Tuesday, December 6, 2011

2.10 Effect of pH on the rate of reaction

 Understand how the functioning of enzymes can be affected by changes in pH

1. Lower PH (acidic) = the rate of reaction gradually decreases. 
Optimum PH = maximum rate = rate of reaction decreases. 
Higher Ph (alkaline conditions) = rate of reaction gradually decreses. 

Graph is more symmetrical. 

Acidic and Alkaline conditions change the shape of the ACTIVE SITE and this slows the reaction. 

2.9 Effect of Temperature on the rate of reaction

 Understand how the functioning of enzymes can be affected by changes in temperature

1. a) Increase in temp = increase in average KE of particles. 
increase in average KE of particles = more frequent collisions = more fruitful reactions. 
2. Particles = Substrate and the Enzyme 
 Reaction = E+S ---> ES(complex)--> E + Product formed. 

Low temp = low KE, few complexes formed and product will be formed slowly (slow rate of reaction)
Higher temp = KE of S and E increase --> more complexes formed = more product formed. 
Optimum temp (peak of curve) = rate of reaction declined very quickly because KE changes the shape of the ACTIVE SITE of the enzyme = denatured. (cannot produce any more product).

2.8b Enzyme Reactions

Understand the role of enzymes as biological catalysts in metabolic reactions. 

1. (Oxidation of oxygen) Respiration C6 H12 O6 + O2 ---> Energy + CO2 + H2O
    Substrate                                          Released          Product

2. Combustion (adding energy) = Without an enzyme - to break down glucose ---> carbon dioxide and water - we have to put energy into the glucose molecule bonds before they break and release a lot of energy.

3. Energy of Activation = initial energy added to glucose molecules.

The shape of the active site is affected by pH. This is why enzymes will only work at a specific pH, as well as a specific temperature. Change the pH (acidic) and the enzyme stops working.
Increasing the temperature to 60°C will cause a permanent change to the shape of the active site. This is why enzymes stop working when they are heated. We say they have become denatured.

Biological systems overcome the energy of activation by THE ENZYME.