Enzyme Features and Reactions Quiz
48 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What role do enzymes play in biochemical reactions?

  • They function as inhibitors.
  • They serve as reactants.
  • They act as catalysts. (correct)
  • They convert energy.

In the process of forming an enzyme-substrate complex, what happens to the energy of activation (Ea)?

  • It increases, resulting in slower reactions.
  • It fluctuates based on temperature.
  • It remains unchanged, promoting stability.
  • It decreases, facilitating faster reactions. (correct)

Which model suggests that the enzyme and its substrate have a complementary shape?

  • Competitive Inhibition Model
  • Lock and Key Model (correct)
  • Allosteric Regulation Model
  • Induced-Fit Model

What is the purpose of the numbering system in enzyme classification?

<p>To indicate the type of reaction catalyzed. (B)</p> Signup and view all the answers

What is a prosthetic group in relation to enzymes?

<p>It is a non-protein part necessary for enzyme function. (D)</p> Signup and view all the answers

What describes the Induced-Fit Model of enzyme action?

<p>Binding of the substrate induces a conformational change in the enzyme. (D)</p> Signup and view all the answers

Which of the following is NOT one of the six classes of enzymes as proposed by the International Union of Biochemistry?

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

What happens to the enzyme after it catalyzes a reaction?

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

What characteristic makes phospholipids amphipathic molecules?

<p>They contain both polar and non-polar components. (D)</p> Signup and view all the answers

Why are fats solid at room temperature?

<p>They have a higher melting point than unsaturated fatty acids. (D)</p> Signup and view all the answers

What role does cholesterol play in animal cells?

<p>It serves as a structural component of cell membranes. (A)</p> Signup and view all the answers

Which of the following is a component of the phospholipid bilayer?

<p>Polar phosphate heads. (C)</p> Signup and view all the answers

What is the base structure of sterols?

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

Which of the following describes the primary difference between saturated and unsaturated fatty acids?

<p>Unsaturated fatty acids contain double bonds between carbon atoms. (A)</p> Signup and view all the answers

What is the primary role of allosteric enzymes in metabolic pathways?

<p>To regulate multi-step reaction pathways through feedback inhibition (B)</p> Signup and view all the answers

What is the function of phosphatidylcholine (PC) in cell membranes?

<p>To provide structural integrity and fluidity. (B)</p> Signup and view all the answers

Which molecule is most commonly associated with animals and humans?

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

What initiates the conversion of zymogens to their active forms?

<p>The removal of specific amino acid residues (A)</p> Signup and view all the answers

How do polar regulatory substances affect gene expression?

<p>They activate receptors that initiate a cascade pathway (C)</p> Signup and view all the answers

What structural representation is commonly used for monosaccharides?

<p>Fischer projection structure (B)</p> Signup and view all the answers

Which of the following is a characteristic of the Haworth structure of monosaccharides?

<p>It results from an intramolecular reaction between carbonyl carbon and hydroxyl group (D)</p> Signup and view all the answers

Which type of carbohydrates are the simplest and regarded as the building blocks?

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

What occurs when an allosteric enzyme is deactivated by feedback inhibition?

<p>The enzyme's activity decreases as concentrations of the end product increase (B)</p> Signup and view all the answers

Which structure do monosaccharides adopt in biological systems?

<p>Cyclic forms such as pyran and furan (A)</p> Signup and view all the answers

What does the notation C18:2Δ9,12 indicate about linoleic acid?

<p>It has 18 carbon atoms and two double bonds at positions 9 and 12. (D)</p> Signup and view all the answers

Why do saturated fatty acids have higher melting points than unsaturated fatty acids?

<p>Saturated fatty acids have linear structures promoting better molecular interactions. (B)</p> Signup and view all the answers

What charges do acylglycerides possess?

<p>They are neutral in nature. (A)</p> Signup and view all the answers

What role do diacylglycerides (DAG) play in cells?

<p>They act as signaling molecules in signal transduction. (B)</p> Signup and view all the answers

Which statement is true regarding the structure of unsaturated fatty acids?

<p>They have cis- double bonds that result in a twisted shape. (C)</p> Signup and view all the answers

What is the unique characteristic of naturally-occurring fatty acids?

<p>They have an even number of carbon atoms. (C)</p> Signup and view all the answers

What can be inferred about the melting point of stearic acid compared to linoleic acid?

