Q: Which of the following chemical equations correctly represents the reaction catalyzed by lactase?

$$\mathrm{Lactose} + \mathrm{H}_2\mathrm{O} \xrightarrow{\text{lactase}} \mathrm{Glucose} + \mathrm{Galactose}$$

Question 1

Which enzyme is responsible for breaking down lactose into glucose and galactose in the small intestine?

Accepted Answer

Lactase

Question 2

A person consumes a glass of milk and their blood glucose level is measured over the next hour. If their blood glucose rises significantly, what does this most likely indicate about their lactase activity?

Accepted Answer

They are lactase persistent

Question 3

Which of the following chemical equations correctly represents the reaction catalyzed by lactase?

Accepted Answer

$$\mathrm{Lactose} + \mathrm{H}_2\mathrm{O} \xrightarrow{	ext{lactase}} \mathrm{Glucose} + \mathrm{Galactose}$$

Question 4

If an individual is lactase non-persistent, what is most likely to happen to the lactose they consume?

Accepted Answer

It is fermented by bacteria in the large intestine, producing gas

Question 5

Which of the following best explains why measuring blood glucose after lactose ingestion is a good indicator of lactase activity?

Accepted Answer

Lactase converts lactose into glucose, which is absorbed and raises blood glucose levels

Question 6

A hydrogen breath test is performed after lactose ingestion. Which result would indicate lactase non-persistence?

Accepted Answer

High hydrogen levels in the breath

Question 7

Why does fermentation of lactose in the large intestine lead to symptoms of lactose intolerance?

Accepted Answer

Fermentation produces gas and acids, causing bloating and discomfort

Question 8

If a person’s blood glucose does NOT rise after drinking milk, but their hydrogen breath test is positive, what is the most likely explanation?

Accepted Answer

They are lactase non-persistent

Question 9

Which of the following is a direct product of lactose hydrolysis by lactase?

Accepted Answer

Galactose

Question 10

A researcher wants to test for lactase persistence in a population. Which combination of tests would provide the most reliable results?

Accepted Answer

Blood glucose test after lactose ingestion and hydrogen breath test

Question 11

Which of the following best describes the fate of lactose in the digestive tract of a lactase persistent individual?

Accepted Answer

Lactose is hydrolyzed in the small intestine and absorbed as glucose and galactose

Question 12

Which of the following symptoms is most likely to occur in a lactase non-persistent individual after consuming dairy products?

Accepted Answer

Bloating and flatulence

Question 13

A student’s blood glucose rises from 90 mg/dL to 140 mg/dL after drinking milk. What does this suggest about their lactase status?

Accepted Answer

They are likely lactase persistent

Question 14

Which of the following is NOT a possible reason for a false negative result in a blood glucose test for lactase activity?

Accepted Answer

The individual consumed a high-protein meal before the test

Question 15

Which of the following best explains why some populations have a high prevalence of lactase persistence?

Accepted Answer

Cultural evolution favoring dairy consumption led to selection for lactase persistence alleles

Question 16

If a person is lactase non-persistent, which of the following would you expect to see after they drink a glass of milk?

Accepted Answer

No change in blood glucose and increased hydrogen in breath

Question 17

Which of the following best describes the role of water ($$\mathrm{H}_2\mathrm{O}) in $$the hydrolysis of lactose?

Accepted Answer

Water acts as a reactant, breaking the glycosidic bond in lactose

Question 18

A patient has normal blood glucose after lactose ingestion but experiences bloating and high hydrogen in breath. What is the best explanation?

Accepted Answer

They are lactase non-persistent and ferment lactose in the large intestine

Question 19

Which of the following is a valid alternative test for determining lactase persistence, besides blood glucose and hydrogen breath tests?

Accepted Answer

Genetic testing for lactase persistence alleles

Question 20

Which of the following best summarizes the relationship between lactase persistence and human evolution?

Accepted Answer

Lactase persistence evolved in populations with a history of dairy farming, providing a nutritional advantage

Lactase Enzyme Activity and Lactose Tolerance: Blood Glucose Data Analysis

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