitive inhibition on K_M?

<p>Decreases. (D)</p> Signup and view all the answers

How does the K_M value change in competitive inhibition?

<p>It increases. (B)</p> Signup and view all the answers

What type of complex is formed during uncompetitive inhibition?

<p>Inactive enzyme-substrate-inhibitor complex (ESI). (C)</p> Signup and view all the answers

In competitive inhibition, how is the substrate binding affected?

<p>It is unaffected. (A)</p> Signup and view all the answers

Which inhibitor type stabilizes the enzyme-substrate complex?

<p>Uncompetitive inhibitor. (A)</p> Signup and view all the answers

What does a low K_i value imply about an inhibitor?

<p>It binds tightly to the enzyme. (D)</p> Signup and view all the answers

What is the role of K_M in enzyme catalysis?

<p>To determine the concentration at which half the active sites are occupied. (C)</p> Signup and view all the answers

Which enzyme is targeted by the drug Lisinopril?

<p>Angiotensin-Converting Enzyme (ACE). (D)</p> Signup and view all the answers

In which type of inhibition is V_max decreased but K_M unchanged?

<p>Non-competitive inhibition. (C)</p> Signup and view all the answers

What indicates effective inhibitor drugs for a given enzyme reaction?

<p>Low K_i values. (A)</p> Signup and view all the answers

Which statement is true regarding the effect of different inhibitors on V_max?

<p>Uncompetitive and non-competitive inhibitors decrease V_max. (B)</p> Signup and view all the answers

What does [Vmax]{.math.inline} represent in a reaction?

<p>The maximum velocity at saturating substrate concentrations (A)</p> Signup and view all the answers

How is the Michaelis constant [KM]{.math.inline} defined?

<p>It is the substrate concentration at 50% of [<em>V</em><del>max</del>]{.math.inline} (D)</p> Signup and view all the answers

What type of plot is the Lineweaver-Burk Plot derived from?

<p>Taking the reciprocal of the Michaelis-Menten equation (C)</p> Signup and view all the answers

In an Eadie-Hofstee Plot, what does the y-intercept represent?

<p>The maximum reaction velocity [<em>V</em><del>max</del>]{.math.inline} (B)</p> Signup and view all the answers

What mathematical transformation is used in the Eadie-Hofstee Plot?

<p>Inverting the Michaelis-Menten equation and multiplying by [<em>V</em><del>max</del>]{.math.inline} (D)</p> Signup and view all the answers

Which of the following statements about [KM]{.math.inline} is true?

<p>It relates to the reaction at half maximal velocity (C)</p> Signup and view all the answers

What characteristic does the Michaelis-Menten curve display in its graphical representation?

<p>A rectangular hyperbola shape (D)</p> Signup and view all the answers

What is the significance of the intercept in a Lineweaver-Burk Plot?

<p>It helps to determine [<em>V</em><del>max</del>]{.math.inline} and [<em>K</em><del><em>M</em></del>]{.math.inline} (D)</p> Signup and view all the answers

Flashcards

Catabolism

Breaking down complex molecules into simpler ones, releasing energy in the process. This energy is stored in ATP.

Catabolic Enzymes

Enzymes that speed up catabolic reactions by lowering the activation energy required to break down molecules.

Activation Energy

The minimum energy required for a chemical reaction to occur. Imagine it as the 'kickstart' energy needed to get a reaction going.

Enzymes

Catalysts that accelerate metabolic reactions by lowering activation energy. They act like 'helpers' in speeding up reactions.

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Hydrolysis

A process that uses water to break bonds between molecules. Think of it like adding water to a puzzle to separate the pieces.

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Enzyme Commission Number (EC Number)

A specific sequence of four numbers that classifies an enzyme based on its reaction type and specificity.

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Active Site

The part of an enzyme where the substrate binds and undergoes a chemical reaction.

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Cofactor

A non-protein molecule that is essential for an enzyme's function.

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Coenzyme

A type of cofactor that is loosely bound to an enzyme and can be easily removed.

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Prosthetic Group

A type of cofactor that is tightly bound to an enzyme and is essential for its activity.

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Metal Ion Cofactors

Small inorganic ions that assist in enzyme catalysis, either free or bound to the enzyme.

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Organic/Metallo-Organic Cofactors

Organic molecules that are essential for enzyme function and are usually derived from vitamins.

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Holoenzyme

The complete enzyme along with its coenzyme (non-protein) and/or metal ion, forming the active form.

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Apoenzyme/Apoprotein

The protein portion of an enzyme, inactive on its own.

