2
0
2
5
Enzymes – High-Yield Summary
THE
BIOCHEM
MENTOR
,Enzymes 1 THE BIOCHEM MENTOR
My dear students,
Biochemistry is a beautiful and fascinating subject, and I feel honored to help share its
wonders with you. These notes are meant to serve as high-yield, last-minute aids—they are
not a replacement for a proper understanding of the concepts.
As someone with 12 years of teaching experience, my advice is this: attend your classes
attentively, master the concepts thoroughly, and then use these notes as a helpful guide before
exams.
Wishing you clarity, confidence, and all the very best in your studies!
—Your proud guide in learning
THE BIOCHEM MENTOR. www.thebiochemmentor.carrd.co
Chapter 6 Lehninger: Enzymes - High-
Yield Summary
Major Sections Covered:
1. Enzyme fundamentals - definitions, properties,
structure-function
2. Classification system - all 6 EC classes with examples
3. Summary Kinetics - Michaelis-Menten, Lineweaver-
Burk plots, parameters
4. Inhibition types - competitive, non-competitive,
uncompetitive, irreversible
5. Allosteric regulation - cooperativity, regulatory
mechanisms
6. Clinical applications - diagnostic markers, genetic
diseases, drug targets
7. Essential equations and formulas
8. 5 Practice MCQs with solutions
This copy is licensed to you by The Biochem Mentor. Please support learning – do not share. www.thebiochemmentor.carrd.co 1
, Enzymes 2 THE BIOCHEM MENTOR
6.1 Introduction to Enzymes
Key Definitions
• Enzymes: Highly specialized protein catalysts that accelerate biochemical reactions
• Substrate: Molecule acted upon by enzyme
• Active site: Specific region where substrate binds and catalysis occurs
• Cofactor: Non-protein helper (metal ions: Fe²⁺, Mg²⁺, Mn²⁺, Zn²⁺)
• Coenzyme: Organic cofactor (derived from vitamins)
• Prosthetic group: Tightly/covalently bound cofactor
• Holoenzyme: Complete enzyme with cofactors
• Apoenzyme: Protein portion alone
Enzyme Classification (EC Numbers)
• Oxidoreductases – catalyze electron transfer. Example:
Lactate dehydrogenase (converts lactate ↔ pyruvate).
• Transferases – transfer functional groups between
molecules. Example: Alanine transaminase (ALT)
(transfers amino group from alanine to α-ketoglutarate).
• Hydrolases – catalyze hydrolysis reactions (breaking
bonds with water). Example: Amylase (breaks starch into maltose).
• Lyases – break or form bonds without hydrolysis or oxidation. Example: Aldolase (splits
fructose-1,6-bisphosphate into DHAP and G3P).
• Isomerases – catalyze isomerization within a molecule. Example: Phosphoglucose
isomerase (converts glucose-6-phosphate ↔ fructose-6-phosphate).
• Ligases – catalyze bond formation using ATP. Example: DNA ligase (joins DNA
fragments).
Historical Milestones
• Eduard Buchner (1897): Cell-free fermentation
• James Sumner (1926): First enzyme crystallization (urease)
• Haldane: Enzyme-substrate
binding theory
6.2 How Enzymes Work
Fundamental Principles
• Enzymes accelerate reaction
rates, NOT equilibrium position
• Rate enhancement: 10⁵ to 10¹⁷
fold
• Mechanism: Lower activation energy (ΔG‡)
This copy is licensed to you by The Biochem Mentor. Please support learning – do not share. www.thebiochemmentor.carrd.co 2
0
2
5
Enzymes – High-Yield Summary
THE
BIOCHEM
MENTOR
,Enzymes 1 THE BIOCHEM MENTOR
My dear students,
Biochemistry is a beautiful and fascinating subject, and I feel honored to help share its
wonders with you. These notes are meant to serve as high-yield, last-minute aids—they are
not a replacement for a proper understanding of the concepts.
As someone with 12 years of teaching experience, my advice is this: attend your classes
attentively, master the concepts thoroughly, and then use these notes as a helpful guide before
exams.
Wishing you clarity, confidence, and all the very best in your studies!
—Your proud guide in learning
THE BIOCHEM MENTOR. www.thebiochemmentor.carrd.co
Chapter 6 Lehninger: Enzymes - High-
Yield Summary
Major Sections Covered:
1. Enzyme fundamentals - definitions, properties,
structure-function
2. Classification system - all 6 EC classes with examples
3. Summary Kinetics - Michaelis-Menten, Lineweaver-
Burk plots, parameters
4. Inhibition types - competitive, non-competitive,
uncompetitive, irreversible
5. Allosteric regulation - cooperativity, regulatory
mechanisms
6. Clinical applications - diagnostic markers, genetic
diseases, drug targets
7. Essential equations and formulas
8. 5 Practice MCQs with solutions
This copy is licensed to you by The Biochem Mentor. Please support learning – do not share. www.thebiochemmentor.carrd.co 1
, Enzymes 2 THE BIOCHEM MENTOR
6.1 Introduction to Enzymes
Key Definitions
• Enzymes: Highly specialized protein catalysts that accelerate biochemical reactions
• Substrate: Molecule acted upon by enzyme
• Active site: Specific region where substrate binds and catalysis occurs
• Cofactor: Non-protein helper (metal ions: Fe²⁺, Mg²⁺, Mn²⁺, Zn²⁺)
• Coenzyme: Organic cofactor (derived from vitamins)
• Prosthetic group: Tightly/covalently bound cofactor
• Holoenzyme: Complete enzyme with cofactors
• Apoenzyme: Protein portion alone
Enzyme Classification (EC Numbers)
• Oxidoreductases – catalyze electron transfer. Example:
Lactate dehydrogenase (converts lactate ↔ pyruvate).
• Transferases – transfer functional groups between
molecules. Example: Alanine transaminase (ALT)
(transfers amino group from alanine to α-ketoglutarate).
• Hydrolases – catalyze hydrolysis reactions (breaking
bonds with water). Example: Amylase (breaks starch into maltose).
• Lyases – break or form bonds without hydrolysis or oxidation. Example: Aldolase (splits
fructose-1,6-bisphosphate into DHAP and G3P).
• Isomerases – catalyze isomerization within a molecule. Example: Phosphoglucose
isomerase (converts glucose-6-phosphate ↔ fructose-6-phosphate).
• Ligases – catalyze bond formation using ATP. Example: DNA ligase (joins DNA
fragments).
Historical Milestones
• Eduard Buchner (1897): Cell-free fermentation
• James Sumner (1926): First enzyme crystallization (urease)
• Haldane: Enzyme-substrate
binding theory
6.2 How Enzymes Work
Fundamental Principles
• Enzymes accelerate reaction
rates, NOT equilibrium position
• Rate enhancement: 10⁵ to 10¹⁷
fold
• Mechanism: Lower activation energy (ΔG‡)
This copy is licensed to you by The Biochem Mentor. Please support learning – do not share. www.thebiochemmentor.carrd.co 2
