Complete Summary and Solutions for Enzymes and Bioenergetics – NCERT Class XI Biotechnology, Chapter 4 – Enzyme Mechanisms, Thermodynamics, Exercises

Comprehensive summary and explanation of Chapter 4 'Enzymes and Bioenergetics' from the NCERT Class XI Biotechnology textbook, covering enzyme classification, substrate interaction models, factors affecting activity, inhibition, energy transformations, thermodynamic laws, ATP function, and answers to all textbook exercises and questions.

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Enzymes and Bioenergetics: Class 11 NCERT Chapter 4 - Ultimate Study Guide, Notes, Questions, Quiz 2025

Full Chapter Summary & Detailed Notes - Enzymes and Bioenergetics Class 11 NCERT

Overview & Key Concepts

Chapter Goal: Explore enzymes as biocatalysts and bioenergetics principles. Exam Focus: Classification, kinetics (Michaelis-Menten), inhibition types, thermodynamics laws, ATP role. 2025 Updates: Emphasis on allosteric regulation, real-world enzyme applications (e.g., antibiotics). Fun Fact: Enzymes speed reactions a million-fold without changing. Core Idea: Enzymes lower activation energy; energy transformations follow thermodynamics. Real-World: Enzyme defects cause diseases like PKU; ATP fuels cellular work. Ties: Links to biomolecules (Ch3), cellular processes (Ch5). Expanded: All subtopics point-wise with tables, diagram descriptions for visual learning.
Wider Scope: From enzyme structure-function to energy laws; integrates catalysis with thermodynamics.
Expanded Content: Detailed on 4.1 (all subsections) and 4.2, including tables/figures.

4.1 Enzymes: Classification and Mode of Action

Definition & Properties: Biocatalysts speeding biochemical reactions in vivo/in vitro; highly specific, unchanged, enhance rate tremendously.
Composition: Mostly proteins (MW 20k-1M Da); exceptions: ribozymes (catalytic RNA); activity affected by conformation/denaturation.
Cofactors: Required for activity; coenzymes (organic, vitamin-derived, Table 4.1) or metal ions (Table 4.2); holoenzyme = apoenzyme + cofactor; prosthetic group if tightly bound.
Table 4.1 Summary: Biocytin (B7, CO2 transfer); CoB12 (B12, alkyl); FAD (B2, electrons); CoA (B5, acyl/alkyl); NAD (B3, hydride); PLP (B6, amino); TPP (B1, aldehydes); THF (B9, C1); transient carriers from vitamins.
Table 4.2 Summary: Fe2+/3+ (catalase/peroxidase); Cu2+ (cytochrome oxidase); Mg2+ (DNA pol); Mn2+ (arginase); K+ (pyruvate kinase); Mo2+ (nitrogenase); Zn2+ (carbonic anhydrase); Ni2+ (urease).

Diagram Note: Tables 4.1 & 4.2 (Description)

Tabular format listing coenzymes/vitamins/roles and metals/enzymes; use for memorization—e.g., NAD from B3 transfers H- in redox.

4.1.1 Classification of Enzymes

IUB System (1964, 7 Classes): Based on reaction type; avoids ambiguity for new enzymes (Table 4.3).
Table 4.3 Summary: 1. Oxidoreductases (e- transfer); 2. Transferases (group transfer); 3. Hydrolases (to water); 4. Lyases (double bonds); 5. Isomerases (isomeric forms); 6. Ligases (ATP-coupled condensation); 7. Translocases (ion/molecule across membrane).
Isozymes: Multiple forms same reaction, different AA composition/properties; e.g., hexokinase (4 forms tissues); LDH (5 forms human anaerobic metabolism).

Diagram Note: Table 4.3 (Description)

Class number, name, reaction type; visualize as reaction categories for classification recall.

Enzyme Active Site

Structure: Small pocket/cleft for substrate fit; 3D from polypeptide portions; bonds: electrostatic, H-bonds, van der Waals, hydrophobic.
Role: Site of catalysis; substrate portion fits precisely.