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Why are enzymes so important?

Enzymes are biological catalysts that accelerate (speed up) biochemical reactions in the body.

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What is metabolism?

The sum of all chemical reactions occurring within a living organism.

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Anabolism/Anabolic reactions

Metabolic reactions that build complex molecules from simpler ones, requiring energy.

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Catabolism/Catabolic reactions

Metabolic reactions that break down complex molecules into simpler ones, releasing energy.

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Endergonic reaction

Reactions that require energy to proceed; input energy is greater than the energy output.

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Exergonic reaction

Reactions that release energy; energy output is greater than the energy input.

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How do enzymes work?

Enzymes lower the activation energy for a reaction. This makes the reaction happen faster.

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Lock and Key Model

A simple model that describes the enzyme-substrate interaction. The substrate fits perfectly into the active site, like a key fitting into a lock.

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Induced Fit Model

A more accurate model of enzyme-substrate interaction. The active site changes shape to fit the substrate, like a flexible glove adjusting to a hand.

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Vmax

The maximum velocity of a reaction when the substrate concentration is at a saturating level. It represents the highest rate at which the enzyme can work.

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Km (Michaelis Constant)

The substrate concentration required to achieve half of the maximum reaction velocity (Vmax). It indicates how efficiently an enzyme can bind and process its substrate.

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Substrate Concentration ([S])

The concentration of the substrate, denoted by [S], which is the amount of the specific molecule that the enzyme acts upon in a reaction.

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Michaelis-Menten Curve

A graphical representation of the relationship between the initial reaction velocity (V0) and the substrate concentration ([S]). It reveals the characteristics of enzyme kinetics, including Vmax and Km.

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Lineweaver-Burk Plot

A linear transformation method to analyze the Michaelis-Menten equation. It involves taking the reciprocal of both sides of the equation. By plotting 1/V against 1/[S], the graph yields a straight line.

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Eadie-Hofstee Plot

Another method to linearize the Michaelis-Menten equation. It plots V against V/[S], resulting in a straight line where the y-intercept represents Vmax, the x-intercept gives Vmax/Km, and the slope equals -Km.

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Km: Significance

Represents the concentration of the substrate at which the reaction velocity is half of the maximum velocity (Vmax). It's an important indicator of an enzyme's affinity for its substrate.

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Michaelis-Menten Equation

The Michaelis-Menten equation describes the relationship between the initial reaction velocity (V0) and the substrate concentration ([S]), providing a mathematical framework for understanding enzyme kinetics.

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Km: Half-Saturation Point

The substrate concentration at which half of the enzyme's active sites are occupied by substrate molecules.

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Vmax (Maximum Velocity)

The maximum rate at which an enzyme can catalyze a reaction under ideal conditions, where all enzyme active sites are saturated with substrate. It reflects the enzyme's catalytic efficiency.

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Competitive Inhibition

A type of enzyme inhibition where the inhibitor competes with the substrate for binding to the enzyme's active site. The inhibitor binds reversibly to the same site as the substrate.

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Non-competitive Inhibition

A type of enzyme inhibition where the inhibitor binds to an enzyme at a site different from the substrate binding site. This binding alters the enzyme's conformation, reducing its activity. The effect is not overcome by increasing substrate concentration.

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Uncompetitive Inhibition

A type of enzyme inhibition where the inhibitor only binds to the enzyme-substrate complex (ES), not the free enzyme (E). This binding prevents the formation of product and reduces both Vmax and Km.

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Competitive Inhibition: Km and Vmax

In competitive inhibition, Km is increased, while Vmax remains unchanged. The inhibitor raises the substrate concentration needed to reach half-maximal velocity.

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Non-competitive Inhibition: Km and Vmax

In non-competitive inhibition, Km remains unchanged, while Vmax is decreased. The inhibitor effectively reduces the overall enzyme activity.

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Uncompetitive Inhibition: Km and Vmax

In uncompetitive inhibition, both Km and Vmax are decreased. The inhibitor effectively lowers the enzyme's affinity for substrate and its maximum catalytic rate.

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Ki (Inhibitor Constant)

A measure of an inhibitor's affinity for an enzyme. A lower Ki value signifies a tighter binding and a more potent inhibitor.

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Enzymes as Drug Targets

Enzymes are crucial drug targets in various diseases because they play vital roles in important metabolic pathways. Inhibiting or activating specific enzymes can effectively treat or control these conditions.

