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Microbes · Chapter 3: Enzymes

Year 11 SCX · About 17 minutes with activities · Turn your sound on

Chapter 3 · Enzymes
Fridge: 4 °C2 days
Warm: 35 °C2 days
Hot: 70 °C2 days
Enzymes slowedfew collisions
Near optimumfast respiration
Denaturedrespiration stops
No enzymehigh activation energy
With enzymelower activation energy
Amino acid chainamino acids bonded together
Globular proteinits own 3D shape
Digests foodoutside the cell
Respirationinside the cell
Active sitesubstrate binds here
Substratethe reactant
Productsafter the reaction
Wrong shapecan’t bind
Cold: 10 °Cless kinetic energy
Warm: 40 °Cmore kinetic energy
Few collisions
More collisions
More collisionsmore kinetic energy
Optimum: fastestabout 40 °C
Denaturesshape changes
Working enzyme
Denatured
Substrate fits
Can’t bindactive site changed
Still denaturedcooled from 70 to 40 °C
Optimum pHfastest rate
Acidicshape changes
Alkalineshape changes
Temperatureyou set it
pHyou set it
Rate: products per minute

Chapter 3 recap

  • Enzymes are biological catalysts: proteins that speed up reactions by lowering the activation energy. The substrate binds to the active site, and its shape gives the enzyme its specificity.
  • Mechanism: substrates collide with the enzyme → the enzyme-substrate complex forms → the enzyme catalyses the reaction → products leave and the enzyme is reused.
  • Temperature and pH: below the optimum, fewer collisions, so a slower rate. Above it, the enzyme denatures: the active site changes shape permanently, so the substrate no longer fits.
  • Next: Chapter 4 · Bacterial growth

Why does temperature change how fast bacteria grow?

Chapter 3 · About 17 minutes · sound on

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