Enzymes Flashcards
(23 cards)
What is an enzyme?
Biological catalyst made of protein.
How do enzymes affect metabolic reactions?
Speeds up reactions without being used up.
What is the role of enzymes in intracellular reactions?
Catalyses reactions inside the cell.
What is the role of enzymes in extracellular reactions?
Catalyses reactions outside the cell.
Give one example of an intracellular enzyme.
Catalase
Give one example of an extracellular enzyme.
Amylase
What is the lock and key hypothesis?
Enzyme active site is a perfect match for substrate shape.
What is the induced fit hypothesis?
Active site changes shape to fit substrate
What is an enzyme-substrate complex?
Temporary complex formed when substrate binds enzyme.
How do enzymes lower activation energy?
They bring substrates together in correct orientation and stress bonds.
What is the effect of temperature on enzyme activity?
Increases rate up to optimum, then denatures
What is the temperature coefficient (Q10) formula?
Q10 = (rate at higher temp) / (rate at lower temp)
What is the effect of pH on enzyme activity?
Each enzyme has an optimum pH; outside this range, denatures.
What is the effect of substrate concentration on enzyme activity?
Increases rate until saturation point.
What is the effect of enzyme concentration on enzyme activity?
Increases rate if excess substrate is available.
What is a cofactor?
Non-protein substance needed for enzyme activity.
What is a coenzyme?
Organic cofactor often derived from vitamins.
Give one example of a cofactor
Chloride ion for amylase.
Give one example of a coenzyme.
NAD
What is a competitive inhibitor?
Competes for active site; similar shape to substrate
What is a non-competitive inhibitor?
Binds elsewhere, changes active site shape.
What is the difference between reversible and non-reversible inhibition?
Reversible: binds weakly. Non-reversible: binds permanently.
What is end-product inhibition?
Product of reaction inhibits enzyme that produced it.
