sci_bio
Enzymes
Chapter summary, hard words and model exam answers for ICSE Class 10 Hindi.
Free online summary and notes (ICSE Class 10 Hindi). Read it here, no PDF download needed.
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Biology · CBSE 10 · ICSE 10 · GCSE (AQA, Edexcel, OCR)
Summary
They lower the activation energy a reaction needs to start. One enzyme molecule can work thousands of times per second.
The substrate binds, forming an enzyme-substrate complex. Products form, no longer fit, and are released - the enzyme is free again.
Above the optimum temperature, or at extreme pH, the active site changes shape and the substrate no longer fits. Denaturation is permanent.
Competitive inhibitors sit in the active site; non-competitive ones bind elsewhere and change the enzyme's shape. Many medicines and poisons work this way.
Hard words & meanings
| catalyst | a substance that speeds up a reaction without being used up |
| active site | the shaped region of an enzyme where the substrate binds and reacts |
| substrate | the molecule an enzyme acts on and converts to products |
| denaturation | the permanent change in an enzyme's shape from high temperature or extreme pH |
| optimum | the temperature or pH at which an enzyme works fastest |
| activation energy | the minimum energy needed to start a reaction; enzymes lower it |
| competitive inhibitor | a molecule that blocks the active site, stopping the substrate entering |
| specific | an enzyme catalyses only one reaction because of its active site shape |
Model exam answers, grammar & audio
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