Overview
This lecture covers the basics of metabolism, focusing on definitions, types of metabolic reactions, enzyme function, and enzyme regulation, which are essential for understanding cellular processes and exam preparation.
Metabolism: Key Concepts
- Metabolism is the sum of all chemical reactions within a cell or organism.
- Anabolism builds complex molecules using ATP (energy input required).
- Catabolism breaks down complex molecules, releasing energy.
- Oxidation removes electrons from a molecule, breaking bonds.
- Reduction adds electrons to a molecule, forming new bonds.
Energy Principles in Biology
- Energy cannot be created or destroyed, only converted from one form to another.
- Chemical energy stored in bonds is vital for both living organisms and many non-biological processes.
- Organisms obtain energy by breaking down carbohydrates, lipids, and proteins.
Enzymes and Chemical Reactions
- Enzymes are proteins that speed up chemical reactions by lowering activation energy.
- The substrate binds to the enzyme at the active site, similar to a lock and key.
- Enzymes only work with specific substrates due to their unique active site shapes.
Role of Cofactors and Coenzymes
- Enzymes require cofactors (non-protein helpers) to function.
- Cofactors can be inorganic (e.g., magnesium, zinc, copper) or organic (coenzymes).
- Coenzymes are organic cofactors, often derived from vitamins (e.g., NAD from B3, FAD from B2).
Enzyme Activity and Environmental Effects
- Enzyme activity is optimal at specific temperatures, pH, and salt concentrations.
- Extreme conditions denature enzymes, causing loss of function.
- Denaturation explains why fevers can inhibit bacterial growth.
Enzyme Regulation
- Allosteric regulation occurs when a molecule (not the substrate) binds to an enzyme, altering its activity.
- Allosteric regulation ensures just the right amount of product is made.
- Product inhibition is a form of allosteric regulation where the product inhibits enzyme activity.
Enzyme Inhibition
- Competitive inhibition: a molecule similar to the substrate binds to the active site, blocking substrate access.
- Non-competitive inhibition: a molecule binds elsewhere on the enzyme, changing its shape and function.
- Antibiotics like sulfa drugs use competitive inhibition to block bacterial enzymes.
Key Terms & Definitions
- Metabolism — sum of all chemical reactions in an organism.
- Anabolism — building complex molecules from simpler ones, requiring energy.
- Catabolism — breaking down complex molecules to release energy.
- Oxidation — loss of electrons from a molecule.
- Reduction — gain of electrons by a molecule.
- Enzyme — protein that accelerates chemical reactions.
- Substrate — molecule upon which an enzyme acts.
- Active Site — region of the enzyme where the substrate binds.
- Cofactor — non-protein molecule needed for enzyme activity.
- Coenzyme — organic cofactor, often derived from vitamins.
- Allosteric Regulation — regulation of enzyme activity by binding of a molecule at a site other than the active site.
- Competitive Inhibition — inhibition where molecules compete for the active site.
- Non-Competitive Inhibition — inhibition where molecules bind elsewhere, altering enzyme shape.
Action Items / Next Steps
- Review definitions and understand the differences between anabolism, catabolism, oxidation, and reduction.
- Study the mechanisms of enzyme function and regulation, especially competitive and non-competitive inhibition.
- Prepare for the upcoming exam by focusing on content up to the first half of the provided PowerPoint slides.