Im doing a chemistry lab about acids and base and need help?

Question

heres the link to the lab:

http://www.box.net/shared/kusfiongoo

could you help me with the observations, procedure, and questions

Answer 1

Enzymes are proteins. Proteins are complex 3D molecules made of amino acids and the 3D structure ultimately determines the function of the enzymes because it permits the binding of CERTAIN substrates with the correct molecular geometry.

What maintains the structure of an enzymes:

1. Hydrogen bonds

2. Van-der-waals forces

3. Ionic interactions (salt bridges) between basic and acidic amino acid side chains

3. Covalent bonds (disulfide linkages between cysteine residues)

From what I see in your lab your are testing different compounds with differing pH values.

For an enzyme to function properly it must stay within a very narrow range of physical and chemicals parameters.

pH change has two affects:

1. Affects the active site, especially in those enzymes which use acid-base reaction in their catalytic process

2. affects the ionization of acidic and basic side chains and alters the "salt bridges" formed between acid and basic amino acids and can lead to denaturation of the protein.

So,

1. Water - neutral (pH = 7)

    Vinegar - acidic (5% acetic acid, pH=2.2)

    Lemon juice - acidic (citric acid, pH=1.8-2.3)

    Baking soda - basic (sodium bicarbonate, pH=8.3)

    Milk of magnesia - basic (magnesium hydroxide, pH=10.5)

pH of 7 is neutral, this is the pH of distilled water, anything less then that is acidic and anything more then 7 is basic.

2. By testing the different substances you will quickly see under which condition the browning of the apple will happen slower or faster, obviously the solution that in which the browning happens fastest will be the most "ideal" condition for the particular enzyme which catalyzes the process. I would also say that since the enzymes in cells are "adapted" to operate under cellular pH which is about 7 or neutral, the reaction should be fastest in the distilled water

3. As stated before, enzymes operature in a narrow range, in terms of pH, temperature, ionic strenght, etc. as you move away from that range, there will be a steady decrease in the turnover number, number of reactants, or substrates converted to products per second until you get to a point where there will be a sharp drop, at this point the enzyme is denatured or the ionization of acidic and basic amino acids residues in the active site are severely altered  

4. Because those chemicals that are closest to the "optimal" pH at which the enzyme naturally operates, have much less effect on changing the ionization of amino acid side changes then does agents which are farther from that optimum.