<p>Stearic acid has a higher melting point than linoleic acid. (A)</p> Signup and view all the answers

What is the primary function of triacylglycerides (TAG)?

<p>To serve as the storage form of fatty acids. (C)</p> Signup and view all the answers

What are co-enzymes derived from?

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

What happens to water-soluble vitamins in the body?

<p>They must be consumed daily (B)</p> Signup and view all the answers

Which function do metal cofactors perform in an enzyme?

<p>Induce specific lock geometry (D)</p> Signup and view all the answers

How does the proximity and orientation effect facilitate catalysis?

<p>By minimizing activation energy (A)</p> Signup and view all the answers

What can prolonged deficiency in vitamin co-enzymes lead to?

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

What is the role of metals as cofactors in enzymes?

<p>Coordinate with amino acids to stabilize enzyme structure (C)</p> Signup and view all the answers

What was traditionally theorized about enzyme-substrate interaction regarding the transition state?

<p>Enzyme distorts the substrate towards the transition state (A)</p> Signup and view all the answers

What does the Collision Theory of Reaction state?

<p>Colliding particles must have proper orientation and energy (C)</p> Signup and view all the answers

What does transition state stabilization involve in enzyme activity?

<p>The transition state making better contacts with the enzyme's active site (B)</p> Signup and view all the answers

Which of the following accurately describes the role of electrostatic catalysis in enzyme activity?

<p>It enhances electrostatic interactions through a desolvation effect (B)</p> Signup and view all the answers

How does acid-base catalysis enhance reaction rates in enzymatic processes?

<p>Through a cascade of protonation and deprotonation events (D)</p> Signup and view all the answers

What characterizes covalent catalysis in enzymatic reactions?

<p>Transient covalent bonds formed during the reaction (C)</p> Signup and view all the answers

Which amino acid residue is known to facilitate acid-base catalysis as a base catalyst?

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

What is a key feature of the enzyme superoxide dismutase's active site?

<p>It has charged functional groups that stabilize intermediates (B)</p> Signup and view all the answers

Which of the following components can form intermediate covalent bonds in enzyme activity?

<p>Prosthetic groups such as B-vitamins and metals (B)</p> Signup and view all the answers

What is the primary result of desolvation in the active site of an enzyme?

<p>Lowered local dielectric constant enhancing electrostatic interactions (B)</p> Signup and view all the answers

Flashcards

What are enzymes?

Enzymes are globular proteins that act as catalysts in biochemical reactions, speeding up the rate of reactions without being consumed in the process.

What is the active site?

The active site is a specific region within an enzyme where the substrate binds and the catalytic reaction occurs.

What is the enzyme-substrate complex (ES)?

The enzyme-substrate complex (ES) is formed when the substrate binds to the active site of the enzyme.

How do enzymes affect the activation energy (Ea)?

Enzymes lower the activation energy (Ea) of a reaction, making it easier for the reaction to occur and speeding it up.

Signup and view all the flashcards

What is the Lock and Key Model of enzyme action?

The Lock and Key Model proposes that the enzyme and substrate have complementary shapes, like a key fitting into a lock, allowing for precise binding.

Signup and view all the flashcards

What is the Induced-Fit Model of enzyme action?

The Induced-Fit Model suggests that the enzyme's active site is flexible and changes shape upon substrate binding, leading to a tighter fit.

Signup and view all the flashcards

What are enzyme prosthetic groups?

Enzyme prosthetic groups are non-protein components essential for the proper functioning of some enzymes.

Signup and view all the flashcards

How are enzymes classified?

Enzymes are classified into six major groups based on the types of reactions they catalyze, according to the International Union of Biochemistry (IUB).

Signup and view all the flashcards

Allosteric Enzymes

Enzymes that can be activated or deactivated by molecules that bind to a site other than the active site.

Signup and view all the flashcards

Feedback Inhibition

A mechanism where the end product of a metabolic pathway inhibits the activity of an enzyme earlier in the pathway.

Signup and view all the flashcards

Proteolytic Modification

Activation of an enzyme by removing a portion of its amino acid sequence.

Signup and view all the flashcards

Zymogen

An inactive precursor of an enzyme.

Signup and view all the flashcards

Transcriptional Control

Regulation of gene expression that determines the amount of enzyme produced.

Signup and view all the flashcards

Monosaccharides

Simple sugar molecules that are the building blocks of carbohydrates.

Signup and view all the flashcards

Fischer Projection

A two-dimensional representation of a monosaccharide that shows the spatial arrangement of its atoms.