Models of Enzyme-Substrate Interaction

Fischer’s Lock and Key (1894): Rigid complementary fit; substrate as key into enzyme lock (Fig. 4.1).
Koshland’s Induced Fit (1958): Flexible; substrate induces enzyme conformational change for binding/catalysis; hand-glove analogy (Fig. 4.2).

Fig. 4.1: Lock and Key Model (Description)

Enzyme (lock) + substrate (key) → ES complex; rigid pre-shaped active site.

Fig. 4.2: Induced Fit Model (Description)

Enzyme + substrate → conformational change in enzyme → ES complex; flexible site adjusts.

Enzyme Specificity

Types: Group (related substrates); absolute (one substrate); stereospecific (one isomer, e.g., D-amino oxidase); geometrical (cis/trans, e.g., fumarase fumarate-malate).
Basis: Ideal catalytic group arrangement from specificity.

4.1.2 Factors Affecting Enzyme Activity

Temperature: Rate increases to optimum (40-45°C most; 37°C human), then falls (denaturation); bell curve (Fig. 4.3); exceptions: Taq pol (100°C thermophiles).
pH: Bell curve; optimum unique (6-8 most; pepsin 1-2, acid phos 4-5, alkaline phos 10-11); extremes inactivate (Fig. 4.4).
Substrate Concentration: Rate proportional till saturation (Vmax); hyperbolic curve (Fig. 4.5).
Modulators: Inhibitors/activators (detailed later).

Fig. 4.3: Temperature Effect (Description)

Bell-shaped: Velocity vs. Temp; peak at optimum, drop post-denaturation.

Fig. 4.4: pH Effect (Description)

Bell-shaped: Velocity vs. pH; peak at optimum, low at extremes.

Fig. 4.5: Substrate Concentration (Description)

Hyperbolic: Velocity increases, plateaus at Vmax (saturation).

4.1.3 Unit of Enzyme Activity

Enzyme Unit (U): Catalyzes 1 µmol substrate/min under standard conditions (IUB 1964).
Katal (kat): 1 mol/s (1 kat = 6×10^7 U); preferred SI unit.

4.1.4 Specific Activity

Definition: Units/mg enzyme protein; measures purity in mixtures.

4.1.5 Mechanism of Enzyme Action

Thermodynamics: ΔG determines spontaneity; ΔG‡ (activation energy) rate; enzymes lower ΔG‡, not ΔG/equilibrium.
Transition State: High-energy intermediate; enzymes stabilize to speed equilibrium.
Kinetics: E + S ⇌ ES → E + P; Michaelis-Menten (1913): v0 = Vmax [S] / (Km + [S]); Km = [S] at Vmax/2; hyperbolic plot (Fig. 4.6).
Interpretations: Low [S] proportional; high [S] Vmax; Km affinity measure (low Km = high affinity).

Fig. 4.6: Michaelis-Menten Plot (Description)

Hyperbola: v0 vs. [S]; asymptote Vmax, Km at ½ Vmax.

4.1.6 Enzyme Inhibition

Types: Irreversible (tight bind, e.g., penicillin transpeptidase, aspirin cyclooxygenase); Reversible (dissociates: competitive, non-competitive, uncompetitive).
Competitive: Inhibitor mimics substrate, competes active site; increases Km, Vmax unchanged; overcome by high [S] (Figs. 4.7, 4.8).
Non-Competitive: Binds other site, E or ES; decreases Vmax, Km unchanged; not overcome by [S] (Figs. 4.9, 4.10).
Uncompetitive: Binds only ES; decreases Vmax/Km; not overcome (Fig. 4.11).

Fig. 4.7: Competitive Inhibition (Description)

E + S → ES → P; E + I → EI (no ESI); competition at site.

Fig. 4.8: Competitive Plot (Description)

Lines intersect y-axis (same Vmax); inhibitor shifts Km right.

Fig. 4.9: Non-Competitive (Description)

E + I → EI; ES + I → ESI (no product); separate sites.

Fig. 4.10: Non-Competitive Plot (Description)

Lines parallel; lower Vmax, same Km.

