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Questions and Answers
What is the primary function of enzymes in biological reactions?
What is the primary function of enzymes in biological reactions?
Which of the following statements accurately describes the 'induced-fit' model of enzyme action?
Which of the following statements accurately describes the 'induced-fit' model of enzyme action?
Which of the following is NOT a factor affecting enzyme activity?
Which of the following is NOT a factor affecting enzyme activity?
What is the most likely reason an enzyme might lose its activity at high temperatures?
What is the most likely reason an enzyme might lose its activity at high temperatures?
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What is the term for the specific point at which an enzyme reaches its maximum rate of reaction?
What is the term for the specific point at which an enzyme reaches its maximum rate of reaction?
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Which type of inhibitor binds to the enzyme's active site, directly competing with the substrate?
Which type of inhibitor binds to the enzyme's active site, directly competing with the substrate?
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Which of the following is a common characteristic of irreversible inhibitors?
Which of the following is a common characteristic of irreversible inhibitors?
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Why is the 'lock-and-key' model considered an oversimplification compared to the 'induced-fit' model?
Why is the 'lock-and-key' model considered an oversimplification compared to the 'induced-fit' model?
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Flashcards
Enzymes
Enzymes
Biological catalysts that speed up chemical reactions.
Activation Energy
Activation Energy
The energy required to initiate a chemical reaction.
Lock-and-Key Hypothesis
Lock-and-Key Hypothesis
A model where enzyme and substrate fit together without changing shape.
Induced-Fit Hypothesis
Induced-Fit Hypothesis
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Factors Affecting Enzyme Activity
Factors Affecting Enzyme Activity
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Vmax
Vmax
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Km (Michaelis constant)
Km (Michaelis constant)
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Enzyme Inhibitors
Enzyme Inhibitors
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Study Notes
Enzymes
- Enzymes are protein catalysts
- They speed up chemical reactions in living organisms
- Enzymes are crucial for life processes
- James B. Sumner isolated and crystallized enzymes in 1926
- All proteins?
- High molecular weight (MW)
- Catalysts (FAST AND FURIOUS)
- Active outside cells
- Water-soluble, amphoteric molecules
- Specificity
Enzyme Action
- Molecules must collide to react
- Collisions must have sufficient kinetic energy to break chemical bonds (activation energy)
- Higher temperatures increase molecular movement and the likelihood of collisions and bond breakage
- Enzymes lower activation energy needed for reactions to proceed
- Enzymes speed up reactions by binding to substrates in the active site
- The active site is specific to a particular substrate
Enzyme Classes
- Oxidoreductases: oxidation-reduction reactions (e.g., cytochrome oxidase, lactate dehydrogenase)
- Transferases: transfer functional groups (e.g., acetate kinase, alanine deaminase)
- Hydrolases: hydrolysis (addition of water) (e.g., lipase, sucrase)
- Lyases: removal of groups of atoms without hydrolysis (e.g., oxalate decarboxylase, isocitrate lyase)
- Isomerases: rearrangement of atoms within a molecule (e.g., glucose-phosphate isomerase, alanine racemase)
- Ligases: joining of two molecules using energy from ATP (e.g., acetyl CoA synthetase, DNA ligase)
Enzyme Activity
- Temperature: optimal temperature for human enzymes is 37°C; most enzymes denature at 70°C
- pH: optimal pH values vary; pepsin (pH 2) and trypsin (near pH 9). Extreme pH values cause denaturation.
Enzyme Inhibitors
- Irreversible inhibitors: permanently bind to the active site (e.g., nerve gases, pesticides)
- Reversible inhibitors: bind temporarily; competitive (compete with substrates) and non-competitive inhibitors.
- Noncompetitive inhibitors: bind to a different site affecting enzyme-substrate binding while not interfering with the substrate.
Cofactors and Coenzymes
- Cofactors: non-protein enzyme helpers (inorganic, organic)
- Coenzymes: organic cofactors (often vitamins)
- Examples: NAD, FAD, CoA, thiamine pyrophosphate, flavin mononucleotide
- Coenzymes often aid in electron or functional group transfer
- Metal ions also behave as enzyme cofactors
Holoenzymes and Apoenzymes
- Holoenzyme: active enzyme with non-protein component
- Apoenzyme: inactive enzyme without non-protein component
- Cofactors could be metal ions or small organic molecules (coenzymes)
Enzyme Regulation
- Allosteric activation/inhibition: modulator molecules regulate enzyme activity by binding to allosteric sites (modulator site)
- Feedback inhibition: end product of a metabolic pathway shuts down the pathway
- Example: isoleucine synthesis
Zymogens
- Zymogens (pro-enzymes): inactive enzyme forms that need a specific event for activation
- Cleavage of a proteolytic chain is needed to activate the enzymes, it is irreversible
- Example: trypsin, chymotrypsin
Enzyme Localization
- Enzymes are often located in specific parts of cells
- Compartmentalization of enzymes increases efficiency
- E.g., mitochondria contain enzymes for cellular respiration
Additional Notes
- Vmax = maximum rate of reaction
- Km = affinity of an enzyme to substrate (where velocity is half Vmax)
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Description
This quiz covers the essential functions of enzymes, their role as catalysts in biochemical reactions, and different classes of enzymes such as oxidoreductases and transferases. Learn about the importance of enzymes in life processes and how they facilitate chemical reactions by lowering activation energy. Test your knowledge on key concepts related to enzyme action and specificity.