Signup and view all the flashcards

Haworth Structure

A three-dimensional representation of a monosaccharide in its cyclic form.

Signup and view all the flashcards

Co-enzymes

Vitamins that serve as co-enzymes, helping enzymes function properly. Examples include vitamin B complex and vitamin C.

Signup and view all the flashcards

Cofactors

Minerals or metals that assist enzymes in their functions. They help enzymes bind to substrates and maintain their shape.

Signup and view all the flashcards

Recommended Dietary Allowance (RDA)

The minimum amount of essential nutrients that should be consumed daily to maintain good health. This can be obtained from food sources or supplementation.

Signup and view all the flashcards

Proximity and Orientation Effect

Enzymes bring substrate molecules together at their active site, increasing the chance of a successful reaction by ensuring proper orientation and proximity.

Signup and view all the flashcards

Transition State Stabilization

The enzyme changes shape to stabilize the transition state, the unstable intermediate form of substrates during a reaction. This lowers the activation energy needed for the reaction.

Signup and view all the flashcards

Collision Theory of Reaction

For a reaction to occur, reacting molecules must collide with enough energy and in the correct orientation.

Signup and view all the flashcards

Activation Energy (Ea)

The minimum amount of energy required for a reaction to occur. Enzymes lower the activation energy, speeding up the reaction.

Signup and view all the flashcards

Enzyme Active Site

The specific region on an enzyme where substrates bind and the catalytic reaction takes place.

Signup and view all the flashcards

Electrostatic Catalysis

The enzyme's hydrophobic active site excludes water, lowering the dielectric constant and enhancing electrostatic interactions between the substrate and the enzyme.

Signup and view all the flashcards

How does Electrostatic Catalysis work?

The lack of water in the active site allows for stronger electrostatic interactions between the substrate and the enzyme's charged amino acids.

Signup and view all the flashcards

Acid-Base Catalysis

Amino acid side chains in the enzyme's active site can donate or accept protons (H+ ions), facilitating the reaction by creating more reactive intermediates.

Signup and view all the flashcards

Covalent Catalysis

The enzyme forms a temporary covalent bond with the substrate. This can involve amino acid residues or non-protein prosthetic groups.

Signup and view all the flashcards

Example of Covalent Catalysis

In chymotrypsin, a serine residue forms a transient acyl-serine covalent bond with the protein substrate, helping break the substrate down.

Signup and view all the flashcards

Prosthetic Groups

These are non-protein components of enzymes, like B-vitamins and metals, that can also form transient covalent bonds with substrates during covalent catalysis.

Signup and view all the flashcards

What is the key advantage of the transition state stabilization?

By binding more tightly to the transition state, the enzyme lowers the activation energy of the reaction, making it proceed more rapidly.

Signup and view all the flashcards

Fatty Acid Notation

A shorthand way to represent fatty acids, indicating the number of carbon atoms, number of double bonds, and positions of double bonds.

Signup and view all the flashcards

Cis-Double Bond Effect

The presence of a cis-double bond in an unsaturated fatty acid creates a bend in the molecule, making it less linear and packed.

Signup and view all the flashcards

Saturated vs. Unsaturated Fatty Acids

Saturated fatty acids have only single bonds between carbons, while unsaturated fatty acids have at least one double bond.

Signup and view all the flashcards

Melting Point and Fatty Acid Structure

Saturated fatty acids have higher melting points due to their linear structure allowing for more intermolecular forces.

Signup and view all the flashcards

Acylglycerides

Esters formed from glycerol and fatty acids, serving as energy storage or signaling molecules.

Signup and view all the flashcards

Mono-, Di-, Triacylglycerides

Acylglycerides with one, two, or three fatty acids attached to glycerol, respectively.

Signup and view all the flashcards

Diacylglycerides (DAG) Function

DAG act as signaling molecules, transmitting signals within cells.

Signup and view all the flashcards

Triacylglycerides (TAG) Function

TAG serve as the primary storage form of fatty acids, found in oils and fats.

Signup and view all the flashcards

What are phospholipids?

Phospholipids are molecules with a phosphate group attached to a diacylglyceride. The phosphate group is polar, making the head hydrophilic, while the fatty acid tails are hydrophobic. This makes them amphipathic

Signup and view all the flashcards

What are the primary types of phospholipids?

Phospholipids can be classified based on the molecule attached to the phosphate group. Common examples include phosphatidylethanolamine (PE), phosphatidylcholine (PC), and phosphatidylserine (PS).