Fig. 4.11: Uncompetitive (Description)

ES + I → ESI (traps ES); no free E bind.

4.1.7 Allosteric Enzymes

Characteristics: Multi-subunit; regulatory site + active site; sigmoidal kinetics (Fig. 4.12); don't obey Michaelis-Menten.
Regulation: Modulators bind regulatory site, alter substrate affinity; key metabolic regulators.

Fig. 4.12: Allosteric Kinetics (Description)

Sigmoidal curve: v0 vs. [S]; cooperative binding.

4.2 Brief Introduction to Bioenergetics

Overview: Energy transformation/use in cells; exergonic (release) to endergonic (consume); governed by thermodynamics.
4.2.1 Laws of Thermodynamics: Predict direction/work; not mechanism/speed.
First Law: Energy conserved (ΔE = Q - W); system + surroundings constant; path-independent.
Second Law: Entropy (S, disorder) universe increases; spontaneous if ΔS_total > 0; life maintains low S via energy input (food/light), but eventual equilibrium post-death.
Combined (Gibbs Free Energy): ΔG = ΔH - TΔS; predicts spontaneity (ΔG < 0 spontaneous); at const T/P; useful work available.
Closed System: ΔE = ΔH - PΔV; enthalpy for biochemicals.
ATP: Universal Currency: From exergonic (oxidation/light) to endergonic (synthesis/transport/contraction); ADP + Pi → ATP (endergonic); ATP → ADP + Pi (7.3 kcal/mol); nucleotide structure (Fig. 4.13).

Fig. 4.13: ATP Structure (Description)

Adenine-ribose with α/β/γ phosphates; phosphoester bonds; hydrolysis at γ.

Summary

Enzymes: Catalysts lowering ΔG‡; classified by reaction; regulated by factors/inhibitors/allostery.
Bioenergetics: Thermodynamics govern energy flow; ATP central.

Why This Guide Stands Out

Enzyme-focused: Kinetics plots, inhibition comparisons, thermo equations. Free 2025 with point-wise, tables for quick scan; diagram desc for sketching practice.

Key Themes & Tips

Aspects: Specificity, regulation, energy principles.
Tip: Mnemonics for classes (OR THY LIG = Oxidoreductases, Transferases, Hydrolases, Lyases, Isomerases, Ligases); plot MM curve for kinetics.

Exam Case Studies

Penicillin: Irreversible inhibition of cell wall enzyme. Allosteric: Hb O2 binding cooperative.

Project & Group Ideas

Model enzyme kinetics with simulations.
Debate: Irreversible vs. reversible inhibition in drugs.
Research: Enzyme engineering in biotech.

Key Definitions & Terms - Complete Glossary

All terms from chapter; detailed with examples, relevance. Expanded: 25+ terms grouped; depth for recall, interlinks to biomolecules/thermo.

Enzyme

Biocatalyst speeding reactions unchanged. Relevance: Specificity/power. Ex: Ribozymes RNA exception. Depth: Proteins mostly; denaturation loses activity.

Cofactor

Non-protein helper. Relevance: Activity essential. Ex: NAD hydride transfer. Depth: Coenzyme (vitamin) or metal; holo/apoenzyme.

Oxidoreductase

Class 1: e- transfer. Relevance: Redox. Ex: Dehydrogenases. Depth: First IUB class.

Isozyme

Multiple forms same reaction. Relevance: Tissue-specific. Ex: LDH 5 forms. Depth: Different properties, same function.

Active Site

Catalytic pocket. Relevance: Substrate fit. Ex: 3D bonds hold S. Depth: Small % enzyme; non-covalent interactions.

Lock and Key Model

Rigid complementary fit. Relevance: Early hypothesis. Ex: Fischer 1894. Depth: Pre-shaped site; Fig 4.1.

Induced Fit Model

Flexible change on binding. Relevance: Modern view. Ex: Koshland 1958. Depth: Aligns residues; hand-glove; Fig 4.2.

Stereospecificity

One isomer acted. Relevance: Chirality. Ex: D-amino oxidase. Depth: 3D arrangement key.

