Enzymes

Induced-fit hypothesis

Enzyme and substrate molecule collide; enzyme changes shape to make the active site fit around the molecule more closely
Oppositely charged groups on active site and substrate are close together, also holds substrate in place (enzyme-substrate complex)
As the enzyme changes shape, the substrate undergoes strain which destabilises it, making the reaction happen more easily
Products different shape from substrate, so no longer fit in active site; move away
Enzyme catalyses same reaction with a different substrate

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Molecules in a gas/liquid have natural kinetic energy; so constantly collide with each other
Temperature increases; kinetic energy increases. Molecules move faster and collide more often and with greater force
More collisions = more product = increased reaction rate

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Applying heat makes molecules vibrate, putting strain on the bonds that hold the molecule together
In large molecules, vibration can break weaker bonds (H and ionic)
These bonds are the ones that hold the tertiary structure together, thus maintaining the shape of the active site
Increased heat = increased bond breakage
Structure loses the shape needed to keep the active site working
Thus, rate of reaction decreases

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Measure of H+ concentration
H+ ions can interfere with H and ionic bonds of the tertiary structure of an enzyme; thus the concentration of H+ ions has a direct effect on how well the tertiary structure of an enzyme is held together
H+ ions attracted to negative groups on active site, thus alter charges around active site and change its shape
Optimum pH = tertiary structure shape that best accomodates substrate
Enzymes work in a considerably narrow pH range
Only denature when pH changes violently

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