Lc 7. Enzymes (Metabolism) Flashcards
What occurs during chemical reactions between molecules?
Bond breaking and forming
A molecule must become highly unstable before bonds can break.
What is required for a molecule to undergo bond breaking?
Absorption of energy
A molecule must become highly unstable before bonds can break.
What is the activation energy (EA) in the context of chemical reactions?
The energy barrier that must be overcome for a reaction to occur.
True or False: For some reactions, thermal energy at room temperature is sufficient to overcome the activation barrier.
True
How do enzymes affect metabolic reactions?
They lower energy barriers.
What characterizes spontaneous reactions in terms of rate?
They are still really slow.
Provide an example of a spontaneous reaction.
Hydrolysis of sucrose to glucose and fructose.
What happens to the hydrolysis of sucrose at room temperature without enzymes?
It would sit for years without appreciable hydrolysis.
What is the reactant that an enzyme acts on called?
Substrate
What is the active site of an enzyme?
The region on the enzyme that binds to the substrate.
What is responsible for enzyme specificity?
The complementary fit between the enzyme and substrate.
What happens to enzymatic activity as substrate concentration increases?
It initially increases.
What occurs when all enzymes are occupied with substrate?
The reaction rate will plateau.
What happens when all substrate is depleted?
The reaction rate will decrease.
What are cofactors and coenzymes?
Helpers that bind to the enzyme.
What are cofactors typically made of?
Non-protein substances, including metal atoms such as zinc, iron, and copper.
What do coenzymes include?
Organic substances, including vitamins.
What is competitive inhibition?
An inhibitor binds the active site of the enzyme due to similar structure.
What characterizes non-competitive regulation (allosteric regulation)?
Activity can be altered by molecules acting at a site other than the active site.
What is an allosteric enzyme?
An enzyme whose activity can be altered by binding at an allosteric site.
What happens to allosterically regulated enzymes made from polypeptide subunits?
They oscillate between two shapes: one catalytically active and the other inactive.
What effect does an activating molecule have on an allosteric enzyme?
It stabilizes the shape with functional active sites.
What effect does an inhibiting molecule have on an allosteric enzyme?
It stabilizes the inactive form of the enzyme.
What type of inhibitor is often the product of the pathway in allosteric regulation?
Inhibitor