Km

[S] at Vmax/2. Relevance: Affinity. Ex: Low Km high affinity. Depth: Michaelis constant.

Vmax

Max velocity. Relevance: Saturation. Ex: All sites occupied. Depth: Enzyme amount dependent.

Competitive Inhibition

Site competitor. Relevance: Overcome by S. Ex: Statins HMG-CoA. Depth: ↑Km, Vmax same; Fig 4.8.

Non-Competitive Inhibition

Other site bind. Relevance: Not overcome. Ex: Heavy metals. Depth: ↓Vmax, Km same; Fig 4.10.

Allosteric Enzyme

Regulatory site. Relevance: Metabolic control. Ex: Phosphofructokinase. Depth: Sigmoidal; Fig 4.12.

Activation Energy (ΔG‡)

Barrier to reaction. Relevance: Rate determinant. Ex: Enzymes lower. Depth: Transition state energy.

Entropy (S)

Disorder measure. Relevance: Spontaneity. Ex: Universe ↑S. Depth: Second law.

Free Energy (ΔG)

ΔH - TΔS. Relevance: Predicts direction. Ex: <0 spontaneous. Depth: Gibbs; useful work.

ATP

Energy currency. Relevance: Exergonic to endergonic. Ex: Hydrolysis 7.3 kcal. Depth: Adenine-ribose-phosphates; Fig 4.13.

Holoenzyme

Apo + cofactor. Relevance: Active form. Ex: NAD-dependent dehydrogenase. Depth: Complete catalyst.

Prosthetic Group

Tightly bound cofactor. Relevance: Permanent. Ex: Heme in catalase. Depth: Covalent.

Enzyme Unit (U)

1 µmol/min. Relevance: Activity measure. Ex: Standard conditions. Depth: IUB; katal alternative.

Specific Activity

U/mg protein. Relevance: Purity. Ex: Increases purification. Depth: Tracks isolation.

Geometrical Specificity

Cis/trans isomers. Relevance: Shape. Ex: Fumarase. Depth: Double bond form.

Absolute Specificity

One substrate. Relevance: High precision. Ex: Trypsin peptides. Depth: Extreme selectivity.

Group Specificity

Related substrates. Relevance: Broad. Ex: Proteases amides. Depth: Functional group.

Uncompetitive Inhibition

ES binder only. Relevance: Traps complex. Ex: Rare, some metals. Depth: ↓Vmax/Km; Fig 4.11.

Tip: Group by enzyme (structure/kinetics) vs. bioenergetics (thermo/ATP); examples link to diseases. Depth: Equations for thermo. Errors: Confuse Km/Vmax. Historical: Fischer 1894. Interlinks: Ch3 vitamins. Advanced: Lineweaver-Burk plots. Real-Life: Lactase intolerance (low enzyme). Graphs: Fig 4.6 MM. Coherent: Action → Factors → Kinetics → Regulation → Energy. For easy learning: Flashcard terms with ex.

60+ Questions & Answers - NCERT Based (Class 11) - From Exercises & Variations

Based on chapter + expansions. Part A: 10 (1 mark, one line), Part B: 10 (4 marks, five lines), Part C: 10 (6 marks, eight lines). Point-wise for marks.

Part A: 1 Mark Questions (10 Qs - Short)

1. What are enzymes?

1 Mark Answer: Biocatalysts that speed biochemical reactions without changing.

2. Name the non-protein enzyme example.

1 Mark Answer: Ribozymes (catalytic RNA).

3. What is holoenzyme?

1 Mark Answer: Apoenzyme + cofactor.

4. Which vitamin derives NAD?

1 Mark Answer: Niacin (B3).

5. Name Class 1 enzymes.

1 Mark Answer: Oxidoreductases (e- transfer).

6. What are isozymes?

1 Mark Answer: Multiple forms catalyzing same reaction.

7. Who proposed lock and key model?

1 Mark Answer: Emil Fischer (1894).

8. Define Km.

1 Mark Answer: Substrate concentration at half Vmax.

9. What is competitive inhibition?

1 Mark Answer: Inhibitor competes for active site.

10. What is ΔG?

1 Mark Answer: Free energy change (ΔH - TΔS).

Part B: 4 Marks Questions (10 Qs - Medium, Five Lines Each)

1. Describe enzyme cofactors.

4 Marks Answer:

Non-protein components required for activity.
Coenzymes: Organic, vitamin-derived (e.g., NAD from B3).
Metal ions: e.g., Zn2+ in carbonic anhydrase.
Holoenzyme: Apo + cofactor; prosthetic if tight-bound.
Role: Carry groups (e.g., hydride in NAD).

