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BI2.1-5 | Enzyme — Practice Quiz

Practice 8 questions · Untimed · Unlimited attempts

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Q1 BI2.1 1 pt

An enzyme requires a non-protein organic molecule derived from niacin (vitamin B₃) to function. This helper molecule is best described as:

A An apoenzyme
B A coenzyme
C A holoenzyme
D An isoenzyme

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Q2 BI2.1 1 pt

According to the IUBMB classification, an enzyme that transfers a functional group from one molecule to another belongs to the class of:

A Oxidoreductases
B Hydrolases
C Transferases
D Ligases

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Q3 BI2.2 1 pt

The currently accepted model for enzyme-substrate interaction states that the active site is flexible and changes shape upon substrate binding. This model is known as:

A The lock-and-key model
B The induced fit model
C The allosteric model
D The Michaelis-Menten model

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Q4 BI2.2 1 pt

An enzyme has a Km of 2 mM. At a substrate concentration of 2 mM, the reaction rate will be:

A Equal to Vmax
B Equal to ½Vmax
C Equal to zero (no reaction)
D Equal to 2 × Vmax

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Q5 BI2.3 1 pt

A competitive inhibitor of an enzyme will:

A Decrease Vmax without changing Km
B Increase the apparent Km without changing Vmax
C Decrease both Km and Vmax
D Irreversibly destroy the enzyme

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Q6 BI2.3 1 pt

Aspirin irreversibly acetylates the enzyme cyclooxygenase (COX). A patient takes aspirin in the morning. By evening, the anti-inflammatory effect is still present because:

A Aspirin has a very long half-life in the blood
B The inhibited COX molecules cannot recover — new enzyme must be synthesised to restore activity
C Aspirin is a competitive inhibitor that stays bound for many hours
D COX is only active in the morning

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Q7 BI2.4 1 pt

A patient presents with chest pain. Which serum enzyme marker is considered the gold standard for diagnosing acute myocardial infarction?

A ALT (SGPT)
B Amylase
C Troponin I or T
D Alkaline phosphatase (ALP)

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Q8 BI2.5 1 pt

A patient with jaundice has the following blood results: ALT = 45 U/L (mildly elevated), AST = 100 U/L (AST:ALT ratio = 2.2), ALP = 380 U/L (markedly elevated), GGT = 290 U/L (markedly elevated). The most likely diagnosis is:

A Acute viral hepatitis — because transaminases are elevated
B Acute pancreatitis — because ALP is elevated
C Obstructive jaundice — because ALP and GGT are both markedly elevated
D Myocardial infarction — because AST is elevated

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