Activation energy

Question 1

Activation energy

Answer 1

This is the energy needed to start a reaction
Enzymes lower this and speed up the rate of reaction without altering the temperature at which it occurs. Different reactions have different activation energies
The changes of shape of both active site and substrate bring reactive groups of enzyme and substrate close to each other, weakening bonds in the substrate so the reaction takes place at a lower activation energy

Question 2

Factors which effect enzyme activity:

Temperature

Answer 2

An increase in temperature, increases the rate of reaction up to an optimum temperature because the molecules move faster as the heat energy raises the kinetic energy leading to more successful collisions (reactions)
However if the temperature increases beyond the optimum temperature, the rate of reaction decreases?stops as more kinetic energy causes the enzymes to vibrate more.

Question 3

Factors which effect enzyme activity:

pH (Power of Hydrogen)

Answer 3

pH is a measure of the H+ ion concentration. The 3D shape (tertiary structure) of an enzyme is held by ionic and hydrogen bonding. Changes in pH alter the ionic charge and break bonds. This changes the shape of the active site so no E/S complexes form causing denaturation.
Every enzyme has it’s own optimum p H range although most are around neutral (pH 7)
-Buffers are used to maintain a constant pH

Question 4

Factors which effect enzyme activity:

Substrate concentration

Answer 4

An increase substrate, increases the rate of reaction up to a point where all the active sites on the enzymes are full.
When all the active sites are full, then the concentration of enzyme will become a limiting factor on the rate of reaction.

Question 5

Factors which effect enzyme activity:

Enzyme concentration

Answer 5

An increase in enzymes, increases the rate of reaction as there are more active sites available. (so more E/S complexes form)
This continues as long as there is excess substrate.