Multiple Choice
At which pH does the enzyme pepsin become most active?
2. Water
pH
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At pH 7, what is the net charge of both pantothenate and phosphopantothenate in aqueous solution?
A
Pantothenate: -1, Phosphopantothenate: -1
B
Pantothenate: 0, Phosphopantothenate: -1
C
Pantothenate: 0, Phosphopantothenate: 0
D
Pantothenate: -1, Phosphopantothenate: -2
Verified step by step guidance1
Step 1: Understand the chemical structures of pantothenate and phosphopantothenate. Pantothenate is a vitamin B5 derivative, and phosphopantothenate is its phosphorylated form. Both molecules contain functional groups that can ionize depending on the pH of the solution.
Step 2: Identify the ionizable groups in pantothenate and phosphopantothenate. Pantothenate has a carboxyl group (-COOH) that can lose a proton to become negatively charged (-COO⁻) at pH 7. Phosphopantothenate has both a carboxyl group and a phosphate group (-PO₄H) that can lose protons to become negatively charged (-PO₄²⁻).
Step 3: Consider the pH of the solution (pH 7). At this pH, the carboxyl group of pantothenate will be deprotonated, resulting in a net charge of -1. For phosphopantothenate, both the carboxyl group and the phosphate group will be deprotonated, resulting in a net charge of -2.
Step 4: Compare the net charges of pantothenate and phosphopantothenate. Pantothenate has a net charge of -1 due to the deprotonation of its carboxyl group. Phosphopantothenate has a net charge of -2 due to the deprotonation of both its carboxyl group and phosphate group.
Step 5: Conclude that at pH 7, the net charges are Pantothenate: -1 and Phosphopantothenate: -2, based on the ionization states of their functional groups in aqueous solution.
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