Enzymes Flashcards
What is a enzyme ?
A biological catalyst that speeds up the rate of a chemical reaction, without being used up
Give an example of an enzyme that catalyses intracellular reaction
DNA Helicase - Breaks down hydrogen bonds between adjacent nucleotides
Give 2 examples of enzymes that catalyse extracellular reactions
Amylase - Catalyses digestion of starch
Trypsin - Catalyses hydrolysis of peptide bonds
Explain the induced fit model
Shape of the active site is not directly complementary to substrate
Active site slightly shifts to form enzyme-substrate complexes
Explain the lock and key model
Suggests the active site is complementary to only 1 substrate
What 5 factors effect rate of reaction (enzymes)
Enzyme Concentration Substrate Concentration Concentration of inhibitors pH Temperature
How does substrate concentration affect rate of reaction ?
Given that enzyme concentration is fixed, rate increases proportionally to substrate concentration. Rate levels off when maximum number of Enzyme-Substrate complexes form at any given time.
How does enzyme concentration affect rate of reaction ?
Given that substrate is in excess, rate increases proportionally to enzyme concentration.
Rate levels off when maximum number of ES complexes form at any given time.
How does temperature affect the rate of reaction ?
Rate increases as kinetic energy increases and peaks at optimum temperature
Above optimum temperature Ionic and Hydrogen bonds break, active site no longer complementary to substrate (denatured)
How does pH affect rate of reaction ?
Outside the optimum pH range H+ and OH- ions interact with the hydrogen and ionic bonds, causing tertiary structure to change (Denatured)
How do competitive inhibitors work ?
Bind to the active site since they have a similar shape to the substrate. Which temporarily prevents enzyme-substrate complexes from forming
Increasing substrate concentration decreases their effect
How do non-Competitive inhibitors work ?
Binds at allosteric site
Causes the active site to change shape (Permanent)
Increasing substrate concentration doesn’t change rate of reaction
What is end-product inhibition ?
One of the products of a reaction acts as a inhibitor, which prevents further formation of products
What are irreversible inhibitors ?
Permanently prevent formation of Enzyme-Substrate complexes by strong covalent bonds
What are reversible inhibitors ?
Bind to enzyme temporarily, by H-bonds of ionic bonds
