1. Metabolism
8.1

2. Essential Idea: Metabolic reactions are regulated in response
to the cell’s need.
8.1
Metabolism
Understandings:
Metabolic pathways consist of chains and cycles of enzyme-catalyzed reactions
Enzymes lower the activation energy of the chemical reactions that they catalyze
Enzyme inhibitors can be competitive or non-competitive
Metabolic pathways can be controlled by end-product inhibition
Applications:
End-product inhibition of the pathway that coverts threonine to isoleucine
Use of databases to identify potential new anti-malarial drugs
Skills:
Calculate and plot rates of reaction from raw experimental results
Distinguish different types of inhibition from graphs at specified substrate concentration

3. Metabolism Sum of all chemical reactions in a body Anabolic Catabolic
Build complex molecules
Break down complex molecules
Endergonic
Exergonic
Biosynthetic
Degradative
Photosynthesis
Cellular respiration

4. Metabolic pathways catalyst Occurs in specific compartment of cell
Most reactions are sequence of events

5. Induced fit model – enzyme undergoes change in conformation as it interacts with substrate
Still requires proper shape of enzyme and substrate
Enzyme is undergoing conformational change
Change in R groups of A.A. upon interaction with substrate
Complex high level proteins
Active site

6. Enzymes work by lowering activation energy (AE)
AE is the energy required to destabilize existing bonds
Enzyme reduce energy needed to break/change bonds
DO NOT change amount of product formed

7. Mechanism of enzyme action
repeat
Enzyme changes shape to fit substrate and enzyme-substrate complex forms
AE is lowered, atoms are rearranged, product is released
Surface of substrate Contacts active site
E + S  ES  E + P

8. Competitive Inhibition
Similar structure
Competitive Inhibitors – a molecule binds into the active site, blocking access to the substrate
Decrease rate in reaction
Examples: Sulfanilamide  blocks PABA – prevents production of folic acid in bacteria
Can be reversible or irreversible
If reversible, can be overcome
by increasing substrate concentration

9. Non-competitive Inhibition
Non-competitive Inhibitors – bind elsewhere on enzyme and forces change in shape of active site
allosteric inhibition
Distorted active site no longer allows substrate to bind
Examples:
Metallic ions (Hg)
Allosteric inhibitor leaves – enzyme becomes functional again

10. End Product Inhibition
Shut down
Used to regulate metabolic pathways
Final product acts as an allosteric inhibitor to the first enzyme in the series
Low product amount, allosteric inhibitor leaves and process resumes
Enough product made