Скачать или смотреть 3. Enzymes | Introduction, Classification & Mechanism of Action | MBBS Biochemistry | USMLE Step 1

𝐒𝐮𝐛𝐬𝐜𝐫𝐢𝐛𝐞 𝗙𝐨𝐫 𝗠𝐨𝐫𝐞 𝗜𝐧𝐟𝐨𝐫𝐦𝐚𝐭𝐢𝐨𝐧 𝐨𝐧 𝗛𝐞𝐚𝐥𝐭𝐡 👩‍⚕‍ 𝐚𝐧𝐝 𝗠𝐞𝐝𝐢𝐜𝐢𝐧𝐞💉🩺💊
📌𝗜𝗻𝘀𝘁𝗮𝗴𝗿𝗮𝗺 :   / clinical.learning  

Enzymes | Introduction, Classification & Mechanism of Action | MBBS Biochemistry | USMLE Step 1

👋 Hello future doctors! Enzymes are the biological catalysts of life, accelerating reactions essential for metabolism, signaling, and energy production. Understanding their nature, classification, and mechanism of action is crucial for mastering biochemistry and clinical applications.

This lecture explains the basics of enzymes, their classification into six major classes, and the step-by-step mechanism of enzyme action — simplified for MBBS, NEET PG, FMGE, and USMLE Step 1. 🧬📚

🌟 Introduction to Enzymes

Definition: Biological catalysts (mostly proteins, some RNAs like ribozymes).

Key Features:
• Increase reaction rate without being consumed.
• Highly specific for substrates.
• Work under mild physiological conditions.
• Activity regulated by pH, temperature, substrate concentration.

Clinical Importance: Basis for lab tests (ALT, AST, ALP, CK, LDH) and drug targets (statins, allopurinol).

🌟 Classification of Enzymes (IUBMB – 6 Major Classes)

1️⃣ Oxidoreductases – catalyze redox reactions.
• Example: Lactate dehydrogenase, Cytochrome oxidase.

2️⃣ Transferases – transfer functional groups.
• Example: Aminotransferases, Kinases.

3️⃣ Hydrolases – hydrolytic cleavage.
• Example: Lipase, Protease, Amylase.

4️⃣ Lyases – non-hydrolytic group removal/addition.
• Example: Aldolase, Decarboxylase.

5️⃣ Isomerases – intramolecular rearrangements.
• Example: Phosphoglucose isomerase, Racemases.

6️⃣ Ligases (Synthetases) – join molecules using ATP.
• Example: DNA ligase, Pyruvate carboxylase.

👉 Mnemonic: “Over The HILL” = Oxidoreductase, Transferase, Hydrolase, Isomerase, Lyase, Ligase.

🌟 Mechanism of Enzyme Action

1️⃣ Substrate Binding

Enzyme + Substrate → Enzyme–substrate complex.

Models:
• Lock & Key model – rigid fit (substrate fits like a key).
• Induced Fit model – enzyme changes conformation to bind substrate (more accepted).

2️⃣ Catalysis (Transition State Formation)

Enzyme lowers activation energy.

Stabilizes transition state → faster product formation.

3️⃣ Product Formation & Release

Enzyme–substrate → Enzyme–product → Product released.

Enzyme regenerated for reuse.

🩺 Clinical Correlations

Enzyme assays: ALT/AST (liver), CK-MB (cardiac), ALP (bone/liver).

Drug targets:
• Statins (HMG-CoA reductase).
• Methotrexate (dihydrofolate reductase).
• Allopurinol (xanthine oxidase).

Deficiency diseases:
• G6PD deficiency → hemolysis.
• Lysosomal enzyme defects → storage disorders.

🎯 Exam Integration

Enzyme classes = guaranteed recall questions.

Mechanism = Lock & Key vs Induced Fit model.

Clinical links = favorite case-based MCQs.
👉 Mastering this forms the base for all enzyme kinetics & inhibition questions in USMLE & NEET PG.

👉 Don’t forget to Subscribe and tap the 🔔 bell for more high-yield enzyme & metabolism lectures!

👍 If this lecture helps you, please like and share it with your classmates. Your support motivates us to keep producing simplified, exam-focused content. 🙌

❓Want the next lecture on Allosteric Enzymes & Feedback Regulation with classic examples (PFK-1, ATCase, Carbamoyl phosphate synthetase)? Drop your request in the comments! 😊

#Enzymes #EnzymeClassification #EnzymeMechanism #MedicalBiochemistry #USMLEStep1 #MBBSLectures #FMGE #NEETPG #LockAndKeyModel #InducedFitModel #BiochemistryLecture #MedicalStudents