Enzymes Flashcards
(22 cards)
What is an enzyme?
A biological catalyst that speeds up chemical reactions without being used up.
What is the structure of an enzyme?
Globular protein with a specific active site that binds to substrates.
What is the active site?
The region on an enzyme where the substrate binds and the reaction occurs.
What is enzyme specificity?
Enzymes are specific to their substrate due to the complementary shape of the active site.
What is the lock and key hypothesis?
The substrate fits exactly into the enzyme’s active site, like a key in a lock.
What is the induced fit hypothesis?
The active site changes shape slightly to fit the substrate more closely.
What is activation energy?
The minimum energy required for a reaction to occur. Enzymes lower this.
How do enzymes lower activation energy?
By stabilising the transition state and weakening bonds in the substrate.
What factors affect enzyme activity?
Temperature, pH, enzyme concentration, substrate concentration, and inhibitors.
How does temperature affect enzyme activity?
Increases rate up to an optimum, then decreases due to denaturation.
How does pH affect enzyme activity?
Each enzyme has an optimum pH; extreme changes denature the enzyme.
What are cofactors?
Non-protein components required for enzyme activity (e.g., metal ions or vitamins).
What are coenzymes?
Organic cofactors that temporarily bind to the enzyme and help in the reaction.
What are prosthetic groups?
Permanently bound cofactors (e.g., haem group in catalase).
What is a competitive inhibitor?
A molecule that competes with the substrate for the active site, reducing enzyme activity.
What is a non-competitive inhibitor?
A molecule that binds to a site other than the active site, altering the enzyme’s shape and reducing activity.
What is end-product inhibition?
A form of negative feedback where the product of a reaction inhibits the enzyme earlier in the pathway.
What is an intracellular enzyme?
An enzyme that functions within the cell (e.g., catalase).
What is an extracellular enzyme?
An enzyme secreted by cells that functions outside the cell (e.g., amylase, trypsin).
What is the Q10 temperature coefficient?
A measure of the rate of change of a biological or chemical system as a consequence of increasing the temperature by 10°C.
What is the effect of enzyme concentration on rate?
Increased enzyme concentration increases the rate until substrate becomes limiting.
What is the effect of substrate concentration on rate?
Increased substrate increases rate until all active sites are occupied (saturation).