2. Explain enzyme classification.

4 Marks Answer:

IUB 1964: 7 classes by reaction type.
1: Oxidoreductases (redox).
3: Hydrolases (hydrolysis).
6: Ligases (ATP synthesis).
7: Translocases (transport).

3. Differentiate lock and key vs. induced fit.

4 Marks Answer:

Lock-key: Rigid complementary fit (Fischer).
Induced fit: Substrate induces enzyme change (Koshland).
Lock: Pre-shaped site.
Fit: Flexible alignment for catalysis.
Ex: Hand-glove in fit.

4. Describe temperature/pH effects.

4 Marks Answer:

Temp: Bell curve; optimum 37°C human, denaturation high.
pH: Bell; optimum 6-8, extremes inactivate.
Ex: Pepsin acidic (1-2).
Substrate: Hyperbolic to Vmax.
Factors alter velocity.

5. What is Michaelis-Menten kinetics?

4 Marks Answer:

v0 = Vmax [S] / (Km + [S]).
Km: [S] at ½ Vmax (affinity).
Hyperbolic plot.
Low [S]: Proportional.
High [S]: Saturation.

6. Explain competitive inhibition.

4 Marks Answer:

Inhibitor mimics S, active site bind.
↑Km, Vmax same.
Overcome by high [S].
Ex: Penicillin transpeptidase.
Reduces active E.

7. Describe non-competitive inhibition.

4 Marks Answer:

Binds non-active site, E/ES.
↓Vmax, Km same.
Not overcome by [S].
Ex: Cyanide cytochrome oxidase.
Lowers functional E.

8. What are allosteric enzymes?

4 Marks Answer:

Multi-subunit, regulatory site.
Sigmoidal kinetics.
Modulators alter affinity.
Metabolic regulators.
Ex: Hb cooperative.

9. State first law of thermodynamics.

4 Marks Answer:

Energy conserved (ΔE = Q - W).
System + surroundings constant.
No creation/destruction.
Interconvertible forms.
Path-independent.

10. Explain ATP role.

4 Marks Answer:

Universal energy currency.
Exergonic to endergonic transfer.
Hydrolysis: ATP → ADP + Pi (7.3 kcal).
Synthesis in oxidation/light.
Used in synthesis/transport/contraction.

Part C: 6 Marks Questions (10 Qs - Long, Eight Lines Each)

1. Describe enzyme structure and models.

6 Marks Answer:

Proteins (ribozymes exception); MW 20k-1M Da.
Active site: Pocket for S fit, non-covalent bonds.
Lock-key: Rigid fit (Fischer 1894, Fig 4.1).
Induced fit: Conformational change (Koshland 1958, Fig 4.2).
Specificity: Group/absolute/stereo/geometrical.
Ex: D-amino oxidase stereo.
Cofactors essential (Tables 4.1/4.2).
Holoenzyme active form.

2. Explain enzyme classification and isozymes.

6 Marks Answer:

IUB 7 classes (Table 4.3): Reaction-based.
1: Oxidoreductases e-.
2: Transferases groups.
3: Hydrolases water.
4-7: Lyases/isomerases/ligases/translocases.
Isozymes: Same reaction, different forms.
Ex: LDH 5 human tissues.
Different AA/properties.
Adapt to needs.