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Angiotensin Converting Enzyme (ACE) Inhibition in Hypertension

The enzyme Angiotensin Converting Enzyme (ACE) is targeted by drugs like Lisinopril to inhibit its activity in the Renin-Angiotensin-Aldosterone System (RAAS) and effectively reduce blood pressure.

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Acetylcholinesterase (AChE) Inhibition in Alzheimer's

The enzyme Acetylcholinesterase (AChE) is targeted by drugs like Donepezil to inhibit its breakdown of acetylcholine, a neurotransmitter involved in memory and cognition.

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Monoamine Oxidase (MAO) Inhibition in Parkinson's

The enzyme Monoamine Oxidase (MAO) is targeted by drugs like Selegiline and Moclobemide to inhibit its breakdown of dopamine, a neurotransmitter involved in movement and mood.

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Cyclooxygenase (COX) Inhibition in Inflammation

Non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen and naproxen inhibit Cyclooxygenase (COX) enzymes, which are involved in producing prostaglandins, inflammatory mediators.

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Study Notes

Enzymes

  • Enzymes are specialized, catalytically active biological macromolecules that act as specific, efficient catalysts of chemical reactions in aqueous solutions.
  • Most enzymes are globular proteins, but some are RNA molecules, like ribozymes and ribosomal RNA nucleotides.
  • Enzymes are named by adding "-ase" to the name of the substrate or a phrase describing the action.
  • Enzymes are classified based on the type of reaction they catalyze (e.g., oxidoreductases, transferases, hydrolases, lyases, isomerases, ligases).
  • Enzymes have a unique 3D structure, including an active site.
  • Enzyme activity can be affected by cofactors which are non-protein components:
    • metal ions (e.g., Mg2+, Zn2+, Fe2+, Ca2+)
    • organic cofactors (coenzymes): often derived from vitamins or other organic molecules.
  • Enzymes are important because they catalyze (speed up) biochemical reactions, which can be slow otherwise and/or would not occur.
  • Metabolism consists of anabolism, which involves building complex molecules from simpler ones, and catabolism, which is the breakdown of complex molecules into simpler ones.
  • Enzymes play a crucial role in both anabolic and catabolic reactions.
  • Enzymes lower the activation energy required for reactions to occur.
  • Enzymes bind to the substrate (reactant) at their active site, forming an enzyme-substrate complex that speeds up the conversion of the substrate to product.
  • The rate of enzyme-catalyzed reactions is affected by several factors, including: temperature, pH, substrate concentration, and enzyme concentration.

Enzyme Kinetics

  • Enzyme kinetics is the study of the rates of enzyme-catalyzed reactions.
  • The Michaelis-Menten equation describes the relationship between substrate concentration, enzyme concentration, and reaction rate.
  • Km is the Michaelis constant, and it represents the substrate concentration at which the reaction rate is half of its maximum.
  • Vmax is the maximum reaction velocity that can be achieved with a saturating amount of substrate.
  • Michaelis-Menten kinetics are often analyzed using a "double-reciprocal plot" (Lineweaver-Burk plot).
  • Enzyme activity can be regulated by inhibitors:
  • Competitive inhibitors block substrate binding to the active site; by increasing substrate concentration, the inhibition can be reversed..
  • Non-competitive inhibitors bind to an allosteric site, which alters the enzyme's active site shape; increasing substrate concentration will not reverse the inhibition, the inhibition will stay.
  • Uncompetitive inhibitors bind only to the enzyme-substrate complex (ES). Changing substrate concentration does not change the inhibition.

Enzyme Inhibition

  • Enzyme inhibitors reduce enzyme activity.
  • Competitive inhibition occurs when inhibitor molecules bind to the active site, preventing substrate binding.
  • Non-competitive inhibition occurs when the inhibitor binds to an allosteric site, changing the enzyme's shape and hindering its function.
  • Uncompetitive inhibition involves inhibitor binding to the enzyme-substrate complex, reducing the enzyme's ability to produce the product.
  • Irreversible inhibitors permanently inactivate enzymes, whereas reversible inhibitors can be released from the enzyme.
  • Enzyme inhibition can be harnessed for therapeutic purposes.

Important Enzymes and Their Functions

(This section requires the data from the OCR'd text) Some examples of specific enzymes and their functions are important in this section but the data is necessary to complete. For example, what enzyme catalyzes what reaction for what disease? Enzyme, substrate, product or reaction are key data points to complete this section.

Enzyme Classification

(This section requires the data from the OCR'd text) Information about enzyme classes as well as type of reactions they catalyze is important here. Add detailed classification examples for a thorough summary.

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