16 Questions
What is the definition of an enzyme?
A substance that increases the rate of a chemical reaction without being itself changed in the process
What is the suffix added to the substrate of the reaction to name an enzyme?
-ase
What are the general properties of enzymes?
All enzymes are proteins (except some catalytic RNA)
What is the role of enzymes in biological cells?
To make chemical reactions occur fast enough to support life
How do enzymes affect the rate of a chemical reaction?
They increase the rate of a chemical reaction without being changed themselves
What is the enzyme nomenclature based on?
The action performed or the substrate of the reaction
What is the role of a coenzyme in enzymatic reactions?
It catalyzes the transfer of electrons or oxygen
Which class of enzymes catalyzes the transfer of a chemical group other than hydrogen or oxygen from one substance to another?
Transferases
What is the role of Hydrolases?
Catalyze the hydrolysis of a substrate by adding water to cleave specific bonds
What do oxidoreductases mainly catalyze?
The transfer of electrons or oxygen
Which major class of enzymes catalyzes the joining of two substrates using ATP as an energy source?
Ligases
What is the transition state in a chemical reaction?
The point at which the reaction event can occur
How does an enzyme accelerate the rate of a reaction?
By providing an alternate reaction pathway with lower energy of activation
What is the active site in an enzyme?
A special pocket or cleft formed by folding of the protein
What is the characteristic feature of an enzyme's activity on a specific substrate?
Its specificity in acting only on a particular substrate.
What is the role of apoenzyme in enzymatic reactions?
It is the protein part that binds to coenzymes.
Study Notes
- Enzymes are biological catalysts that increase the rate of chemical reactions in biological cells without being changed themselves.
- They are proteins (except for some catalytic RNA) and are highly specific, acting on specific substrates.
- Enzymes do not undergo chemical change during a reaction and may require cofactors, which can be coenzymes or metal ions.
- Holoenzyme is the complex of apoenzyme (protein) and cofactor, while cofactors can be tightly or loosely bound.
- Enzymes can be classified into six major categories based on the type of reaction they catalyze: oxidoreductases, transferases, hydrolases, isomerases, lyases, and ligases.
- Oxidoreductases catalyze the transfer of electrons or hydrogen atoms, while transferases catalyze the transfer of a chemical group other than hydrogen or oxygen.
- Hydrolases catalyze the hydrolysis of a substrate, while isomerases catalyze geometric or structural changes within a molecule.
- Lyases catalyze simple splitting of the substrate without adding water, and ligases catalyze the joining of two substrates using ATP as an energy source.
- Enzymes lower the activation energy of a reaction, allowing it to proceed rapidly by providing an alternate reaction pathway.
- The active site is a special pocket or cleft within an enzyme where the substrate binds and the reaction takes place.
Test your knowledge on enzymes with this quiz covering enzyme structure, properties, classification, factors affecting enzyme activity, types of enzyme inhibitors, and mechanisms of enzyme regulation. Also includes the use of plasma enzymes for diagnosing clinical diseases.
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