3. Discuss factors affecting activity.

6 Marks Answer:

Temp: ↑ to optimum (37°C), then denaturation (Fig 4.3).
pH: Bell, unique optimum (pepsin 2) (Fig 4.4).
[S]: Hyperbolic to Vmax (Fig 4.5).
Modulators: Inhibitors/activators.
Ex: Taq 100°C stable.
Optimum balances structure/activity.
Extremes alter ionization/conformation.
Saturation: Enzyme limiting.

4. Elaborate Michaelis-Menten mechanism.

6 Marks Answer:

E + S ⇌ ES → E + P.
Lowers ΔG‡, not ΔG.
Equation: v0 = Vmax [S]/(Km + [S]).
Km: Affinity (low = high).
Hyperbola (Fig 4.6).
1913 Michaelis-Menten.
ES intermediate key.
Equilibrium faster.

5. Compare inhibition types.

6 Marks Answer:

Irreversible: Tight, permanent (penicillin).
Competitive: Site rival, ↑Km (Fig 4.8).
Non-comp: Other site, ↓Vmax (Fig 4.10).
Uncomp: ES only, ↓Vmax/Km (Fig 4.11).
Reversible dissociate.
Ex: Aspirin irreversible.
Regulates activity.
Drug targets.

6. Explain allosteric enzymes.

6 Marks Answer:

Don't obey MM; sigmoidal (Fig 4.12).
Regulatory + active sites.
Modulators bind, alter affinity.
Cooperative subunits.
Metabolic pathway keys.
Ex: ATCase feedback.
Positive/negative effectors.
Dynamic regulation.

7. Describe first/second laws.

6 Marks Answer:

First: ΔE = Q - W; conserved.
System-surroundings constant.
Second: ΔS_universe >0 spontaneous.
Entropy disorder ↑.
Life low S via energy input.
Post-death ↑S decomposition.
Direction prediction.
Not rate.

8. What is free energy and ATP?

6 Marks Answer:

ΔG = ΔH - TΔS; <0 spontaneous.
Useful work at T/P.
ATP: Currency from exergonic.
Hydrolysis energy release.
Structure: Adenine-ribose-3P (Fig 4.13).
Used in endo processes.
Synthesis in mito/photo.
Central transfer.

9. Discuss enzyme specificity types.

6 Marks Answer:

Group: Related substrates (proteases).

Absolute: One S (urease urea).

Stereo: One isomer (D-oxidase).

Geometrical: Cis/trans (fumarase).

Basis: Binding/catalytic arrangement.

Enhances efficiency.

Prevents side reactions.

Models explain (lock/fit).

10. Outline enzyme units and mechanism.

6 Marks Answer:

Unit: 1 µmol/min; katal 1 mol/s.
Specific: U/mg purity.
Mechanism: Lowers ΔG‡ transition state.
ES complex intermediate.
ΔG unchanged, rate ↑.
Thermodynamic properties key.
Spontaneous if ΔG<0.
Kinetics describe rate.

Tip: Diagrams for inhibition; equations for thermo. Easy: Structured lists.

Key Concepts - In-Depth Exploration

Core ideas with examples, pitfalls, interlinks. Expanded: All concepts 4.1-4.2 with steps/examples for easy learning.

Cofactors & Coenzymes

Vital helpers. Steps: 1. Bind apo, 2. Carry groups, 3. Regenerate. Ex: NAD reduces to NADH in glycolysis. Pitfall: Confuse coenzyme/metal. Interlink: Vitamins Ch3. Depth: Table 4.1 roles; transient in catalysis.

Enzyme Classification

Reaction-based. Steps: Identify type (e.g., hydrolysis=hydrolase), assign class. Ex: Lactase hydrolase. Pitfall: Forget translocase (7th). Interlink: Metabolism Ch5. Depth: Table 4.3; EC numbers advanced.

Isozymes

Tissue variants. Steps: Same catalysis, vary AA for regulation. Ex: CK-MB heart damage. Pitfall: Same as isoforms. Interlink: Diagnostics. Depth: LDH electrophoresis.

Active Site & Models

Catalysis locus. Steps: Lock: Fit rigid; Fit: Induce change. Ex: Hexokinase glucose. Pitfall: Rigid vs. dynamic. Interlink: Specificity. Depth: Figs 4.1-2; bonds list.

