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Biochemistry: Enzyme Index

Enzymes
Factors Affecting Enzymes: Substrate concentration
Factors Affecting Enzymes: pH
Factors Affecting Enzymes: Temperature
Inhibitors
Enzymes and Homeostasis
Enzymes and Biotechnology
Catalase
Haemoglobin
The Steroids

Topic Chapters Index

 

The Induced Fit Hypothesis (Daniel Koshland in 1959)

  • Some proteins can change their shape (conformation).

  • When a substrate combines with an enzyme, it induces a change in the enzyme's conformation.

  • The active site is then moulded into a precise conformation.

  • Making the chemical environment suitable for the reaction.

  • The bonds of the substrate are stretched to make the reaction easier (lowers activation energy).

This explains the enzymes that can react with a range of substrates of similar types

 

 

BIOCHEMISTRY

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Enzyme Mechanisms

The substrate

  • The substrates of an enzyme are the reactants that are activated by the enzyme.

  • Enzymes are specific to their substrates.

  • The specificity is determined by the active site.

 

The Lock and Key Hypothesis (Emil Fischer in 1890)

  • Fit between the substrate (S) and the active site of the enzyme (E) is exact.

  • Like a key fits into a lock very precisely.

  • Temporary structure called the enzyme-substrate complex formed.

  • Products (P) have a different shape from the substrate.

  • Once formed, they are released from the active site.

  • Leaving it free to become attached to another substrate.

Lock and Key hypothesis

This explains enzyme specificity.

This explains the loss of activity when enzymes denature.

 

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