wed 10 19 05

Lecture 10/19
Test results are online. He looks at improvement to curve grades, so keep working hard. Problem set is posted and due next Wednesday.
• Chapter 6 Enzymes
• 3 ½ billion years- need enzymes catalyst to start protein building and life.
• Power of catalyst = we eat 20-40 pounds of ATP a day and enzymes can recycle this mass.
• Table 6-1 cofactors- metal or cations- help enzyme function. Bind reversible but usually sticks. Cofactors are not transformed by enzymes.
• Table 6-2 Coenzymes are also required for activity. It is a truly revisable interaction. Usually require more than just protein; dietary vitamins. NAD very much needed but usually not produced, need dietary precursor or nicotiniz acid (niacin) not a coenzyme. It has to be transferred into it by enzyme.
• Table 6-3 4,200 known genes of the E.Coili, 2,000 of then have been assigned to metabolic function. Given 3 numbers to for function.
• Figure 6-1 the substrate binds to an enzyme. The active site cleaves the internal peptide bond. (In the picture) The red spot is Amino R groups that are important to catalyst enzyme. The neighbor stick is called the active site. Most of the grey stuff is needed because if you mess with the structure the activity stops.
• Figure 6-2 Free energy chemical profile. Down hill is a chemically favored. Free energy barrier ΔG‡ S-> P
• Overhead Reaction velocity for unimolecule reaction:
Vcat = K{S} + Cuncat.
K is the rate constant. Cuncat is usually 0
K is large enough to ignore Cuncat
How do G‡ and K related? G‡ is the activation energy and the K is the rate.
From transition state theory
K inversely proportional to e^ΔG‡/RT
R is the gas constant, T is absolute K
• ΔG‡ p->S has a larger free energy. Can reach equilibrium
• Figure 6-3 Enzymes do not change chemically. Can accelerate catalyst to equilibrium. They lower the free energy barrier. Usually hills because of substrate interaction. The enzyme is unchanged.
• Table 6-5 Very effective in increasing the rates.
• Figure 6-5 (Fault to picture-creating 2 sticks forward should =backwards) A) energy is used to break stick. B.) Lock and key – poor –model- enzyme active site optimized binding to the stick, energy lowered first because of magnetic interaction, makes bigger a bigger energy to climb. C.) Use of transition state. Some energy for ES (enzyme substrate) complex, but the enzyme complements the shape, with catalyst bending, makes ‡ less dramatic, so it can happen faster.
• Figure 6-6 ΔG‡ for energy enzyme catalyst fashion does not mean it is the same pace in the backwards motion.
• Figure 6-7 There is entropy (chemical potential energy): linkage of bonds, entropy changes, changing the rates.
• Figure 6-8 Directed acid-base properties. In active site, give chemical properties. R groups can be changed by what is in their neighborhood. Can be helped by enzymes. To make stronger base, put close to acid. Make water by adding H, which makes it a stronger acid and a better leaving group. This guides the rate.