Specificity Types

Precision levels. Steps: Bind S, catalyze selectively. Ex: Trypsin Arg/Lys. Pitfall: Overlap group/stereo. Interlink: Drug design. Depth: 4 types with ex.

Factors Affecting Activity

Environmental controls. Steps: Temp ↑kinetic energy, excess denature; pH ionize residues. Ex: Pepsin stomach acid. Pitfall: Ignore optimum range. Interlink: Industrial enzymes. Depth: Figs 4.3-5; [S] saturation.

Michaelis-Menten Kinetics

Rate equation. Steps: 1. E+S=ES, 2. ES→P, 3. Plot hyperbola. Ex: Sucrase sucrose. Pitfall: Km not Vmax. Interlink: Inhibition plots. Depth: Fig 4.6; low/high [S] behaviors.

Enzyme Inhibition

Rate reducers. Steps: Comp: Compete site; Non: Allosteric; Un: Trap ES. Ex: Methanol ethanol comp alcohol deh. Pitfall: Vmax/Km effects. Interlink: Pharma. Depth: Figs 4.7-11; reversible/irrev.

Allosteric Regulation

Modulator control. Steps: Bind reg site, change conformation, alter affinity. Ex: PFK AMP activator. Pitfall: Sigmoidal vs. hyperbolic. Interlink: Pathways Ch5. Depth: Fig 4.12; cooperative.

Thermodynamics Laws

Energy rules. Steps: First: Conserve (ΔE=Q-W); Second: ↑S (ΔS>0). Ex: ATP hydrolysis ΔG<0. Pitfall: Life defies second (temp low S). Interlink: Bioenergetics. Depth: Equations; closed system.

Free Energy & ATP

Work predictor. Steps: Calc ΔG, if <0 spontaneous; ATP couples. Ex: Glu → G6P +ΔG, ATP makes feasible. Pitfall: ΔG vs. ΔG‡. Interlink: Ch5 processes. Depth: Fig 4.13; 7.3 kcal hydrolysis.

Advanced: Hill equation allostery. Pitfalls: Inhibition plots. Interlinks: Ch2 organelles (mito ATP). Real: Statins comp inhib. Depth: Transition state theory. Examples: LDH isozymes diagnosis. Graphs: MM/inhibition. Errors: Coenzyme vs. cofactor. Tips: Steps for models; table comparisons.

Solved Examples - From Text with Simple Explanations

Expanded; steps for understanding; key figures/processes.

Example 1: Lock and Key (Fig 4.1)

Simple Explanation: Rigid puzzle fit.

Step 1: Enzyme site shaped for S.
Step 2: S inserts precisely.
Step 3: Forms ES, catalyzes.
Step 4: Releases P, E free.
Simple Way: Key turns lock without force.

Example 2: Induced Fit (Fig 4.2)

Simple Explanation: Glove molds to hand.

Step 1: S approaches loose site.
Step 2: Binding induces shape change.
Step 3: Aligns catalytic groups.
Step 4: Reaction, release.
Simple Way: Hand stretches glove for fit.

Example 3: Competitive Inhibition (Fig 4.7)

Simple Explanation: Fake key blocks real.

Step 1: I binds site like S.
Step 2: Blocks ES formation.
Step 3: High S displaces I.
Step 4: Vmax same, Km ↑.
Simple Way: Traffic jam at door, more cars clear.

Example 4: Michaelis-Menten Plot (Fig 4.6)

Simple Explanation: Speed vs. fuel curve.

Step 1: Low [S], linear rise.
Step 2: Mid [S]=Km, half max.
Step 3: High [S], plateau Vmax.
Step 4: Saturation all bound.
Simple Way: Car accelerates then cruises.

Example 5: ATP Hydrolysis

Simple Explanation: Battery discharge.

Step 1: ATP binds enzyme.
Step 2: Hydrolyzes γ bond.
Step 3: Releases energy/ADP/Pi.
Step 4: Powers endo reaction.
Simple Way: Coin from vending machine.

