figure 6.1 the complexity of metabolism. figure 6.5 the relationship of free energy to stability,...
TRANSCRIPT
Figure 6.1 The complexity of metabolism
Figure 6.5 The relationship of free energy to stability, work capacity, and spontaneous change
Figure 6.6 Energy changes in exergonic and endergonic reactions
Figure 6.7 Disequilibrium and work in closed and open systems
Figure 6.8 The structure and hydrolysis of ATP
Figure 6.9 Energy coupling by phosphate transfer
Figure 6.10 The ATP cycle
Figure 6.11 Example of an enzyme-catalyzed reaction: Hydrolysis of sucrose
Figure 6.12 Energy profile of an exergonic reaction
http://www.stolaf.edu/people/giannini/flashanimat/enzymes/transition%20state.swf
Figure 6.13 Enzymes lower the barrier of activation energy
Figure 6.14 The induced fit between an enzyme and its substrate
Figure 6.15 The catalytic cycle of an enzyme
Figure 6.16 Environmental factors affecting enzyme activity
Characterizing enzymes
• Vmax - rate when enzyme is saturated with substrate
• KM – substrate concentration that allows reaction to proceed at 1/2 Vmax
• KM – useful as a measure of how tightly an enzyme binds its substrate– Low KM means tight binding, high KM
means weak binding
• Enzyme kinetics
Characterizing enzymes
• Turnover number: Vmax/enzyme concen.
– typically about 1000 substrate molecules processed per second per enzyme molecule, but can be much higher
Enzyme Turnover number (per second)
Carbonic anhydrase 600,000
Acetycholinesterase 25,000
Amylase 18,000
Penicillinase 2,000
DNA Polymerase 15
Measuring enzyme activity
• One unit of an enzyme is defined as the amount that will catalyze a defined amount of substrate in one minute under specified conditions.
• For catalase:
one unit decomposes 1mole H2O2 at 250C at pH 7.
What to measure for rate?
• Amount of substrate used over a specified time.
OR
• Amount of product accumulated over a specified time.
• Which to use???
Figure 6.17 Inhibition of enzyme activity
Figure 6.18 Allosteric regulation of enzyme activity
Figure 6.19 Feedback inhibition
Figure 6.20 Cooperativity