Enzymes

[!def]
biological catalysts^[catalysts: a substance that speeds up a chemical reaction, or lowers the temperature or pressure needed to start one, without itself being consumed during the reaction.]

Functions

Speed up metabolic reactions

Lowers activation energy

All metabolic reactions need enzymes.

How it works
Substrate fits into enzyme
active site
ref. shape of molecules complementary
lock and key
substrate&water close together within enzyme
product produced, enzyme unchanged
lower activation energy

Names

Starch amylase
Protein protease
Lipid lipase
Maltase maltase
Sucrose sucrasew

-ase

Structure

enzyme enzyme
+ <-> enzyme-reactant complex <-> +
reactant product

[!def] Substrate(Reactant)
A substance on which an enzyme reacts

[!def] Enzyme-substrate complex
What is formed when a enzyme and substrate bind

[!def] Product
The substance produced then a enzyme acts on a substance

[!def] Active Site
The part of the enzyme that binds when an enzyme act on a substrate

Properties

Specificity: describes enzyme action, only specific substrates fit into a particular enzyme
Lock and key: one specific key(reactant) fits perfectly in a particular lock(enzymes). A model for how enzymes work
Complementary(互补): describes the shape of a specific substrate that fits into a specific enzyme.

Activation Energy

[!def]
The energy needed for the substrate to chemically change into products

Enzymes lower the activation energy of a reaction, so reactions can take place at lower temperatures.

Factors affecting enzyme rates

  • Temperature
  • pH
  • concentration
  • pressure
  • substrate concentration
    All enzymes has a optimum temperature/pH,

TEMPERATURE

kinetic energy of enzyme and substrate molecules increase
activation energy of the reaction can more readily be provided at a higher temperature
frequency collisions
formation of enzyme-substrate complexes increase
rate of reaction increase

lose its shape
denatured
active site is no longer complementary
enzyme-substrate complexes cannot form