Signup and view all the flashcards

Why are phospholipids important for cells?

Phospholipids form the basis of cell membranes. Their amphipathic nature allows them to self-assemble into bilayers, with the hydrophilic heads facing the aqueous environment and the hydrophobic tails forming a barrier.

Signup and view all the flashcards

What are sterols?

Sterols are lipids with a specific structure: a four-ring perhydrocyclopentanophenantrene base. They can be found in plants, fungi, and animals.

Signup and view all the flashcards

What is cholesterol?

Cholesterol is a type of zoosterol, found in animals and humans. It has four rings (A, B, C, D) with a total of 27 carbon atoms. It is an important component of cell membranes.

Signup and view all the flashcards

How does cholesterol differ from other sterols?

Cholesterol has a hydroxyl group on carbon 3 and a double bond between carbons 5 and 6. It has specific methyl substituents at carbons 10 and 13, and a larger alkyl chain attached at carbon 17.

Signup and view all the flashcards

What is the primary function of sterols?

Sterols, like cholesterol, are important for cell membrane structure and fluidity. They also serve as precursors for the synthesis of other important molecules like steroid hormones.

Signup and view all the flashcards

How do unsaturated and saturated fatty acids affect fat and oil at room temperature?

Unsaturated fatty acids have lower melting points than saturated fatty acids. Oils, which are rich in unsaturated fatty acids, are liquid at room temperature. Fats, rich in saturated fatty acids, are solid at room temperature.

Signup and view all the flashcards

Study Notes

Enzyme Features and Reactions

  • Enzymes are globular proteins that catalyze biochemical reactions.
  • The active site is the region within the enzyme where the substrate binds.
  • The enzyme-substrate complex forms, lowering the activation energy, facilitating a faster reaction.
  • The enthalpy of the reaction remains constant.
  • Enzyme kinetics studies the reaction velocity.

Enzyme Models

  • Lock and Key Model: Enzyme and substrate have complementary shapes. Substrate fits into the active site like a key into a lock.
  • Induced Fit Model: Initially loose binding of the substrate induces a conformational change in the enzyme, resulting in a tighter fit.

Enzyme Classification

  • Enzymes are categorized based on the reaction they catalyze.

  • Six major classes:

    • Oxidoreductases: Oxidation-reduction reactions
    • Transferases: Transfer of a chemical group
    • Hydrolases: Bond breakage by addition of water
    • Lyases: Bond breakage without water addition
    • Isomerases: Intramolecular rearrangements/isomerization
    • Ligases: Bond formation by joining two molecules.

  • Enzymes are numbered using a four-digit code (e.g., 4.3.2.1). The first number represents the major class.

Enzyme Prosthetic Groups

  • Prosthetic groups (co-enzymes and co-factors) are non-protein components necessary for enzyme function.
  • Vitamins (e.g., B-complex, Vitamin C) serve as co-enzymes, not stored in the body.
  • Minerals or metals (e.g., zinc) serve as co-factors.

Mechanisms of Enzyme Catalysis

  • Proximity and Orientation Effect: Substrates brought together at the active site, properly oriented for efficient reaction.
  • Transition State Stabilization: The enzyme stabilizes the transition state, making the reaction more favorable.
  • Electrostatic Catalysis: Water exclusion at the hydrophobic active site lowers dielectric constant, enhancing electrostatic interactions.
  • Acid-Base Catalysis: Amino acid side chains act as proton donors or acceptors, changing substrate reactivity.
  • Covalent Catalysis: Transient covalent bonds form between enzyme and substrate.
  • Metal Ion Catalysis: Metal ions can bind substrates, facilitate electron transfer, or stabilize charges.

Enzyme Regulation

  • Compartmentation: Enzymes localized in specific organelles.
  • Covalent Modification: Phosphate addition or removal alters enzyme activity.
  • Allosteric Regulation: Binding of effectors (molecules) alters enzyme conformation and activity.
  • Proteolytic Activation: Cleavage of inactive precursor (zymogen) to activate enzyme.
  • Transcriptional Control: Gene regulation controls enzyme production.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

BIOCHEM LEC PDF

Description

Test your knowledge on enzymes, their features, and the various models explaining their function. This quiz covers enzyme classification, reaction mechanisms, and kinetics, allowing you to explore how enzymes catalyze biochemical reactions effectively.

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser