biology

i want a enzymes chapter flashcard

enzymes

Enzymes are biological catalysts — special proteins that speed up chemical reactions in living organisms without being used up in the process.

They help in digestion, respiration, photosynthesis, and almost every metabolic reaction in the body.

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🔹 2. Nature of Enzymes

• Most enzymes are proteins in nature.

• Some are RNA molecules with catalytic activity → called ribozymes.

• They are specific in their action (each enzyme acts on a specific substrate).

• They work under mild temperature and pH (usually body temperature and near-neutral pH).

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🔹 3. Chemical Composition

Enzymes may be:

1.   Simple enzymes → made up of only proteins.
Example: Pepsin, Trypsin

2.   Conjugated (complex) enzymes → made up of a protein part and a non-protein part.

Part	Description
Apoenzyme	Protein part (inactive alone)
Cofactor	Non-protein part (helps enzyme work)
Holoenzyme	Active enzyme = Apoenzyme + Cofactor

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🔹 4. Types of Cofactors

1.   Prosthetic group:

o   Firmly attached to enzyme.

o   Example: Haem in catalase.

2.   Coenzyme:

o   Loosely attached organic molecule (often derived from vitamins).

o   Example: NAD⁺, FAD.

3.   Metal ions:

o   Act as activators by forming bonds with the enzyme or substrate.

o   Example: Mg²⁺, Zn²⁺, Cu²⁺.

enzyme action

Lock and Key Model

• Proposed by Emil Fischer (1894).

• The enzyme’s active site fits exactly with the substrate — like a key fits into a lock.

🌀 Induced Fit Model

• Proposed by Koshland (1958).

• The enzyme slightly changes shape to fit the substrate perfectly during the reaction.

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🔹 6. Factors Affecting Enzyme Activity

Factor	Effect
Temperature	Activity increases with temperature up to an optimum point (usually ~37°C), then decreases.
pH	Each enzyme works best at a specific pH (e.g., Pepsin → acidic, Amylase → neutral).
Substrate concentration	Reaction rate increases until all enzyme molecules are occupied (saturation point).
Enzyme concentration	More enzyme = faster reaction (if substrate is available).
Cofactors / Inhibitors	Cofactors increase activity; inhibitors decrease or stop it.

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🔹 7. Enzyme Inhibition

1.   Competitive inhibition:

o   Inhibitor competes with substrate for the enzyme’s active site.

o   Example: Malonate inhibits succinate dehydrogenase.

2.   Non-competitive inhibition:

o   Inhibitor binds at another site (not the active site) and changes enzyme shape.

Enzymes are biological catalysts — special proteins that speed up chemical reactions in living organisms without being used up in the process.

They help in digestion, respiration, photosynthesis, and almost every metabolic reaction in the body.

---

🔹 2. Nature of Enzymes

• Most enzymes are proteins in nature.

• Some are RNA molecules with catalytic activity → called ribozymes.

• They are specific in their action (each enzyme acts on a specific substrate).

• They work under mild temperature and pH (usually body temperature and near-neutral pH).

---

🔹 3. Chemical Composition

Enzymes may be:

1.   Simple enzymes → made up of only proteins.
Example: Pepsin, Trypsin

2.   Conjugated (complex) enzymes → made up of a protein part and a non-protein part.

Part	Description
Apoenzyme	Protein part (inactive alone)
Cofactor	Non-protein part (helps enzyme work)
Holoenzyme	Active enzyme = Apoenzyme + Cofactor

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🔹 4. Types of Cofactors

1.   Prosthetic group:

o   Firmly attached to enzyme.

o   Example: Haem in catalase.

2.   Coenzyme:

o   Loosely attached organic molecule (often derived from vitamins).

o   Example: NAD⁺, FAD.

3.   Metal ions:

o   Act as activators by forming bonds with the enzyme or substrate.

o   Example: Mg²⁺, Zn²⁺, Cu²⁺.

classification of enzymes

🔹 8. Classification of Enzymes (Based on Type of Reaction)

(As per International Union of Biochemistry)

Class	Type of Reaction	Example
1. Oxidoreductases	Oxidation/reduction	Dehydrogenase
2. Transferases	Transfer of groups	Transaminase
3. Hydrolases	Hydrolysis	Lipase, Protease
4. Lyases	Removal/addition of groups without hydrolysis	Decarboxylase
5. Isomerases	Rearrangement within molecule	Isomerase
6. Ligases (Synthetases)	Joining of two molecules	DNA ligase

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🔹 9. Importance of Enzymes

• Control metabolic reactions.

• Lower activation energy.

• Help in digestion (amylase, lipase, pepsin).

• Used in industries (detergents, brewing, cheese making, etc.).

• Used in diagnostics (e.g., enzyme tests for liver and heart diseases).

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In Summary

 

Term	Meaning
Enzyme	Biological catalyst
Apoenzyme	Protein part of enzyme
Cofactor	Non-protein helper
Holoenzyme	Complete active enzyme
Optimum temperature	Temperature at which enzyme works best
Inhibitor	Slows or stops enzyme activity