Overview
This lecture explains what enzymes are, how they function as biological catalysts, the models of enzyme action, their specificity, and the effects of temperature on enzymes.
What Are Enzymes?
- Enzymes are proteins that speed up chemical reactions in living organisms.
- They act as biological catalysts and are not used up in reactions.
- Enzymes help break down large molecules like proteins, carbohydrates, and fats.
How Enzymes Work
- Enzymes can break molecules apart or join them together.
- The molecule an enzyme acts on is called a substrate.
- The specific area where the substrate binds is called the active site.
Models of Enzyme Action
- Lock and Key Model: The active site has a shape exactly complementary to its substrate.
- Induced Fit Model: The active site changes shape to fit the substrate as it binds, helping to break chemical bonds.
Enzyme Specificity
- Each enzyme has a unique active site and only catalyzes one specific reaction.
- The enzyme's name usually ends in "-ase"; for example, protease for proteins, carbohydrase for carbohydrates, and lipase for lipids.
- Enzyme specificity allows the body to control different reactions by producing different enzymes.
Effects of Temperature on Enzymes
- Enzymes are proteins and can lose their shape ("denature") at high temperatures.
- Denaturation alters the active site, so it no longer fits the substrate and the reaction stops.
- Most human enzymes denature at around 40°C, but some enzymes in other environments can withstand higher temperatures.
Quiz Questions Reviewed
- Enzymes are not made of carbohydrates; they are proteins (False).
- Lipase enzymes cannot break down carbohydrates; each enzyme is specific (True).
- Not all enzymes denature at 40°C; some work at higher temperatures (False).
Key Terms & Definitions
- Enzyme — a biological catalyst that speeds up chemical reactions without being used up.
- Substrate — the specific molecule an enzyme acts upon.
- Active Site — the region of the enzyme where the substrate binds.
- Denature — a change in shape of the enzyme, usually due to high temperature, causing loss of function.
- Catalyst — a substance that speeds up a chemical reaction without being consumed.
Action Items / Next Steps
- Review and memorize definitions and enzyme models.
- Complete any additional quizzes or revision activities provided.
- Check the recommended next video for further biology revision.