Tuesday, October 28, 2008

Lab 2 Enzyme Catalyst

Hey guys! Today in class we took the 8.2 quiz. Since our essay was canceled, (thanks Ms. Lyon!) we prepped for the lab.

Lab 2: Enzyme Catalyst (Factors Influencing Enzyme Activity)

Enzymes are biological catalysts capable of speeding up chemical reactions by lowering activation energy. One benefit of enzyme catalysts is that the cell can carry out complex chemical activities at relatively low temperatures.

Regions that play important roles in catalytic activity
  1. Active Site: The area of the enzyme which binds to the substrate(s) and aids in the chemical reaction.
  2. Allosteric Site: Involved in forming the proper 3D shape when linked with specific cofactors.

These regions allow enzymes to be highly specific in terms of the reactions they will catalyze and under the condition they work best.

Enzyme Reactions

Enzymes combine reversibly with specific substrates to form an enzyme-substrate complex. This then forms the products of the reactions.

The equation for enzyme reactions is as follows:

Enzyme + Substrate → Enzyme-Substrate Complex → Enzyme + Product

It is important to remember that the enzyme is not consumed in the reaction and can recycle to work with additional substrate molecules. Each enzyme is specific for a particular reaction because its amino acid sequence is unique, which causes it to have a unique 3D structure. The active site is the part of the enzyme that interacts with substrate, so that any substance that blocks or changes the shape of the active site affects the activity of the enzyme.

Factors Influencing Enzyme Activity include

1. Time course of enzyme activity
2. Enzyme concentration
3. Temperature
4. pH
5. Substrate Concentration
6. Ionic concentration

Any of these factors, if altered from the optimal state, will influence the way the enzyme reacts with the substrate.

Some conclusions you should make

1. The rate of a reaction is determined by measuring the accumulation of one of the products or by measuring the disappearance of the substrate (reactant).
2. The rate of a reaction is the slope of the linear (straight) part of the graph that describes the accumulation of product (or decrease in substrate) as time progresses.
3. Reaction rate may be affected by temperature, pH, substrate concentration, and enzyme concentration.

Multiple Choice Questions

1. If an enzyme is added to a solution where its substrate and product are in equilibrium, what would occur?
a. Additional product would be formed
b. additional product would be formed
c. the reaction would change from endergonic to exergonic
d. the free energy of the system would change
e. nothing; the reaction would stay at equilibrium

2. In describing enzyme feature, enzymes:
a. are composed primarily of polypeptides, which are polymers of amino acids.
b. can bind prosthetic groups such as metal ions that participate in enzyme reactions
c. have defined structures.
d. bind their substrates at active sites.
e. all statements are true

3. Which of the following is not a true type of enzyme inhibition?
a. allosteric inhibition
b. competitive inhibition
c. noncompetitive inhibition
d. denaturation inhibition
e. feedback inhibition

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