Tip: Sketch plots; link to real enzymes.

Quick Revision Notes & Mnemonics

Concise for all subtopics; mnemonics for recall. Covers enzymes to ATP.

4.1 Enzymes Basics

Biocatalysts specific/powerful (Mnemonic: "E-S-P" - Enhance Speed Precisely).
Cofactors: Coenzymes vitamins, metals ( "CV M" - Carry Vitamins Metals).
Holo: Apo + Cof ( "HAC Full Active" - HAC).

Classification

7 Classes: O-T-H-L-I-L-T (Oxido-Trans-Hyd-Ly-Isom-Lig-Translo).
Isozymes: Tissue variants ( "IT Vary Function Same" - ITVS).

Models & Specificity

Lock: Rigid fit; Fit: Induce change ( "LIF Rigid Dynamic" - LIF).
Specificity: G-A-S-G (Group-Abs-Stereo-Geom).

Factors

Temp/pH: Bell curves optimum ( "BPO Peak Optimum" - BPO).
[S]: Hyperbolic Vmax ( "SH V Sat" - SHV).

Kinetics & Units

MM: v=V[S]/(K+[S]); Km half ( "MM H Half Affinity" - MMH).
Unit: µmol/min; Specific U/mg ( "US Purity" - USP).

Inhibition

Comp: ↑Km V same; Non: ↓V Km same; Un: Both alter ( "CUN Changes Unique" - CUN).
Irrev: Permanent ( "IP Tight" - IPT).

Allosteric

Sigmoidal reg site ( "SR Coop Metabolic" - SRCM).

4.2 Bioenergetics

First: Conserve ΔE=Q-W ( "FC Balance" - FCB).
Second: ↑S spontaneous ( "SS Disorder Up" - SSD).
ΔG=ΔH-TΔS <0 go ( "GHT Negative" - GHT).

ATP

Currency hydrolysis energy ( "CHE Power" - CHP); ADP+Pi synth.

Overall Mnemonic: "Enz Cof Class Mod Spec Fact Kin Inh Allo Ther ATP" (ECCM SFKI TA). Flashcards: One per subtopic. Easy: Bullets, bold keys.

Key Terms & Processes - All Key

Expanded table; 25+ rows for reference.

Term/Process	Description	Example	Usage
Enzyme	Biocatalyst unchanged	Amylase starch	Catalysis
Coenzyme	Vitamin-derived carrier	NAD redox	Group transfer
Holoenzyme	Complete active	Lactate deh + NAD	Activity
Oxidoreductase	e- transfer	Cytochrome oxidase	Redox
Hydrolase	Hydrolysis	Pepsin proteins	Digestion
Isozyme	Variant forms	LDH tissues	Regulation
Active Site	Catalytic cleft	Hexokinase pocket	Binding
Lock and Key	Rigid fit	Fischer model	Interaction
Induced Fit	Conform change	Koshland glove	Dynamic
Stereospecificity	Isomer select	D-amino oxidase	Chirality
Km	½ Vmax [S]	Affinity measure	Kinetics
Vmax	Saturation rate	All ES active	Capacity
Competitive Inhibition	Site rival	Sulfa drugs	↑Km
Non-Competitive	Other site	Lead poisoning	↓Vmax
Allosteric Site	Regulator bind	PFK AMP	Control
Activation Energy	Reaction barrier	Enzymes lower	Rate
ΔG	Free energy	<0 spontaneous	Direction
Entropy	Disorder	Universe ↑	Second law
ATP	Energy currency	Hydrolysis 7.3 kcal	Transfer
Prosthetic Group	Tight cofactor	FAD flavoproteins	Permanent
Enzyme Unit	1 µmol/min	Standard assay	Quantify
Specific Activity	U/mg protein	Purity check	Isolation
Geometrical Specificity	Cis/trans	Fumarase	Isomer
Uncompetitive Inhibition	ES trap	Lithium some	↓Vmax/Km
Transition State	High energy intermediate	ES stabilizes	Catalysis
Exergonic	Energy release	Glucose oxidation	ΔG<0