Multiple Choice
Covalent modification of an enzyme usually involves phosphorylation / dephosphorylation of:
7. Enzyme Inhibition and Regulation
Phosphorylation
Struggling with Biochemistry?
Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
When the active site of an enzyme is phosphorylated on one of its catalytic amino acid residues, the overall _______________ charge of phosphate groups would _____________ the affinity for a polar, negatively charged substrate.
A
positive; lower.
B
negative; lower.
C
negative; increase.
D
positive; increase.
E
positive; not change.
F
neutral; not change.
Verified step by step guidance1
Identify the nature of the phosphate group: Phosphate groups carry a negative charge due to their chemical structure.
Consider the effect of adding a negatively charged phosphate group to the enzyme's active site: This will increase the overall negative charge of the active site.
Analyze how the increased negative charge at the active site affects the interaction with a polar, negatively charged substrate: Like charges repel each other, so the increased negative charge will likely decrease the affinity for a negatively charged substrate.
Review the options provided: We are looking for an option that describes an increase in negative charge and a decrease in affinity.
Select the correct answer based on the analysis: The correct choice is 'negative; lower', indicating that the phosphorylation increases the negative charge and lowers the affinity for the negatively charged substrate.
Related Videos
Related Practice
Phosphorylation practice set
Problem sets built by lead tutorsExpert video explanations