28 Questions
What type of components are cofactors in enzymes?
Inorganic ions
What causes a conformational change in troponin C during muscle contraction?
Binding of Ca2+
What is required for the catalytic activity of enzymes?
Native protein conformation
What do coenzymes act as in enzymatic reactions?
Catalysts
What did Eduard Buchner demonstrate in 1897 regarding enzymes?
Cell-free yeast extracts can ferment sugar to alcohol
What do regulatory mechanisms of enzymes include?
Noncovalent binding to regulatory proteins and binding of allosteric modulators
What is a prosthetic group in relation to enzymes?
A coenzyme or metal ion tightly bound to the enzyme protein
Which inorganic ion serves as a cofactor for cytochrome oxidase enzymes?
Fe3+
Why do enzymes exhibit a very high degree of specificity?
They bind tightly to the transition state of reactions
What is the main role of enzymes as biological catalysts?
Lower reaction activation barriers
Where do enzyme-catalyzed reactions take place?
Active site
Why are enzymes often regulated through multiple methods?
To allow for exquisite control of every chemical process in a cell
What part of an enzyme together with its bound coenzyme and/or metal ions forms a holoenzyme?
Apoenzyme
What is the function of troponin I in muscle contraction?
Inhibits muscle contraction
What is the range of molecular weight for enzymes?
<12,000 to >1 million
What occurs in the active sites of enzymes during catalysis?
Conversion of product to substrate
In metal ion catalysis, how do metals assist in reactions?
By stabilizing transition states and mediating redox reactions
What must be true for catalysis to occur?
The new pathway has a lower activation energy than the uncatalyzed pathway
What do enzymes affect in a reaction?
Reaction rates
What do metal ions do in metal ion catalysis?
Stabilize charged reaction transition states
How are metal ions involved in metal ion catalysis?
They help orient the substrate and stabilize transition states
What concept explains the catalytic power of enzymes by binding tightly to specific states?
Transition state theory
What percentage of known enzymes require metal ions for catalytic activity?
Nearly 1/3
Which type of RNA can also catalyze reactions?
Ribozymes
What does the term 'Transition state (‡)' represent in a reaction?
The stage where decay to substrate or product are equally likely
What is the difference between ∆G‡uncat and ∆G‡cat in a reaction?
Activation energy for uncatalyzed and catalyzed reactions
What is the starting point for either the forward or reverse enzymatic reaction?
Ground state
What do catalysts do to the activation energy and the reaction rate?
Decrease activation energy and increase reaction rate
Test your knowledge on the mechanism of muscle contraction by watching informative videos. Understand how Ca2+ release triggers a series of events leading to muscle contraction. Check your understanding with this quiz!
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