B5. Enzymes Flashcards
(19 cards)
What are enzymes?
Enzymes are biological catalysts that speed up chemical reactions without being used up or changed themselves.
What are enzymes made of?
Proteins.
What is the active site of an enzyme?
A specially shaped region of the enzyme where the substrate binds and the reaction takes place.
What is meant by the “lock and key” model of enzyme action?
The enzyme’s active site fits exactly with its specific substrate, like a key fitting into a lock.
Why are enzymes specific to particular reactions?
Because only substrates with the correct shape can fit into an enzyme’s active site.
What factors affect the rate of enzyme activity?
Temperature, pH, enzyme concentration, and substrate concentration.
What happens to enzyme activity as temperature increases (before the optimum)?
The rate of reaction increases because particles move faster and collide more often with enough energy.
What is the optimum temperature for most human enzymes?
Around 37°C.
What happens to an enzyme when the temperature becomes too high?
The enzyme denatures: its active site changes shape, so it can no longer bind to the substrate.
What does it mean when an enzyme is “denatured”?
Its structure is permanently changed, and it can no longer function properly.
How does pH affect enzyme activity?
Each enzyme works best at a specific pH; if the pH is too high or too low, the enzyme may denature.
Give an example of an enzyme that works best at low pH and where it is found.
Pepsin, which works in the stomach at an acidic pH.
How does substrate concentration affect enzyme activity?
Increasing substrate concentration increases the reaction rate up to a point, after which all active sites are occupied and the rate levels off.
How does enzyme concentration affect enzyme activity?
Increasing enzyme concentration increases the rate of reaction, provided there is enough substrate available.
What would happen to a reaction if the enzyme was missing?
The reaction would still occur but much more slowly, if at all.
Name three examples of enzymes and their functions.
Amylase: breaks down starch into simple sugars.
Protease: breaks down proteins into amino acids.
Lipase: breaks down lipids into fatty acids and glycerol.
What does it mean that enzymes lower the activation energy of a reaction?
They reduce the amount of energy needed to start the reaction.
What would a graph of enzyme activity vs temperature look like?
It rises steadily to the optimum temperature, then falls sharply as the enzyme denatures.
What would a graph of enzyme activity vs pH look like?
A peak at the optimum pH with a drop-off on either side (looks like a bell-shaped curve).
