controlling enzymes: regulatory strategies Flashcards
(25 cards)
What are enzymes?
Enzymes are catalysts.
How specific are enzymes?
Enzymes are highly specific.
By how much do enzymes increase reaction rates?
Enzymes can increase reaction rates by 10^6 or more.
What do enzymes accelerate?
Enzymes accelerate reactions.
What do enzymes lower to facilitate reactions?
Enzymes lower activation-energy barriers.
What are reversible inhibitors?
Reversible inhibitors stop substrate binding or change active site to stop the reaction.
What are the regulatory strategies of enzymes?
Multiple enzyme forms, proteolytic activation, covalent modification, feedback inhibition, allosteric control.
What are isoenzymes?
Isoenzymes are multiple forms of enzymes that differ in amino acid sequence but catalyse the same chemical reaction.
Where are isoenzymes often expressed?
In distinct tissues/organelles or at distinct stages of development.
What is proteolytic activation?
Proteolytic activation is a process where an inactive enzyme precursor is activated by cleaving peptide bonds.
What is the role of initiator caspases in apoptosis?
Initiator caspases activate executioner caspases by proteolysis.
What are zymogens?
Inactive precursors of enzymes stored in zymogen granules.
Fill in the blank: Protein phosphorylation is the addition of a _______ to an amino acid with an OH group.
phosphate group
What enzyme transfers a phosphate group during phosphorylation?
Protein kinase.
What enzyme removes a phosphate group during dephosphorylation?
Protein phosphatase.
What amino acids can be phosphorylated?
Serine, threonine, or tyrosine.
What is feedback inhibition?
When the end product of an enzyme pathway inhibits the first reaction in that pathway.
What does CTP inhibit in RNA synthesis?
CTP inhibits ATCase activity.
What is allosteric control?
Regulation of an enzyme by binding an effector molecule at a site other than the enzyme’s active site.
True or False: Hemoglobin is an enzyme.
False.
What is the cooperative binding of oxygen in hemoglobin?
Binding of one oxygen increases the likelihood that the remaining chains will bind oxygen.
What is the effect of 2,3-BPG on hemoglobin?
2,3-BPG stabilizes the T state and lowers O2 affinity of Hb.
What are hemoglobinopathies?
Diseases caused by mutations in hemoglobin, often single amino acid mutations.
What is sickle cell anemia caused by?
A point mutation that changes glutamate to valine.
