Enzymes 101 Flashcards
(49 cards)
What is the primary role of enzymes in biological systems?
To act as biological catalysts that speed up chemical reactions without being consumed
Under what conditions do enzymes typically operate?
37°C, pH ~7.0, 1 atm pressure, and in aqueous solution
Do enzymes change the ΔG of a reaction?
No, enzymes do not affect the free energy change (ΔG) of a reaction
What is the effect of enzymes on activation energy (ΔG‡)?
Enzymes lower the activation energy, increasing reaction rate
What are the six main classes of enzymes in EC classification?
Oxidoreductases, Transferases, Hydrolases, Lyases, Isomerases, Ligases
(𝑶𝒙𝘦𝘯 𝑻𝒓𝘪𝘤𝘬 𝑯𝒚𝘳𝘢𝘹𝘦𝘴 𝑳𝒚𝘪𝘯𝘨 𝑰𝘯 𝑳𝒊𝒈𝘩𝘵𝘰𝘶𝘴𝘦𝘴)
What does EC 1.1.1.1 represent?
Alcohol:NAD⁺ oxidoreductase (alcohol dehydrogenase)
What is the function of an enzyme’s active center?
It binds substrates and contains the chemical groups that catalyze reactions
What is the role of regulatory centers in enzymes?
They bind modulators that regulate enzymatic activity
In the context of enzymes, what are cofactors?
Non-protein molecules that assist enzyme activity, either inorganic ions or organic molecules (coenzymes)
What is a coenzyme?
An organic cofactor that can be loosely or tightly bound to the enzyme
(It is NOT an enzyme itself)
Give examples of coenzymes.
NAD⁺, FAD, CoA
In the context of enzymes, what is a prosthetic group?
A coenzyme that is tightly or covalently bound to the enzyme
What is an isoenzyme?
Different molecular forms of an enzyme that catalyze the same reaction but differ in properties
Where are enzymes localized in cells?
In specific compartments like mitochondria, cytosol, or endoplasmic reticulum
What does ΔG < 0 indicate about a reaction?
That the reaction is spontaneous (exergonic)
What does ΔG > 0 indicate?
That the reaction is non-spontaneous (endergonic)
What is ΔG‡ and why is it important?
Activation energy; it determines the rate of a reaction
Which step in a reaction do enzymes affect?
They lower the activation energy (ΔG‡) to speed up the reaction
What is the enzyme-substrate complex?
A transient intermediate formed when the enzyme binds the substrate
What is the lock-and-key model?
A model where the enzyme and substrate fit exactly without conformational change
What is the induced fit model?
A model where the enzyme adjusts its shape to better fit the substrate
Why do enzymes bind the transition state more tightly than the substrate?
To stabilize the transition state and lower activation energy
What is acid-base catalysis?
Catalysis involving proton transfer from or to the enzyme or cofactor
What is the difference between specific and general acid-base catalysis?
Specific uses H⁺/OH⁻ from water; general uses ionizable side chains
