Enzymes Flashcards
(17 cards)
What is an enzyme and what is its main function?
An enzyme is a globular protein that acts as a biological catalyst, speeding up chemical reactions by lowering the activation energy required.
What is activation energy and how do enzymes affect it?
Activation energy is the minimum energy needed to start a chemical reaction. Enzymes lower this energy threshold to allow reactions to occur more easily at body temperature.
What is the active site of an enzyme?
The region on the enzyme where the substrate binds. It is highly specific to the shape of the substrate.
Describe the induced fit model.
The enzyme slightly changes shape to fit the substrate better, creating an enzyme-substrate complex that facilitates the reaction.
What is the difference between anabolic and catabolic reactions?
Anabolic reactions build complex molecules (require energy), while catabolic reactions break down molecules (release energy). Enzymes can catalyze both.
What is a coenzyme?
A non-protein organic molecule, often derived from vitamins, that assists enzymes by transferring electrons, atoms, or functional groups.
What is a cofactor?
An inorganic substance (e.g., metal ions like Zn²⁺ or Fe²⁺) that helps enzymes function properly.
How does temperature affect enzyme activity?
Enzyme activity increases with temperature up to an optimal point (~37°C). Beyond this, high heat denatures the enzyme, altering its shape and deactivating it.
How does pH affect enzyme activity?
Each enzyme has an optimal pH range. Deviations from this range can denature the enzyme and reduce activity.
What is enzyme denaturation?
The loss of an enzyme’s shape (and function) due to factors like high temperature or extreme pH.
How does substrate concentration affect enzyme activity?
Increasing substrate concentration increases reaction rate until all enzymes are saturated. Beyond that, the rate levels off.
How does enzyme concentration affect enzyme activity?
Higher enzyme concentration can increase reaction rate if sufficient substrate is available.
What are competitive inhibitors?
Molecules that resemble the substrate and compete for binding to the active site, blocking substrate access.
What are non-competitive inhibitors?
Molecules that bind elsewhere on the enzyme, changing its shape and rendering the active site ineffective.
How do heavy metals inhibit enzymes?
Heavy metals like Pb²⁺ and Hg²⁺ act as non-competitive inhibitors by irreversibly altering the enzyme’s shape.
What is the role of thyroxin in metabolism?
Thyroxin is a hormone from the thyroid gland that increases cellular metabolism and oxygen consumption.
What happens to enzymes after a reaction?
Enzymes are not consumed in the reaction and can be reused multiple times.
