Enzymes Flashcards
(29 cards)
What is an enzyme?
A biological catalyst used to speed up chemical reactions by lowering the activation energy.
True or false: Enzymes are consumed in reactions.
False
a ___ reaction happens spontaneously and releases energy.
Exergonic
A ___ reaction is non-spontaneous and uses up energy.
Endergonic
What are substrates?
Substrates are specific reactants that are involved in reactions. Each enzyme has a specific substrate they catalyze.
What is the enzyme-substrate complex?
A temporary molecule formed when the substrate binds to the enzyme. When an enzyme binds to its substrate, it undergoes a conformational change or temporary change in shape.
What is the active site?
The portion of the enzyme where the substrate will bind
What’s the difference between the lock and key hypothesis and the induced fit hypothesis?
The lock and key hypothesis states that enzymes and substrates naturally fit together like a lock and key
The induced fit hypothesis suggests that an enzyme has to change shape (conform) to accomodate the binding of an substrate
What is a cofactor?
A non-organic, non-protein group that binds to an enzyme.
Often positively charged ions (Ex: metals like Mg)
What is a coenzyme?
An organic non-protein that binds to enzyme, often derived from vitamins.
What conditions and factors affect enzyme activity?
Enzyme and substrate concerntration
Inhibitors (competitive and noncompetitive)
Allosteric regulation
Inhibition (positive and negative)
pH and temperature
How does an increase in enzymes affect chemical reactions?
Greatly increases the rate of reaction
How does an increase in substrate affect chemical reactions?
Increases the rate of reaction until it hits the saturation point where the maximum rate of reaction is reached. The rate will then plateau.
True or false: Cells can restrict the location of enzymes to certain locations.
True
What is enzyme inhibition?
Enzyme inhibitors lower the rate at which an enzyme catalyzes a reaction
They bind to an enzyme and decrease it’s activity
What is the difference between competitive and non-competitive inhibition?
Competitive: Binds with active site to block its ability to bind with the substrate
Non-competitive: Binds with a site outside of the active site and changes the shape of the enzyme
What is a binding site outside of the active site called?
Allosteric site
What is allosteric regulation?
The regulation of an enzyme by binding to an allosteric site
What is the difference between positive allosteric control and negative allosteric control?
Positive: Stabilizes enzyme shape and causes a higher affinity for the substrate
Negative: inhibits enzyme and causes a lower affinity for the substrate
What is feedback inhibition?
When the product of a metabolic process becomes an allosteric regulator of an enzyme from earlier in the process.
What is precursor activation?
When the substrate of reaction accumulates and activates the enzyme
How does pH and temperature effect enzymes?
When outside of the optimal range, reaction rate decreases - at extremes enzymes can denature.
What are the 6 classes of enzymes?
Oxidases/ reductases
Transferases
Hydrolases
Ligases
Lyases
Isomerases
Which class of enzymes rearrange atoms to make substrates more reactive?
Isomerases
